HK1086151B - Apparatus for transducing video signals and/or audio signals in a vehicle - Google Patents

Description

Device for converting video signals and/or audio signals in a vehicle

Technical Field

The invention relates to reproducing center channel information in a vehicle multi-channel audio system.

Background

By way of background, U.S. patents nos. 5870484, 5333200, 4569074, an article entitled "Gradient Loudspeakers" by Harry f.olson on the first volume, page 304, of the society of sound engineers, the speaker, and "Spatial Hearing," by Jens Blauert, second edition 1983, published by MIT press, massachusetts, are cited.

Disclosure of Invention

According to the present invention, an audio image is generated in the center of a video display mounted on a vehicle.

If a real, actual sound source is indeed present at the desired location, the signal generated by the actual sound source or sources present at the listener's ear coincides with the signal received by the listener's ear. In an audio system with a video display where the loudspeakers are located far away from the location where the video display is located, if a real, actual loudspeaker is located at the actual location of the video display, signals (which may be modified or processed) are applied to these loudspeakers so that they are sent to the listener's ear (the output of all sound sources combined together may reproduce the same signal information) which is consistent with the signal at the listener's ear.

The position of the simulated image can be controlled by controlling the intensity of the incoming sound, which is controlled as a function of the direction of the sound source. There are many ways to control the directivity of a sound source. One of these methods is to use a bank of multiple, compact frequency converters, where the directivity control is maintained at a frequency with a wavelength equal to twice the distance between the elements.

Therefore, the amount of transmission of the signal transmitted by the group of frequency converters in one direction is greater than the amount of transmission in the other direction. According to one aspect of the invention, a video display is mounted in the middle of a vehicle. The voice signals reproduced by the transducer group installed on the right side of the vehicle (e.g., included in the center channel signal) are concentrated toward the left side of the vehicle, and the voice signals reproduced by the transducer group installed on the left side of the vehicle are concentrated toward the right side of the vehicle. A vehicle occupant sitting on the right side of the vehicle is actually closer to the right side of the transducer group than to the left side. Whereas a vehicle occupant sitting on the left side of the vehicle is actually closer to the left-hand inverter group than to the right-hand inverter group. And the directional characteristic of the transducer group is such that it emits less energy in the direction towards the closer seat and more energy in the direction towards the farther seat. Time intensity switching (time intensity switching) can be implemented using directional transducer groups to simultaneously generate signals for a plurality of asymmetrically distributed passengers, with a perceived image in the center of the vehicle near the video display. The set of frequency converters has the outstanding advantage of being capable of controlling the directivity of signals at low frequency (such as 200Hz-1.5 KHz).

According to the inventive technique, the desired acoustic signal is generated at the ear of the listener by processing the associated level and/or associated time delay of the signal resulting from the reconstruction of the signal close to the low frequency signal present at the ear of the listener, essentially with the signal position between the pair of actual sound sources. It is also possible to process the relative polarities of the signals for a plurality of sound sources and/or the relative phases according to a function of the frequency of the signals to produce regions that are outside the space between the actual sound source locations that are perceptible. The present invention provides an auditory signal that uses cross-talk cancellation techniques and HRTF processing.

According to another aspect of the invention, the effective height of the sound source is adjustable so that the sound source is perceived in the case where the sound source is positioned at a different height than the actual speaker. The perception of signal height can be changed by changing the content of the transmitted signal spectrum.

Other features, objects, and advantages of the invention will be apparent from the description which follows, taken in conjunction with the accompanying drawings in which:

drawings

FIG. 1 illustrates a system for reconstructing center channel information in a multi-channel sound system of a vehicle, in accordance with one embodiment of the present invention;

FIG. 2 shows another configuration of the system for reconstructing center channel information in a multi-channel sound system of a vehicle;

FIG. 3 illustrates a scheme in which the speakers of the multi-channel sound system are placed in proximity to a video display that is placed on the headrest of the front seat of the vehicle;

FIG. 4 shows an alternative embodiment of the present invention in which the speaker and video display are mounted to the rear of the front seat of the vehicle;

FIG. 5 shows another alternative embodiment of the present invention in which the speakers are positioned near a centrally located video display;

FIG. 6 shows another embodiment of the present invention;

FIG. 7 is a circuit diagram according to one embodiment of the present invention, the circuit being connected to a set of frequency converters;

FIG. 8 is an alternative circuit diagram according to one embodiment of the present invention, which is connected to a set of frequency converters;

FIG. 9 is an alternative embodiment of the present invention wherein directional speakers are mounted near a centrally located video display, which are oriented to emit sound primarily toward the rear of the vehicle;

FIG. 10 is an alternative embodiment of the present invention wherein a directional speaker is mounted near the centrally located video display and is oriented to emit sound primarily toward the video display, thereby reflecting the emitted sound away from the display screen toward the rear of the vehicle; and

FIG. 11 is a transfer function of an exemplary balancer.

Detailed Description

Referring to the drawings, and in particular to FIG. 1, there is shown a sound system 100 in which center channel information can be recreated in a vehicle multi-channel sound system. Fig. 1 includes a video display 120 mounted in the center of the vehicle (e.g., mounted in/on the roof of the vehicle), a speaker 101 mounted in the center, speakers 102, 103 mounted on the left and right sides of the vehicle, respectively, proximate rear seats 160, 170, speakers 112, 113 mounted on the left and right sides of the vehicle, respectively, proximate front driver and passenger seats 140, 150, and a speaker 111 mounted in/on the center of the front dash. The speaker 101 is oriented at the same angle as the video display 120, but is not co-located with the video display 120. The centrally located speaker 101 may be located at a different height than the video display, such as in a center console connected to the floor. Speakers 102, 103, 112, 113 represent other speakers that may be present in the vehicle. In practice the number of loudspeakers may be more or less than the number of loudspeakers shown.

When the height of the centrally-mounted speaker 101 is different from the height of the video display 120 (e.g., the centrally-mounted speaker 101 is located in the console and the video display 120 is located in the roof), the visual images displayed on the video display 120 may not be fully combined with the associated audible images, and as a result, the illusion that the person displayed on the video display 120 is indeed speaking is affected. By processing the signal reproduced by the centrally located speaker 101 in such a way that the reproduced signal is perceived as if it were actually at the height of the video display 120, it is possible to reduce this effect.

The perception of the height of the sound source is mainly based on the spectral content of the signal heard by the listener. By varying the spectral content of the signal heard by the listener in a predetermined manner, the listener's perception of the high position of the signal source can be varied. This is achieved by placing a signal processing means (which may be analogue or digital) that changes the spectral content of the signal heard by the loudspeaker and the listener, wherein the signal processing uses a filter that represents the difference between the main correlation transfer function (HRTF) of the sound source detected at the actual sound source position and the HRTF of the sound source detected at the desired azimuth angle. In the art, HRTF detection methods are well known. More specifically, the required transfer function can be determined according to the following steps, wherein the desired transfer function can be realized by the signal processing means:

in step 1, a first transfer function H1(j ω) is detected, the input from the sound source at the sound source height would be the sound pressure at the ear of the listener. In the above example, the sound source is located in a console placed in the center of the floor, and the listener is seated in the seat 160 or 170.

In step 2, a second transfer function H2(j ω) is detected, and the sound pressure at the ears of the listener is derived from the input to the sound source located at the height required to perceive the sound source. In the above example, the desired sound source location is the location of the video display 120 mounted on the roof of the vehicle.

At step 3, a third transfer function H3(j ω) is calculated by calculating the difference between the first and second transfer functions, wherein:

H3(jω)＝H2(jω)/H1(jω)

a typical transfer function for a balancer is shown in fig. 11. The curve shows the difference comparison from a height of +45 degrees to a height of-45 degrees in the main correlation transfer function (HRTF) of a representative listener. A counterpoise provides the listener with a signal consistent with a sound source at a substantial altitude of +45 degrees, wherein the counterpoise is located in the signal path of the signal, which is provided to a loudspeaker with a transfer function at an azimuth of-45 degrees. For efficiency of operation, it is not necessary that the balancer exactly conform to the desired curve. It is sufficient to fit the curve in the interval between about 4KHz and 14 KHz. If different heights are included, the peak frequency (about 5.7KHz in FIG. 11) and the tilt frequency (about 11KHz in FIG. 11) will be offset. If it is desired to move the perceived azimuth downward, rather than upward, a curve having the opposite characteristics of fig. 11 is desired. That is, in order to shift the perceived image from the actual speaker at +45 degrees elevation to the desired-45 degrees azimuth, a balancer with a minimum of 5.7KHz and a maximum of 11KHz should be used.

Next, by using a balancer with a transfer function H3(j ω) for a signal for speakers positioned at a different height than the video display 120, the signal reproduced by the speakers can be perceived by a listener positioned at the height of the video display 120.

The information contained in the transfer function H3(j ω) is mainly concentrated in the high frequency region. That is, a signal for sensing an azimuth of a sound source in an acoustic system is mainly concentrated on a high frequency region. Another embodiment can be achieved with improved audio and visual image synthesis by placing the high-frequency reproduced sound source in proximity to the video display. The individual sound sources reproducing the low and medium frequency information can be placed at a different height from the high frequency device. For example, in a multi-channel vehicle system, the high frequency center channel information is reproduced by a high frequency transducer (e.g., a tweeter) near a video display (e.g., a roof or seat back mounted video display), while the remainder of the spectrum of the center channel information is reproduced by a low/mid frequency transducer (or combination of transducers) at a location that is at a different height than the high frequency transducer. This embodiment is resilient in assembly, as only a small device needs to be positioned at the display to properly combine the perceived sound with the visual image.

Fig. 2 shows another sound system configuration 200 comprising a centrally located speaker 201, two (left and right) video displays 220, 221 located behind or in line with each of two (left and right) front seats 240 and 250, respectively (e.g., in the back rest or headrest of seats 240 and 250), a speaker 211 located in the center of the dashboard, two (left and right) speakers 212, 213 located on either side of the dashboard, respectively, and two (left and right) speakers 202, 203 located on either side of the vehicle, such as in the pillars, side walls, or doors of the vehicle, respectively. In this configuration, the rear passenger seats 260, 270 are in line with each of the two video displays 220, 221.

According to one embodiment of the present invention, the centrally located speaker 201 can be mounted on a console in the center of the vehicle. According to another embodiment of the invention, it can also be installed at any position of the vehicle center line. Since the speakers producing center channel information are not positioned at the same azimuth as the video displays 220, 221 corresponding to the passenger seats 260, 270, it is desirable to produce a simulated image of the center channel information as perceived near each video display 220, 221. The emulated image is based on a phenomenon known as sum-and-locate, whereby the same signal from two (or more) sound sources located at the same azimuth is transmitted, so that the listener can perceive the location of the emulated image somewhere between the sound sources, based on the relative strengths of the signals from the sound sources and the relative time delays of the signals from the two sound sources. As described above, the speakers 202, 203, 212, 213 may also transmit other signals simultaneously (e.g., the speakers 202, 212 transmit signals for the left channel of a stereo or multi-channel sound system and the speakers 203, 213 transmit signals for the right channel). The speakers 202, 203, 212, 213 may represent other speakers already present in the vehicle. The number of other loudspeakers actually used may be larger or smaller than the number of loudspeakers shown. The processing of the center channel signal may be done independently of the processing of the other signals.

The location of the desired signal is determined based on the signals present at the listener's ear and the processing of those signals, which is determined by the number, location and characteristics of all sound sources reproducing the desired signal (e.g., horn, etc.). At the rear of the vehicle 200, a speaker 201 reproduces center channel information. In addition, the center channel information is provided to speakers 202 and 203 in order to generate simulated images of the center channel information in the vicinity of video displays 220 and 221. By recreating the center channel information from loudspeakers symmetrically distributed about the centerline of the vehicle, it is possible to simultaneously produce the desired simulated images for both the left and right rear seat passengers.

Due to the symmetry it is simple to adjust the relative levels and relative delays of the signals of the loudspeakers 202 and 203 corresponding to the level and delay of the signal of the loudspeaker 201 in order to obtain the desired effect. It should be noted here that although the correlation level and delay of the signals used are considered, this is for convenience only. Of real concern is the relative sound pressure level at the listener's ear due to each sound source reproducing a particular signal. The gain of other parts of the signal chain (including any amplification and loudspeakers for the auditory position transfer function) is assumed to be equal, taking into account the relevant level of the signal used, so that when it is constant a relatively large signal is used as a compensation quantity, that is to say the signal level is adjusted so that the sound pressure at the ear of the listener caused by the sound source receiving the signal of the increased level is greater than the sound pressure at the ear of the listener caused by the other sound source or sources being used for comparison.

Increasing the level of signals applied to speakers 202 and 203 relative to the signals applied to speaker 201 causes the simulated image to shift away from speaker 201 toward speakers 202 and 203, corresponding to the occupants of left rear seat 260 and right rear seat 270, respectively. Delaying the signal of the centrally mounted speaker 201 relative to the signal applied to the speakers 202 and 203 also causes the simulated image to shift away from the speaker 201 toward the speakers 202 and 203, corresponding to the occupants of the left and right rear seats 260 and 270, respectively. Proper selection of the relative levels and/or relative delays can effectively position the simulated images near the video displays 220 and 221. The correlation level and the correlation delay adjustment can be used alone or in combination to achieve the desired result. The exact processing is done according to the particular arrangement of system components in the vehicle. The level of the centre channel signal of the loudspeakers 202, 212, 203, 213 may be less than, equal to or greater than the level of the signal of the loudspeakers 211, 201, depending on the characteristics of the vehicle and the sound reproducing element used. The level of the center channel signal of the speakers 212, 213 relative to the level of the speaker 211 may be different from the level of the center channel signal of the speakers 202, 203 relative to the level of the speaker 201. Likewise, the signals of the loudspeakers 201, 211 may be delayed with respect to the signals of the loudspeakers 202, 212, 203, 213, or vice versa. The delayed signal of speaker 201 relative to speakers 202, 203 may be the same as or different from the delayed signal of speaker 211 relative to speakers 212, 213. The actual delay may also be selected based on vehicle specific characteristics (such as the length of the channel from each speaker to the listener's location) and the selected sound reproducing element. It should be noted that in the above discussion of correlation delays, correlation delays can be generated from one signal relative to another, where only one signal may have an actual time delay in the correlation process with the signal, or where two signals are delayed to different magnitudes.

One possible method of determining the relative class and delay of a rear seat passenger will be described below. As in the illustrated embodiment, it is first assumed that only speaker 201 has center channel information. In this case, the center channel information can be perceived at the position of the speaker 201. The center channel information needs to be located at the position of the video displays 220 and 221. To this end, the loudspeakers 202 and 203 also have center channel information. The level of center channel information for speakers 202 and 203 is increased until listeners sitting at seats 260 and 270 perceive the position of the center channel information as approximately corresponding (at least in height) to the position of video display positions 220,221, respectively.

The discussion above does not take into account the front seat. It is necessary to locate the center channel information in the front seat at the position of the speaker 211, which is easily achieved (by using only the center channel information for the speaker 211). Alternatively, it may be desirable to create a simulated image of the center channel information for each front passenger that is relatively far from the centerline of the vehicle for the left and right drivers and passengers, respectively (one embodiment places the simulated image directly in front of the driver and front passenger positions). This solution can be implemented in the front seat in the same way as described above in relation to the rear seat. Thus, the speakers 212, 213 may additionally also have a center channel signal to move the perceived position of the desired center channel signal.

The center channel information of the reproduced speaker 201 (and possibly also the speakers 202, 203) may affect the positioning of the center channel information by the front seat passenger. The center channel information output by speaker 201 (and/or speakers 202, 203) may move the perceived position of the center channel information of the front seat occupant toward the rear of the vehicle, away from the desired position at the front of the vehicle. To compensate for this, a delay may be added to the center channel information for speaker 201 (and speakers 202, 203 if desired) to ensure that the center channel information for speaker 211 (and possibly speakers 212, 213) arrives at front seats 240 and 250 first before the center channel information for speaker 201 (or speakers 202 or 203).

A delay is added to the center channel information that only speaker 201 has to move the perceived image of the front seat occupant backward toward the front of the vehicle, which moves the simulated images of the listeners located in left rear seat 260 and right rear seat 270 further toward speakers 202 and 203, respectively. To move the simulated image of the rear seat occupant backward to the desired position, the level of center channel information for speakers 202 and 203 may be reduced, a delay may be added to the center channel signals for speakers 202 and 203 relative to the signal for speaker 201, or a combination of delay and level adjustment may be used.

In an embodiment where there is not good left/right symmetry about the center line of the environment, such as in the front seat area of a vehicle, the shape of the diaphragm area around the driver is different from the shape of the diaphragm area around the passenger, so the relative levels and delays of the speaker signals (e.g., center channel signal) that determine the signal that should be reproduced need to be adjusted individually to achieve the desired effect. That is, the level and delay of the center channel signal applied to speaker 212 relative to the level and delay of the center channel signal applied to speaker 211 may be different than the level and delay of the center channel signal applied to speaker 213 relative to the level and delay of the center channel signal applied to speaker 211.

Fig. 3 is a diagram illustrating an arrangement according to one embodiment of the present invention in which the speakers of the multi-channel sound system are located near a video display mounted in the back of the seat back or headrest of the front seat of the vehicle. Fig. 3 includes front (i.e., left and right) seats 340, 350, rear seats 360, 370, left and right speakers 304, 305 mounted in the roof of the vehicle (e.g., the left and right speakers 304, 305 may alternatively be positioned at another location on the video displays 320, 321, such as in the back of the seat), each front seat carrying a video display 320, 321. Alternatively, the video displays 320, 321 may be in the roof of the vehicle. Fig. 3 also includes left, right and center front speakers 312, 313, 311, respectively, mounted in the instrument panel, and left and right speakers 302, 303, respectively, mounted to the sides and front of left and right rear passenger seats 360, 370. Alternatively, the speakers 312 and 313 may be mounted to the side of the vehicle rather than in the dashboard.

In this configuration, the left and right speakers 304, 305 in the roof are positioned at about the same azimuth as the video displays 320, 321. In fig. 3 they are located slightly behind the position of the video displays 304, 305, but they may also be in line with the displays or even slightly ahead of the position of the displays. The left and right speakers 304, 305 are constructed so that they can each transmit a signal having center channel information. Therefore, since the speakers 304, 305 on opposite sides of the vehicle transmit the center channel signal (e.g., a passenger sitting on the left side of the vehicle will perceive a simulated image closer to the center of the vehicle due to the center channel information transmitted by the speakers 305 on the right side of the vehicle), a listener sitting in the rear seat 360 or 370 may hear the composite signal of the signals transmitted by the left and right speakers 304, 305, wherein the simulated image perceived by the listener in the seat may move slightly toward the center of the vehicle.

To compensate for the simulated image closer to the center of the vehicle, a small amount of center channel information needs to be passed to the left and right speakers 302, 303. This balances the transmission of the center channel information so that the final perceived position of the simulated image moves closer to being in line with the video display.

For embodiments where the speakers 304, 305 are mounted on the roof of the vehicle, the speakers are located at a different height than the video display. Similar signal processing as previously described in fig. 11 can be used to shift the azimuth of the perceived image downward to better align with the video display. Thus, the characteristics of the shape of the balancer will be opposite to those shown in fig. 11.

Fig. 4 is a diagram illustrating an alternative embodiment of the present invention in which speakers 422, 423, 424, 425 are installed at left and right sides of each front seat back. The video display 420 is mounted in the roof of the vehicle in line with or slightly behind the two front passenger seats 440, 450. The left and center channel signals of the multi-channel sound system are transmitted through left and right speakers 422, 423, respectively, of the left front passenger seat 440. Center channel and right channel signals for a surround sound system (surround sound system) are transmitted through left and right speakers 424, 425, respectively, of a right front passenger seat 450. The perceived position of the center channel signal will shift slightly to the right of the right speaker 423 as a result of the center channel signal being emitted by speaker 424 so that it is perceived by the left rear seat passenger, and to the left of the left speaker 424 as a result of the center channel signal being emitted by speaker 423 so that it is perceived by the right rear seat passenger, the perceived position of each image being approximately in-line with the azimuth of the video display 420. This arrangement of loudspeakers is called L-C-R. Other speakers may be used with this configuration. For example, speakers can be located in left and right rear doors (not shown), if desired.

Fig. 5 is a diagram depicting an alternative embodiment of the present invention in which the speakers and video display (if present, not shown in fig. 5) are mounted in the instrument panel. The embodiment of fig. 5 shows an L-C-R arrangement of speakers at the front of the vehicle, similar to the arrangement described above with respect to fig. 4 for a rear seat passenger. It therefore has a speaker 512 mounted in the instrument panel in front of the left passenger, a left speaker 514 mounted on the left side of the vehicle, a speaker 513 mounted in front of the right passenger, and a right speaker 515 mounted on the right side of the vehicle. A video display can be placed in the center of the instrument panel or a pair of displays can be placed to the left and right of the centerline of the vehicle. The left channel and center channel surround sound signals are transmitted through a left speaker 514 and a speaker 512 mounted in the left dash, respectively. Center channel and right channel surround sound signals are transmitted through a speaker 513 and a right speaker 515, respectively, of a right front passenger seat 550, which are housed in the right dash panel. In this embodiment, the center channel information is directly transmitted to each passenger in the front seat through the speakers 512 and 513. The position of the center channel signal in front of each front passenger is sensed without the need for a simulated image method. This arrangement has also proven beneficial for reproducing music alone, in the absence of a video display.

FIG. 6 is a diagram illustrating an alternative embodiment 600 of the present invention. Fig. 6 includes left and right front seats 640, 650, left and right rear seats 660, 670, left and right directional speakers 642 and 652. In the embodiment shown in fig. 6, each directional speaker includes a pair of transducers (sometimes referred to as transducer groups) located to the left and right of a centrally located video display 620. A group of frequency converters may be two or more frequency converters if desired. But it is not necessary to use directional loudspeaker sets. Any known method for configuring a loudspeaker to emit relatively much energy in one direction but not the other and past an available point of the sound spectrum may be used for a directional loudspeaker. For example, a tweeter or a transducer having a sound emitting surface with a wavelength greater than that of the sound to be reproduced is directed towards the loudspeaker. For ease of description, the following discussion will refer to the transducer groups as directional speakers. The frequency converter group has the unique advantage that it otherwise requires a large physical structure to accomplish, since at low frequencies it is possible to obtain the required directional performance.

In the embodiment of fig. 6, the sets of frequency converters 642, 652 are mounted in or on the seats 640, 650. Alternatively, the sets of transducers 642, 652 may be mounted to either side of the video display, at the same or different elevation (e.g., in the roof or floor) as the video display 620. The left inverter bank 642 transmits more energy to the right side of the vehicle relative to the forward transmission of the inverter bank 642. Therefore, as shown in fig. 6, the left transducer group 642 outputs more sound in the direction of the right seat 670 than in the direction of the front or left seat 660. Conversely, as shown in fig. 6, the right transducer group 652 may output more sound in the direction of the left seat 670 than in the direction of the front or right seat 670. This effect is advantageous for a listener in the rear seats 660, 670 to listen to the sound image of the transducer groups 642, 652 on the vehicle centre line simultaneously.

The directivity can compensate for the relative arrival time difference of each directional speaker to the seat. If the signals of the transducer groups are the same, the sound of the left transducer group 642 will arrive at the seat 660 before the sound of the right transducer group 652 arrives at the seat 660. This relative time difference will typically cause a listener in seat 660 to perceive that the signal present (as described above) is located closer to left transducer bank 642 than right transducer bank 652. Similarly, a listener in the seat 670 perceives the presence of a signal located closer to the right transducer bank 652 than the left transducer bank 642. The directional characteristic of the frequency converter group is selected to compensate the correlation time difference, and a time-intensity exchange technology is used. At the seat 660 location, the sound of the transducer group 642 arrives before the sound of the transducer group 652 arrives, but the directionality of the transducers is specified such that the sound level received by the seat 660 directed to the speakers 642 is lower than the received sound level directed to the speakers 652, so the perceived location of the emitted center channel signal (emitted from the transducer groups of the system) moves towards the location of the video display 620. At the same time, the orientation of the transducer groups moves the position of the center channel information perceived by the passengers in the seats 670 towards the position of the video display 620.

This technique can also be used for multi-channel sound systems, for example, where there are separate left, center, right, left surround and right surround signals. The technique can also be connected to a stereo system. In a stereo system arrangement, a bank of transducers 642 transmits left channel information and a bank of transducers 652 transmits right channel information. The orientation of the transducer groups is chosen such that when there is an equal signal of the same kind in each channel, the signal is perceived by each passenger to be located approximately in the middle of the two orientation transducer groups. In stereo systems or two-channel matrix surround sound systems, such as dolby or other surround coded 2-channel systems, speech information may also be included in both stereo signal channels.

Unlike the loudspeaker which is most suitable for controlling the direction of the signal at high frequencies, the transducer group can control the direction at low frequencies, which range from 200Hz to 1.5 KHz. The frequency range of 200Hz to 1.5KHz is an important range for controlling the position of the sound image perceived by the listener, and in the embodiment described herein, control over the main portion of this frequency range helps to control the positioning of the image. The directional control provided by the set of frequency converters makes it possible to simultaneously generate an independent, stable central image-sound structure for each of a plurality of rear seat passengers.

The frequency range over which the directional control is maintained is determined primarily by the distance between the transducer elements. The highest frequency that can be controlled is the frequency with a wavelength twice the element distance. Beyond this frequency, multiple lobes in the pointing mode begin to appear. To control pointing up to 1.5KHz, the element distance should be approximately 4.5 feet. Elements with a spacing greater than 4.5 feet still provide good pointing control, which can be used in other embodiments. A component distance of, for example, about 7 feet can achieve 1KHz control and has been found to be sufficient.

The frequency converter obtains directional corrections at low frequencies by using destructive interference. Specific signal processing can be used to obtain the desired pointing mode. This signal processing will be described in more detail in fig. 7 and 8, as described below.

To obtain the available directivity, the sets of frequency converters 642 and 652 may use simple or more complex techniques. Fig. 7 and 8 depict signal processing for the two element groups shown in fig. 6 (e.g., groups of transducers 642, 652 at left block 640 and right block 650, including left and right transducers 642a, 642b, 652a, 652b, respectively). Fig. 7 is a circuit diagram 700 of a connection to a bank of frequency converters 642, according to an embodiment of the invention. This embodiment simply reverses the relative polarity of the frequency converter 642a with respect to 642b and the relative polarity of the frequency converter 652a with respect to 652b in each of the frequency converter groups 642, 652, respectively. In one embodiment, frequency converters 642b and 652a have non-inverting poles and frequency converters 642a and 652b have inverting poles. Each of the transducer groups 642, 652 is then in a dipole radiating mode, having a maximum amount of radiation along a direction of a line passing through the centers of the two transducers, and a minimum amount of radiation in a direction orthogonal to the direction of the maximum amount of radiation. The transducer groups 642, 652 are arranged such that closer listeners are closer to or in the direction of the "inactive" transducer group, while listeners on the opposite side of the vehicle are closer to or in the direction of the maximum emission. For example, the passenger in the seat 660 is in or near the direction of the inactive transducer 642 and closer to the direction of the maximum firing volume of the transducer 652. The level difference is used to cause the perceived location of the signals simultaneously transmitted by the transducers to move away from closer transducers to more distant transducers. One advantage of this arrangement is that only one amplifier 730 is required (the electrical connections to each frequency converter can be reversed to change the relative polarity as required).

In some applications, the associated level difference produced by the simple bipolar directional loudspeaker arrangement described above may also be greater than the desired level difference. An improvement of the present invention is that still using only one amplifier 730, the depth of inefficiency due to varying sensitivity of the frequency converter 642a relative to 642b of the frequency converter bank 642 or sensitivity of the frequency converter 652a relative to 652b of the frequency converter bank 652 can be reduced. This can be done by changing the voice coil of one transducer (one voice coil has a higher or lower impedance than the other to create different voltage sensitivities between the two transducers). In one embodiment, two frequency converters are used, one having a nominal DC impedance of 2 ohms and the other having a nominal DC impedance of 8 ohms. It is known how to scale the impedance of a frequency converter without significantly altering the response to a frequency function. When the bank of frequency converters is driven by a single amplifier 730, the higher impedance frequency converter has a lower output relative to the lower impedance frequency converter. The frequency converter bank is no longer in the mode of fig. 8 and the correlation level difference between the levels 660 and 670 is reduced. In one embodiment, the impedance of the sound diagram for speakers 642a and 652b is higher than for speakers 642b and 652a, respectively. Alternatively, a resistor can be placed in series with one of the inverters in each pair to reduce its output.

Fig. 8 is an alternative circuit diagram 800 for interfacing with a bank of frequency converters, in accordance with one embodiment of the present invention. Any desired first order gradient pointing mode (from a group of 2 elements) can be generated. By acting on destructive interference, the frequency-varying group can have directivity at low frequencies (e.g., frequencies having wavelengths greater than the element distance). That is, signal processing is used to cause the outputs of individual groups of elements to destructively interfere, the extent of destructive interference varying as a function of angle. EQ blocks 860 and 870 represent the signal processing required to control the pointing of two component groups. As shown in fig. 7, the correlation polarity and correlation level may be used to obtain the available directivity. Additional flexibility can be obtained if additional control is possible. In the embodiment of fig. 8, EQ blocks 860 and 870 allow for controlling the correlation level of the signal of each element according to a frequency function, the correlation phase resulting from the frequency function, and the correlation time delay of the signals of element groups 652a and 642 b.

In fig. 7, the reversal of the polarity of the elements of the two element groups is described. The embodiment shown in fig. 7 is a bipolar emission mode. In order to change the angle at which the invalidity occurs in the group of frequency converters, the relative time delay of the signals of each group of elements can be adjusted. For example, if a time delay is added to the signal for element 642a at 642b, the null in the transmit mode will rotate to the left of the transducer bank. When the time delay is set to a time taken for a distance as long as the sound travels and the element pitch (the elements have opposite polarities and equal output levels), a cardioid pattern (which is one possible case of the first order gradient pattern) can be obtained. In this case, signal nulling occurs, positioned in the direction of the line starting from the centre of the group of transducers and directed towards the delayed element (642 a). There is a maximum amount of emissions in the direction 180 degrees opposite the signal null position. In addition to using simple time delays (and opposite polarities if desired), more complex balancers may be used, in which the correlation level and phase derived from a function of frequency is controlled to obtain a particular transmission mode. The transmission mode that changes according to the frequency function can be obtained by changing the correlation level and the phase obtained according to the frequency function. The frequency response effects that produce destructive interference can be compensated for with the additional balancers.

Furthermore, it is possible to transmit different signals in different directions simultaneously from the same set of frequency converters as the commercial Bose3-2-1 system incorporated by reference herein. For example, the center channel information can be transmitted from the groups of frequency converters 642 and 652 in a direction toward the middle of the vehicle. Meanwhile, the set of converters 642 may emit a left front channel signal (in a multi-channel surround sound system) toward the front of the seat 660 or toward the left side of the vehicle, while the set of converters 652 may emit a right channel signal toward the front of the seat 670 or toward the right side of the vehicle. Additional signals can also be transmitted, each with its own transmission mode.

The pairs of transducers 642a, 642b or 652a, 652b of the sets of transducers 642 and 652 can also be used in another manner to obtain the desired position of the perceived image. The transducer bank elements are capable of signal processing in order to control the signals present at the user's ear. These techniques are generally feasible when the exact location of the listener is known. One way to achieve this control is to use cross-talk cancellation and HRTF processing methods. It is well known in the art that cross-talk cancellation and HRTF processing methods can also be used in home sound systems.

Crosstalk cancellation allows the system to control the signal at each listener's ear individually using speakers placed in the outer space (as opposed to using headphones). (the inherent nature of the headset allows individual control of the signal to each individual's ear). When using speakers outside the space, crosstalk cancellation essentially provides "headphone-like" control of the signals present at each person's ear. Once signal control is obtained at each ear of the listener, the desired sound signal can be generated using the filter-based HRTF. For example, for a listener sitting in the seat 660, cross-talk cancellation and HRTF filtering are used for center channel signal reconstruction by the set of frequency converters 642, such that if the actual sound source is located at the center video display 620 in the vehicle, left and right ear signals are generated at each listener's ear that coincide with the signals that should be present at the listener's ear. Using these techniques, it is possible to directly generate a signal at the ear of a listener in accordance with a sound source signal of any azimuth. It is also possible to process different signals with different HRTF filters simultaneously and recreate these signals simultaneously from a bank of frequency converters. For example, the center channel signal may be HRTF filtered to allow the listener to position the center channel information at the location of the video display 620, while the HRTF processed left channel signal is perceived to be at an azimuth position that is tilted to the left (e.g., 30 degrees to the left of the line separating the centers of the seats 660 and 640, or other desired angle). These and other signals can be recreated simultaneously from the bank of frequency converters 642. Similar processing can also be used for R and for the center signal of the set of frequency converters 652. The HRTF signal processing for the left and right channels may be the same for both sets of frequency converters 642 and 652, but the processing of the center channel information requires some differences. For the set of frequency converters 642 the center channel information should be positioned at the right side of the set of frequency converters, while for the set of frequency converters 652 the center channel information should be positioned at the left side of the set of frequency converters.

When the frequency converter bank uses HRTF processing, the aforementioned definition of element distances, which is directed to the frequency converter bank, is not required. Any transducer distance is possible. However, embodiments with smaller element distances allow the listener to move over a larger range without significantly degrading the desired experience.

HRTF processing can also be used in conjunction with directional speakers such as the 3-2-1 system described previously.

Fig. 9 shows an alternative embodiment of the invention. In this embodiment, directional speakers 925, shown here as a set of two transducers, are mounted in the roof, slightly behind the video display 920. The directional mode of the transducer array emits less energy toward the front seat 940 and 950 passengers and relatively more energy toward the rear seat passengers (rear seats and other rear speakers not shown). Directional modes having a hypercardioid, or similar first order gradient mode are useful. The launch mode towards the front seat passenger is ineffective. Such positioning minimizes the likelihood that the directional speaker 925 will cause a front seat occupant positioning movement.

Fig. 10 depicts another alternative embodiment of the present invention, similar to that shown in fig. 9. In fig. 10, the directional speaker 1025 is positioned so that its direction of maximum emission is directed toward the video display (rather than away from that direction as in fig. 9). Note that the rear seat and the rear speaker are not shown. The directional speakers 1025 emit acoustic energy toward the video display 1020 so it can be reflected back off the display 1020 toward the rear seat occupant. It is difficult to set the pointing mode for such an orientation that the front seat passenger is not affected and the rear seat passenger still obtains the correct characteristics. In this embodiment, the signal directed to the speaker 1025 may be delayed relative to a signal acting on the vehicle front speaker containing the same information, thereby reducing the shift in perceived image position that may occur on the front seat occupant. The firing pattern used by this embodiment defines the firing pattern toward the rear seat occupant as invalid. In this arrangement, a small amount of directional sound of the transducer group will reach the rear seat position. The sound of the set of transducers will first become reflected away from the video display before reaching the rear seating position.

Thus, as shown in the foregoing detail, embodiments of the present invention provide a method and apparatus for sensing an audio image at or near the location of a video display in a vehicle. While embodiments of the invention have been shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Other embodiments include speakers mounted in doors, pillars, seats, consoles, roofs, etc., using techniques that produce simulated sound images at or near the video display, as well as at other desired locations.

In addition, it should be understood that a variety of different signals and signal types may use the concepts described above. For example, the described embodiments focus on the arrangement of center channel information provided by a surround sound system. Alternatively, a simulated image comprising speech may be obtained in the vicinity of a video display by transmitting a signal or portions of a speech signal having other content to one or more speakers of a mono-frequency or stereo system. For example, the added signal may be a mono or center channel signal containing speech, or the like, or other signals. These "added" signals may be present in their original form or, alternatively, may be obtained by a decoding system/device. For example, the surround channel signals are derived from stereo channel sources, left-right add-subtract synthesis, pre-logic decoding, or other matrix decoding mechanisms, etc.

Various other embodiments of the invention are possible using the above-described methods and techniques in conjunction with different configurations of speakers and the like. The methods and techniques may be used for either the front or rear of a vehicle, or both. In some embodiments, a video display (e.g., a television, connected to a video recorder, DVD, navigation display) may be attached to the front of the vehicle for front seat passengers or placed at the rear of the vehicle for rear seat passengers. The video display mounted in the roof of the vehicle can be folded flat against the roof of the vehicle when not in use, folded down when in use, or otherwise secured down. The display at the front of the vehicle may be hidden when not in use or may be fixedly visible. May be any type of display including, but not limited to, CRT, LCD, plasma, projection (front or back), OLED, or any other possible display that may be used.

Therefore, to address the interaction between the front and rear seat subsystems, some of the techniques of the rear seat system described above can be used in the front and rear seat subsystems. For example, it is possible that the perception of the original position of the center channel of a front seat passenger can be influenced depending on the position of the speakers at the rear of the vehicle and the amount of center channel information provided to their speakers at the rear of the vehicle. Therefore, it is desirable that most of the energy is emitted from the front seat speakers (see 111, 112, 113 in fig. 1, 211, 212, 213 in fig. 2, 311, 312, 313 in fig. 3, 411, 412, 413 in fig. 4) toward the rear seat of the vehicle, and a small amount of energy is emitted from the rear seat speakers (see 102, 103, 101 in fig. 1, 202, 203, 201 in fig. 2, 302, 303, 301 in fig. 3, 423, 424 in fig. 4) toward the front of the vehicle, so that the perception of the center image by the front passenger in the vehicle is affected as little as possible.

It is also possible to delay the signals transmitted by the rear seat loudspeakers (see 102, 103, 101 in fig. 1, 202, 203, 201 in fig. 2, 302, 303, 301 in fig. 3, 422, 423, 424, 425 in fig. 4) in dependence on the signals of the front seats (see 101 in fig. 1, 211, 212, 213 in fig. 2, 311, 312 in fig. 3) so that the signals from the front loudspeakers influence the positioning in the front seats more strongly than the signals from the front seats in the rear of the vehicle.

Further, the front portion of the vehicle is more likely to be symmetrical with respect to the center line of the vehicle than the rear portion of the vehicle. For example, at the front, the driving zone may protrude further outward, the front dash panel may protrude further outward, and the driving zone may resemble a more calloused area, relative to the passenger seat. In order to produce a favorable change in the sound image produced, it is possible to use techniques which, as described above, influence the signal orientation towards the front of the vehicle.

Various embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Claims (16)

1. An apparatus for converting a video signal and an associated audio signal in a vehicle, comprising:

the video signal and associated audio signal source in the vehicle, including center channel information,

a first video display and a second video display constructed and arranged to be mounted in said vehicle to transform said video signals and display visual image characteristics, an

First and second viewer seats constructed and arranged in the vehicle to enable first and second viewers in the first and second viewer seats to view the images,

left and right front seats constructed and arranged in the vehicle,

the device comprises:

a first directional speaker remote from the first video display comprising a pair of left electro-acoustic transducers constructed and arranged as a group and mounted in a back rest of a left front seat positioned in front of the first viewer seat,

a second directional loudspeaker remote from said second video display comprising a pair of right electro-acoustic transducers constructed and arranged as a group and mounted in the back of a front right seat positioned in front of said second viewer seat, and

signal processing circuitry constructed and arranged to connect the audio signal source to the first and second directional speakers, thereby processing the audio signals such that the first and second viewers can perceive sound emanating from the respective first and second video displays, emitted by the first and second directional speakers,

wherein the signal processing circuit is constructed and arranged to vary the spectral content of the audio signals applied to the first and second directional loudspeakers so as to vary the perceived elevation of sound output by the first and second directional loudspeakers as perceived by the respective first and second viewers at the respective first and second viewer seats by applying a filter having a filtering transfer function H3(j ω) for each of the first and second directional loudspeakers, the filtering transfer function H3(j ω) representing the difference between a head related transfer function H1(j ω) and a head related transfer function H2(j ω), wherein the transfer function H1(j ω) is a head related transfer function between a source located at the actual position of the first or second directional loudspeaker and at least one ear of the respective first or second viewer located in the respective first or second seat, the transfer function H2(j ω) is a head related transfer function between a source located at the location of the respective first or second video display and at least one ear of the respective first or second viewer located in the respective first or second seat,

the filtering transfer function H3(j ω) for each of the first and second directional speakers corresponds to a filtering transfer function H2(j ω)/H1(j ω) for the respective first or second directional speaker, and

the signal processing circuitry includes crosstalk cancellation processing and is constructed and arranged to use head related transfer function processing to adjust the relative magnitudes and time delays of the audio signals applied to the first and second directional speakers so as to cause the respective first and second viewers in the respective first and second viewer seats to perceive the azimuth of the sound output by the first and second directional speakers so that the viewer in either of the viewer seats perceives the center channel information as if it were transmitted from one of the video display positions.

2. The apparatus of claim 1, wherein the first and second video displays are at a different height relative to the respective first and second viewers than the respective first and second directional speakers.

3. The apparatus of claim 1, wherein the audio signal source further comprises center, left and right channels having associated information, respectively, the first portion of the spectral content comprising the center channel information, the first directional speaker further emitting left channel audio signal information, the second directional speaker further emitting right channel audio signal information.

4. The apparatus of claim 1, further comprising at least third and fourth speakers for left and right viewer seats, respectively, wherein the signal processing circuit also delivers the source of audio signals to the left and right speakers.

5. The apparatus of claim 4, wherein the third and fourth speakers emit respective left and right channel information from an audio signal source and each of the third and fourth speakers also emits a portion of center channel information.

6. The apparatus of claim 5 wherein the size of center channel information applied to said third and fourth speakers is adjustable so that a viewer in either of said viewer seats perceives the center channel information as if it were emitted from one of the video display locations.

7. The apparatus of claim 5 wherein the signal processing circuitry adjusts the relative time delays applied to the center channel signals of the third and fourth speakers relative to the center channel signals of the first and second directional speakers so that a viewer in either of the viewer seats perceives the center channel information as if the center channel information was emitted from one of the video display locations.

8. The apparatus of claim 1 further comprising at least third and fourth speakers mounted in the vehicle roof, respectively, behind said first and second video displays and in front of the viewer's head when the viewer is in the seat, said signal processing circuit delivering said source of audio signals to said third and fourth speakers.

9. The apparatus of claim 1 wherein said signal processing circuitry delivers said source of audio signals to said left pair of electro-acoustic transducers and said right pair of electro-acoustic transducers, said signal processing circuitry constructed and arranged to process said audio signals so that a viewer in a viewer seat behind said left front seat and a viewer in a viewer seat behind said right front seat both perceive sound emitted by said electro-acoustic transducers originating from respective first and second video displays.

10. The apparatus of claim 1, wherein the associated audio signal source comprises a center channel, the center channel further comprising speech information.

11. The apparatus of claim 1, wherein the first and second directional speakers are constructed and arranged to emit primarily high frequency portions of the audio signal.

12. The apparatus of claim 11 further comprising a third speaker mounted in the vehicle, the third speaker not being proximate to the first or second video display and being constructed and arranged to emit a mid-frequency portion of the audio signal in response to the high-frequency portion emitted by the first and second directional speakers.

13. An apparatus for converting an audio signal in a vehicle, comprising:

an audio signal source in the vehicle, including left, center and right channels having information associated therewith, and

a first pair of seats disposed in the vehicle on left and right sides of a centerline of the vehicle,

the device comprises:

a first speaker mounted to a left side of the vehicle,

a second speaker mounted to a right side of the vehicle,

a third directional loudspeaker mounted to the left of the vehicle centerline to the right of the first loudspeaker, comprising a pair of left electro-acoustic transducers constructed and arranged as a group,

a fourth directional speaker installed on the right side of the center line of the vehicle and on the left side of the second speaker, including a pair of right electro-acoustic transducers constructed and arranged as a group, and

signal processing circuitry connecting the audio signal source to the first and second speakers and third and fourth directional speakers,

wherein the first loudspeaker emits left channel information, the second loudspeaker emits right channel information, the third and fourth directional loudspeakers emit center channel information, and

the signal processing circuitry is constructed and arranged to process the audio signals such that each of first and second listeners seated in respective first and second seats perceives sound emitted by the first and second speakers, the third and fourth directional speakers, and corresponding to the center channel as if emitted from a position in front of the listener,

the signal processing circuitry being constructed and arranged to process the audio signals acting on the third and fourth directional loudspeakers so as to change the perceived elevation of sound output by the first and second loudspeakers as perceived by the respective first and second listeners in the respective first and second seats by applying a filter having a filtering transfer function H3(j ω) for each of the third and fourth directional loudspeakers, the filtering transfer function H3(j ω) representing the difference between a head related transfer function H1(j ω) and a head related transfer function H2(j ω), wherein the transfer function H1(j ω) is a head related transfer function between the source of the actual position of the third or fourth directional loudspeaker and at least one of the head related ears of the respective first or second listener located in the respective first or second seat, the transfer function H2(j ω) is a head related transfer function between a source located in front of the respective first or second seat and at least one ear of the respective first or second listener located in the respective first or second seat,

the filtering transfer function H3(j ω) for each of the third and fourth directional speakers corresponds to a filtering transfer function H2(j ω)/H1(j ω) for the respective third or fourth directional speaker, and

the signal processing circuitry includes crosstalk cancellation processing and is constructed and arranged to use head related transfer functions for processing to adjust the relative magnitudes and time delays of the audio signals applied to the third and fourth directional speakers so as to cause the respective first and second listeners in the respective first and second seats to perceive the azimuth of the sound output by the third and fourth directional speakers so that the listener in either of the seats perceives the center channel information as if the center channel information were emitted from a position in front of the listener.

14. The apparatus of claim 13, wherein the first pair of seats is a front seat in the vehicle, and the first and second speakers and the third and fourth directional speakers are disposed behind the front seat.

15. The apparatus of claim 14, wherein at least a third directional speaker is housed in the back of one of the front seats and a fourth directional speaker is housed in the back of the other of the front seats.

16. The apparatus of claim 13, wherein the first and second speakers further emit center channel information.