HK1079034B - System and method of vehicle audio surround modes - Google Patents

Description

System and method for in-vehicle audio surround mode

Technical Field

The present invention relates to an in-vehicle surround audio system, and more particularly to a surround audio system having multiple modes of operation.

Disclosure of Invention

In one aspect of the invention, an audio system for a vehicle having a plurality of seats includes a plurality of input channels including surround channels. The audio system further includes a plurality of operating modes. The first mode of operation is characterized by the perceived loudness at each of the seats being substantially equal, forming an equalization pattern by weighting the frequency response at each seat substantially equally, and forming a balance pattern by weighting the sound pressure level measurements at each seat substantially equally. The second mode of operation is characterized by a perceived loudness at said one seat being greater than perceived loudness at other seats, the equalization being formed by weighting the frequency response at the one seat more heavily than the frequency response at the other seats, and the equalization being formed by weighting the sound pressure level measurement at the one seat more heavily than the sound pressure level measurements at the other seats.

In another aspect of the invention, a method of forming an equalization approach for a multi-channel surround audio system including a plurality of seat vehicles includes weighting a frequency response at one seat more heavily than frequency responses at other seats.

In another aspect of the invention, a method of forming an equalization approach for a multi-channel surround audio system including a plurality of seat vehicles includes weighting a frequency response at one seat more heavily than sound pressure level measurements at other seats.

In another aspect of the invention, a front/rear attenuation system (fade system) for a vehicle audio system includes a plurality of seats and a plurality of speakers. The speakers include a front speaker, a middle speaker, and a rear speaker. The audio system includes a plurality of input channels including surround channels. The front/rear attenuation system includes a plurality of operating modes. The first mode of operation is characterized in that the radiation of the front loudspeaker is influenced by said front/rear damping system in the case of front damping. The second mode of operation is characterized in that the radiation of the front loudspeaker is not affected by the front/rear damping system in the case of front damping.

Other features, objects, and advantages of the invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.

Drawings

Fig. 1 is a block diagram of an audio system according to the present invention;

FIG. 2 is an acoustic environment suitable for the present invention;

FIGS. 3A-3E are various diagrams illustrating an aspect of the present invention;

fig. 4A-4E are diagrams of the acoustic environment of fig. 2 illustrating another aspect of the present invention.

Fig. 5A, 5B, 6A and 6B are diagrams of the acoustic environment of fig. 2, which also illustrate another aspect of the present invention.

Detailed Description

Although the elements of the several diagrams in the figures are illustrated as discrete elements in a block diagram and referred to as "circuitry," unless otherwise indicated, the elements may be formed as a microprocessor executing software instructions, including Digital Signal Processing (DSP) instructions. Unless otherwise indicated, the signal lines may be formed as separate analog signal lines, separate digital signal lines with appropriate signal processing to process separate streams of audio signals, or elements of a wireless communication system. Unless otherwise specified, the audio signal may be encoded in digital or analog form using a suitable analog-to-digital or digital-to-analog converter.

For the sake of simplicity, the phrases "radiation of an audio signal in a corresponding channel a (here channel a is the channel identifier of the multi-channel system)" or "radiated acoustic energy of a signal in a corresponding channel a" are expressed as "radiated channel a", and "acoustic energy of a corresponding signal B (here B is the identifier of the audio signal)" is expressed as "radiated signal B", it being understood that the acoustic radiation means converts an audio signal in analog or digital form into acoustic energy.

Referring now to the drawings and in particular to FIG. 1, there is shown an audio system according to the present invention. The N-channel audio signal source 2 is communicatively coupled to the signal processing circuit 4 via a signal line 6. The control circuit 3 may be communicatively coupled to the audio signal source 2, to the signal processing circuit 4, and directly to the m-channel amplifier 8. The control circuit 3 has an input for receiving manually input information or control information relating to the operating conditions of the vehicle or both. The signal processing circuit 4 is communicatively connected to the m-channel amplifier 8 through a signal line 10. The m-channel amplifier 8 (here, "m" is a number) is coupled to speakers denoted by 12FL (front left), 12FC (front center), 12FR (front right), 12IL (middle left), 12IC (middle center), 12IR (middle right), 12RL (rear left), 12RR (rear right), and 12W (subwoofer) through a signal line 14. The number and configuration of speakers may be different from the present example.

The N-channel audio signal source 2 may be a conventional audio signal source such as a CD or DVD player, a digital storage device (such as a mass storage device or a random access memory) or a radio tuner. Hereinafter, a 5.1 (i.e., n ═ 5.1, which indicates 5 directional channels and one LFE (low frequency effects) channel signal source will be used. The audio signal source may have more than 5 directional channels (i.e., n-6.1, 7.1.) and no low frequency effect channels (i.e., n-5, 6, 7.). The n-channel signal source typically includes some channels (typically left (L), right (R), and center (C) channels) that appear to be perceived acoustically from the front; these channels will be referred to as front channels hereinafter. An n-channel signal source typically includes some channels as if the acoustics were perceived from behind; these channels will be referred to as surround channels hereinafter.

For best results, the n channels include the back channel or surround channels. If the n channels do not include a back channel or surround channel, the signal processing circuit 4 may include a signal processing circuit for providing surround channels. Examples of such signal processing circuits are MA, Framingham, Bose corporationDecoding circuit or CenterpointM decoding circuit, or Pro of CA, San Francisco, Dolby CorporationII decoding circuit or ProII a decoding circuit.

The signal processing circuit 4 receives n-channel input signals from an audio signal source, processes these signals and supplies the processed audio signals as an output stream to an amplifier 8. The signal processing may include an equalization circuit having a circuit or the like. The amplifier 8 has m output channels. In the following example, m is 9, but m may be greater or less than 9, in which case there may be m or more speakers or other devices in the playback system (playback system). Speakers 12FL-12W may be conventional speakers and each speaker may include one or more acoustic drivers and one or more acoustic elements, such as an enclosure, port, waveguide, horn, or passive radiator. Here, one or more of the speakers 12FL-12W may include more than one acoustic driver, which may include a cross circuit (crossover circuit). Some elements, such as volume control elements, may affect the gain applied to the audio signal by the amplifier 8, which is not shown in this figure. The signal processing circuit 4 and the amplifier 8 may be combined in one single device. Additional components for applying passive signal processing to the amplified audio signal may be provided after the amplifier 8. The control circuit 3 will be explained in more detail below.

Fig. 2 shows an example of an acoustic environment suitable for use with the present invention. The interior of the vehicle (such as a racing car or a minivan) includes front seats 16FL and 16FR, middle seats 16IL and 16IR and rear seats 16RL, 16RM and 16 RR. Speakers 12FL-12W may be provided around the interior of the vehicle as shown in the drawings. Typical speaker types and positions of the speaker 12FL are full range (full range), mid range (mid) or bass acoustic drivers in the left front of the driver's seat, such as a tweeter unit provided in a door on the driver's side, in an instrument panel or in a left a-pillar; for speaker 12FC, it is a limited-frequency range speaker near the middle of the dashboard; for speaker 12IL, it is a full range speaker in front of the middle seat and behind the front seat, such as in the left rear door; for speaker 12IC, which is a full-range or limited-range acoustic driver in the mid-seat, such as in the back-seat facing console; for speaker 12RL, it is a full range speaker behind the left rear seat, such as on the left side of the tailgate or near the left rear beam of the vehicle. Speakers 12FR, 12IR and 12RR are typically the same type of speaker symmetrically disposed with speakers 12FL, 12IL and 12RL, respectively. Speaker 12W may be a subwoofer and may be disposed at a conventional location, such as behind, below, or near the rear seat. The video monitor 18 may be positioned in front of the center seats 16IL and 16IR and toward the rear of the vehicle interior, such as in a drop-down device in the console or in the roof of the vehicle. Video monitors may also be provided in other locations such as the seat back.

The configuration of fig. 2 is exemplary, and some other configuration may be present. Any one of the speakers 12FL, 12FC, 12FR, 12IL, 12IC, 12IR, 12RL and 12RR may have the configuration of the speaker 12FC of fig. 2 in which the speaker is a limited-frequency range speaker that reproduces high or medium high frequencies, and low-frequency signals associated with signals reproduced by the limited-frequency range speaker are redirected to a full-frequency range speaker or a bass or subwoofer, such as speaker 12W. Any of the speakers 12FL, 12FC, 12FR, 12IL, 12IC, 12IR, 12RL, and 12RR may have the configuration of the speaker 12FL in which there is more than one acoustic driver. The two acoustic drivers may be separate, such as one located in the passenger door and one located in the a-beam. Other speakers may be provided around the vehicle compartment.

It is a feature of the present invention to provide a plurality of surround modes. In the first mode (hereinafter referred to as the "normal surround mode"), the balance, attenuation performance and balance take into account the entire passenger compartment, and the perceived loudness does not vary significantly from seat to seat. In the second mode (hereinafter referred to as "rear surround mode"), the equalization, attenuation performance and balance weights the rear seats more heavily than the front seats, and the perceived loudness at the front seats is lower than the perceived loudness at the middle and rear seats. In a third mode, hereinafter referred to as "front surround mode", the equalization, attenuation performance and balance weights the front seats more heavily than the rear seats, and the perceived loudness at the front seats is greater than the perceived loudness at the middle and rear seats. In a fourth mode (hereinafter referred to as "driver surround mode"), the equalization and balancing weights the driver's seat more heavily than other seats, and the perceived loudness at the driver's seat is greater than the perceived loudness at the other seats. In all four modes, weighting more heavily may include applying measurements and listening to certain seats, excluding other locations.

The normal surround mode is appropriate when both the front seat passenger and the rear seat area passenger are interested in audio programming. The back surround mode is appropriate when the audio program content is of greater interest to passengers at the rear seats in the vehicle passenger compartment, for example, if the audio content is related to the visual images being displayed on a monitor, or if the front seat passengers wish to talk, or if the driver wishes to focus on some other audio stimulus, such as a navigation system. The front surround mode is appropriate if the rear passenger is not interested in the audio program, if the vehicle rear passenger wishes to lower the acoustics (e.g., if the rear seat has a sleeping child), or if the rear passenger is not present at all. The driver surround mode is suitable if there are no front passengers in an environment similar to the front surround mode.

As described above, one example of a case where the back surround mode is appropriate is when audio program content is related to a visual image being displayed in a monitor. Monitors for displaying visual images associated with movies are often positioned so as to be viewable by the rear passengers but not by the front passengers. The audio program is not relevant to or distracting from the front passengers, or the audio program may even be annoying, or dangerous, since it is associated with a visual image in the movie that is not visible to the front passengers. In addition, the acoustic quality can be equalized and balanced based on the front passengers (people not related to the audio program) in the case of influencing the middle and rear passengers (for which the audio program is important). The normal front/back attenuation mode is also not suitable in certain situations, for example, if the audio program is associated with a visual image on a monitor. In the normal front/rear damping mode of the vehicle, in an extreme case, the perceived loudness of the front speaker radiation is much higher than the loudness of the rear speaker radiation. If the audio program is associated with a visual image on a monitor, its corresponding extreme front/back attenuation situation is more appropriate, so that the amplitude of the mid-speaker radiation is much higher than the intensity of the rear and front speaker radiation.

Fig. 3A-3E illustrate the perceived loudness performance of the audio system in various modes. Fig. 3A illustrates some of the icons used in other figures. The perceived loudness indicator 30 shows the reference perceived loudness. The reference perceived loudness is typically the perceived loudness at the location(s) of most interest, or at a fading bias (bias) location (described below). The perceived loudness indicator 32 shows a perceived loudness that is audibly less than the reference perceived loudness indicator 30. The perceived loudness indicator 34 shows a perceived loudness that is audibly less than the perceived loudness indicator 32. The icons are used to indicate general relationships and inaccurate measurements. The icons are for comparison in a single figure only; for example, the perceived loudness indicated by the amplitude indicator 30 may vary from figure to figure.

In the normal surround mode shown in fig. 3B, the perceived loudness of the radiation at all listener positions is nearly the same, as indicated by the amplitude indicators 20FL-20 RR.

In the rear surround mode shown in fig. 3C, the perceived loudness at the middle seat and the perceived loudness at the rear seats are approximately the same, while the perceived loudness at the front seats is significantly less than the perceived loudness at the middle and rear seats.

In the driver surround mode shown in fig. 3D, the perceived loudness at the driver's seat is higher than the perceived loudness at the other seats.

In the front surround mode shown in fig. 3E, the perceived loudness at the front seats is higher than at the middle and rear seats.

Generally, a higher "perceived loudness" is associated with a higher average sound pressure level. The setting of different perceived loudness at different seats is usually achieved by significantly attenuating or even noise suppressing the loudspeakers closest to the lower perceived loudness regions. In a variation, such as shown in fig. 3B, the audio signals for the front speakers may be low pass filtered by low pass filter 28 so that some speakers are used to radiate bass audio energy rather than high frequency audio energy.

An important factor of acoustic quality is the frequency response. Frequency response adjustment and modification is typically accomplished by using a process called Equalization (EQ), in which some frequency bands are attenuated or amplified relative to others. Equalization is commonly performed to compensate for the non-ideal performance of the speakers used to reproduce the audio signal, as well as to compensate for changes in the transfer function (transfer function) from the speaker to the listener due to the operating environment of the speaker, such as the cabin or the passenger compartment of a vehicle. Equalization typically involves measuring the frequency response of the various speakers at multiple listening positions. The frequency responses at multiple locations are combined in some manner, such as by averaging or weighting (e.g., in a vehicle, the listening position of the driver or front seat may be weighted more heavily than the rear seat weights). The equalization means for modifying the frequency response is formed such that the frequency response curve has a desired shape, such as a flat or slightly sloped smooth shape with minimized peaks and dips.

Different modes and weighted listening areas are considered differently so that differences in the combined frequency response are compensated by the EQ process. Thus, the frequency response of the EQ changes with changes in the surround mode. Improving the frequency response at one listening position may result in a drop in the loudspeaker response at other listening positions. Improving the combined frequency response at one listening position may result in a decrease in the combined frequency response at other listening positions.

Another important factor of acoustic quality is balance. Uniform balance means that at the listening position, a balanced amount of perceived acoustic energy is received from each speaker so that the listener is not primarily positioned (localized) at either speaker. The balance is modified by adjusting the transfer function for the audio signal (which may include equivalent to modifying and attenuating the signal, delaying the signal, changing the signal phase, and other adjustments) so that the listener perceives the sound image without deviating from any particular location. The adjustment may be frequency dependent. Generally, uniform balance is desirable. In some environments, the desired balancing may include delaying the arrival of radiation from the rear speakers to achieve an enhanced spaciousness sensation. Balancing is important if the audio signal is radiated by more than one speaker and the listening position is close to two speakers radiating the same signal. An example is shown in fig. 4A-4B.

Although balance is somewhat perceptual and subjective, two important measures of balance are the sound pressure level (hereinafter) generated at a location due to the energy radiated by each speaker, and the arrival time from each speaker. The determination of the sound pressure level can be achieved by using equal amplitude test tones for each loudspeaker and measuring the sound pressure level at one location. If the sound pressure level measured by each loudspeaker is approximately equal, the balance at that location is better than in the case of widely varying measured sound pressure levels of the loudspeakers. To measure the arrival time, a test tone is emitted from a separate speaker, and the length of time t for the radiation to reach the measurement location is measured. If t is almost the same for all speakers, the balance at the position is more uniform than in the case where the test tone arrives at varying times. The perception of the balance of the radiation of the loudspeaker is a function of t and the sound pressure level. Balancing typically involves weighing time/intensity; for example, the large sound pressure level of one speaker is compensated by applying a delay Δ t to the signal to delay the arrival time from the speaker. Balancing is especially important if the same signal is radiated from more than one loudspeaker. Since the seat and speaker positions are generally fixed and the speakers are asymmetrically arranged with respect to the seat in the vehicle, it is difficult to obtain a desired balance pattern at all positions, and achieving a desired balance pattern at one position may cause deviation from the balance pattern at other positions.

Referring to fig. 4A, a simple example of adjusting the arrival time and radiation intensity to achieve the desired balance result is shown. Operating in normal surround mode, the channel L signal is delivered to speaker 12FL (relatively close to seats 16FL, 16FR, 16IL and 16IR) to radiate channel L. The channel L may also be delivered to the loudspeaker 12IL (relatively close to the seats 16IL, 16IR, 16RL, 16RM and 16RR) to radiate the channel L. It is desirable to prevent a listener at the 16FL position from being positioned at the L radiation of the speaker 12 IL. It is also desirable that the L radiation from speakers 12FL and 12IL reach listening positions 16IL and 16IR simultaneously to avoid the perception of echo. The L signal of the speaker 12IL is delayed by the time delay device 36 so that the radiation from the speaker 12IL arrives at the seat 16FL later than the arrival time of the radiation from the speaker 12FL and so that the radiation from the speakers 12FL and 12IL arrives at the seat 16IL sufficiently close to simultaneously to prevent an echo sensation. In addition, the L signal of speaker 12IL may be attenuated by attenuator 38 such that the intensity of radiation from speaker 12L at seat 16FL is less than the intensity of radiation from speaker 12 FL. For simplicity, the time delay device 36 and the attenuator 38 are shown as discrete blocks. In a practical implementation, the functions performed by the time delay means and the attenuator may be performed by the signal processing circuit 4.

In fig. 4B, operating in the back surround mode, it is not necessary to radiate the channels L for the seats 16FL and 16FR or to consider the positions at the seats 16FL and 16FR where listeners may be located. The channel L signal may be transmitted to the loudspeaker 12IL to radiate the channel L for the seats 16IL, 16IR, 16RL, 16RM and 16 RR. In the back surround mode, the time delay device 36 and attenuator 38 of fig. 4B are not required.

The R and C channels may be adjusted in a manner similar to the L channel.

Fig. 4C-4E illustrate the formation of different seats that are emphasized and specifically considered in the balanced and EQ regimes suitable for various surround regimes. As shown by line 24, measurement (by the measuring device) and listening (by the listener) are performed at positions including all the seating areas, resulting in a normal surround mode EQ manner.

In some implementations of the normal surround mode, the measurements and listening to the areas indicated by lines 25 and 22 may be weighted slightly more heavily than the measurements and listening to the other passenger compartments in the form EQ and balance mode.

Referring to fig. 4C, EQ and balance formation for the front surround mode may use measurement and listening for the area indicated exclusively by line 25.

As shown in fig. 4D, EQ and balancing for the rear surround mode can be formed by measuring an area that does not include the front seat, or by weighting the measurements and listening at the front seat less than the ratio of the measurement and listening weights at other locations in the middle and rear seats. For example, measurements may be taken in the mid and rear seating regions, as indicated by line 26. In some implementations, the measurements and listening of the middle seat area, as shown by line 27, may be weighted more heavily than the measurements and listening of the rear seat areas.

In addition to accounting for different listening areas, the EQ regime in the rear seat mode may be adjusted to produce a different frequency response curve than the normal surround mode. An example of a different frequency response curve is the so-called "X-curve" which is commonly associated with movie soundtracks and is available from the Society of Motion Picture television Engineers' SMPTE Standard 202M-1998(SMPTE, website smite.

Referring to fig. 4E, only the driver seat area is measured and listened to as shown by line 29, resulting in EQ and balance for the driver surround mode. One way to achieve good balance in driver surround mode is to adjust the transfer function applied to the audio signal so that the radiation to each speaker is approximately equal and the radiation arrival time of each speaker is approximately equal and the perceived loudness has the manner of fig. 3A or 3D.

Fig. 5A and 5B and fig. 6A and 6B show the front/rear attenuation performance of the normal surround mode and the rear surround mode. A typical front/back attenuation control system is used to bias the relative amplitudes of the acoustic radiation toward the front of the listening area and the back of the listening area. Adjustment devices, such as knobs and sliders, typically allow a range of settings from one extreme, where the relative amplitude of the acoustic radiation is greatly biased towards the front of the listening position (hereinafter referred to as "front damping"), to the other extreme, where the relative amplitude of the acoustic radiation is greatly biased towards the rear of the listening position (hereinafter referred to as "rear damping"). In the normal surround mode, by setting the front/rear attenuations to the front attenuation shown in fig. 5A, the perceived loudness at the front seats is highest (as indicated by the amplitude indicators 20FL-20 RR), the perceived loudness at the rear seats is lowest, and the perceived loudness at the middle seats is intermediate between the perceived loudness at the front seats and the perceived loudness at the rear seats. In the front attenuation case, the listener tends to be positioned towards the front speakers. In the normal surround mode, by setting the front/rear attenuation to the rear attenuation shown in fig. 5B, the perceived loudness at the rear seats is highest, the perceived loudness at the front seats is lowest, and the perceived loudness at the middle seats is between the perceived loudness at the front seats and the perceived loudness at the rear seats. In the rear attenuation case, the listener tends to be positioned towards the rear speakers.

In the audio system according to the invention the operation of the front/back attenuation function is changed according to different surround modes. For example, a rear surround mode in which the front/rear attenuation is set to the front attenuation is represented as + in fig. 6A, and the perceived loudness at the middle seats is higher than the perceived loudness at the rear seats. In the rear surround mode, the perceived loudness at the front seats may be at a low level separate from the front/rear attenuation control (decouple); the front speakers 12FL, 12FC, and 12FR may be low pass filtered, significantly attenuated, and noise suppressed. In the rear surround mode, in which the front/rear attenuation is set to the rear attenuation as shown in fig. 6B, the perceived loudness at the rear seats is higher than the perceived loudness at the front seats. As previously described, in the rear surround mode, the perceived loudness at the front seats may be at a low level separated from the front/rear attenuation control, and the front speakers 12FL, 12FC, and 12FR may be low pass filtered, significantly attenuated, and noise suppressed.

If desired, the present invention may be implemented through the pre/post attenuation adjustment control described in co-pending U.S. patent application Ser. No.10/367251, filed 2/14/2003, assigned to the same assignee as the present application and incorporated herein by reference.

The selection of the mode is effected by the control circuit 3. The selection may be based on one or a combination of manual selection in which the user selects a mode including a switch setting that selects the mode by switching the current position, automatic selection, and a default system; in said automatic selection, the control circuit selects the mode based on predetermined rules (which typically include manual replacement of the automatically selected rules); in the default system, a mode is selected unless manually replaced. The automatic selection method may include detecting whether the inserted media device is a DVD-audio or super audio cd (sacd) or DVD-video disc, or reading metadata embedded in the source signal. Additionally, the automatic selection method may include detecting a vehicle condition, such as detecting whether the vehicle ignition is in an "on" position or whether the vehicle transmission is a transmission gear or whether the seat is occupied.

Examples of automatic selection include: detecting whether an audio signal source has associated video content; determining whether vehicle ignition is on; if video content is relevant and the ignition is on, the back surround mode is selected and among other conditions the full surround mode is selected.

The present invention has been described using a minivan or racing vehicle having three rows of seats. The principles of the present invention are also applicable to vehicles having two or more rows of seats, such as large trucks or buses.

The vehicle audio system according to the invention has the advantage over conventional vehicle audio systems in that it reduces the disturbance of the audio program to undesired audio programs or regions of the vehicle cabin where the audio program is disturbing or distracting, while providing an improved acoustic experience for other locations of the vehicle cabin.

It will be apparent to those skilled in the art that the specific apparatus and techniques disclosed herein, as well as variations thereof, may be employed in a wide variety of ways without departing from the spirit of the invention. The invention, therefore, is to be construed as embracing each and every novel feature and novel combination of features disclosed herein and limited only by the spirit and scope of the appended claims.

Claims (22)

1. An in-vehicle surround audio system comprising:

a plurality of operating modes, the plurality of operating modes comprising:

a first mode of operation in which radiation corresponding to a plurality of channels including surround channels has substantially equal sound pressure levels at each of a plurality of seats, an equalization pattern that produces substantially similar frequency responses at each of the seats when applied to an audio signal, and an equalization pattern in which sound pressure level measurements for each of a plurality of speakers at each of the seats are substantially equal, an

A second mode of operation in which the sound pressure level at a first seat is greater than the sound pressure level at the other seats for radiation of a plurality of channels including surround channels, an equalization pattern that when applied to an audio signal produces a substantially smoother frequency response at the first seat than at the other seats, and an equalization pattern in which the sound pressure level of each speaker is substantially equal at the first seat and is not equal at the other seats.

2. The vehicular audio system of claim 1, wherein the first seat comprises a rear seat.

3. The vehicular audio system according to claim 1, wherein the first seat comprises a driver's seat.

4. The car audio system of claim 1, wherein the plurality of operating modes further includes a third mode in which a sound pressure level at a second seat is greater than sound pressure levels at other seats, an equalization pattern that when applied to an audio signal produces a frequency response at the second seat that is substantially smoother than frequency responses at the other seats, and an equalization pattern in which a sound pressure level of each of a plurality of speakers is substantially equal at the second seat and is not equal at the other seats.

5. The vehicular audio system according to claim 4, wherein the second seat comprises a driver's seat.

6. The vehicular audio system of claim 4, wherein the second seat comprises a front seat.

7. An in-vehicle audio system comprising:

a first equalization pattern that, when applied to audio signals in a plurality of channels including surround channels, produces a substantially smoother frequency response at a first seat of the plurality of seats than at other seats of the plurality of seats;

a second equalization pattern that, when applied to the audio signal, produces a frequency response at each of the plurality of seats having a substantially similar smoothness.

8. The audio system of claim 7, wherein the first seat is one of a middle seat and a rear seat.

9. The audio system of claim 8, wherein the plurality of equalization patterns further comprises a third equalization pattern that, when applied to the audio signal, produces a substantially smoother frequency response at the other of the middle and rear seats.

10. The audio system of claim 9, wherein the third equalization pattern has a target curve, wherein the target curve is an X-curve.

11. The audio system of claim 8, wherein the first equalization pattern has a target curve, wherein the target curve is an X-curve.

12. An in-vehicle audio system comprising:

a plurality of operating modes comprising:

a first mode of operation in which the sound pressure level of radiation corresponding to multiple channels including surround channels is substantially different at a first seat of the plurality of seats than at other seats, and

a second one of the plurality of operating modes wherein a sound pressure level corresponding to radiation of multiple channels including the surround channels is substantially uniform at each seat.

13. The audio system of claim 12, wherein the first seat is one of a middle seat and a rear seat.

14. The audio system of claim 13, further comprising a third mode in which a substantially different sound pressure level is generated at the other of the middle seat and the rear seat.

15. A method for operating an audio system in a vehicle, comprising:

providing a first mode of operation in which at least one of (a) radiation corresponding to a plurality of channels including surround channels has substantially equal sound pressure levels at each of a plurality of seats, (b) an equalization pattern that produces substantially similar frequency responses at each of the seats when applied to the audio signal, and (c) an equalization pattern in which sound pressure level measurements for each of a plurality of speakers at each of the seats are substantially equal, and

providing a second mode of operation in which at least one of (a) the sound pressure level at one seat is greater than the sound pressure level at the other seats, (b) an equalization pattern that produces a substantially smoother frequency response at a first seat than at the other seats when the equalization pattern is applied to the audio signal, and (c) an equalization pattern in which the sound pressure level of each speaker is substantially equal at the first seat and not equal at the other seats, a method for selecting one of the first mode of operation or the second mode of operation,

detecting at least one of (a) an operating condition of the vehicle and (b) a characteristic of a media object played by the media device to provide selection criteria; and

based on the detection, one of the plurality of operating modes is automatically selected.

16. The method of claim 15, wherein the detecting comprises detecting an operating condition of the vehicle.

17. The method of claim 16, wherein the detecting further comprises detecting whether a media object comprises video data, wherein

The second mode is automatically selected if the detection indicates at least one of (a) vehicle ignition on, and (b) transmission is in progress in the drive gear, and the detection further indicates that the media object includes video information.

18. The method of claim 15, further comprising manually replacing the automatically selected results.

19. A method of operating a surround audio system in a vehicle, comprising:

selectively applying one of a plurality of operating modes, the plurality of operating modes including a first operating mode in which at least one of (a) an equalization pattern is formed by weighting one of the plurality of seats more heavily than the other seats, (b) a perceived loudness at one seat is substantially different than the perceived loudness at the other seats, the plurality of operating modes further including a second operating mode in which at least one of (a) an equalization pattern is formed by weighting measurements at the seats substantially equally, and (b) the perceived loudness at each seat is substantially equal; and is

A selection method for selecting one of the plurality of operating modes is provided.

20. A method of operating a surround audio system according to claim 19, wherein the step of providing the selection method comprises providing a device for detecting vehicle operating conditions.

21. A method of operating a surround audio system according to claim 19, wherein the step of providing the selection method comprises providing a detection circuit for detecting a characteristic of a media device being played by the audio system.

22. The method of operating a surround audio system of claim 19, wherein the step of providing the selection method comprises providing a detection circuit for detecting vehicle operating conditions.