JP2009206869A - Acoustic device, acoustic signal processing method, acoustic signal processing program and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rationalize a load amount of a power source, and to suppress generation of abnormal sound and sound quality variation of reproduced sound. <P>SOLUTION: As a load reflection amount of a power unit 800, an ammeter unit 110 detects the total amount of current flowing out from the power unit 800. Then, a coefficient calculation unit 120A calculates an attenuation coefficient CEF based on a detection result by the ammeter unit 110, and lowpass limit processing corresponding to the calculated attenuation coefficient CEF is performed by volume control units 140<SB>L</SB>, 140<SB>R</SB>. In the lowpass limit processing, an attenuation amount of a component in a frequency region near a lowpass resonant frequency with high impedance of a speaker unit 170<SB>j</SB>is made small, and an attenuation amount in other frequency region in a low-pitch band with low impedance of the speaker unit 170<SB>j</SB>is made large. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an acoustic device, an acoustic signal processing method, an acoustic signal processing program, and a recording medium on which the acoustic signal processing program is recorded.

  Conventionally, various electric components are mounted on a moving body such as a vehicle and are used by users. As one of such electrical components, there is a car audio device that is an acoustic device mounted on a car. In such a car audio device, a reproduction sound such as music is output from a speaker disposed at a predetermined position to a vehicle interior space. A listener in the vehicle listens to the sound output from the speaker.

  In general, such a car audio apparatus is supplied with operating power from a so-called accessory power source having a relatively small current capacity. For this reason, it is necessary to prevent an overload to the power supply when outputting a large volume. In order to respond to such a request, a technique for limiting the output volume when the output volume is about to exceed a predetermined value has been adopted.

  As such a technique, a technique is proposed in which a sound waveform is clipped when the volume exceeds a predetermined level, and the volume limiter in the volume limiter is changed in order to suppress the occurrence of the clip when the clip occurs. (See Patent Document 1: hereinafter referred to as “conventional example”). As such a volume limiter, an all-band limiter or a low-frequency limiter is generally employed.

JP 2005-323156 A

  The prior art technique assumes that audio waveform clipping may occur. When such a clip occurs, the audio waveform after the clip is inevitably distorted and an abnormal sound is generated.

  In addition, when the full-band limiter is used as an audio limiter, the listener feels a sense of incongruity due to a dynamic change in sound volume called a so-called “fluffy feeling” or the like, and a feeling of insufficient sound volume. In addition, if a normal low frequency limiter with a flat frequency characteristic is used as the audio limiter, the lack of volume can be suppressed, but the balance between the high frequency and the low frequency is disrupted, creating a sense of incongruity for the listener. .

  For this reason, there is a need for a technique that can suppress a change in sound quality that causes a listener to feel uncomfortable while optimizing the load amount of the power source. Meeting this requirement is one of the problems to be solved by the present invention.

  The present invention has been made in view of the above circumstances, and provides an acoustic device and an acoustic signal processing method capable of optimizing the load amount of a power source and suppressing the occurrence of abnormal noise and the change in sound quality of reproduced sound. The purpose is to provide.

  The invention according to claim 1 is an acoustic device that receives a supply of operating power from a power supply and reproduces and outputs sound from a speaker unit, and detecting means that detects a load reflection amount that reflects the load amount of the power supply; Calculating means for calculating an attenuation coefficient of a signal component of a predetermined bass frequency band including a low frequency resonance frequency of the speaker unit based on a detection result by the detection means; and the low frequency resonance frequency in the predetermined bass frequency band; Attenuating means for attenuating an acoustic signal based on a calculation result by the calculating means while setting an attenuation rate of a peripheral band to be smaller than attenuation rates of other bands in the predetermined bass frequency band. It is a characteristic acoustic device.

  The invention according to claim 8 is an acoustic signal processing method used in an acoustic device that receives operation power from a power supply and reproduces and outputs sound from a speaker unit, and reflects the load amount of the power supply. A detection step of detecting a quantity; a calculation step of calculating an attenuation coefficient of a signal component in a predetermined bass frequency band including a low-band resonance frequency of the speaker unit based on a detection result in the detection step; and the predetermined bass Attenuating the acoustic signal based on the calculation result in the calculation step while setting the attenuation rate of the band around the low-band resonance frequency in the frequency band to be smaller than the attenuation rate of the other band in the predetermined bass frequency band An acoustic signal processing method comprising: an attenuation step.

  A ninth aspect of the invention is an acoustic signal processing program that causes an arithmetic means to execute the acoustic signal processing method according to the eighth aspect.

  A tenth aspect of the invention is a recording medium in which the acoustic signal processing program according to the ninth aspect of the invention is recorded so as to be readable by a calculation means.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant description is omitted.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. In the first embodiment, an audio device that is mounted on a vehicle and reproduces audio content having a two-channel stereo configuration will be described as an example.

<Configuration>
FIG. 1 shows a schematic configuration of an acoustic device 100A according to the first embodiment. The acoustic device 100 </ b> A is configured to operate with power supplied from the power supply device 800. The power supply device 800 is also supplied with operating power for the electrical components 900 ₁ , 900 ₂ ,... Other than the acoustic device 100A. For this reason, the total amount of current flowing out from the power supply device 800 changes in accordance with the operating conditions of the acoustic device 100A and the electrical components 900 ₁ , 900 ₂ ,.

As shown in FIG. 1, the acoustic device 100A includes an ammeter unit 110 serving as a current detecting unit serving as a detecting unit, a coefficient calculating unit 120A serving as a calculating unit, and a sound source unit 130. The acoustic device 100A also includes volume control units 140 _L and 140 _R as attenuation means, and digital / analog conversion units (DACs) 150 _L and 150 _R. Furthermore, the acoustic device 100A includes power amplification units (AMP) 160 _L and 160 _R and speaker units 170 _L and 170 _R.

The ammeter unit 110 is disposed near the current supply terminal of the power supply device 800 and constantly detects the total amount of current flowing out from the power supply device 800. That is, power supply from the power supply device 800 is performed to the acoustic device 100A and the electrical components 900 ₁ , 900 ₂ ,... Via the ammeter unit 110. The detection result by the ammeter unit 110 is sent from the ammeter unit 110 to the coefficient calculation unit 120A as detected current value data DCD in digital format. Here, the total amount of current flowing out of the power supply device 800 detected by the ammeter unit 110 directly reflects the load amount of the power supply device 800.

The coefficient calculation unit 120A receives the detected current value data DCD from the ammeter unit 110. Then, the coefficient calculating unit 120A calculates the attenuation coefficient CEF based on the detected current value data DCD. The attenuation coefficient CEF calculated in this way is sent from the coefficient calculation unit 120A to the volume adjustment units 140 _L and 140 _R.

A possible value of the attenuation coefficient CEF is “0” or more. As the value of the attenuation coefficient CEF increases, the attenuation of the bass band component in the volume adjustment units 140 _L and 140 _R configured as described later increases. Here, when the value of the attenuation coefficient CEF is “0”, the bass band component is not attenuated in the volume adjustment units 140 _L and 140 _R configured as described later. In addition, when the current value (total amount of current flowing out from the power supply device 800) indicated by the detected current value data DCD is equal to or less than a predetermined value, the value of the attenuation coefficient CEF is monotonously non-decreasing as the current value increases. If the current value is equal to or greater than the predetermined value, the value of the attenuation coefficient CEF increases as the current value increases.

  Note that the calculation algorithm in the coefficient calculation unit 120A is determined in advance based on experiments, simulations, experiences, and the like.

The sound source unit 130 generates an audio data signal ADD _L for the left channel (hereinafter also referred to as “L channel”) and an audio data signal ADD _R for the right channel (hereinafter also referred to as “R channel”) from the audio content. Generate. For example, in the case where the acoustic device 100A is a device that reproduces audio content recorded on a recording medium such as a compact disc (CD), the sound source unit 130 includes a reading unit that reads the audio content from the recording medium, Channel data extracting means for generating the audio data signals ADD _L and ADD _R from the reading result by the reading means is provided. When the acoustic device 100A is a device that reproduces audio content acquired by receiving broadcast waves, the sound source unit 130 includes a content extraction unit that extracts audio content from the broadcast wave reception results, and the content extraction. Channel data extraction means for extracting the audio data signals ADD _L and ADD _R from the extraction result of the means is provided.

The audio data signal ADD _L generated by the sound source unit 130 is sent to the volume adjustment unit 140 _L. Also, the audio data signal ADD _R generated by the sound source unit 130 is sent to the volume adjustment unit 140 _R.

Each of the volume adjustment units 140 _j (j = L, R) receives the attenuation coefficient CEF from the coefficient calculation unit 120A and the audio data signal ADD _j from the sound source unit 130. Then, the volume adjustment unit 140 _j performs a low-frequency limit process corresponding to the attenuation coefficient CEF for a predetermined low-frequency component in the audio data signal ADD _j . As shown in FIG. 2, the volume adjustment unit 140 _j having such a function includes a filter unit 141 as filtering means, a multiplication unit 142 as multiplication means, and a subtraction part 143 as subtraction means.

The filter unit 141 receives the audio data signal ADD _j from the sound source unit 130. The filter unit 141 allows the input signal to pass with the pass rate of the frequency characteristics shown in FIG. That is, in principle, the filter unit 141 functions as a low-pass filter (LPF) that passes a low-frequency band component, but a pass rate in a frequency region near a low-frequency resonance frequency LRF _j of a speaker unit 170 _j described later. However, it has the characteristic which becomes lower than the other frequency area | region in a bass band.

Therefore, the filter unit 141, the audio data low band resonance frequency LRF _j passage rate of the frequency components near the in signal ADD _j, taken smaller than the passage rate of the components of the other frequency regions in the bass band Yes. The result of passing at such a pass rate corresponding to the frequency is sent from the filter unit 141 to the multiplication unit 142 as a filtered data signal FLD _j .

Returning to FIG. 2, the multiplication unit 142 receives the filtering data signal FLD _j from the filter unit 141 at the input terminal A. Further, the multiplication unit 142 receives the attenuation coefficient CEF from the coefficient calculation unit 120A at the input terminal B. Then, the multiplication unit 142 performs a multiplication process of the reception result at the input terminal A and the reception result at the input terminal B. The result of this multiplication processing is sent as a multiplication data signal MPD _j from the output terminal C of the multiplication unit 142 to the subtraction unit 143.

The subtractor 143 receives the audio data signal ADD _j from the sound source unit 130 at the input terminal D. The subtracting unit 143 receives the multiplication data signal MPD _j from the multiplying unit 142 at the input terminal E. Then, the subtraction unit 143 performs a subtraction process in which the reception result at the input terminal E is subtracted from the reception result at the input terminal D. The result of the subtraction process is sent as an adjustment sound volume data signal CVD _j from the output terminal F of the subtraction unit 143 to the DAC 150 _j .

The adjusted sound volume data signal CVD _j generated as described above has a low frequency band in a manner corresponding to the value of the attenuation coefficient CEF, compared to the audio data signal ADD _j , when the value of the attenuation coefficient CEF is not “0”. Attenuation is applied to the component. Further, the attenuation rate in the frequency region near the low frequency resonance frequency LRF _j is smaller than the attenuation rate in other frequency regions in the low frequency band according to the characteristics of the pass rate of the filter unit 141.

Returning to FIG. 1, each of the DACs 150 _j (j = L, R) receives the adjusted sound volume data signal CVD _j from the sound volume adjusting unit 140 _j . The DAC 150 _j converts the adjustment volume data signal CVD _j that is a digital signal into an analog signal. The conversion result is sent to the AMP 160 _j as an analog conversion signal ACS _j .

Each of the AMPs 160 _j (j = L, R) receives the analog conversion signal ACS _j from the DAC 150 _j . The AMP 160 _j power-amplifies the analog conversion signal ACS _j . The amplification result is sent as an output audio signal AOS _j to the speaker unit 170 _j .

Each of the speaker units 170 _j (j = L, R) includes a speaker. The speaker unit 170 _j receives the output audio signal AOS _j from the AMP 160 _j . Then, the speaker unit 170 _j performs sound reproduction according to the output sound signal AOS _j and outputs the reproduced sound from the speaker.

Note that the speaker unit 170 _j generally has the characteristics shown in FIG. 4 as the frequency characteristics of the sound pressure level and the frequency characteristics of the impedance. That is, the low frequency resonance frequency LRF _j is a frequency within the low frequency band. Further, in the vicinity of the low-range resonance frequency LRF _j, the sound pressure level close to the sound pressure level of a frequency band higher than the low band resonance frequency LRF _j is maintained, and, from the impedance is much other frequency regions of the bass band large. For this reason, the sound component in the vicinity of the low-band resonance frequency LRF _j can be remarkably reduced in power required to obtain the same sound pressure level as compared with the sound component in the other frequency region of the low-frequency band. It has become.

<Operation>
Hereinafter, the operation of the acoustic device 100A configured as described above will be described.

  In acoustic device 100A, ammeter unit 110 constantly detects the total amount of current flowing out from power supply device 800. Then, the ammeter unit 110 sends the detection result to the coefficient calculation unit 120A as detected current value data DCD (see FIG. 1).

The coefficient calculation unit 120A that has received the detected current value data DCD calculates the attenuation coefficient CEF based on the detected current value data DCD. Then, the coefficient calculation unit 120A sends the calculated attenuation coefficient CEF to the volume adjustment units 140 _L and 140 _R (see FIG. 1).

In this state, audio data signal _{ADD j (j = L, R} ) generated by the sound source unit 130, when sent to the volume adjustment unit 140 _j, the volume adjustment unit 140 _j, given in the audio data signal ADD _j A low-frequency limit process corresponding to the attenuation coefficient CEF is performed on the low-frequency band component. The audio data signal ADD _j will be described below assuming that it has a frequency distribution as shown in FIG.

In such a low-frequency limit process, first, the filter unit 141 passes a predetermined low-frequency band component of the audio data signal ADD _j with the above-described frequency characteristic passing rate shown in FIG. As a result, the filter unit 141, the audio data signal ADD low pass rate of the frequency components near the resonant frequency LRF _j in _j is filtered data in another becomes smaller aspect than the pass rate of the components in the frequency domain in the bass band A signal FLD _j is generated (see FIG. 5B). The filtering data signal FLD _j thus generated is sent to the multiplication unit 142 (see FIG. 2).

Receiving the filtering data signal FLD _j , the multiplication unit 142 performs a multiplication process of the filtering data signal FLD _j and the attenuation coefficient CEF sent from the coefficient calculation unit 120A to generate a multiplication data signal MPD _j (FIG. 5 ( C)). The multiplication data signal MPD _j thus generated is sent to the subtracting unit 143 (see FIG. 2).

Receiving the multiplication data signal MPD _j , the subtraction unit 143 performs a subtraction process for subtracting the multiplication data signal MPD _j from the audio data signal ADD _j to generate an adjustment volume data signal CVD _j (see FIG. 5D). The adjusted sound volume data signal CVD _j thus generated is sent to the DAC 150 _j .

And the frequency distribution of the audio data signal ADD _j of FIG. 5 (A), as seen by comparing the frequency distribution of the adjustment volume data signal CVD _j in FIG. 5 (D), the by low frequency limit processing volume control unit 140 _j The generated adjustment sound volume data signal CVD _j is configured such that the attenuation in the frequency region near the low-band resonance frequency LRF _j is smaller than the attenuation in other frequency regions in the low frequency band. As a result, in the attenuation of the bass band component in the volume adjustment unit 140 _j , the attenuation amount of the component in the frequency region near the low-band resonance frequency LRF _j where the impedance of the speaker unit 170 _j is high is small, and the impedance of the speaker unit 170 _j The attenuation in other frequency regions in the low bass band is large. For this reason, when low-frequency limit processing is performed to reduce power consumption, the volume of the low-frequency band component is lower than when low-frequency limit processing of the above-described conventional method with flat frequency characteristics is performed. Low frequency limit processing that can be increased.

The adjusted sound volume data signal CVD _j generated by the sound volume adjusting unit 140 _j is successively subjected to DA conversion processing by the DAC 150 _j and power amplification processing by the AMP 160 _j , and then the output audio signal AOS _j is converted to the speaker unit. 170 _j . Then, reproduced sound according to the output sound signal AOS _j is output from the speaker of the speaker unit 170 _j .

As described above, in the first embodiment, the ammeter unit 110 detects the total amount of current flowing out from the power supply device 800 as the load reflection amount reflecting the load amount of the power supply device 800. Then, based on the detection result by the ammeter unit 110, the coefficient calculation unit 120A calculates the attenuation coefficient CEF, and low-frequency limit processing corresponding to the calculated attenuation coefficient CEF is performed by the volume adjustment units 140 _L and 140 _R. Is called. For this reason, while making the load amount with respect to the power supply device 800 appropriate, the lack of volume etc. can be suppressed.

In the first embodiment, in the low-frequency limit processing performed by the volume adjusting units 140 _L and 140 _R , the attenuation of the frequency domain components near the low-frequency resonance frequency LRF _j with the high impedance of the speaker unit 170 _j is performed. While decreasing the rate, the attenuation rate in the other frequency region in the bass band where the impedance of the speaker unit 170 _j is low is increased. For this reason, the power consumption of the acoustic device 100 </ b> A can be reduced while suppressing the collapse of the balance between the low frequency range and the high frequency range.

  In the first embodiment, the audio waveform is not clipped. For this reason, generation | occurrence | production of the abnormal sound accompanying the clip of an audio | voice waveform can be prevented.

  Therefore, according to the first embodiment, it is possible to optimize the amount of load on the power supply device 800 and to suppress the occurrence of abnormal noise and the change in sound quality of reproduced sound.

[Second Embodiment]
Next, a second embodiment of the present invention will be described mainly with reference to FIG. In the second embodiment as well, as in the case of the first embodiment described above, an audio device that is mounted on a vehicle and reproduces audio content having a two-channel stereo configuration will be described as an example.

<Configuration>
FIG. 6 shows a schematic configuration of an acoustic device 100B according to the second embodiment. As shown in FIG. 6, the acoustic device 100B uses an ammeter unit 110 as a current detection unit that is a part of the detection unit and a coefficient calculation unit as compared with the acoustic device 100A of the first embodiment described above. The only difference is that a signal level detection means which is a part of the detection means and a coefficient calculation unit 120B as a calculation means are provided instead of 120A. Hereinafter, the description will be given mainly focusing on this difference.

The coefficient calculation unit 120B receives the adjustment volume data signals CVD _L and CVD _R from the volume adjustment units 140 _L and 140 _R in addition to the detected current value data DCD from the ammeter unit 110. The coefficient calculation unit 120B detects the respective signal levels of the adjustment sound volume data signals CVD _L and CVD _R based on the received adjustment sound volume data signals CVD _L and CVD _R , and calculates a total signal level combining them. To do. Here, the total signal level calculated in the coefficient calculation unit 120B reflects the power consumption of the acoustic device 100B, and consequently the load amount of the power supply device 800.

Then, the coefficient calculating unit 120B calculates the attenuation coefficient CEF based on the detection result of the comprehensive signal level and the detected current value data DCD. The attenuation coefficient CEF calculated in this way is sent from the coefficient calculation unit 120B to the volume adjustment units 140 _L and 140 _R.

The possible value of the attenuation coefficient CEF is “0” or more as in the case of the first embodiment described above, and the bass band components in the volume adjustment units 140 _L and 140 _R increase as the value of the attenuation coefficient CEF increases. The attenuation of is increased. Similarly to the case of the first embodiment, when the value of the attenuation coefficient CEF is “0”, the bass band component is not attenuated in the volume adjustment units 140 _L and 140 _R.

  Further, when the detection result of the total signal power is the same, the value of the attenuation coefficient CEF increases as the total amount of current flowing out from the power supply device 800 indicated by the detection current value data DCD increases. It has become. When the total amount of current flowing out from the power supply device 800 indicated by the detected current value data DCD is the same, the value of the attenuation coefficient CEF increases as the total signal power detection result increases. ing.

  The calculation algorithm in the coefficient calculation unit 120B is determined in advance based on experiments, simulations, experiences, and the like.

<Operation>
Hereinafter, the operation of the acoustic device 100B configured as described above will be described.

  In the acoustic device 100B, as in the case of the first embodiment, the ammeter unit 110 constantly detects the total amount of current flowing out from the power supply device 800. Then, the ammeter unit 110 sends the detection result to the coefficient calculation unit 120B as detected current value data DCD (see FIG. 6).

The coefficient calculation unit 120B is supplied with adjusted volume data signals CVD _L and CVD _R from the volume adjustment units 140 _L and 140 _R. The coefficient calculation unit 120B detects the respective signal levels of the received adjusted sound volume data signals CVD _L and CVD _R , and calculates a total signal level combining both. Then, the coefficient calculation unit 120B calculates the attenuation coefficient CEF based on the detection result of the comprehensive signal level and the detected current value data DCD, and sends the attenuation coefficient CEF to the volume adjustment units 140 _L and 140 _R.

In this state, audio data signals generated by the sound source unit _{130 ADD j (j = L,} R) is, when sent to the volume adjustment unit 140 _j, the volume adjustment unit 140 _j, as in the first embodiment Thus, a low-frequency limit process corresponding to the attenuation coefficient CEF is performed on a predetermined low-frequency band component in the audio data signal ADD _j . The adjusted sound volume data signal CVD _j generated by the low-frequency limit processing is sent to the coefficient calculation unit 120B and also sent to the DAC 150 _j .

For adjusting the sound volume data signal CVD _j sent to the DAC 150 _j, after power amplification processing by the DA conversion process and AMP160 _j by DAC 150 _j is performed sequentially, the output audio signal AOS _j is sent to the speaker unit 170 _j . Then, reproduced sound according to the output sound signal AOS _j is output from the speaker of the speaker unit 170 _j .

As described above, in the second embodiment, the ammeter unit 110 detects the total amount of current flowing out from the power supply device 800 as one of the load reflection amounts reflecting the load amount of the power supply device 800. Further, as another load reflection amount, the coefficient calculation unit 120B calculates the overall signal level of the adjusted volume data signals CVD _L and CVD _R reflecting the reproduction volume correlated with the power consumption of the audio device 100B. It detects by doing. Then, the coefficient calculation unit 120B calculates the attenuation coefficient CEF based on the detection result by the ammeter unit 110 and the detection result of the total signal level of the adjustment sound volume data signals CVD _L and CVD _R. Thus, the low-frequency limit processing corresponding to the calculated attenuation coefficient CEF is performed by the volume adjustment units 140 _L and 140 _R. For this reason, while making the load amount with respect to the power supply device 800 appropriate, the lack of volume etc. can be suppressed.

In the second embodiment, as in the case of the first embodiment, in the low-frequency limit processing performed by the volume adjustment units 140 _L and 140 _R , the low-frequency resonance frequency LRF with the high impedance of the speaker unit 170 _{j. While} reducing the attenuation rate of the component in the frequency region in the vicinity of _j , the attenuation rate in the other frequency region in the low frequency band where the impedance of the speaker unit 170 _j is low is increased. For this reason, the power consumption of the acoustic device 100 </ b> B can be reduced while suppressing the collapse of the balance between the low frequency range and the high frequency range.

  In the second embodiment, as in the first embodiment, the audio waveform is not clipped. For this reason, generation | occurrence | production of the abnormal sound accompanying the clip of an audio | voice waveform can be prevented.

  Therefore, according to the second embodiment, it is possible to optimize the load amount of the power supply device 800 and to suppress the generation of abnormal noise and the change in sound quality of reproduced sound.

[Third Embodiment]
Next, a third embodiment of the present invention will be described mainly with reference to FIG. In the third embodiment, as in the case of the first and second embodiments described above, an audio device that is mounted on a vehicle and reproduces audio content having a two-channel stereo configuration will be described as an example.

<Configuration>
FIG. 7 shows a schematic configuration of an acoustic device 100C according to the third embodiment. As shown in FIG. 7, the acoustic device 100C is not provided with the ammeter unit 110 as compared with the acoustic device 100B of the second embodiment described above, and instead of the coefficient calculation unit 120B, detection means The only difference is that the signal level detection means and the coefficient calculation unit 120C as the calculation means are provided. Hereinafter, the description will be given mainly focusing on this difference.

The coefficient calculating unit 120C receives the adjusted sound volume data signals CVD _L and CVD _R from the sound volume adjusting units 140 _L and 140 _R. The coefficient calculation unit 120C detects the respective signal levels of the adjusted sound volume data signals CVD _L and CVD _R based on the received adjusted sound volume data signals CVD _L and CVD _R , and calculates a total signal level combining them. To do. Then, the coefficient calculation unit 120C calculates the attenuation coefficient CEF based on the detection result of the comprehensive signal level. The attenuation coefficient CEF calculated in this way is sent from the coefficient calculation unit 120C to the volume adjustment units 140 _L and 140 _R.

  As described above, the total signal level calculated by the coefficient calculation unit 120C reflects the power consumption of the acoustic device 100C, and consequently the load amount of the power supply device 800.

The value that the attenuation coefficient CEF can take is “0” or more as in the case of the first and second embodiments described above. The larger the value of the attenuation coefficient CEF, the lower the bass in the volume adjustment units 140 _L and 140 _R. The attenuation of the band component is increased. Similarly to the first and second embodiments, when the value of the attenuation coefficient CEF is “0”, the bass band component is not attenuated in the volume adjustment units 140 _L and 140 _R. ing. Furthermore, the value of the attenuation coefficient CEF increases as the detection result of the total signal power increases.

  The calculation algorithm in the coefficient calculation unit 120C is determined in advance based on experiments, simulations, experiences, and the like.

<Operation>
Hereinafter, the operation of the acoustic device 100 </ b> C configured as described above will be described.

In the acoustic apparatus 100C, the coefficient calculation unit 120C, volume adjustment unit 140 _L, 140 adjusted from _R volume data signal CVD _L, the CVD _R are supplied. The coefficient calculation unit 120C detects the respective signal levels of the received adjusted sound volume data signals CVD _L and CVD _R , and calculates a total signal level obtained by combining both. Then, the coefficient calculation unit 120C calculates the attenuation coefficient CEF based on the detection result of the comprehensive signal level, and sends it to the volume adjustment units 140 _L and 140 _R.

In this state, audio data signals generated by the sound source unit _{130 ADD j (j = L,} R) is, when sent to the volume adjustment unit 140 _j, the volume adjustment unit 140 _j, the first and second embodiments Similarly to the case, a low-frequency limit process corresponding to the attenuation coefficient CEF is performed on a predetermined low-frequency band component in the audio data signal ADD _j . The adjusted sound volume data signal CVD _j generated by the low-frequency limit processing is sent to the coefficient calculation unit 120B and also sent to the DAC 150 _j .

For adjusting the sound volume data signal CVD _j sent to the DAC 150 _j, after power amplification processing by the DA conversion process and AMP160 _j by DAC 150 _j is performed sequentially, the output audio signal AOS _j is sent to the speaker unit 170 _j . Then, reproduced sound according to the output sound signal AOS _j is output from the speaker of the speaker unit 170 _j .

As described above, in the third embodiment, the adjusted volume data signals CVD _L and CVD _R reflecting the reproduction volume correlated with the power consumption of the acoustic device 100C as the load reflection amount reflecting the load of the power supply device 800. Is detected by the coefficient calculation unit 120C. Then, the coefficient calculation unit 120C calculates the attenuation coefficient CEF based on the comprehensive signal level. Thus, the low-frequency limit processing corresponding to the calculated attenuation coefficient CEF is performed by the volume adjustment units 140 _L and 140 _R. For this reason, while optimizing the load amount of the power supply device 800. FIG. A lack of volume or the like can be suppressed.

In the third embodiment, similarly to the first and second embodiments, in the low-frequency limit process performed by the volume adjustment units 140 _L and 140 _R , the low-frequency range in which the impedance of the speaker unit 170 _j is high. The attenuation rate of the component in the frequency region near the resonance frequency LRF _j is reduced, and the attenuation rate in the other frequency region in the low frequency band where the impedance of the speaker unit 170 _j is low is increased. For this reason, the power consumption of the acoustic device 100 </ b> B can be reduced while suppressing the collapse of the balance between the low frequency range and the high frequency range.

  In the third embodiment, as in the first and second embodiments, the audio waveform is not clipped. For this reason, generation | occurrence | production of the abnormal sound accompanying the clip of an audio | voice waveform can be prevented.

  Therefore, according to the third embodiment, it is possible to optimize the load amount of the power supply device 800 and to suppress the generation of abnormal noise and the change in sound quality of reproduced sound.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, and various modifications are possible.

  For example, in the above first to third embodiments, the present invention is applied to an audio device that reproduces audio content having a two-channel stereo configuration, but the channel configuration of the audio content is arbitrary, and is a one-channel monaural configuration. Alternatively, for example, a configuration of three or more channels such as a configuration of a 5.1 channel surround system may be used.

In the first to third embodiments, the frequency characteristics of the pass rate of the filter section are the same in the low frequency band other than the vicinity of the low frequency resonance frequency LRF _j as shown in FIG. was such that the rate, for example, as shown in FIG. 8, at the lower band than the low band resonance frequency LRF _j, the higher band than the low band resonance frequency LRF _j, varying the value of the passage rate It can also be done. Such a pass rate value may be determined in accordance with the frequency distribution of the impedance of the speaker unit 170 _j .

Furthermore, for example, as shown in FIG. 9, lower band or than the low band resonance frequency LRF _j in the bass band other than in the vicinity of the low-range resonance frequency LRF _j, in higher bandwidth than the low band resonance frequency LRF _j, frequency It is also possible to change the value of the passing rate according to the above. Such a change in the passing rate may be determined based on the frequency distribution of the impedance of the speaker unit 170 _j .

  The coefficient calculation unit and the volume adjustment unit in the first to third embodiments are configured as a computer including a central processing unit (CPU: Central Processor Unit) and a DSP (Digital Signal Processor), and the function of the control processing unit is configured. It can also be realized by executing the program. These programs may be acquired in the form recorded on a portable recording medium such as a CD-ROM or DVD, or may be acquired in the form of delivery via a network such as the Internet. Good.

1 is a diagram schematically illustrating a configuration of an audio device according to a first embodiment of the present invention. It is a block diagram for demonstrating the structure of the volume adjustment unit of FIG. It is a figure for demonstrating the characteristic of the filter part of FIG. It is a figure for demonstrating the characteristic of the speaker unit of FIG. It is a figure for demonstrating the low-pass limit process by the volume adjustment unit of FIG. It is a figure which shows schematically the structure of the audio equipment which concerns on 2nd Embodiment of this invention. It is a figure which shows schematically the structure of the audio equipment concerning 3rd Embodiment of this invention. It is a figure for demonstrating a modification (the 1). It is a figure for demonstrating a modification (the 2).

Explanation of symbols

100A to 100C ... acoustic device 110 ... ammeter unit (detection means or part of detection means)
Current detection means)
120A ... Coefficient calculation unit (calculation means)
120B ... Coefficient calculation unit (signal level detection as part of the detection means)
Output means and calculation means)
120C ... Coefficient calculation unit (signal level detection means as detection means)
And calculation means)
140 _L , 140 _R ... Volume control unit (attenuating means)
141: Filter section (filtering means)
142 ... Multiplication unit (multiplication means)
143 ... Subtraction unit (subtraction means)

Claims (10)

An acoustic device that receives a supply of operating power from a power source and reproduces and outputs sound from a speaker unit,
Detecting means for detecting a load reflection amount reflecting the load amount of the power source;
Calculation means for calculating an attenuation coefficient of a signal component in a predetermined bass frequency band including a low-band resonance frequency of the speaker unit based on a detection result by the detection means;
While setting the attenuation rate of the band around the low-frequency resonance frequency in the predetermined bass frequency band to be smaller than the attenuation rate of the other bands in the predetermined bass frequency band, the sound based on the calculation result by the calculation unit Attenuating means for attenuating the signal;
An acoustic device comprising:   The acoustic device according to claim 1, wherein the detection unit includes a current detection unit configured to detect a total amount of current flowing out from the power source.   The acoustic device according to claim 1, wherein the detection unit includes a signal level detection unit that detects a level of the signal attenuated by the attenuation unit. The attenuation means is
When the acoustic signal is input and the signal component of the predetermined low frequency band is selectively passed, the pass rate of the band around the low frequency resonance frequency is determined to pass the other band in the predetermined low frequency band. A filtering means that passes less than the rate;
Multiplying means for multiplying the signal passed through the filtering means by the attenuation coefficient;
Subtracting means for subtracting the multiplication result by the multiplying means from the acoustic signal;
The acoustic device according to any one of claims 1 to 3, further comprising:   In the attenuation means, the attenuation rate for a band having a frequency lower than the band around the low-frequency resonance frequency and the attenuation rate for a band having a frequency higher than the band around the low-frequency resonance frequency are the same. The acoustic device according to any one of claims 1 to 4.   The attenuation means is characterized in that an attenuation rate for a band having a frequency lower than a band around the low-band resonance frequency is different from an attenuation rate for a band having a frequency higher than the band around the low-band resonance frequency. The acoustic device according to any one of claims 1 to 4.   The acoustic device according to claim 1, wherein the acoustic device is mounted on a moving body. An acoustic signal processing method used in an acoustic device that receives a supply of operating power from a power source and reproduces and outputs sound from a speaker unit,
A detection step of detecting a load reflection amount reflecting the load amount of the power source;
A calculation step of calculating an attenuation coefficient of a signal component in a predetermined bass frequency band including a low-band resonance frequency of the speaker unit based on a detection result in the detection step;
While setting the attenuation rate of the band around the low-frequency resonance frequency in the predetermined bass frequency band to be smaller than the attenuation rate of other bands in the predetermined bass frequency band, the sound is generated based on the calculation result in the calculation step. An attenuation step to attenuate the signal;
An acoustic signal processing method comprising:   An acoustic signal processing program that causes an arithmetic means to execute the acoustic signal processing method according to claim 8.   10. A recording medium in which the acoustic signal processing program according to claim 9 is recorded so as to be readable by an arithmetic means.

Images