JP2006323395A - Signal processing apparatus and sound reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain proper signal processings, even if a FIR filter of short-length top is used. <P>SOLUTION: A digital signal inputted from an input terminal 101 is divided and supplied to two signal processing systems, respectively. The digital signal, supplied to one signal processing system, is supplied directly to a 1st input terminal 151 of an FIR filter 105. Also, the signal inputted to the other signal processing system is inputted to a delay unit 102 and is outputted, after a delay of specified time. The signal outputted from the delay unit 102 is attenuated by am attenuator 103 and is then inputted to a 2nd input terminal 152 of the FIR filter 105. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a signal processing device and a sound reproduction device. In particular, the present invention relates to a signal processing apparatus using an FIR filter and a sound reproduction apparatus using the same.

For example, a reverberation adding device that performs reverberation processing for each frequency band that is divided into bands is known (for example, see Patent Document 1). However, the “reverberation processing” referred to here is processing for the “reverberation characteristics (length, depth, etc.)” (bottom row of the first page).
No. 1-12320

  Many electronic devices have been proposed in which an impulse response of a system such as a signal transmission path is measured and the response is reproduced by an FIR filter configured in a signal processing device. For example, in a reverberation adding device using an FIR filter, an impulse response of a room is measured, and a reproduced signal having the same reverberation characteristic as that of hearing the sound in the actually measured room is completely separated by an FIR filter that reproduces this response. Can be heard in the environment.

  In the sound reproducing apparatus using the FIR filter, the impulse response representing the transfer characteristic from the speaker to the both ears is measured, and the FIR filter that reproduces this response is provided in the signal processing device, whereby the sound reproducing apparatus using headphones is used. While reproducing, it is possible to generate a sound image localization effect equivalent to that when reproducing using a speaker system.

  However, in such a signal processing apparatus, when a filter having a convergence time and a frequency response faithful to the measured impulse response is to be configured with high accuracy by the FIR filter, it is necessary to use an FIR filter having a long tap length. . Therefore, in order to perform such signal processing, a large number of signal processing devices are required, resulting in an expensive and large-scale system.

  The present application has been made in view of the above points, and the problem to be solved is that in the conventional apparatus, when an FIR filter is to be configured with high accuracy, an FIR filter having a long tap length is used. Must be used. Therefore, in order to perform such signal processing, a large number of signal processing devices are required, resulting in an expensive and large-scale system.

  For this reason, in the present invention, the output of the signal processing means is input in the middle of the FIR filter, and according to this, good signal processing is performed even if an FIR filter with a short tap length is used. Can be.

  According to the first aspect of the present invention, since the output of the signal processing means is input in the middle of the FIR filter, good signal processing can be performed even if an FIR filter with a short tap length is used. It can be done.

  According to the invention of claim 2, the output signal from the signal processing means is further improved by being added to the output delayed by the time corresponding to the initial reflected sound by the plurality of delay elements of the FIR filter. Signal processing is performed.

  According to the invention of claim 3, the signal processing means delays the input digital audio signal, attenuates the delayed signal, and outputs the first processing means. The signal processing is specifically realized by providing a second signal processing unit that delays the delayed signal by a time different from that of the processing unit and outputs the delayed signal further attenuated than the first processing unit. It is something that can be done.

  According to a fourth aspect of the present invention, there is provided addition means for adding the output signal from the first processing means, the output signal from the second signal processing means, and the input digital audio signal, and the output from the addition means. By supplying the signal to the FIR filter, better signal processing can be performed.

  Further, according to the invention of claim 5, since the output of the signal processing means is inputted in the middle of the FIR filter, good signal processing can be performed even if a FIR filter with a short tap length is used, and good acoustics can be obtained. Playback can be performed.

  According to the invention of claim 6, the output signal from the delay attenuating means is further improved by being added to the output delayed by the time corresponding to the initial reflected sound by the plurality of delay elements of the FIR filter. Sound reproduction is performed.

  According to the invention of claim 7, the signal processing means delays the input digital audio signal, attenuates the delayed signal, and outputs the first digital audio signal. The sound reproduction can be specifically realized by providing a second processing means for delaying the delayed signal by a time different from that of the processing means and outputting the delayed signal further attenuated than the first processing means. It can be done.

  According to the eighth aspect of the invention, there is provided addition means for adding the output signal from the first processing means, the output signal from the second processing means, and the inputted digital audio signal, and the output signal from the addition means. Is supplied to the FIR filter, so that better sound reproduction can be performed.

  As a result, in the conventional apparatus, it is necessary to use an FIR filter having a long tap length when attempting to configure the FIR filter with high accuracy. Therefore, in order to perform such signal processing, a large number of signal processing devices are required, and there is a problem that the system becomes expensive and large-scale. The point can be easily eliminated.

  That is, in the signal processing apparatus according to the present invention, the signal processing means for delaying and attenuating the input digital audio signal, and the FIR filter for performing the convolution processing of the impulse response representing the acoustic transfer characteristic on the input digital audio signal The FIR filter includes a plurality of delay elements, a plurality of multipliers that multiply the output from the delay elements by a predetermined coefficient, and a plurality of adders that add the output signals from the multipliers. The output signal from the processing means is input between a plurality of delay elements of the FIR filter.

  In the sound reproducing device of the present invention, the input digital audio signal is subjected to convolution processing of an impulse response representing acoustic transfer characteristics, and the output signal from the signal processing means is converted into an analog signal. Conversion means, and electroacoustic conversion means for converting an output signal from the conversion means into audible sound, and the signal processing means includes delay attenuation means for delaying and attenuating the input digital audio signal, and input An FIR filter that performs convolution processing of an impulse response representing an acoustic transfer characteristic on a digital audio signal. The FIR filter includes a plurality of delay elements and a plurality of multiplications that multiply outputs from the delay elements by a predetermined coefficient. And a plurality of adders for adding the output signals from the multiplier, and the output signal from the delay attenuation means is a plurality of FIR filters. In which the input comprising between delay elements.

  Hereinafter, a signal processing device and a sound reproduction device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a processing block of a signal processing apparatus according to the first embodiment of the present invention. In FIG. 1, digital signals input from an input terminal 101 are supplied to two signal processing systems. The digital signal supplied to one signal processing system is directly input to the first input terminal 151 of the FIR filter 105. The signal input to the other signal processing system is input to the delay unit 102 and output after being delayed for a predetermined time. The signal output from the delay unit 102 is attenuated by the attenuator 103 and then input to the second input terminal 152 of the FIR filter 105.

  The FIR filter 105 is configured as shown in FIG. A digital signal input from the input terminal 101 is supplied to a plurality of delay elements 222 connected in series. The signals delayed by these delay elements 222 are sequentially transferred between the delay elements 222 based on the clock of the sampling period. The signals extracted from the output terminals of the respective delay elements 222 are respectively supplied to the coefficient multipliers 223 and multiplied by predetermined coefficients. The multiplication results from the coefficient units 223 are added by the adder circuit 224 and output from the output terminal 253.

  In such an FIR filter 105, FIG. 3A shows an example of a measured impulse response. On the other hand, since the tap length of the FIR filter 105 is finite, when it is constituted by an ordinary FIR filter as shown in FIG. 2, only a response up to the tap length can be constituted, and the response is shown in FIG. Thus, playback is continued until time t1 (B in FIG. 3), and thereafter it is interrupted.

  On the other hand, when the signal A in FIG. 4 delayed by time t1 and further attenuated is input to the FIR filter via the delay unit 102, the FIR filter 105 outputs a response as shown in FIG.

  Therefore, the configuration shown in FIG. 1 is applied, and the input signal and the signal delayed and delayed by t1 are input to the FIR filter 105, and the output is a combination of C of FIG. 3 and B of FIG. That is, a response as shown in FIG. 4C is obtained, and the impulse response time can be substantially increased. At this time, since the delayed signal output from the delay unit 102 is attenuated by the attenuator 103, the response shown in FIG. 3C and the response shown in FIG. 4B are smoothly connected.

  Further, the FIR filter 105 shown in FIG. 2 is provided with a second input terminal 152, and an output signal from the attenuator 103 is supplied to the second input terminal 152. The signal input to the second input terminal 152 is added by an adder 225 with a signal delayed through a plurality of delay elements 222, in the case of FIG. In other words, the adder 225 is connected in series with the plurality of delay elements 222 and is provided at a position that serves as a boundary between the initial reflected sound and the dispersed sound between the plurality of delay elements 222.

  For example, the sound that reaches the listener with the sound output from the speaker system in the listening room is roughly classified into the initial reflected sound and the dispersed sound. The signal input to the second input terminal 152 is added to the signal supplied to the delay element 222 on and after the stage corresponding to the dispersed sound, so that a sound that is heard in the speaker system in the listening room more. A place can be realized.

  The length of the initial reflected sound varies depending on the size of the listening room. Therefore, the position where the adder 252 is inserted and disposed is the same as the delay element 222 in the second stage as shown in FIG. What is necessary is just to change suitably according to the magnitude | size of the assumed listening room not only between the delay elements 222 of the 3rd stage. That is, according to the configuration of the first embodiment, the added response portion is a portion excluding the vicinity of the rising edge of the impulse response.

  Here, in the vicinity of the rise of the impulse response, the early reflection sound occupies the reverberation of the room such as the listening room as described above. However, the latter half of the impulse response is a response centered on the dispersed sound and has a characteristic different from that of the initial reflected sound. Therefore, adding a response based on the signal delayed by the delay device 102 after the impulse response rising vicinity in this way adds an impulse response portion close to dispersed sound, and can be a more natural response.

  Therefore, according to the first embodiment, it is possible to reproduce a long impulse response even if an FIR filter with a short tap length is used, so that the scale of signal processing can be greatly reduced, and this can be applied to an IC for digital signal processing, The number of ICs used can be greatly reduced when configured with. Accordingly, the system can be configured at a low cost by reducing the mounting area, reducing the power consumption.

  Thus, according to the apparatus according to the first embodiment, the signal supplied to one signal processing system is supplied to the attenuator and the delay device, and the signal supplied to the other signal processing system is directly input to the FIR filter. At the same time, the attenuated and delayed signal is input to an adder provided in the middle of the FIR filter. As a result, an undelayed signal, that is, a digital signal input from the input terminal 101 is first input to the FIR filter, and the signal delayed when the impulse response is approximately completed is now in the middle of tapping the FIR filter. To be manpowered.

  That is, the impulse response corresponding to the dispersed sound is output from the FIR filter based on the input delayed signal as described above. As a result, the length of the response by the FIR filter becomes equivalent to the addition of the tap length after the tap inserted in the middle, and a long impulse response can be made even with a short tap length FIR filter, and a more natural response It can be.

  The signal supplied to one signal processing system is delayed and attenuated by a delay unit and an attenuator, and the attenuated and delayed signal is added to the signal supplied to the other signal processing system and then input to the FIR filter. With this configuration, the FIR filter first receives a signal that is not delayed, that is, the digital signal itself that is input from the input terminal.

  Then, the signal delayed when the impulse response of the input digital signal is almost completed is input to the FIR filter again. As a result, the length of the response due to the apparent FIR filter is doubled, and a long impulse response can be created even with an FIR filter with a short tap length.

  FIG. 5 illustrates a processing block of a signal processing apparatus according to the second embodiment of the present invention. In FIG. 5, the digital signal input from the input terminal 101 is supplied to two signal processing systems. A signal supplied to one signal processing system is input to the delay unit 102, delayed by at least two different delay times, and then output. The signals having different delays extracted from the delay unit 102 are attenuated by the attenuators 103 a and 103 b, added by the adder circuit 104, and input to the second input terminal 152 of the FIR filter 105.

  Then, an impulse response is convolved with the signal input to the FIR filter 105 using a coefficient set in advance in the FIR filter 105, and then output from the output terminal 106. The configuration of the FIR filter 105 is the same as that of the FIR filter shown in FIG. The other configuration is the same as in FIG.

  In the signal processing apparatus according to the second embodiment, the digital signal input from the input terminal 101 is input to the first input terminal 151 of the FIR filter 105 and also to the delay device 102. The signal input to the delay unit 102 is output from the output terminals R1 and R2 as output signals delayed by the delay unit 102 with different delay times. In the case of the second embodiment, the delay time of the signal output from the output terminal R2 of the delay device 102 is longer than the delay time of the signal output from the output terminal R1 of the delay device 102.

  The two delayed signals output from the delay unit 102 are supplied to the attenuators 103a and 103b, respectively, and are attenuated. In this case, the attenuation rate of the attenuator 103b is larger than the attenuation rate of the attenuator 103a. Output signals from these attenuators 103 a and 103 b are added by the adder circuit 104 and supplied to the second input terminal 152 of the FIR filter 105.

  In the FIR filter 105, an impulse response is convolved with the digital signal input to the first input terminal 151 and output from the output terminal 153. Subsequently, the FIR filter 105 is delayed and input to the second input terminal 152. Among the attenuated signals, an impulse response corresponding to the dispersed sound is convoluted with the signal output from the attenuator 103 a and output from the output terminal 153. At this time, since the signal delayed by the attenuator 103a is attenuated to a predetermined level, the impulse response of the signal input to the first input terminal 151 is smoothly connected as in the case shown in FIG. 4C.

  Further, the impulse response corresponding to the dispersed sound is convolved with the delayed and attenuated signal from the attenuator 303b input to the second input terminal 352 of the FIR filter 305 and output from the output terminal 353. The At this time, since the signal output from the output terminal R2 of the delay unit 302 is further attenuated by the attenuator 303b than the signal output from the attenuator 303a, the impulse response of the signal output from the attenuator 303a is obtained. Subsequently, it is output from the FIR filter 305 in a state smoothly connected to the impulse response output from the attenuator 303a.

  Therefore, according to the second embodiment, the time t1 to be further delayed through the delay device in the above-described embodiment of FIG. 1 becomes plural, and the tap length of the FIR filter can be further shortened.

  Further, FIG. 6 illustrates processing blocks of a signal processing device according to the third embodiment of the present invention. 6, the output signal of any one of the signals output from the delay unit 102 of the above-described embodiment of FIG. 5, the output signal of R2 in this example, and the output signal from the attenuator 103b is the attenuator 103b. To the adder circuit 104, and after being attenuated by the attenuator 407, returns to the input stage of the delay device 102.

  That is, the signal attenuated by the subtracter 407 is added by the adder circuit 408 provided at the front end of the delay device 102 and input to the input end of the delay device 102. In the case of the third embodiment, the output signal R1 supplied to the attenuator 103a may be supplied to the attenuator 407.

  Further, FIG. 7 illustrates processing blocks of a signal processing device according to the fourth embodiment of the present invention. In FIG. 7, another delayed signal R3 is extracted from the delay unit 102 of the above-described embodiment of FIG. 5, attenuated by the attenuator 507, and then fed back to the input stage of the delay unit 102. That is, the signal attenuated by the attenuator 507 is added by the adder circuit 508 provided in the previous stage of the delay device 102, and the signal added with the digital signal input from the input terminal 101 is supplied to the delay device 102. .

  The attenuation factors of the attenuators 407 and 507 of the third and fourth embodiments are determined by the relationship with the delay time of the delayed signal output from the delay device 102. That is, when the delay time output from the delay unit 102 is long, the amount of attenuation of the delayed signal is increased, and the impulse response output from the FIR filter 105 is attenuated so as to be close to the actually measured impulse response. The attenuation factors of the devices 407 and 507 are set.

  On the contrary, when the delay time output from the delay unit 102 is short, the amount of attenuation of the delayed signal is small, and the impulse response output from the FIR filter 105 is actually measured as described above. The attenuation factors of the attenuators 407 and 507 are set so as to be close to. The delay time of the signal supplied to the attenuators 407 and 507 of the ninth and tenth embodiments is arbitrarily set.

  That is, according to these third and fourth embodiments, the output signal of the delay device is further fed back to the input terminal of the delay device, so that the delayed signal is attenuated and then input to the delay device again. As a result, the input attenuated at a constant ratio is repeatedly input to the FIR filter at a constant period, whereby the apparent tap length of the FIR filter can be further increased.

  Therefore, according to the third and fourth embodiments, a long impulse response can be reproduced even with the use of an FIR filter with a short tap length, so that the scale of signal processing can be greatly reduced. When using signal processing ICs, the number of ICs used can be greatly reduced. Accordingly, it is natural that the mounting area can be reduced, the power consumption can be reduced, and the system can be configured at low cost.

  8 and 9 show an embodiment in which the signal processing device according to the present invention is applied to a sound reproducing device.

  First, FIG. 8 shows the overall configuration of a sound reproducing apparatus using headphones. In FIG. 8, the analog audio signal input from the audio input terminal 61 is converted by the A / D converter 62 into a digital signal, for example, a digital audio signal of 44.1 KHz. The digitized signal is input to the signal processing device 63, where filtering for localizing the sound image out of the head is performed.

  That is, the signal processing content in the signal processing device 63 is, for example, that a total of four types of impulse responses from two sound sources placed in front to both ears are measured in advance, and the measured characteristics are shown in FIG. Convolve with a simple filter.

  In FIG. 9, the signals input to the first and second input terminals 71 and 72, for example, the signals of the L and R channels, are supplied to the filters 73 and 74 and the filters 75 and 76, respectively. The signals from these filters 73 and 75 are added by an adder 78, and the signals from the filters 74 and 76 are added by an adder 78. These added signals are taken out to the first and second output terminals 79 and 80.

  Here, the filters 73 to 76 use the signal processing apparatus using the FIR filter shown in FIGS. 1 and 5 to 7. The signals output to the output terminals 79 and 80 are converted into analog audio signals of L and R channels by the D / A converter 64 and amplified by the amplifier 65, and then a pair of speaker units of the headphone system 66. Supplied to each.

  Accordingly, a listener who is wearing the headphone system 66 on the head and listening to the sound output from the headphone system 66 feels as if he / she is listening to the sound reproduced from the speaker system. That is, the center and localization of the sound output from the left and right speaker units of the headphone system 66 are not located in the listener's head, but are located out of the head and in front of the head.

  According to the present invention, the filters 73 to 76 can simplify the FIR filter by adopting the above-described configuration, and provide a small and inexpensive sound reproducing device.

  In the embodiment shown in FIG. 8 and FIG. 9, the sound reproducing apparatus that obtains the out-of-head localization feeling of the sound image reproduced using the headphones has been shown. However, this portion is used as the speaker reproduction and extends to the outside of the two speakers. The present invention can also be applied as a replacement for FIR processing in a system in which a sound image is localized.

  That is, in the apparatus shown in FIGS. 8 and 9, a filter for convolving the impulse response from the sound source to both ears is configured using a signal processing apparatus as shown in FIGS. For example, the out-of-head feeling or the forward localization feeling of the reproduced sound image is greatly improved as compared with the conventional FIR filter having the same sampling frequency and the same total number of taps.

  Further, in the examples shown in FIG. 8 and FIG. 9, an acoustic reproduction device that obtains a sense of out-of-head localization of a sound image reproduced using headphones has been shown. It can also be applied to systems that do this.

  Furthermore, if the present invention is applied to a sound field simulation system, a long response time can be reproduced with a small number of taps. As a result, it is possible to construct a reverberation generator with a rough time interval compared to the sampling time with dense pulses distributed at each sampling time. As a result, the sound field can be reproduced more faithfully.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

It is a processing block diagram of the signal processing apparatus which concerns on the 7th Embodiment of this invention. It is a block diagram of the FIR filter used in 1st Embodiment. It is a diagram which shows the example of the measured impulse response. It is a diagram showing a signal delayed by time t1 and further attenuated. It is a processing block diagram of the signal processing apparatus which concerns on the 2nd Embodiment of this invention. It is a processing block diagram of the signal processing apparatus which concerns on the 3rd Embodiment of this invention. It is a processing block diagram of the signal processing apparatus which concerns on the 4th Embodiment of this invention. It is a block diagram of embodiment of the sound reproduction apparatus by this invention. It is a block diagram of embodiment of the sound reproduction apparatus by this invention.

Explanation of symbols

  101, 151, 152 ... input terminal, 102, 407, 507 ... delay device, 103 ... attenuator, 104, 408, 504 ... adder circuit, 105 ... FIR filter, 106, 153 ... output terminal, 222 ... delay element, 223 ... Coefficient unit, 224, 225 ... Adder, 61 ... Audio input terminal, 62 ... A / D converter, 63 ... Signal processing device, 64 ... D / A converter, 65 ... Amplifier, 66 ... Headphone system, 71 ... 1st input terminal 72 ... 2nd input terminal 73-76 ... Filter, 77, 78 ... Adder, 79, 80 ... Output terminal

Claims (8)

Signal processing means for delaying and attenuating the input digital audio signal;
A FIR filter that performs convolution processing of an impulse response representing acoustic transfer characteristics on the input digital audio signal;
The FIR filter is
A plurality of delay elements;
A plurality of multipliers for multiplying the output from the delay element by a predetermined coefficient;
A plurality of adders for adding output signals from the multiplier;
An output signal from the signal processing means is input between the plurality of delay elements of the FIR filter. The signal processing device according to claim 1,
The output signal from the signal processing means is
The signal processing apparatus, wherein the signal is added to an output delayed by a time corresponding to an initial reflected sound by the plurality of delay elements of the FIR filter. The signal processing device according to claim 1,
The signal processing means includes
First processing means for delaying the input digital audio signal and attenuating and outputting the delayed signal;
Second signal processing means for delaying the human-powered digital audio signal by a time different from that of the first processing means, and outputting the delayed signal after further attenuation than the first processing means. A signal processing apparatus. The signal processing device according to claim 3,
Adding means for adding the output signal from the first processing means, the output signal from the second signal processing means, and the input digital audio signal;
An output signal from the adding means is supplied to the FIR filter. Signal processing means for performing convolution processing of an impulse response representing acoustic transfer characteristics on the input digital audio signal;
Conversion means for converting an output signal from the signal processing means into an analog signal;
Electroacoustic conversion means for converting the output signal from the conversion means into audible sound,
The signal processing means includes
Delay attenuation means for delaying and attenuating the input digital audio signal; and an FIR filter for performing convolution processing of an impulse response representing the acoustic transfer characteristic on the input digital audio signal;
The FIR filter is
A plurality of delay elements, a plurality of multipliers for multiplying outputs from the delay elements by a predetermined coefficient, and a plurality of adders for adding output signals from the multipliers,
The sound reproduction apparatus according to claim 1, wherein an output signal from the delay attenuating means is input between the plurality of delay elements of the FIR filter. The sound reproducing device according to claim 5,
The sound reproduction apparatus, wherein an output signal from the delay attenuating means is added to an output delayed by a time corresponding to an initial reflected sound by the plurality of delay elements of the FIR filter. The sound reproducing device according to claim 5,
The signal processing means includes
First processing means for delaying the input digital audio signal and attenuating and outputting the delayed signal;
A second processing means for delaying the input digital audio signal by a time different from that of the first processing means and further outputting the delayed signal after being attenuated more than the first processing means. A sound reproducing device characterized by the above. The sound reproducing device according to claim 7,
Adding means for adding the output signal from the first processing means, the output signal from the second processing means, and the input digital audio signal;
The sound reproduction apparatus, wherein an output signal from the adding means is supplied to the FIR filter.

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