JP3214936B2 - Signal processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus which executes a microprogram and performs various numerical calculation processes on an input digital signal.

[0002]

2. Description of the Related Art Conventionally, when switching from audio data of one tone to audio data of another tone in an electronic musical instrument, an audio device, or the like during a performance or playing a music source, noise is generated when the tone is suddenly switched. Therefore, it is necessary to gradually lower the volume of audio data of a certain timbre and gradually increase the volume of audio data of another timbre for switching. This is called crossfade. Conventionally, in an electronic musical instrument, an audio device, or the like, there is a case where a certain sound is spatially panned from left to right or right to left (sound image is localized).

In recent years, the technology of digital signal processors (digital signal processors (DSPs)) that execute microprograms and perform various numerical calculations on input digital signals has advanced, and semiconductor manufacturing has been progressing. As technology advances, DSPLS
I is becoming readily available. For this reason, some recent electronic musical instruments and audio devices include a cross-fade circuit for performing the above-described cross-fade and a pan circuit for performing the pan, which are built in DSPLSI and built therein.

FIG. 12 is a block diagram showing an example of the configuration of a conventional crossfade circuit constituted by such DSPLSI. In this figure, reference numerals 1 and 2 denote digital audio data D _I1 and D ₁ of different timbres, respectively. input _{terminal I2} is inputted, 3 is a multiplier for multiplying the multiplication coefficient having the properties shown in a of the audio data D _I1 and 13 inputted from the input terminal _{1 k 1 (0 ≦ k 1} ≦ 1) And 4, a multiplication coefficient k having the characteristic shown in FIG. 13B with the audio data D _I2 input from the input terminal 2.
₂ (0 ≦ k ₂ ≦ 1), 5 is an adder that adds the output data of the multipliers 3 and 4, and 6 is one audio data in which the output data of the adder 5 is mixed. an output terminal is output as D _O. According to such a configuration, with a simple configuration, by linear interpolation, it is possible to switch smoothly to the audio data D _I2 inputted from the input terminal 2 from the audio data D _I1 which is inputted from the input terminal 1.

FIG. 14 is a block diagram showing a configuration example of a conventional pan circuit constituted by the DSPLSI described above. In FIG.
An input terminal to which _I is input, and 8 is a multiplication coefficient A (0 ≦ A ≦
An input terminal to which 1) is input, and 9 is an arithmetic unit that performs the operation of (1-x) on the multiplication coefficient A and outputs the multiplication coefficient (1-A).

[0006] 10 is audio data D _I and the multiplication coefficient A
Multiplier for multiplying the bets, the output terminal 11 is the output data of the multiplier 10 is output as the audio data D _OR the R channel, 12 the audio data D _I and the multiplication factor (1
-A), and 13 is an output terminal from which output data of the multiplier 12 is output as L-channel audio data D _OL .

In such a configuration, the multiplication coefficient A is set to 0
From 1 to 1, the sound radiated from the speakers (not shown) connected to the output terminals 11 and 13 spatially pans from left to right, and conversely, changes the multiplication coefficient A from 1 to 0. Then, the sound radiated from the speakers (not shown) connected to the output terminals 11 and 13 spatially pans from right to left.

[0008]

By the way, the above-mentioned D
In the conventional cross-fade circuit constituted by the SPLSI, since the operations in the multipliers 3 and 4 and the adder 5 are based on the sum of products in the integer form, as shown at the intersection c between a and b in FIG. , When the multiplication coefficients k ₁ and k ₂ are both _１ ／, the output data of the multipliers 3 and 4 are D _I1 / 2 and D _I2 / 2, respectively. Since the power is proportional to the square of the amplitude, the power corresponding to each output data of the multipliers 3 and 4 is 1/4 of the audio data D _I1 and D _I2 , respectively.
Will be.

Therefore, even if the output data of each of the multipliers 3 and 4 is added by the adder 5, the power corresponding to the audio data D _O output from the output terminal 6 is _{equal to} the audio data D _I1 or D _I2. Is reduced to 比 べ compared to the case of only one of the above. Here, since the electric power and the sound pressure are in a proportional relationship, the sound pressure corresponding to the audio data D _O is also １ ／ compared to the case where only one of the audio data D _I1 and D _I2 is used. I will. That is, there is a drawback that the volume of the audibility is not constant during the crossfade.

Further, in the conventional pan circuit constituted by the DSPLSI described above, since the arithmetic operations in the arithmetic unit 9 and the multipliers 10 and 12 are basically based on the sum of products in the form of integers, the multiplication coefficient A = 0 and a certain space Assuming that the audible power of the sound radiated from the speaker (not shown) disposed on the left side of the above is P ₀ and the multiplication coefficient A is 、, the same reason as in the above-described cross-fade circuit is obtained. Accordingly, the power of the acoustic audibility which is respectively emitted from the speaker (not shown) disposed respectively left and the right of a certain space, thus both become P _0/4. Therefore,
As shown in FIG. 15, the power of the audible sound at a portion spatially equal to the left and right speakers (not shown) is P.
_0/2, on the acoustic audibility power, i.e., while maintaining the sound pressure constant, it is impossible to move to the left and right sound images spatially, there is a problem that the operation of the bread becomes unnatural Was.

The present invention has been made under such a background, and it is possible to cross-fade a plurality of audio signals while keeping a sound pressure perceived by a sound constant, or to spatially shift a sound image right and left. It is an object to provide a signal processing device that can be moved.

[0012]

According to a first aspect of the present invention, there is provided a storage means having one input terminal and a plurality of output terminals, and the input means for the storage means. Write the audio signal to the end, read the audio signal from the output end of the plurality of systems at a speed different from the writing speed, and control the phases of the read audio signals of the plurality of systems to be different from each other. more Starring creating a storage control unit, together with the crossfading each other audio signals of the plurality of systems, by calculating the coefficient values of the plurality of multiplication coefficients for controlling the temporal change in sound pressure of the audio signal of the plurality of systems for calculation means, and a plurality of multiplying means for multiplying the plurality of audio signals read by the storage control means and the plurality of multiplication coefficients, respectively. And calculation means, and a mixing means for mixing the audio signals of the plurality of systems multiplication coefficients are multiplied comprising,
It is characterized in that a pitch change is performed on the audio signal input to the storage means, the temporal change in sound pressure being controlled. According to a second aspect of the present invention, there is provided a storage unit having one input terminal and a plurality of output terminals, and an audio signal is written to the input terminal with respect to the storage unit, and an audio signal is written from the plurality of output terminals. Reading the audio signal at a speed different from the writing speed,
A storage control means for controlling the phases of the read audio signals of the plurality of systems to be different from each other; an audio signal for cross-fading the audio signals of the plurality of systems to each other and mixing the audio signals of the plurality of systems. multiple sound pressure of the audio signal is generated by calculating the coefficient values of the plurality of multiplication coefficients for controlling so as to be temporally constant
And computing means, o of the plurality of systems the storage control means has read - a plurality of multiplying means for multiplying the audio signal and the plurality of multiplication coefficients respectively, the audio signals of a plurality of lines multiplication coefficients are multiplied Mixing means for mixing, wherein a pitch change is performed on the audio signal input to the storage means while maintaining a constant sound pressure. According to a third aspect of the present invention, in the second aspect of the present invention, the plurality of calculating means squares the plurality of multiplication coefficients to keep the sound pressure of the mixed audio signal constant over time. The calculation is performed so that the sum is constant. According to a fourth aspect of the present invention, in the first aspect of the present invention, the operation of the signal processing device is controlled by executing a microprogram, and the plurality of arithmetic units are controlled by the plurality of arithmetic units. It is realized as a part of a microprogram, and is characterized in that it calculates each coefficient value of the plurality of multiplication coefficients and each of the plurality of systems of audio signals.

[0013]

According to the first aspect of the present invention, the storage control means writes the audio signal to the input end of the storage means and outputs the audio signal from the output ends of the plurality of systems at a speed different from the writing speed. read out. that time,
The storage control means controls the phases of the read audio signals of the plurality of systems to be different from each other. The plurality of calculating means calculate coefficient values of a plurality of multiplication coefficients for cross-fading the plurality of audio signals with each other and simultaneously controlling a temporal change in sound pressure of the plurality of audio signals. Create by The plurality of multiplying means respectively multiply a plurality of audio signals read from the storage means by the storage control means and a plurality of multiplication coefficients calculated by the plurality of calculating means. The mixing means mixes the plurality of audio signals multiplied by the multiplication coefficient. Then, a pitch change is performed on the audio signal input to the storage means, the temporal change of the sound pressure being controlled. According to the second aspect of the present invention, the storage control means writes the audio signal to the input end of the storage means and reads out the audio signal from the output ends of the plurality of systems at a speed different from the writing speed. . At this time, the storage control means controls the phases of the read audio signals of the plurality of systems to be different from each other. Duplicate
The number calculating means is used to cross-fade a plurality of audio signals with each other and to control a plurality of audio signals obtained by mixing the plurality of audio signals so that the sound pressure of the audio signal is temporally constant. A coefficient value of the multiplication coefficient is created by calculation. The plurality of multiplying means respectively multiply a plurality of audio signals read from the storage means by the storage control means and a plurality of multiplication coefficients calculated by the plurality of calculating means. The mixing means mixes the plurality of audio signals multiplied by the multiplication coefficient. Then, a pitch change is performed on the audio signal input to the storage means while keeping the sound pressure constant. Further, according to the third aspect of the present invention, the plurality of calculation means are configured to make the sum of squares of the plurality of multiplication coefficients constant in order to keep the sound pressure of the audio signal mixed by the mixing means constant over time. Calculate so that According to the fourth aspect of the present invention, the plurality of arithmetic means realized as a part of the microprogram for controlling the operation of the signal processing device execute each of the plurality of multiplication coefficients by executing the microprogram. A coefficient value and a plurality of audio signals are calculated.

[0014]

An embodiment of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing a configuration of a pitch change circuit to which the signal processing apparatus according to a first embodiment of the present invention, in this figure, an input terminal 14 to the audio data D _I is inputted, 15 is a delay For R
An AM, along with the audio data D _I input from the input terminal 14 to output the write address WA from the address generating circuit 16 shown in FIG. 2 is written, read address RA ₁ is outputted from the address generating circuit 16 and audio data D _D1 and D _D2 which is the pitch modulation from RA ₂ is read.

In the address generation circuit 16 of FIG.
Reference numeral 7 denotes a subtraction counter which performs a countdown operation in synchronization with the sampling frequency φ and outputs a write address WA. The subtraction counter 17 is provided in the delay RAM 15.
Counting down from the last address to the top address sequentially, and counting down to the top address,
The countdown is performed again from the last address. 18 is
As shown in FIGS. 4A and 4B, a low-frequency oscillator (LFO) for outputting sawtooth-shaped low-frequency data D _L1 and D _L2 180 ° out of phase with each other. An adder 20 adds the low-frequency data D _L1 and outputs a read address RA _1, and an adder 20 adds the write address WA and the low-frequency data D _L2 and outputs a read address RA ₂ .

According to such a configuration, the audio data D _I is written in the delay RAM 15 in order from the last address to the top address, and the low-frequency data D _L1 and D _L2 are written in the write address WA. The audio data D _D1 and D _D2 stored at the read addresses RA ₁ and RA ₂ respectively added are read from the delay RAM 15. Low-frequency data D to be added respectively to the write address WA in order to obtain a read address RA ₁ and RA _{2
Since L1} and D _L2 are serrated, the read address RA ₁
And RA ₂ are sequentially delayed with respect to the write address WA, and the pitch of the audio data D _D1 and D _D2 is reduced according to the inclination of the sawtooth-shaped low-frequency data D _L1 and D _L2 .

In FIG. 1, reference numeral 21 denotes an input terminal to which a multiplication coefficient A (0.ltoreq.A.ltoreq.1) having the characteristic shown in FIG. ) To obtain a multiplication coefficient (1) having the characteristic shown in FIG.
-A), the arithmetic unit 23 outputs √ for the multiplication coefficient A
an arithmetic unit that performs an operation of x and outputs a multiplication coefficient √A, 24
Is an arithmetic unit that performs an operation of √x on the multiplication coefficient (1-A) and outputs a multiplication coefficient √ (1-A). 25 is a multiplier for multiplying the audio data D _D1 by the multiplication coefficient √A,
26 is a multiplier for multiplying the audio data _DD2 by the multiplication coefficient √ (1-A); 27 is an adder for adding the output data of the multiplier 25 and the output data of the multiplier 26; output data is output is output as the audio data D _O.

FIG. 3 is a block diagram showing the configuration of the arithmetic unit 23. In FIG. 3, reference numeral 29 denotes an input terminal to which input data _xn is input, 30 denotes a subtractor to which input data _xn is input to a first input terminal, and 31 denotes output data of the subtractor 30 to a first input terminal. Is input, and 32 is an adder 3
An output terminal 1 of the output data is output as the output data y _n. 33 the output data of the adder 31 is delayed by one calculation time period is a delay circuit for outputting a data y _n-1, the data y _n-1 is input to the second input of the adder 31 At the same time. The multiplier 34 squares the data y _n-1 and outputs the output data y _n-1 ²
To the second input terminal of the subtractor 30.

Here, when the operation of the arithmetic unit 23 is expressed by a recurrence equation, the following equation (1) is obtained. In _{y n = x n -y n-} 1 2 + y n-1 ··· (1) (1) formula, when x _n = A, data y _n n →
Extreme for ∞, because the roots of a quadratic equation representing the convergence to (2), y _n = {square root} A is obtained from the arithmetic unit 23. y = A−y ² + y (2) Since the arithmetic unit 24 has the same configuration as the arithmetic unit 23, the description thereof is omitted.

[0020] In this arrangement, when the audio data D _I is inputted from the input terminal 14, generated by the address generating circuit 16, together with the audio data D _I is written to the write address WA of the delay RAM 15, generated by the address generating circuit 16, the audio data D _D1 and D _D2 from the read address RA _'1 and RA' ₂ is the pitch modulation delay RAM15 is read out.

On the other hand, the multiplication coefficient A (0) input from the input terminal 21 and changing like the waveform shown in FIG.
.Ltoreq.A.ltoreq.1, the operation unit 22 performs the operation of (1-x), and the operation unit 22 outputs the multiplication coefficient (1-A). The multiplication coefficient 乗 算 (1-A) having the characteristics shown in FIG. In addition, the arithmetic unit 23 performs an operation of √x on the multiplication coefficient A, and the arithmetic unit 2
3 outputs a multiplication coefficient √A having the characteristic shown in FIG.

Thus, the multiplier 25 multiplies the audio data D _D1 by the multiplication coefficient √A, and
6 multiplies the audio data _DD2 by the multiplication coefficient √ (1-A), the adder 27 adds the output data of the multiplier 25 and the output data of the multiplier 26, and outputs the pitch-changed audio. through an output terminal 28 as data D _O.

As described above, conventionally, the multiplication coefficient A
And (1-A) in multipliers 25 and 26
Since the audio data _DD1 and _DD2 are directly multiplied, the multiplication coefficients A and (1-A) change from 0 to 1 and from 1 to 0 as shown in FIG. Although the sound output from the speaker (not shown) has a perceived audible volume that is periodically reduced to provide the tremolo effect, according to the first embodiment described above, the multiplication coefficients √A and √ Since (1-A) is multiplied by audio data D _D1 and D _D2 in multipliers 25 and 26, respectively, as shown in FIG. 5B, the multiplication coefficients A and (1-A) are 0 to 1 and 1 to 0
Also at the part where the transition is made, the sound volume is smoothly connected without lowering the audibility.

Next, a second embodiment of the present invention will be described. FIG. 6 is a block diagram showing a configuration of a pan circuit to which a signal processing apparatus according to a second embodiment of the present invention is applied. In this figure, parts corresponding to the respective parts in FIG. Description is omitted. In FIG.
35 a multiplier for multiplying the multiplication coefficient √A audio data D _I, the output terminal 36 is the output data of the multiplier 35 is output as the audio data D _OR the R channel,
37 audio data D _I and the multiplication factor √ (1-A) and a multiplier for multiplying, 38 output data of the multiplier 37 is L
This output terminal is output as audio data D _OL of the channel.

In such a configuration, the multiplication coefficient A is set to 0
From 1 to 1, the sound radiated from the speakers (not shown) connected to the output terminals 36 and 38 spatially pans from left to right, and conversely, changes the multiplication coefficient A from 1 to 0. Then, the sound radiated from the speakers (not shown) connected to the output terminals 36 and 38 spatially pans from right to left.

In this case, when the power corresponding to the sound of one channel is P ₀ , the power corresponding to the sound of the R channel is A × P ₀ , and the power corresponding to the sound of the L channel is (1-1). A) × P ₀ , so that the power of the audible sound, that is, the sound pressure, at the portion spatially equidistant from the left and right speakers (not shown) is represented by the multiplication coefficient A, as shown in equation (3). Is kept constant regardless of the value of. A × P ₀ + (1−A) × P ₀ = P ₀ (3)

In each of the first and second embodiments described above, in each case, the multiplication coefficients √A and √ (1−1) for pitch change and panning using the arithmetic units 23 and 24 are used. By obtaining A), the sound volume perceived by the sound was kept constant even in the portion where the multiplication coefficient A changed from 0 to 1 and from 1 to 0.

Next, on the basis of the above-described technical idea, contrary to this technical idea, the multiplication coefficient A changes from 0 to 1 and 1
It is also conceivable to increase or decrease the volume of the sound perceived in the transition from 0 to 0. The function x ² , (2x−x ² ) or ³ √
x or the like may be used. These functions x ² , (2x−
7 to 9 show the configurations of the computing units 39 to 41 for computing x ² ) and ³ √x.

In the computing unit 39 in FIG. 7, a multiplier 42 squares the input data x. In a computing unit 40 in FIG.
43 is a multiplier for multiplying the input data x by the multiplication coefficient 2;
44 is a multiplier for squaring the input data x, and 45 is a multiplier 4
3 is a subtractor for subtracting the output data of the multiplier 44 from the output data of No. 3. Further, in the arithmetic unit 41 of FIG.
Is a subtractor to which input data _xn is input to a first input terminal,
47 is an adder to which the output data of the subtractor 46 is inputted to the first input terminal, 48 is a delay circuit for delaying the output data of the adder 47 by one operation time and outputting it as data yn _-1 ; The data y _n-1 is input to a second input terminal of the adder 47 and is input to a multiplier 49 that squares the input data. 50 is a multiplier for multiplying the output data y _n-1 ² and the data y _n-1 of the multiplier 49, and inputs the output data y _n-13 to the second input of the subtractor 46.

Here, when the operation of the arithmetic unit 41 is represented by a recurrence equation, the following equation (4) is obtained. In _{y n = x n -y n-} 1 3 + y n-1 ··· (4) (4) equation, when x _n = A, data y _n n →
Extreme for ∞ is converged, (5) since the roots of a cubic equation in the expression, y = ³ {square root} A is obtained from the arithmetic unit 41. y = A−Y ³ + y (5)

The arithmetic units 39 to 41 described above are replaced with the above-described pitch change circuit (see FIG. 1) and pan circuit (see FIG. 6).
12), or provided at the multiplication coefficient input terminals of the multipliers 3 and 4 of the cross-fade circuit in FIG. 12, the multiplication coefficients A ² , (2A
−A ² ), √A or ³ √A changes as shown in FIG. 10 with respect to the change of the multiplication coefficient A, whereby the sound pressure P on the audibility is changed in accordance with the change of the multiplication coefficient A. As shown in FIG. 11, an unprecedented sound effect can be obtained.

For example, when the arithmetic units 39 to 41 are applied to the pan circuit shown in FIG. 6, the localization of the sound image moves right and left, and the localization of the sound image moves away from or near the listener. When the arithmetic units 39 to 41 are applied to the cross-fade circuit shown in FIG. 12, when the audio data D _{I1 is switched} to the audio data D _I2 , or when the audio data D _{I2 is switched} to the audio data D _I1 , The sound pressure can be reduced to make it less noticeable, or conversely, the sound pressure can be made more noticeable.

The pitch change circuit described above,
As described above, since the pan circuit and the cross-fade circuit are configured by the signal processing device (DSP), a microprogram corresponding to these circuits is actually executed in the DSP. Therefore, the arithmetic units 23, 24, and 39 to 41 described above can be easily realized, so that the conventional linear interpolation technique can be used as it is, and there is no need to add a special circuit.

[0034]

As described above, according to the present invention, in the case where the pitch is changed by crossfading, the configuration such as the table storing the multiplication coefficients can be omitted, so that the memory capacity can be reduced and the configuration can be reduced. The scale can be increased. In the inventions according to claims 2 and 3,
Since the multiplication coefficient is calculated so as to keep the sound pressure constant at the time of the pitch change, when the pitch of the audio signal is changed, only the pitch changes and the sound pressure becomes constant, which is optimal in the pitch change. Conventionally, since the sound pressure is not constant at the time of pitch change, the volume of the sound is periodically reduced due to hearing, and as a result, an unexpected tremolo effect is provided.
According to the invention described in the third aspect, it is possible to prevent such a problem from occurring. Further, in the case where the pitch is changed by crossfading, the sound pressure is always constant throughout the time when the pitch changes. In the invention according to claim 4, a microprogram corresponding to a pitch change circuit or the like is executed on the signal processing device.
A plurality of arithmetic means can be realized without changing the conventional circuit configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a pitch change circuit to which a signal processing device according to a first embodiment of the present invention is applied.

FIG. 2 is a block diagram showing a configuration of an address generation circuit 16;

FIG. 3 is a block diagram showing a configuration of a computing unit 23.

4 is a diagram showing an example of a read address RA _'1 and RA' ₂ of an example and each part of the multiplication coefficient output from the waveform of the circuit shown in Figure 1 of the waveform.

FIG. 5 is a diagram for comparing and explaining the first embodiment of the present invention and a conventional technique.

FIG. 6 is a block diagram showing a configuration of a pan circuit to which a signal processing device according to a second embodiment of the present invention is applied.

FIG. 7 is a block diagram illustrating a configuration of a computing unit 33.

FIG. 8 is a block diagram showing a configuration of a computing unit 34.

FIG. 9 is a block diagram illustrating a configuration of a computing unit 35.

FIG. 10 is a diagram illustrating an example of characteristics of multiplication coefficients A, A ² , (2A−A ² ), √A, and ³ √A.

FIG. 11 is a diagram illustrating an example of characteristics of power P on audibility with respect to multiplication coefficients A, A ² , (2A−A ² ), √A, and ³ √A.

FIG. 12 is a block diagram illustrating a configuration example of a conventional crossfade circuit.

FIG. 13 is a diagram illustrating an example of characteristics of multiplication coefficients k ₁ and k ₂ .

FIG. 14 is a block diagram illustrating a configuration example of a conventional pan circuit.

FIG. 15 is a diagram for explaining inconveniences of the pan circuit shown in FIG. 14;

[Explanation of symbols]

22 to 24, 39 to 41: arithmetic unit, 25, 26, 3
4, 35, 37, 42 to 44, 49, 50 ... multiplier
27, 31, 47 ... adder, 30, 45, 46 ... subtractor, 33, 48 ... delay circuit.

Claims (4)

(57) [Claims] 1. A storage device having one input terminal and a plurality of output terminals, an audio signal is written to the input terminal in the storage device, and the writing speed from the plurality of output terminals is determined. Read out the audio signal at different speeds, and storage control means for controlling the phases of the read multiple audio signals to be different from each other, and cross-fading the multiple audio signals to each other, A plurality of calculating means for calculating a coefficient value of a plurality of multiplication coefficients for controlling a temporal sound pressure change of a plurality of audio signals; and the plurality of audio signals read by the storage control means and the plurality of A plurality of multiplying means for respectively multiplying the multiplication coefficient and a plurality of audio signals multiplied by the multiplication coefficient; That mixture and means, signal processing apparatus temporal variation of sound pressure with respect to the input audio signal in the storage means and performing a pitch change controlled. 2. A storage device having one input terminal and a plurality of output terminals, and an audio signal is written to the input terminal in the storage device, and the writing speed from the plurality of output terminals is determined. Read out the audio signal at different speeds, and storage control means for controlling the phases of the read multiple audio signals to be different from each other, and cross-fading the multiple audio signals to each other, A plurality of operation means for generating coefficient values of a plurality of multiplication coefficients for controlling the sound pressure of an audio signal obtained by mixing a plurality of systems of audio signals so as to be constant over time; A plurality of multiplying means for multiplying the plurality of systems of audio signals by the plurality of multiplication coefficients, respectively; Comprising a mixing means for mixing the audio signals of a plurality of systems which, signal processing apparatus and performs pitch change while maintaining the sound pressure constant with respect to the input audio signal in the storage means. 3. The plurality of calculating means performs a calculation so that the sum of squares of the plurality of multiplication coefficients is constant in order to keep the sound pressure of the mixed audio signal constant over time. 3. The signal processing device according to claim 2, wherein: Wherein said signal processing device operation control is performed by executing a microprogram, said plurality
The calculating means is realized as a part of the microprogram , and calculates each coefficient value of the plurality of multiplication coefficients and the plurality of audio signals. Item 4. The signal processing device according to any one of Items 1 to 3.