JP6505546B2 - Sound effect giving device - Google Patents

Description

  The present invention relates to an acoustic effect providing device.

  2. Description of the Related Art Conventionally, a small and lightweight amplifier simulator that directly plugs in to an output jack of an electric guitar or the like is known. The amplifier simulator is a device that simulates the characteristics of a guitar amplifier or a cabinet. By using the amplifier simulator, when a musical tone is input to a line without passing through the amplifier, it is possible to obtain a tone as if it were reproduced through the amplifier.

  There are amp simulators that can be specialized and simulated to the characteristics of amps well-known for each genre of music, such as classical rock and pop, and there are also multi-effector functions in the amp simulator. Some are prepared. By connecting headphones to the amplifier simulator and playing an electronic musical instrument, the user can easily enjoy musical instrument performance even in an environment such as a home where the amplifier can not be used.

  Also, this amp simulator may be used as part of an effector of another electronic musical instrument.

  When such an amplifier simulator is configured, there is a method of realizing a desired characteristic using an FIR filter based on the measured frequency characteristic.

  However, when realizing arbitrary characteristics with the FIR filter, sufficient frequency resolution can not be obtained unless operations are performed with a high order. That is, the higher the order of the FIR filter, the higher the frequency resolution. Therefore, for example, to obtain double frequency resolution, it is sufficient to double the order.

  However, if the order is doubled, the amount of computation also doubles, and there is a problem that such an increase in load will affect other processes. FIG. 5 shows the measured characteristic of the amplifier (light line) and the approximation characteristic (dark line) by the FIR filter when the amplifier characteristic is approximated by the 63rd FIR filter, but in the vicinity of 100 Hz or 1 kHz, Already, the approximation characteristic by the FIR filter can not only follow the measured characteristic of the amplifier, but even at around 10 kHz, the approximation characteristic by the FIR filter deviates from the characteristic of the measured amplifier and can not follow I understand.

  The present invention was conceived to solve the above problems, and it is an acoustic effect that can improve the filter characteristics of various simulators (not limited to the amplifier simulator) without increasing the amount of calculation. It is intended to provide an application device.

According to the configuration of the present invention, at least a non-recursive first filter processing device for inputting an audio signal and imparting an arbitrary characteristic, and a circuit for inputting an output of the first filtering device and imparting an arbitrary characteristic An acoustic effect applying device having a second filter processing device which is
The first filtering device performs filtering by M multiplications using every other to constant number of coefficients of N non-recursive filters that realize desired characteristics. ,
The second feature of the present invention is basically that the second filter is to filter by L multiplications where N> M + L.

  In the above configuration, the non-recursive first filter processing apparatus (FIR filter in the embodiment to be described later) processes every other coefficient or every constant number of coefficients, thereby suppressing the amount of calculation. Arithmetic with a high order is performed, sufficient frequency resolution can be obtained, and it functions as an arbitrary simulator. On the other hand, the aliasing component generated in the first filtering device is removed in the second filtering device of the cyclic type (IIR filter in the embodiment described later). In this case, the sum (M + L) of the number of multiplications of the first and second filter devices is smaller than the number of multiplications N of the first filter device originally intended to be realized (N> M + L). While suppressing (reducing the calculation load), calculation with a high order can be performed and sufficient frequency resolution can be obtained.

  In the embodiment configuration described later, such a configuration is realized by the DSP, but is not limited thereto. Further, in the configuration of this embodiment, such a configuration is applied to the amplifier simulator, but it goes without saying that the configuration is also effective for other filter processing.

  According to the above configuration of the present invention, in the first non-recursive filter processing apparatus, every other coefficient or every constant number of coefficients is processed, so that the amount of calculation can be reduced and the degree can be increased. Arithmetic operations can be performed to obtain sufficient frequency resolution, and can function as any simulator. That is, while the sum (M + L) of the number of multiplications of the first and second filter devices is smaller than the number N of multiplications of the filter processing of the characteristic to be realized originally (N> M + L), the amount of calculation is suppressed. Also, the calculation with a high order is performed, and sufficient frequency resolution can be obtained, and the excellent effect that the filter characteristics of various simulators can be improved can be achieved.

  Hereinafter, embodiments of the present invention will be described together with illustrated examples.

  FIG. 1 is a block diagram showing an outline of a configuration of an amplifier simulator to which a sound effect application device according to the present invention is applied, centering on a digital signal processor (DSP) 100. As shown in FIG.

  As shown in the figure, the control panel 208 and the DSP 100 are connected to the system bus 200 via the CPU 202, the ROM 204, the RAM 206, and the panel scan circuit 208a. Input / output of command data to each part and timing control of those inputs / outputs are performed. That is, the system bus 200 controls the respective circuits connected thereto by the CPU 202 described later to function as an amplifier simulator.

  The ROM 204 stores a program memory (not shown) that stores programs used in the CPU 202 and the DSP 100 described later, and various necessary data (for example, coefficients used in the DSP 100).

  The RAM 206 temporarily stores various parameters, data, and the like generated under control of the CPU 202.

  The amplifier simulator is provided with an operation panel 208 and the like. The operation panel 208 is provided with switches for setting various effects that can be specialized and simulated to characteristics of an amplifier well-known for each genre of music, such as classical rock and pop. The information set from the operation panel 208 is detected by the scan of the panel scan circuit 208 a and the set value is detected, and is supplied to the CPU 202 via the system bus 200.

  The CPU 202 executes the program read from the ROM 204 to control the above-described components and perform data input / output processing, and the above-described circuits connected by the system bus 200 constitute an amplifier simulator. The program and necessary coefficient data used in the effect imparting unit 120 for applying the DSP 100 to the acoustic effect are read out from the ROM 204 and sent to the DSP 100, and an analog-to-digital converter is input from the line input. A sound effect necessary for musical tone data of a guitar 300 (an electric guitar or the like) input through an (A / D converter) 210 is added in an effect applying unit 120 in the DSP 100. At this time, the effect imparting unit 120 of the DSP 100 has the external memory 140 under control, and performs specific processing based on tone data input from the input terminal of the line input through the analog-digital converter 210. Then, the sampling data is written to the external memory 140, and the sampling data is read from the external memory 140 and output as musical tone data.

  Note that the sound data to which the sound effect is output from the DSP 100 is input to a digital-analog converter (D / A converter) 212 and converted into an analog signal, and the analog signal is converted there by the sound system 214. It is output from the headphones 310 etc. which were plugged in and connected.

  In the configuration of this embodiment, a program for using the DSP 100 for the acoustic effect application unit 120 and necessary coefficient data are read out from the ROM 204 by the CPU 202 and sent to the DSP 100 by the CPU 202, as shown in FIG. In the DSP 100, the FIR filter 120a and the IIR filter 120b are formed, and the effect imparting unit 120 is configured.

  The FIR filter 120a corresponds to the non-recursive first filter processing apparatus according to the present invention, which receives an audio signal and adds an arbitrary characteristic. Further, the IIR filter 120b corresponds to a cyclic second filter processing apparatus according to the present invention, which receives the output of the FIR filter 120a and gives an arbitrary characteristic.

FIG. 3 shows a schematic circuit configuration of the FIR filter 120a. As shown in FIG. 3, a delay circuit Z ^- 110 and a multiplier 12 for multiplying a predetermined coefficient sent from the ROM 204 by the CPU 202 are shown. , And an adder 14 for adding the value of the circuit. The difference between this circuit configuration and the normal one is that the coefficients of N (order N = 127 order) FIR (non-recursive) filters that realize characteristics such as a guitar amplifier are used alternately (between them) The coefficient given to the multiplier 12 is 0, and the portion thereof is not subjected to operation), which is to be filtered by M times of multiplication. The amount of calculation of the FIR filter 120a can be reduced as much as the calculation is not performed.

  On the other hand, the IIR filter 120b is configured of a low pass filter that performs filter processing by L times of multiplication where N> M + L.

  In the above configuration, the FIR filter 120 a processes coefficients every other filter (filtering is performed such that the desired amplifier characteristic is folded to the high frequency side), so the amount of computation is suppressed. However, the calculation is performed with a high order, a sufficient frequency resolution can be obtained, and the filter characteristic of the amplifier simulator can be improved.

  On the other hand, in the IIR filter 120b, for example, a low-pass filter calculation of about the third order is performed to sufficiently attenuate high frequencies, and aliasing components generated in the FIR filter 120a are removed.

  With the above configuration, the sum (M + L) of the number of multiplications of the FIR filter 120a and the IIR filter 120b is smaller than the number N of multiplications of the FIR filter of the characteristic to be realized originally (N> M + L). Even though the amount is reduced (calculation load is reduced), calculation with a high order is performed, and sufficient frequency resolution can be obtained.

  FIG. 4 shows the approximate characteristic by the 127th-order FIR filter 120a of the configuration of the present embodiment and the measured actual amplifier characteristic. However, unlike the case of FIG. It can be seen that the characteristics of the measured amplifier are sufficiently followed. As described above, the calculation amount of the FIR filter 120a is reduced as much as the calculation is not performed, and the low frequency side is considered to be important because the high frequency region above the 10 kHz is generally greatly reduced. However, it can be understood that the desired characteristics can be realized on the lower side.

  According to the configuration of the present embodiment described above, the FIR filter 120 a performs coefficient processing every other filter, and calculations with high order can be performed while obtaining a sufficient frequency resolution while suppressing the amount of calculation. And the sum of the number of multiplications of the FIR filter 120a and the IIR filter 120b (M + L) is smaller than the number of multiplications N of the FIR filter of the characteristic to be realized originally (N> M + L), calculation can be performed in a high order while suppressing the calculation amount, sufficient frequency resolution can be obtained, and filter characteristics of the amplifier simulator can be improved. Become.

  In the present embodiment, the configuration of the present invention is shown as the configuration of the amplifier simulator, but it is of course possible to use the configuration as part of an effect in an electronic keyboard instrument, for example.

  The acoustic effect application device of the present invention is not realized only by the above-described DSP, and can be applied to other circuit configurations. Further, in the above-described embodiment, such a configuration is applied to the amplifier simulator, but it may be effective in other filtering as well, so various changes may be made without departing from the scope of the present invention. Of course.

  The acoustic effect application device of the present invention is effective not only in the amplifier simulator but also in other filtering processes.

It is a block diagram which shows the outline of a structure of the amplifier simulator to which the acoustic effect provision apparatus which concerns on this invention was applied centering on DSP100. FIG. 6 is a functional block diagram showing a state in which the configuration of the effect imparting unit 120 is formed in the DSP 100, the FIR filter 120a and the IIR filter 120b. It is a schematic diagram showing circuit composition of FIR filter 120a. It is explanatory drawing which shows the approximation characteristic by the FIR filter 120a of a 127th present Example Example structure, and the measured actual amplifier characteristic. It is explanatory drawing which shows the approximation characteristic by the 67th conventional FIR filter 120a, and the actual amplifier characteristic measured.

10 delay circuit Z ^-1
12 multiplier 14 adder 100 DSP
120a FIR filter 120b IIR filter 200 system bus 202 CPU
204 ROM
206 RAM
208 Operation Panel 208a Panel Scan Circuit 210 Analog to Digital Converter 212 Digital to Analog Converter 214 Sound System 300 Guitar 310 Headphones

Claims (1)

At least a non-recursive first filtering device for inputting an audio signal and giving an arbitrary characteristic;
An acoustic effect application device having a cyclic type second filter processing device which receives an output of the first filter processing device and gives an arbitrary characteristic;
The first filtering device performs filtering by M multiplications using every other to constant number of coefficients of N non-recursive filters that realize desired characteristics. ,
2. A sound effect applying device characterized in that the second filter performs filter processing by L times of multiplication where N> M + L.