JPS5913680Y2 - Vocoder compression/expansion circuit - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a compression/expansion circuit in a vocoder.

Analyzing the frequency spectrum of a human voice signal, detecting the amplitude value of the analyzed spectrum component with an amplitude value detection circuit,
The same analysis as above is performed on audio signals from other sound sources, and each frequency spectrum component of the audio signal obtained from the analysis result is transmitted to the corresponding one of the above-mentioned ones via a voltage-controlled variable gain amplifier controlled by the detection signal. In a vocoder that controls and sends out signals based on each spectrum component of an input voice signal, when using an audio signal sent out by a performance of an electric musical instrument, an electronic musical instrument, etc. as the sound source for the above, the audio signal is converted into a voice signal. When controlled, the performance can be performed as if it were a chorus.

A vocoder configured as described above requires an amplitude value detection circuit and a voltage-controlled variable gain because it handles microphone input signals with extremely wide bandwidths and dynamic ranges, and musical sound signals from electric and electronic musical instruments. Although it is necessary to widen the dynamic range of the amplifier to a range sufficient for the musical tone signal, doing so is not very desirable as it increases costs.

Therefore, if you try to obtain the same effect by adding a compression/expansion circuit to a vocoder, the conventional compression/expansion circuit shown in Fig. Due to the additive effect, changes in musical instrument performance could not be faithfully conveyed.

That is, in FIG. 1, VO is a vocoder, 1L is a compression circuit, and M is an expansion circuit.The compression circuit and the expansion circuit M constitute a compression/expansion circuit N. A part of the output signal of the amplifier A1 that amplifies the signal Vin input from the input terminal I is supplied to the voltage controlled variable gain amplifier A3.
Negative feedback is applied to the input side of the amplifier A1 via the voltage controlled variable gain amplifier A3. Its gain is controlled by a signal.

Further, the expansion circuit M includes a voltage-controlled variable gain amplifier A2 that inputs the output audio signal of the vocoder-VO, and also receives a part of the output audio signal as input, detects its amplitude value, and uses the detected signal to input the voltage-controlled variable gain amplifier A2. and an amplitude detection circuit E2 that controls the gain of the gain amplifier A2.

The human power signal Vi to the compression/expansion circuit N in such a configuration
The relationship between n and the output signal Vout will be explained.

The input signal voltage is 1, the amplification degrees of the amplifier A1 and the voltage controlled variable gain amplifier A3 are a1, a3, 21 points, respectively.
The signal voltage at point P2 is determined by ■2. 3. Set the output signal voltage to v4, amplitude detection circuit E1. The output signal voltage of E2 is vCl and Vc2, respectively, and the transfer function of vocoder-VO is α
and K2. 3. 4. 5. Ka, Kb are constants, v
2aVe and v3aVe are respectively ■2. If it represents the average value of the amplitude of V3, then if the output signal of the vocoder-VO has no time delay with respect to the input signal, it can be said that V3aVe=αv2aVe, so the following equation holds true.

However, the following relational expression is quoted in the above equation.

2v2aVe to VCl-, 3■3aVeα3 to Vc2
= to 2KaV2aVe, to 4= to 3Kbv3aVeV4
Since Vout and Vl are Vin, the formula is vO
It is expressed as 5α2Vinte in ut=.

Therefore, if the transfer function α of the vocoder vO changes,
Since the output signal Vout changes in proportion to the square of the transfer function α, if a sound source of an electronic keyboard instrument is used as the sound source of the vocoder and the audio signal from the sound source is controlled by keyboard operation, the output signal Vout changes in proportion to the square of the transfer function α. The volume changes according to the number of keys, which is the same as changing the transfer function α, and by providing the compression/expansion circuit N, the volume changes depending on the key press, and when using the tremolo effect, etc. The change in volume becomes larger than necessary and unnatural.

The present invention provides a compression/decompression circuit that does not suffer from the above-mentioned drawbacks.

FIG. 2 is a circuit block diagram showing an embodiment of the compression/expansion circuit according to the present invention, and the output signal of the amplitude detection circuit E that detects the amplitude of the input signal Vin is common to both the compression circuit L and the expansion circuit M. is supplied as a control signal.

The relationship between the input signal Vin to the compression/expansion circuit N' and the output signal Vout in the above configuration according to the present invention will be explained.

Voltage controlled variable gain amplifier A2. The amplification degree of A3 is α.

, the output signal voltage of the amplitude detection circuit E is Vc, and the transfer function of the circuit E is K.

Assuming that the closing and other aspects follow the description of the noise suppression circuit N, Vc=KOV1aVe, α.

= 1 ■ c, °, α. = KoK Engineering ■ 1aVe (However □
is a constant.

)Kokote α1KoK1V1aVe) If 1, ■4 is V
out, Vl is Vin, so the formula ■ is Vout
=αVin.

Therefore, when using the compression/expansion circuit N' according to the present invention,
Transfer function α and output signal V of the vocoder-VO, which is the transmission system
It is proportional to out, and the volume changes naturally as the number of keys pressed increases or decreases.

Note that when a peak detection circuit is used as the amplitude detection circuit E, the sudden rise of the input signal Vin to the input terminal ■ can be faithfully compressed, and the maximum amplitude of the input signal can be kept constant. It is possible to prevent excessive input from being applied to VO.

It goes without saying that the same effect can be obtained even if the amplitude detection circuit E is provided independently for the compression circuit L and the expansion circuit M.

In addition, in the vocoder-VO, when delaying the audio signal using a delay circuit, the output signal of the amplitude detection circuit E input to the expansion circuit M is inputted via a delay circuit equivalent to the above-mentioned delay circuit. do it.

As described above, the compression/expansion circuit according to the present invention can be applied to a vocoder.
It is effective when the volume changes (the transfer function changes) regardless of the level or level of the input signal, such as a vocoder.
It is very effective when used.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram for explaining a conventional compression/expansion circuit used in a vocoder, and FIG. 2 is a circuit block diagram for explaining a compression/expansion circuit according to the present invention. ■・・・Input terminal, O・・・Output terminal, A
1...Amplifier, A2. A3... Voltage variable gain amplifier, E, El. E2...Amplitude detection circuit, Pl, P2...
・Point in the circuit, L... Compression circuit, M...
・Expansion circuit, N, N'... Compression/expansion circuit, V
O・・・Vocoder

Claims (2)

[Scope of utility model registration request] (1) In a compression/expansion circuit used in a vocoder that receives a voice signal and outputs a human vocal tone imitation signal similar to the pronunciation of the voice signal by the voice signal of another sound source, 1. A compression/expansion circuit for a vocoder, characterized in that an amplitude value detection signal of an amplitude detection circuit for detecting an amplitude value is used as a control signal for the compression/expansion circuit. (2) The compression/expansion circuit according to claim 1, wherein the amplitude detection circuit is of a peak detection type.