JP2009094991A - Envelope formation technology - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a downward envelope follower, capable of maintaining sufficient amplitude operation ratio, while reducing bumpings by breezing by tape hiss noise, etc. and detection of dark noise, and to provide a noise removing apparatus, and a small volume enhancing apparatus which is optimized for acoustic sensation. <P>SOLUTION: A CV to be generated is shaped by automatically varying the amplitude operation ratio, by providing an inclination change means in the downward envelope follower and providing various unipolar nonlinear passage means, and the downward envelope follower optimized for acoustic sensation is attained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an envelope generation technique in an amplitude operation device (dynamics processor), and is particularly suitable for hearing in a noise reduction device (downward expander) and a small volume enhancement device (downward compressor). Envelope envelope follower technology and method.

With the widespread use of BD, HD-DVD, and terrestrial digital TV, audio sources having a high dynamic range have become common. However, when enjoying these in a normal listening environment, there may be a problem that a small signal cannot be heard, the volume of the CM is particularly high, and the volume is too loud.

In order to solve such problems, TV sets and AV components incorporating AGC (Automatic Gain Control) are on the market. The same problem also occurs in various media that secondary use these sound sources, so the sound person can change the volume appropriately, or use an amplitude compression device (upward compressor), amplitude limiter (upward limiter) Listening sound is averaged.

However, such an amplitude operation method causes problems related to the operation time constant, such as gradually increasing the volume of a small volume that is desired to be heard clearly, or suddenly decreasing the volume of a large volume that is desired to be lowered. . If the person in charge of the sound changes the sound volume appropriately, it will change while confirming the change in the sound volume, so if it is done properly, it will be optimal for hearing, but the amplitude operation start time (attack time) will be Because it depends on the sense and motor ability, it is difficult to manipulate the amplitude with a transient signal.

For these reasons, in situations where saturation of the transmission system is not allowed, the common use of the amplitude limiting device and the variable volume by human hands is common. However, TV sets and AV components are not realistic methods, but are supported by combining and optimizing various amplitude operation devices such as AGC.

In recent years, the use of a digital amplitude manipulating device has become common, but since it is ineffective for saturation before AD conversion, the digital amplitude manipulating device must also be used as an amplitude limiting device in an analog stage.

As a technique of recording art, it is well known to change the tone color of a drum set using a harmonic component generated by altering a signal waveform by an amplitude operation device or to imitate a guitar by deforming an envelope. However, except for such an example, an ideal amplitude operation device is considered to have zero amplitude operation start time (attack time) and amplitude operation release time (release time).

However, it is difficult to design a low distortion circuit by using a non-linear element such as a diode or a transistor, using a soft clip circuit, a bridge circuit, or a clamp circuit. Usually, in order to realize satisfactory characteristics for acoustic use, a multiplication type amplitude manipulating apparatus using a voltage control resistor or a voltage controlled current source for amplitude manipulation is used.

The multiplication type amplitude operation circuit realized by an analog circuit generates an amplitude operation by generating a multiplication control signal (hereinafter referred to as CV) from the input signal and multiplying the input signal. It is impossible to make it zero. For this reason, by designing a circuit for the amplitude operation start time and amplitude operation opening time when the auditory sensitivity is reduced, practically, the method of approximating the amplitude operation time to zero (see Patent Document 1), the spectrum and amplitude of the signal Methods have been devised (see Patent Document 2 and Patent Document 3) that attempt to improve the sense of incongruity by changing the adaptation accordingly.
PEAK ACCELERATED COMPRESOR United States Patent 5,463,695 WAVE DEPENDENT COMPRESOR United States Patent 5,483,600 FREQUENCY DISCRIMINATE LEVELER United States Patent 5,422,602

In the prior art, by giving frequency characteristics to the CV generation process, zero approximation of the amplitude operation time and improvement of the sense of discomfort are realized. However, when a noise removal device or a small volume emphasis device is configured using the CV generated here, in particular, a sound source having a relatively large level, such as tape and hiss noise, has a spectrum in a wide range, and it becomes unpleasant due to earing. .

The main reason is that the CV linearly shifts from the linear operation to the amplitude operation operation, and the amplitude operation conforming to the loudness level curve is not performed. Therefore, it is desirable to automatically change the amplitude operation ratio in accordance with the signal amplitude in order to reduce unpleasant operations such as breathing and pumping.

The present invention is characterized in that a slope changing means is provided in a CV generating circuit and the amplitude operation ratio is automatically varied. In application to a noise removing device or a small volume emphasizing device, breathing, pumping, etc. particularly in a small volume portion. It is intended to reduce the unpleasant behavior of the.

In a noise elimination apparatus realized by a conventional multiplication type amplitude operation circuit, the gain when the input level is equal to or lower than the operation threshold is linearly reduced as shown in FIG. Further, in the low volume emphasis device realized by reversing the CV, the gain increases linearly when the input level becomes lower than the operation threshold as shown in FIG. 6. FIG. 3 shows the input of the linear amplifier shown for comparison. Output characteristics.

On the other hand, in the present invention, as shown in FIG. 2, by providing the slope changing means (9) in the conventional CV generating circuit, the CV operation along various functions is made possible. The noise elimination device using the CV achieves the gain characteristics as shown in FIG. 5, and the small volume enhancement device realizes the gain characteristics as shown in FIG.

Since the noise reduction device and the low volume emphasis device realized by the present invention function only below the operation threshold (downward), there is a feeling of suppression at a high volume like a general amplitude compression device or amplitude limiter. Does not occur. From this, it can be applied to sound pressure averaging of all acoustic signals that do not require intentional tone color change or envelope deformation, and is expected to be used for TV sets, AV components, and hearing aids.

Downward operation with less discomfort is optimally used for voice signals such as vocals as a sound pressure averaging technique for acoustic signals. In the application to vocoders and hearing aids, the clarity is increased, so that an unvoiced sound enhancement circuit is unnecessary, and the number of parts and MIPS can be reduced. In addition, use in a sustainer or noise gate can be expected to be incorporated into musical instruments and sound adjustment consoles because it can provide a lingering expansion and attenuation effect with little unpleasant motion.

In the circuit example of FIG. 1, an RMS conversion circuit (1) for detecting an input acoustic signal, a threshold setting circuit (3) for outputting a component equal to or less than a threshold set by a variable resistor from the RMS-converted input acoustic signal, and a threshold setting circuit (3) An inclination changing circuit (4) for changing the linear inclination characteristic of the output to a three-fold line inclination characteristic, an envelope information amplifying circuit (5) for amplifying a necessary change amount while reducing a DC component unnecessary for circuit operation, A time constant setting circuit (2) for setting an amplitude operation start time and an amplitude operation opening time, and a phase inversion circuit (6) for generating a CV for a small volume emphasis device.

The RMS conversion circuit (1) corrects auditory sensitivity with a simple logarithmic amplifier and an inverting amplifier, then performs envelope detection with two diodes to which a negative bias is applied, and outputs an effective value. This circuit gives hysteresis characteristics by performing positive feedback from the effective value output point to the simple logarithmic amplifier input, and reduces the sensitivity to unwanted noise such as tape and hiss noise, while having many DC approximate components like microphone pop. Effectively detect unwanted noise.

The threshold setting circuit (3) is a slice level setting circuit using a differential amplifier and is generally used in an amplitude operation device.

The inclination changing circuit (4) is a tri-fold line inclination generating circuit using a threshold value of a diode and a resistor voltage divider, and the inclination characteristic of this portion becomes a downward characteristic. Although it is a simple design in FIG. 1, it is possible to accurately follow the loudness level curve by adding a function of continuously changing the polygonal line inclination and frequency characteristics.

The envelope information amplifying circuit (5) is based on a linear amplifier, but since the envelope information is an effective value, the rising component corresponds to a positive voltage and the falling component corresponds to a negative voltage. In FIG. 1, by inserting a diode in the negative feedback loop, amplification to the rising component is stopped (through), and only the falling component is amplified. In this circuit example, the time constant setting circuit (2) performs zero approximation of the amplitude operation start time and the amplitude operation release time, but the amplitude operation start time by operating the amplification characteristic of the envelope information amplification circuit (5). Amplitude operation opening time operation is also possible.

The time constant setting circuit (2) varies the output point between a negative voltage and zero volts based on the asymmetric envelope information generated by the envelope information amplification circuit (5). In the circuit example of FIG. 1, since the CV input of VCA is fixed to EC + and used, a change in CV between negative voltage and zero volt means that the VCA operation changes from a downward operation to a through operation. A diode inserted in the input / output of the time constant setting circuit (2) by adjusting the slope changing circuit (4) and setting the positive voltage component in the output of the envelope information amplification circuit (5) to about 0.6 V to 0.2 V Envelope information is given to the breakdown voltage region, and the amplitude operation start time and amplitude operation release time are approximated to zero.

The phase inversion circuit (6) can be reduced by switching between the EC + terminal and the EC- terminal of the VCA. However, the phase inversion circuit (6) is generated at the same time in order to avoid complications around the EC + terminal and the EC- terminal.

The resistor connected to the positive / negative power source of the output of the time constant setting circuit (2) is for offset cancellation generated by a diode drop voltage when there is no signal. The VCA CV input used as a global standard has a sensitivity of 6 mV / dB, and the input is generally attenuated to about 1/30. Therefore, the voltage of 0.6 V is corrected to a gain offset of about 3 dB. Is required.

In a strict sense, the circuit example of FIG. 1 is a configuration in which the time constants in the RMS conversion circuit (1) and the threshold setting circuit (3) also affect the operation. The intention is as described above. The operation confirmation is based on the VCA circuit of FIG. 8 and the actual operation circuit of FIG. 9, and the variable resistor is for threshold setting (threshold level).

By applying the present invention to digital signal processing and making the inclination changing circuit (4) correspond to various senses such as vision and touch, adaptive detection of five sense vectors can be performed. From this, it can be used for motion detection of video signals, joint control technology in the robot field, and various vector detection of listeners in stereophonic sound reproduction using a speaker array system.

This is an embodiment constituted by an analog computing unit, a diode, a capacitor, and a resistor. FIG. 2 is a block diagram showing an outline of the circuit operation of FIG. 1. It is an example of the input-output characteristic of the audio equipment which does not have an amplitude operation function. This is an example of input / output characteristics of a conventional noise eliminator (downward expander). It is an example of the input / output characteristic of the noise removal apparatus (downward expander) by utilization of this invention. This is an example of input / output characteristics of a conventional low volume emphasis device (downward compressor). It is an example of a small volume emphasis device (downward compressor) input / output characteristic according to the present invention. It is the VCA circuit connected to FIG. It is an example of the actual circuit of FIG. 1 used for operation confirmation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RMS conversion circuit 2 Time constant setting circuit 3 Threshold setting circuit 4 Inclination changing circuit 5 Envelope information amplification circuit 6 Phase inversion circuit 7 RMS conversion circuit block diagram notation 8 Threshold setting circuit block diagram notation 9 Inclination changing circuit block diagram Notation 10 Envelope information amplifier circuit block diagram notation 11 Time constant setting circuit block diagram notation 12 Phase inversion circuit block diagram notation

Claims (6)

In the control voltage generation procedure in the amplitude operation device (dynamics processor), a down-ward envelope follower characterized by having a detection circuit that gives hysteresis characteristics and a slope changing means that automatically varies the amplitude operation ratio, and Noise reduction device (downward expander) and small volume enhancement device (downward compressor) realized by this downward envelope follower. In the control voltage generation procedure in the amplitude operation device (dynamics processor), when a control voltage is generated by providing a unipolar non-linear passage means at the input and output of the time constant setting circuit that sets the amplitude operation start time and amplitude operation release time Downward envelope follower characterized by shaping the rise time and fall time, and the noise reduction device (downward expander) and low volume enhancement device (downward) realized by this downward envelope follower ·compressor). In the control voltage generation procedure in the amplitude manipulator (dynamics processor), by providing a unipolar non-linear passage means in the envelope information amplification circuit, the rise time and fall time at the time of control voltage generation are shaped and changed independently. Downward envelope follower, and a noise reduction device (downward expander) and a low volume enhancement device (downward compressor) realized by this downward envelope follower. A vocoder that realizes an unvoiced sound enhancement function by a down-ward envelope follower using claims 1, 2, and 3. A hearing aid that realizes an unvoiced sound enhancement function by a down-ward envelope follower using claim 1, claim 2, and claim 3. Software and media including binary code that implements claim 1, claim 2, claim 3, claim 4, and claim 5 by digital signal processing (DSP).

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