SU1363489A2 - Apparatus for converting the dynamic range of audio signals - Google Patents

Abstract

This invention relates to a signal transmission technique. In relation to auth. No. 1058077, the object of the invention is achieved - to improve the accuracy of conversion of the dynamic range of an audio signal by correcting the frequency x-ki in the high-frequency region. The device contains a quadrature phase shifter 1, analog dividers 2 and 3, quadratic detectors 4 and 5, adders 6 and 8, correction blocks (VK) 7.9 and 10 and subtractor 11. At input signal levels that exceed the compression threshold, BC 9 and 10 provide the rise of frequency x-ki in the high-frequency region, which leads to a decrease in the amplitude-frequency x-ki device at these frequencies. As a result, in the output signal, the ratio of vowel and consonant levels is similar to their ratio in the input signal. The signal controlling the parameters of BC 9 and 10 is formed in the subtractor 11 and is equal to the difference between the threshold voltage and the voltage proportional to the function of the corrected Hilbert curve of the output signal. The goal is achieved by introducing BC 9 and 10 and subtractor 11. 3 Il. h (L out. 00 Od oo 4 oo with 1H

Description

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The invention relates to a technique for transmitting signals, mainly for recording and reproducing sound signals.

The purpose of the invention is to improve the accuracy of the dynamic range conversion of the audio signal by correcting the frequency response in the high frequency region.

Fig. 1 shows a block diagram of a device for converting the dynamic range of audio signals; FIG. 2 is a schematic diagram of an additional correction block; Fig. 3 shows the curves of the transmission coefficient (k) of the additional correction unit as a function of the magnitude of the control signal (Unnp) and frequency (& e).

The device for converting the dynamic range of audio signals contains a quadrature phase shifter 1, analog dividers 2 and 3, quadratic detectors 4 and 5, main adder 6, equalizer 7, additional adder 8, additional correction blocks 9 and 10, subtractor 11, The additional correction block contains operational amplifier 12, a serial circuit 13.

A device for converting the dynamic range of audio signals operates as follows.

At small input levels, sound signals, tfe. until the compression threshold, when the dynamic range of the signals is not converted, the control voltage applied to the denominators of analog dividers 2 and 3 is constant and proportional to the threshold voltage, therefore all the spectral components of speech are transmitted to the output of the device without distortion, linear and the action is additional blocks 9 and 10 of the correction for the amplitude-frequency characteristic of the device does not affect.

With input levels of signals that exceed the compression threshold, i.e. when the dynamic range of the audio signals is converted, the signals from the outputs of analog dividers 2 and 3 are fed to the inputs of additional correction blocks 9 and 10. Additional blocks 9 and 10 of the correction provide a rise in the frequency response in the high frequency range (5-7 kHz), which leads to a decrease in the amplitude-frequency characteristic

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The ticks of the device at these frequencies, thus in the output signal, are the ratio of vowel and consonant levels, similar to their ratio in the input signal. The signals corrected in this way arrive at the inputs of the channel for the formation of a control voltage consisting of two quadratic detectors 4 and 5, the main adder 6, the equalizer 7, the additional adder 8. The signal controlling the parameters of the correction circuit is formed in the subtractor 11 and is equal to the difference threshold voltage and voltage proportional to the function of the adjusted output Hilbert envelope. Additional correction blocks can be made in the form of bandpass or resonant amplifiers with adjustable bandwidth and gain.

The simplest method of instrumental implementation of an additional correction block is the selective amplifier shown in Fig. 2,

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built on an operational amplifier 1

12, in the feedback of which a serial loop 13 with an adjustable Q-factor and a transmission coefficient is included.

The resonant frequency of the serial loop is chosen equal to the frequency of suppression of the most obnoxiously sizzling or whistling consonants. With increasing degree of compression increases the value of the signal up-. the addition of the correction unit UuupjB, resulting in the resistance of the channel to the locomotive; On the transistor, the drain-source is reduced, and consequently, the Q-factor of the circuit increases and the transmission coefficient of the correction circuit increases. An increase in the quality factor of the contour, and, consequently, in the steepness of the correction of the amplitude-frequency characteristic of the device, is expedient, since with an increase in the degree of compression it is necessary to suppress only the spectral components of the obtuse-sounding consonants in the narrow

frequency range. In addition, in the proposed device, the control signal of the additional correction unit is tied to the compression threshold and does not depend on its value.

When implementing the device, additional blocks 9 and 10 of the correction were made switchable with three resonant frequencies: 5.6 and 7 kHz, the transmission coefficient of the additional correction block when compressing the dynamic range of speech signals by 10 dB also increased by 10 dB. The initial passband was chosen equal to 1 kHz with compression of the dynamic range of speech signals by 10 dB, the overshoot band decreased by about 3 times. v,

The proposed device for converting the dynamic range of the audio signal in comparison with the prototype improves the accuracy of converting the dynamic range of the audio signal by correcting the frequency response in the high frequency region.

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Claims (1)

Invention Formula A device for converting the dynamic range of audio signals according to Avtosv, No. 1058077, characterized in that, in order to improve the accuracy of the conversion of the dynamic range of the audio signal signal, by correcting the frequency response in the high-frequency region, a subtractor is introduced, while the outputs of the analog dividers are connected to the inputs of quadratic detectors through the corresponding input additional correction blocks, the first input of the subtractor is connected to the second input of the additional adder, and the second input of the subtractor is connected to the output of the corrector, the output of the subtractor is connected to the control inputs of the additional Correction blocks.  Upr1 Opr1 0upr3 13 Feyk. 2 WP F "c. 3 Editor T. Lazorenko Compiled by L.Ananyeva Tehred L.Serdkzhova Order 6381/54 Draw 636 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., D. 4/5 Production and printing company, Uzhgorod, Projecto st., 4 Proofreader S. Shekmar