SU1554012A1 - Device for reducing noise of sound record during playback - Google Patents

Abstract

The invention can be used in audio reproduction equipment, namely, in tape recorders, electrophones, reportage audio reproducing devices, etc. The purpose of the invention is to expand the dynamic range of the operation threshold by automatic adjustment. A noise control device containing a control channel, the input of which is the input of the entire device and the output connected to the input of the amplitude detector, as well as a controlled low-pass filter with a field-effect transistor, introduces a device for additional signal processing in the form of two integrating chains with different constant values time, depending on the sign of the change in the amplitude of the signal, with one of the integrating chains connected between the output of the amplitude detector and the gate of the field-effect transistor, and the other between the divide A voltage source connected to the output of the amplitude detector and a source of the field-effect transistor. 4 il.

Description

The invention relates to the accumulation of information, namely, the technique of sound reproduction, and can be used in various sound reproduction techniques.

The purpose of the invention is to expand the dynamic range of the device by automatically adjusting the threshold.

Fig. 1 shows a block diagram of the device according to the invention; Fig. 2 shows an example of a specific implementation of the block of additional signal processing; Fig. 3 is an example of a phonogram with a varying level of noise processed by a noise-reducing device.

with a fixed threshold level, in Fig. 4, the same phonogram processed by a device with an additional processing unit.

The device contains a control channel 1, an input connected to the input terminal of the device, and an output through an amplitude detector 2 and a divider 3. voltage - to one input of block 4 for additional signal processing, the other input of which is connected to another output of detector 2. The output of block 4 is connected to one input of a controlled low-pass filter 5 (LF), the other input of which is connected to the input terminal of the device.

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The additional signal processing unit k contains two iodine-integrating chains 6 and 7 connecting the output of the detector 2 and the output of the divider 3 to the control inputs of the low-pass filter 5 whose control element is the field effect transistor VT.

The gate of the transistor VT is connected to the output voltage of the detector (in

11dEG) through the integrating chain VD, shunted by the elements Rd and C, with a different time constant when the sign of yIdeg changes, When the signal e increases, the signal goes to the gate of the transistor VT, through the direct resistance of the diode Wg, while lcd decreases diode VI) r is closed by the remaining voltage on C,

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Tzdg will be determined by the resistor 69 at the same time Tedg maximum. Element R6 and Cf are chosen so that 5DTA (is 0.1-0.2 cs a

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The source of the transistor VTf is connected to the side of the output voltage DC (point o, in Fig. 2) through the diode-integrating chain 7 and the VD diode, shunted by the elements RJ- and Cz, the time constant T of this circuit is different for different signs, With an increase in UB% 1, the value of Tmsgdae is determined by the elements R3- and C2 and has a maximum value of Tistmks (i.e. within 1 -2 s), at decreasing 35

U, 4 element RJ-shunted by diode VD, in the forward direction and ti, g minimum (0.05 s).

Thus, the tran tor VT is under dual control, which operates as follows.

The device works as follows.

Until the signal at the input of the entire device has reached a certain Unoco threshold. At which the voltage between the detector output and point a is significantly greater (positive), the cut-off voltage of the transistor VT ,, is closed and the division factor 50 for the transmitted signal has a maximum value.

When increasing the input signal to a value of U6K, the voltage is

between the gate of the transistor VTy and its source on which prek remains (its voltage value, remembered by the capacitance C2, will be less (den

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more) VOK of transistor VT {, in the result of which the latter will open through T} l; gmin, However, if the signal does not exceed a certain value

ip0r Акс Ax T ° when over the 3 potential of the source of the transistor VT, through the element R5 is compared with the voltage of point a, the transistor VTf is again closed, because in a certain range Usx from UWP (up to 1} across the P Mllx the voltage between has more positive values compared to the U0rc of the transistor VT, as a result of which the device again goes into suppression mode.

level. When the value of Ug ,, is greater than U / w, the voltage between the detector output and point a. less than Uort of the transistor VT and the last all the time open. At the same time, the SNF 5 has a maximum transmission coefficient and a maximum frequency range.

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When reducing the input signal

from NRM to sight between Unop.kc. and "OP" (7, and t from the transistor (VT decreases to voltage) (point of contact through the direct resistance of the diode VDr 33 T c7 / and "" However, i3dg will take the value UAe7- through Tslt. mlks because the VDa diode in In this case, the transistor VT1 is closed only through Tzl / mlks and goes into suppression mode. Thus, when playing a phonogram, its front t and back edges will go to the device output without distortion to the value UOOPOS. Untfp is rebuilt to a new value: with increasing iD, MIND Uff (7 is rebuilt during the time TzGmdks (s) In real terms, this time significantly overlaps with the time of the phonogram (Fig. 4). When the UWVM is reduced, it is rebuilt during the time of the ZGD (0.1-0.2 s), i.e., the noise (background) during pauses is not suppressed fixed value, and within a certain range, while the useful signal is not attenuated within the same range.

The range of response level adjustment (tracking) in real devices is 10-12 dB. This means that when VMC.O is installed on UR °, the level of -50 dB noise and background in the pauses will be

1

FIG. 2

 ist on cop. FIG, H

Editor A.Revin

Compiled by I. Makarenko

Tehred M. Hodaaich Proofreader L. Bezkid

Order 459

Girazh 488

VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab. 4/5

".." ..-. "-. - --.- - - - - - ". - - - - - and. „.-, - - - - -. - - - - - - - - Production and Publishing Combine Patent, Uzhgorod, ul. Gagarin, 101

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Claims (1)

Claim A device for reducing the sound of a phonogram during playback, comprising a controlled low-pass filter, the input and output of which are the input and output of the device, and a control channel, the input of which is connected to the input of the controlled low-pass filter, and the output is connected through an amplitude detector to the control input of the latter, characterized in that, in order to expand the dynamic range of operation by automatically adjusting the response threshold, a first-ray diode-integrating circuit is included in it, connected between yield ampli10 'tudnogo detector and control managed -Log lowpass filter and a voltage divider connected in series and the second diodnointegriruyuschaya circuit connected between the output of the amplitude detector 15 and an additional control input managed lowpass filter. FIG. 1 —Hl · / to the input -HV # control channel 1 output, Figure 2.