SU809596A2 - Device for measuring noise level in pauses of speech - Google Patents

Description

(54) DEVICE FOR MEASURING NOISE LEVEL IN SPEECH PAUSES

The invention relates to radio engineering and can be used to determine the level of noise in electroacoustic and radio telephone devices.

According to the main author. St. No 605322 A device for measuring the noise level during speech pauses contains a series-connected amplifier, amplitude detector, synchronous integrator, amplitude selector, first pulse counter, prohibition element, reversible adder, digital-to-analog converter, integrator, executive unit, as well as a second pulse counter and pulse generator . The output of the pulse generator is simultaneously connected to the second input of the synchronous integrator and to the counting input of the second pulse counter, the output of which is simultaneously connected to the zero input of the first pulse counter and the second input of the inhibit element, the second input of the reversible adder connected to the output of the first pulse counter, and the integrator output - to the second input of the amplitude selector WITH.

However, measurement in such a device requires a long time.

The purpose of the invention is to reduce the measurement time.

This goal is achieved in that a device for measuring the noise level during speech pauses, containing a series-connected amplifier, amplitude detector, synchronous integrator, amplitude selector, first pulse counter, prohibition element, reversible adder, digital-to-analog converter, integrator, executive unit, and

5 also a second pulse counter and a pulse generator. The output of the pulse generator is simultaneously connected to the second input of the synchronous integrator and to the counting input of the second pulse counter, the output of which is simultaneously connected to the zero input of the first pulse counter and the second input 5 a common adder is connected to the output of the first pulse counter, and the integrator output is connected to the second input of the amplitude selector, an additional integrator, a scaled amplifier, and m comparison,

the threshold element and the analog key are connected in series; the input of the threshold element is combined with another input of the analog key whose output is connected to the auxiliary input of the pulse generator, the output of the amplitude detector to the input of the additional integrator, and the output of the integrator to the other input of the comparison element.

- The drawing shows the structural electrical circuit of the proposed device.

A device for measuring the noise level during speech pauses contains a series-connected amplifier, amplitude detector 2, synchronous integrator 3, amplitude selector 4, first pulse counter 5, prohibition element b, reversible adder 7, digital-to-analog converter 8, integrator 9. First integrator 9 output simultaneously connected to the second input of the amplitude selector 4 and to the input of the executive unit 10. The output of the amplitude detector 2 is also connected to an additional integrator 11, which, in turn, sequentially connected to the large-scale amplifier 12 and the element 13 of the comparison. The output of the comparison element 13 is simultaneously connected to the signal input of the analog switch 14 and to the input of the threshold element 15, the output of which is connected to the control input of the analog switch 14. The output of the analog switch 14 is connected to the control input of the voltage-controlled pulse generator 16. The output of the pulse generator 16 is connected simultaneously to the second input of the synchronous integrator 3 and to the counting input of the second pulse counter 17, the output of which is simultaneously connected to the zero input of the pulse counter 5 and to the second input of the second element 6. The second input of the reversible adder 7 is connected to the output of the pulse counter 5, and the second input of the comparison element 13 to the output of the integrator 9..

The device works as follows.

i The input signal is a mixture of speech signal and noise, or just noise, fed to the input of amplifier 1, from which output to. input of amplitude detector 2 From the output of amplitude detector 2, the signal is fed to the signal input of synchronous integrator 3, the control input of which is connected to the generator of 16 pulses. At the output of the synchronous integrator 3, the signal is discrete samples with a frequency of 40-50 Hz and the duration of the ISS, the envelope of which is either a mixture of a speech signal with noise, or just noise. The frequency and duration of the samples at the output of the synchronous integrator 3 are determined by the parameters of the pulses of the generator 16. The RC charge time constant of the synchronous integrator 3 circuit is chosen to ensure high linearity equal to

and the discharge time of the specified RC synchronous integrator circuit 3

RA1P imp / 25.

The feed-through factor Kg from the device input to the output of the synchronous integrator 3 is selected from

.

where K is the gain of the amplifier 1;

K 2 .- the transmission coefficient of the amplitude detector 2; Kj is the transmission coefficient of the synchronous integrator 3. From the output of the synchronous integrator 3, the signal arrives at the .signal .input of the amplitude selector 4, from the output of which to the counting input of the counter 5 pulses. Input zeroing the first counter 5 pulses connected to the output of the second counter 17 pulses on the counting, the input of which receives pulses from the generator 16.

Thus, the pulse counter 5 is filled with pulses from the output of the amplitude selector 4 during the measuring cycle determined by the filling time of the second pulse counter 17. The volume of the second counter is 17 impulses selected from the condition

 sc "g rp

about .

where Tpf, is the average duration of the natural pause in the speech signal;

fq is the initial pulse frequency of the generator of 16 pulses.

In order for the voltage level at the output of the integrator 9 to be close to the probable level equal to the actual value of the signal at the input of the device, the volume of the first counter 5 is selected from the condition

-o, s

(i:

Nt4.

The signal from the output of the first counter 65 5 pulses simultaneously enters

at the input Adds the reversing adder 7 and the first input of the element 6 prohibition. The other input of the prohibition element 6 receives pulses from the output of the second counter 17. In case of overflow of the first counter 5 during the time determined by the filling time of the second counter 17, each overflow pulse from the output of the first counter 5 arriving at the input Addition is reversible about the armature 7, one step increases the voltage level at the output of the digital-to-analog converter 8, the output of which through the integrator 9 is connected to the control input of the amplitude selector 4. The transfer ratio of the integrator 9 is equal to one. An increase in the voltage at the control input of the amplitude selector 4 leads to the fact that the average number of pulses per unit time from the output of the amplitude selector 4 arriving at the counting input of the first counter 5 stops causing its overflow. If there are no overflow pulses at the output of the first counter 5, the prohibition element 6 permits the passage of pulses from the output of the second counter 17 to the input. Subtracting the reversible adder 7. At the same time, every pulse from the output of the second counter 17, entering the input. Subtracting the reversible adder 7, decreases one step is the voltage level at the output of the digital analog converter 8;

Thus, a change in the direction at the control input of the amplitude selector 4 causes at its output a change in the average number of pulses, the amplitude of which exceeds the specified control level. The average number of pulses stabilized at the output of the amplitude selector 4 is determined by the volume of the first counter of 5 pulses, and the volume of the first counter of 5 pulses is selected so that the level is voltage-. neither at the control input a11 of the on-switch selector 4 was close to the vertical value of the actual value of the signal level at the input of the device. The voltage level from the output of the computer 9 simultaneously arrives at the input of the execution unit.

10. When the value of the specified level is lower than the pre-trigger value, that execution unit 10 registers this Level as the probable noise level at the device input, measured during a speech pause.

Simultaneously from the output of the amplitude detector 2, the signal is fed to the input of an additional integrator

11, the RC time constant of which the circuit is chosen is larger than the input value of the duration of the natural pause in the speech signal and is in the order of 1.5 seconds. From the output of the additional integrator 11, the direct voltage is fed to the input of the large-scale amplifiers 12, and the pass-through gain of the input of the device to the output of the large-scale amplifier 12 is selected from

0

Kof K -Kj-K -K j l,

where K is the gain transmission coefficient tel 1;

K J is the transmission coefficient of the amplitude detector 2; transfer coefficient of the additional integrator 11; the gain of the large-scale amplifier 12.

Thus, in the steady state, the voltage level at the output of the scale amplifier 12 is equal to or very close to the voltage level at the output of the integrator 9. In the case, for example, of a sharp decrease

S the signal level at the input of the device, which corresponds to the beginning of the speech pause, the voltage level at the output of the additional integrator 11 and, accordingly, at the output of the head amp 12 at a time of 1.5 s, will begin to decrease. The voltage level from the output of the scale amplifier 12 is fed to one of the outputs of the comparison element 13, to another input of which the voltage level from the output of the integrator 9 arrives. The error voltage from the output of the comparison element 13 simultaneously enters the input of the threshold element 15 and

0 input of an analog switch 14. When the magnitude of the error voltage at the output of the comparison element 13 exceeds the threshold level U ;, equal to, for example

five

.

where and o is the voltage level corresponding to the change in the low-end digital-to-analog converter 8.

The threshold element 15 generates a voltage level which, on the control input of the analog key 14, OTKjftiBaeT it, and the error voltage from the output of the comparison element 13, through the public key 14, goes to the control input of the pulse generator 16, increasing its frequency. Similarly, the comparison element 13, the analog key 14 and the threshold element 15 operate with a sharp increase in the input signal, which corresponds to a speech signal input to the device. Increasing the frequency of the pulse generator 16 reduces the time required for setting the voltage level at the output of the digital-analog converter. The presence of the threshold element 15 and the analog switch 14 is necessary so that at small values of the error the frequency of the pulse generator 16 is not affected by the voltage level drift at the output of the scale amplifier 12.

Assuming that the voltage level at the output of the comparison element 13 during installation at the output of the digital-to-analog converter 8 changes discretely and therefore the frequency of the generator 16 also changes discretely, the time for setting the voltage level at the output of the digital-analog converter 8 is determined by devices, in the case of a decrease in this level will be determined by the following expression

 “. JNcMo Nc4.o

TUST-KP to, fo- Kr-Kcc-Ko-N V

where K UH / UP is the coefficient, character: the measuring value of the threshold of the element 15; .. Kf is the slope of the generator 16 at the control input K. - transfer coefficient

Element 13 Comparison

the number of tunable levels at the digital-analog output. Converter depending on the change in the signal URV signal at the device input.

Claims (1)

1. USSR author's certificate No. 605322, cl. H 04 B 3/46, 1978.