JPH057184A - Background noise power detector - Google Patents

Abstract

PURPOSE:To attain talking without a sense of disorder by preventing background noise listened by a recipient from being unnecessarily increased. CONSTITUTION:A comparator 8 compares an output of an adder 3 with an output of a 2nd multiplier 9 and outputs an output of the adder 3 when an output of the adder 3 is smaller as an integration value and outputs an output of the 2nd multiplier 9 as an integration value when the output of the 2nd multiplier 9 is smaller. A selection circuit 4 selects the output of the adder 3 when the output of the adder 3 is smaller than the output of the 2nd multiplier 9 and selects the output of the 2nd multiplier 9 when larger to output the selected output as an integration value of noise power. A 3rd multiplier 5 obtains a background noise power by dividing the output of the selection circuit 4 being the integration value of the noise power with an integration gain 1/(1-beta) being the integration value of the noise power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detection of background noise power value of a PCM signal.

[0002]

2. Description of the Related Art A conventional background noise power detector outputs the output value of a silent part power value detector 12 having an input terminal 11 and an output terminal 13 as it is as a background noise power value, as shown in FIG. It was

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
digital Speech Interpolati
on) device sends the signal of the silent section on the transmitting side to the D on the opposite station.
By transmitting the background noise power value to the receiving side of the SI device without sending it to the receiving side, the efficiency of the line is improved. If the background noise is not heard during this silent period, the receiver will feel uncomfortable as if the line with the other party was disconnected.
The DSI device on the receiving side inserts noise corresponding to the transmitted background noise power value into the line of the receiver. This allows
The receiver can feel as if he or she is hearing the background noise from the sender when there is no sound, and does not feel any discomfort during a call.

However, the silent part power value detector 12 described above is used.
In some cases, the voiced and silent detector may determine that the word head in a conversation is a silent part.In this case, the power value of the word head is set as the background noise power value, and a value larger than the actual background noise power is set. I will send it. Further, when impulse noise is superposed on a noise signal at the time of silence on the transmitting side due to an error in the transmission path, the influence of the square of the sampled value appears in the noise power value. Therefore, the output result of the silent part power value detector becomes a value considerably larger than the original noise power value that does not include impulse noise. Normally, the sound / silence detector included in the silent portion power value detector 12 is designed so that the judgment of the sound / silence does not change with the impulse noise of about one sample, and this impulse noise is detected in the silent section. To the extent that it occurs sporadically, this power value is transmitted as the background noise power value of the silent part. On the receiving side, in order to generate noise equivalent to the transmitted background noise power value and insert it into the line,
There was a problem in that the background noise was heard unnecessarily loud and the caller felt uncomfortable.

An object of the present invention is to make it possible to carry out a call without feeling uncomfortable without causing the background noise heard by the listener to increase unnecessarily.

[0006]

In order to achieve the above object, the present invention provides a background noise power detector for detecting the background noise power value of a PCM signal, the silent portion power for detecting the noise power value of a silent portion. A value detector, a delay circuit for delaying the integrated value of the noise power value by one update time of the noise power, and an output value of the delay circuit for multiplying the integrated value of the noise power value one update time before by the integral gain. 1 multiplier, an adder that adds the output value of the first multiplier and the output of the silent part power value detector, and the noise power value that is the output of the silent part power value detector is multiplied by an integral gain. And a second multiplier that calculates an integrated value when the detected noise power values are continuous,
The output value of the second multiplier and the output value of the adder are compared with each other, and the output value of the adder is smaller than the output value of the second multiplier according to the result of the comparator. In this case, the output value of the adder is selected, and if it is larger, the output value of the second multiplier is selected and output as an integrated value of the noise power value, and the output value of this selection circuit. A third multiplier for dividing the integrated value of the noise power value by the integral gain and outputting it as the background noise power value is provided.

[0007]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a background noise power detector according to an embodiment of the present invention. In FIG. 1, the PCM signal input to the input terminal 1 is input to the silent part power value detector 2. The silent part power value detector 2 detects the power value in the section where the built-in sound / silence detector determines that there is no sound, and outputs it at each update interval of the background noise power value.

When the selection circuit 4 selects the output of the adder 3, the adder 3, the delay circuit 7, and the first multiplier 6 operate an integrator having an integral gain β (for example, 0.9). Formed,
The integration result appears at the output of the adder 3. The second multiplier 9 forms an integrator, and the output of the silent part power value detector 2 has an integral gain 1 / (1-β) (for example, 10.0) of this integrator.
By multiplying by, the integrated value when the detected output value of the silent part power value detector 2 is continuous is obtained. The comparator 8 compares the output of the adder 3 which is the integrated value of the noise power value with the output of the second multiplier 9 which is the integrated value when the output value detected by the silent part power value detector 2 is continuous. However, when the output value of the adder 3 is smaller, the output value of the adder 3 is output as an integrated value, and when the output value of the second multiplier 9 is smaller, the second multiplier 9 The output value of is output as an integrated value. The selection circuit 4 selects the output value of the adder when the output value of the adder 3 is smaller than the output value of the second multiplier 9, and selects the output value of the second multiplier 9 when it is larger. It is selected and output as the integrated value of the noise power value. Third multiplier 5
Is a background noise power value obtained by dividing the output value of the selection circuit 4, which is the integrated value of the noise power value, by the integration gain 1 / (1-β) (for example, 10.0), and outputs it from the output terminal 10. To do. By this operation, when the background noise power value becomes larger than the detected noise power value, it takes time due to the integration effect, and conversely, when the noise power value becomes small, small noise is immediately generated. It is updated to the power value.

[0010]

As described above, according to the present invention, the power value of the word head is used as the background noise power value of the silent part, and a value larger than the actual noise power value is output, and the silent part power value is detected. Even if impulse noise is superimposed on the noise signal due to transmission line error, the background noise power value is larger than the detected noise power value by installing an integrator at the output end of the silent part power value detector. If it becomes, it takes time due to the integration effect. In addition, it is extremely rare that the word head part is mistaken for a silent part and that impulse noise is continuously generated, and the normal noise power value is immediately returned.
In this way, when the noise power value changes from a large value to a small value, it is immediately updated to a small power value. Therefore, when applied to the DSI device, the background noise heard by the listener does not unnecessarily increase, and the effect that the call can be made without any discomfort can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a background noise power detector according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional background noise power detector.

[Explanation of symbols]

2 Silent power value detector 3 adder 4 selection circuit 5 Third multiplier 6 First multiplier 7 Delay circuit 8 comparator 9 Second multiplier

Claims (2)

[Claims] 1. A background noise power detector for detecting a background noise power value of a PCM signal, comprising: a silent portion power value detector for detecting a noise power value of a silent portion; A delay circuit that delays by the update time, a first multiplier that multiplies the integrated value of the noise power value one update time before, which is the output value of the delay circuit, by the integral gain, the output value of the first multiplier, and the silence. An adder for adding the output of the power unit value detector and the noise power value which is the output of the silent unit power value detector is multiplied by an integral gain, and the integrated value when the detected noise power value is continuous. And a comparator that compares the output value of the second multiplier with the output value of the adder, and the output value of the adder is determined by the result of the comparator. If it is smaller than the output value of the 2 multiplier, the adder An output value is selected, and if it is larger, a selection circuit that selects the output value of the second multiplier and outputs it as an integrated value of the noise power value, and an integrated value of the noise power value that is the output value of this selection circuit A background noise power detector composed of a third multiplier that divides by the integral gain and outputs as a background noise power value. 2. A noise power value is prevented from sharply increasing by providing an integrator at the output end of the silent part power value detector, and the noise power value by the integrator is compared with the taken noise power value. A background noise power detector adapted to successively adapt to a smaller noise power value by setting the smaller value to the integral value of the integrator.