JPH1168593A - Noise canceller - Google Patents

Abstract

(57) [Problem] To provide a noise canceller capable of improving the intelligibility of a call from background noise on the transmission side without complicating processing and configuration. SOLUTION: On a receiving side, a frequency band not masked by the background noise is calculated by a speaker output signal on which the background noise sent from the transmitting side is superimposed, and a frequency band not masked by the obtained background noise is calculated. ,
That is, a filter having a frequency characteristic opposite to that of the background noise is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise canceller for improving the intelligibility of a call under background noise generated in mobile communication and the like.

[0002]

2. Description of the Related Art The intelligibility of a call deteriorates when a call is heard from a background of noise. In order to remove background noise, which is a cause of poor call intelligibility, that is, poor call quality,
A noise canceller for removing background noise is required on either the transmitting side or the receiving side, and such a noise canceller has been conventionally known.

[0003]

Normally, when background noise is removed on the receiving side, it is necessary to obtain noise information such as the background noise level from the transmitting side. For this reason, the conventional noise canceller has a problem that the processing and configuration of the entire communication system become complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. A noise canceller installed on the receiving side does not complicate the processing and configuration of the entire communication system, and uses background noise on the transmitting side. It is an object of the present invention to obtain a noise canceller capable of improving the intelligibility of a call having deteriorated quality.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention determines whether or not a received signal is masked by a background noise on a transmitting side by a speaker output signal in a frequency domain, and determines whether the received signal is masked. A level determiner for transmitting information on a frequency band to a noise filter, and a noise reduction device for forming a band-pass filter according to a frequency band not masked by the background noise calculated by the level determiner to remove background noise of a speaker output signal The receiving side calculates a frequency band that is not masked by the background noise based on the speaker output signal on which the background noise sent from the transmitting side is superimposed, and calculates the frequency band that is not masked by the background noise. An unmasked frequency band, that is, a filter having a frequency characteristic opposite to that of background noise A.

As shown in FIG. 3, in the embodiment of the present invention, a level determination unit 11 receives a speaker output signal Ss and converts the speaker output signal Ss from time domain to frequency domain signal data. Data converter 11
01, an output signal of the data converter 1101, and a data level determiner 1102 for determining and detecting a frequency exceeding a predetermined threshold value a (FIG. 2), and an output signal of the data level determiner 1102 as an input. And a passband detector 1103 that determines the lowest frequency fL and the highest frequency fH among the frequencies exceeding a predetermined threshold value a, and determines a frequency that is not masked by noise.

In the embodiment of the present invention, the noise elimination filter 12 receives the output signal of the passband detector 1103 and determines a filter coefficient. The bandpass filter designer 1201 and the bandpass filter designer 1
The bandpass filter 1202 receives the output signal of the filter 201 and forms a filter having a filter coefficient determined by the bandpass filter designer 1201.

According to such a configuration, when a speaker output signal on which background noise is superimposed is passed through the configured filter, the frequency components not masked by the background noise are emphasized, and the frequency components masked by the background noise are suppressed. Is done. Therefore, background noise on the transmitting side is suppressed, and intelligibility of the call is improved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram of a noise canceller according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a noise canceller to which an output signal Ss to a speaker is input. The noise canceler 1 includes a level determiner 11 to which a speaker output signal Ss is input, and an output signal of the level determiner 11 and a speaker. And a noise removal filter 12 to which the output signal Ss is input.

In FIG. 1, reference numeral 2 denotes a D / A converter for receiving the output of the noise canceller 1, and 3 denotes a D / A converter 2
And 4, a speaker receiving the output of the amplifier 3.

FIG. 2 is a waveform diagram in the frequency domain. The level determiner 11 searches the frequency components of the speaker output signal Ss on which the background noise is superimposed as shown in FIG.
The highest frequency is fH. Here, the threshold value a is a value for discriminating between the background noise and the call voice. If the threshold value a is equal to or larger than a, it is determined that only the call voice is masked. A frequency band between the two frequencies fL to fH is not masked by the background noise, and the frequency band information is sent to the noise removal filter 12.

As shown in FIG. 2B, the noise elimination filter 12 has a frequency band f not masked by the background noise according to the frequency band calculated by the level determiner 11.
The bandpass filters of L to fH are configured.

When the loudspeaker output signal Ss on which the background noise is superimposed passes through the noise elimination filter 12, FIG.
As shown in (2), the frequency components not masked by the background noise are emphasized, and the frequency components masked by the background noise are suppressed. As a result, background noise is suppressed in terms of audibility, and intelligibility of the call is improved.

FIG. 3 is a detailed block diagram of the noise canceller 1 for showing details of the level determiner 11 and the noise removal filter 12. The level determiner 11 includes a data converter 1101 to which the speaker output signal Ss is input, a data level determiner 1102 connected to the output side of the data converter 1101, and a pass connected to the output side of the data level determiner 1102. And a band detector 1103.

In the level determiner 11, a speaker output signal (digital) Ss is first converted from a time domain to a frequency domain by a data converter 1101. Based on the speaker output signal Ss converted to the frequency domain by the data converter 1101, the data level determiner 1102 detects a frequency exceeding the threshold value a. This threshold a
Are shown in FIG. 2 (A).

Next, the passband detector 1103 determines the lowest frequency fL and the highest frequency fH among the frequencies exceeding the threshold a, and determines the frequency bands fL to fH that are not masked by noise. And a noise removal filter 1
Output to 2.

The noise elimination filter 12 is a level determinator 1
1, a band-pass filter designer 1201 connected to the output side of the passband detector 1103, and a band-pass filter 1202 connected to the output side of the band-pass filter designer and receiving the speaker output signal Ss. Consists of

The bandpass filter design unit 1201 determines the frequency bands fL to fL determined by the passband detector 1103.
Based on H, a filter coefficient of the bandpass filter 1202 is calculated. The bandpass filter 1202 is a digital filter, and its filter coefficients are used as the filter coefficients calculated by the bandpass filter designer 1201. A filter characteristic based on the filter coefficient is shown in FIG.

When the loudspeaker output signal Ss on which noise, which is a digital signal, is passed through the band-pass filter 1202, that is, the noise removal filter 12, the loudspeaker output is obtained as shown in FIG. Signal noise is suppressed.

[0020]

As is apparent from the above description, according to the present invention, the frequency band which is not masked by the background noise on the receiving side by the speaker output signal on which the background noise sent from the transmitting side is superimposed. And a filter with a frequency characteristic that is not masked by the background noise obtained, that is, a filter having a frequency characteristic opposite to that of the background noise is configured. Thus, it is possible to improve the intelligibility of the call from the background noise.

[Brief description of the drawings]

FIG. 1 is a block diagram of a noise canceller according to an embodiment of the present invention.

FIG. 2 is a waveform diagram in the frequency domain for illustrating the operation of the present invention.

FIG. 3 is a detailed block diagram of a noise canceller.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 noise canceller 2 D / A converter 3 amplifier 4 speaker 11 level determiner 12 noise elimination filter 1101 data converter 1102 data level determiner 1103 passband detector 1201 bandpass filter design unit 1202 bandpass filter Ss speaker output signal a Threshold

Claims (2)

[Claims] 1. A level determiner for determining, in a frequency domain, whether a received signal is masked by background noise on a transmitting side by a speaker output signal, and sending information of a frequency band not masked to a noise filter; A noise canceller comprising: a band-pass filter according to a frequency band not masked by a background noise calculated by a determiner; and a noise removal filter for removing a background noise of a speaker output signal. 2. The noise canceller according to claim 1, wherein the level determiner receives the speaker output signal and converts the speaker output signal from time domain to frequency domain signal data, and the data converter. A data level judging device which receives an output signal of the device and judges and detects a frequency exceeding a predetermined threshold; and a data level judging device which receives the output signal of the data level judging device and selects one of the frequencies exceeding the predetermined threshold. A passband detector that determines the lowest frequency and the highest frequency, and determines a frequency that is not masked by noise, wherein the noise removal filter receives an output signal of the passband detector, and A band-pass filter designer for determining coefficients, and an output signal of the band-pass filter designer, Noise canceller characterized in that it is composed of a band-pass filter constituting the filter having a filter coefficient determined by.