JPS6021612A - Graphic equalizer - Google Patents

Abstract

PURPOSE:To suppress noise superimposed on an input signal by controlling a level of a signal of each band with a coefficient based on the S/N of each band. CONSTITUTION:The input signal is divided into n-bands by band-pass filter groups 41-4n, a level of each band is adjusted depending on a control signal from a demultiplexer 150 by means of programmable level adjusting devices 51- 5n and signals of each band whose level is adjusted are added by an adder 60 and outputted. The input signal whose band is divided is fed to rectifier smoothing device groups 80-8n, converted at an A/D converter 100 and stored in an RAM 130 via a microcomputer 120. The computer 120 obtains the noise suppressing coefficient based on the level information of each band stored in the RAM 130 so as to estimate the level eliminated for noise. Since the level at a band having a low S/N is lowered largely much more than that at a band having a high S/N, the noise superimposed on the input signal is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a graphic equalizer in audio equipment.

Conventional configurations and their problems Regarding audio equipment, the performance of Aivi/FM receivers has improved dramatically, but depending on the reception environment, noise such as beats may be mixed in, making the sound very difficult to listen to. Sometimes I put it away. This is especially true in cases where the receiver is mobile, such as a car stereo. Conventionally, noise has been suppressed by using a graphic equalizer to attenuate the level of the band where noise exists.

Next, a conventional graphic equalizer will be explained. Figure 1 shows the Q-groove origin of a conventional graphic equalizer, where (Iυ~(In) is a bandpass filter, (2+)
~ (2n) is a level adjuster, (埒 is a limiter, and 6 (j is an input operation section.)
The operation of the equalizer will be explained below. First, the input signal is divided into bands by a bandpass filter rlYOυ~(1n), and the level is adjusted using the level adjuster group υ~(2n) based on the input signal from the input operation section). An adder (7) adds the outputs of each level adjuster and outputs the result.

However, the graphics with the above conventional configuration
Attempting to suppress input signal noise using an equalizer requires a trial and error process, and when the nature of the noise changes, the characteristics of the graphic equalizer must be reset from the input operation section, which is very troublesome. It had the problem that.

OBJECTS OF THE INVENTION The present invention solves the problems of the prior art described in 2. It is an object of the present invention to provide a graphical system that can automatically detect quasi-stationary noise superimposed on an input signal, especially an audio signal, and suppress it. The purpose is to provide an equalizer.

Structure of the Invention The present invention is a graphic equalizer comprising a band division means, a level adjustment means, an addition means, an input operation means, a storage means, an S/N ratio estimation means, and a control means. By controlling the level of the signal in each band using the number of threads based on the S/N ratio of each band, noise superimposed on the input signal can be suppressed.

Description of examples Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows the cause of grooves in the graphic equalizer in one embodiment of the present invention. In the 219th
θ~(4n) is a band pass filter, fill~(5n
) is a programmable level adjuster, - is an adder, 4 is an input projection unit, 枳) to (8n) are rectifiers and smoothers, □□□ is a multiplexer, (100) is an analog-to-digital converter (hereinafter referred to as a VD converter) ), (110) is the interface, (12,0) is the microcomputer, (180
) is random access memory (hereinafter referred to as RAM), (
140) is a read-only memory (hereinafter referred to as RO11, 4), and (150) is a demultiplexer.

The input signal is n by a bandpass filter MOη~(4n)
Band-divided programmable level adjuster I
The level of each band is adjusted according to the control signal from the demultiplexer (150,) by I'&ill~(5+), and the level-adjusted signals of each band are added and output by addition W i4.Programmable Level Hka
D ~ (6n) of N Phi m can also be set by inputting from the input operation unit (71) in the conventional example and the stud.On the other hand, the input signal band-divided by the bandpass filter 51 uv ~ (4n) 5;) Flow smoothing g: 'i Gunsuke ~ (8n) was also sent, and the multi-flexor was colored red, A/
/L) A converter (100) converts the analog ↓i to a digital quantity, passes through the interface (110) and the microcomputer (120), and stores it in the RAM (l s
o). Microcomputer (120)
is based on the good news of the level of each band stored in RAiVl (180), and reduces the tube noise suppression coefficient Ci as follows, where C1: noise suppression coefficient lsi+Nil: input signal level of i-th band lNo1l
:Estimated noise level i of the first band :Band hole@(1,) This coefficient Ci is sent to the programmable level adjuster Sento~(5n) via the interface (110) and the demultiplexer (150). In the equation (0), if the noise estimation is successful and 1Nil=lNoil, then the level of the equation (t1) is multiplied by 1sil, and the level from which the noise is removed is estimated. In this way, the level of the band with a low S/N J-t is lowered to a greater extent than that of a band with a high S/N ratio, so the noise superimposed on the input signal is suppressed.

The estimated noise level of the i-th band 1 Noil is calculated as follows:
If the input signal is a voice, there will always be a silent section in which no voice is generated, so only noise will exist in that section, and furthermore, the temporal fluctuations of the noise will be gradual. Assuming that the noise is quasi-stationary, the section with the lowest level in a sufficiently long period of observation is the silent section, so by setting the level ISi + N11 of each band in that section to the estimated noise level 1Noil,・ν; is used to estimate the sound. If this sufficiently long interval 1 [, - (this is called the noise search time) is set to 2 to 8 seconds at a normal conversation speed, the noise can be estimated without much error. A program for the computer (120) is written.

FIG. 3 shows a flowchart I7 of the microcomputer of this embodiment, and its control procedure will be explained below. After initial setting, input signal lsi+Ni1 is read and the first I
1 [Calculate the sound suppression coefficient Ci and output Ci via the interface. Then, in order to estimate the sound, the section with the lowest level within the noise search time is searched, and the input signal level of each band in that section is set to 1 Noil'.

After 11↓, it is determined whether the E-sound search time has ended, and if it has ended, the estimated noise level that has already been obtained (
Estimation obtained by Noil and this noise search? /
Find the average value of the diI sound level lNo1, register +1 which is close to it as the constant noise level 1tjO11, clear the noise search timer, and set the input signal ISi+Ni again.
Returning to the process of importing l.

In this way, according to this embodiment, the noise superimposed on the quasi-stationary voice can be suppressed by controlling the microcomputer (120) from the input (t:, r 1 signal of the bow level ISi+Nil). .

In addition, in the control procedure according to this embodiment, the noise suppression coefficient 01 is directly passed through the interface (1zo) to the programmable level adjuster B"l"j'υ~(5n)J
t is output, but to improve the sound quality, the input operation section σψ
By using a method of superimposing the characteristics of the 4.1 sound suppression coefficient Ci on the characteristics of the graphic equalizer, which is set in advance, it becomes possible to simultaneously improve sound quality and suppress noise.

Effects of the Invention According to the present invention, 'jb area control means, level El'
d adjustment means, addition means, input operation means, notation td means, S/
Since the N ratio estimating means and the control means were increased by (ηi"1), 1.
An excellent graphic equalizer that can estimate the S/N ratio of the IJ wavenumber band and adjust the level of each band based on that information to suppress quasi-stationary noise superimposed on the audio signal. It is possible to realize this.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional graphic equalizer, FIG. 2 is a block diagram of a graphic equalizer according to an embodiment of the present invention, and 814 is a flowchart of a microcomputer of the graphic equalizer according to an embodiment of the present invention. be. 0～(4n)...Homare) i loading element l overfilter, f51
1~(5n8...Programmable level tone IK ei;
, (i!I)...adder, (to...input operation part, (81)-(8n)...rectification smoother, (6);)
・Multiplexer, (100) =・A/D converter, (
110) -I:/'I -7 Ace, (120)・
...Microcomputer, (130),, = RAI
Vl, (140) -ROhl, (150) - Demultiplexer agent Yoshihiro Kuramoto

Claims (1)

[Claims] 1. A band dividing means for dividing an input signal into a plurality of frequency bands, a level adjusting means for adjusting the level of each output of the band dividing means using a control signal, and an adding means for adding each output of the level adjusting means. and - input operation means for externally controlling the level adjustment means, storage means for storing each output of the band division means, and information on the level of each band of the input signal stored in the storage means. S/N ratio estimation means for estimating the S/N ratio for each band based on the information; and S/N ratio estimation means for estimating the S/N ratio for each band based on the information;
and control means for supplying a control signal to the level adjustment means in order to increase or decrease the level of each band according to the level of the /N ratio.