KR20080064768A - Apparatus and method for noise removal - Google Patents

Abstract

An apparatus and a method for removing noises around a communication terminal are provided to adjust a level of a sound signal containing the noise inputted through a microphone or a sensor, to remove the sound signal of exceeding the pre-set limit input level and to amplify an active sound more so as to keep the level of the sound which is finally outputted in a uniform state. A noise removal apparatus comprises a reference current setting part(140), a variable amplification part(150), a reference level convergence part(120), and an input level limit part(130). The reference current setting part sets reference current by an average value obtained by rectifying a sound signal. The variable amplification part amplifies input current of the inputted sound signal according to a gain proportional to voltage of the sound signal. The reference level convergence part makes the input level of the sound signal converge in a pre-set reference level. The input level limit part removes the sound signal exceeding the pre-set limit input level. A frequency limiting part(190) attenuates components of more than pre-set frequency.

Description

Ambient noise removing device and method {APPARATUS AND METHOD FOR NOISE REMOVAL}

The present invention relates to an apparatus and a method for removing ambient noise, particularly in a communication device that receives a user's voice signal through a microphone or a sensor and transmits it to a counterpart by wire or wireless, or a device that receives a specific sound source. Or it relates to an ambient noise removing apparatus and method for removing the ambient noise input with a specific sound source.

A communication device that receives a user's voice signal and transmits it to the other party by wire or wirelessly may include, for example, a telephone used at home or a mobile communication terminal that can be used while on the move. There may be a communication headset device.

On the other hand, a device that receives a specific sound source, for example, to hear whether arteries, intestinal noise, blood vessels, as well as heart sounds and respiratory sounds generated in the body to check whether or not the normal state There may be leak detectors used to detect leaking water in the pipes used in electronics.

The communication device for receiving the user's voice signal or the device receiving the specific sound source receives the user's voice signal or the specific sound source through a microphone or a sensor, and the noise generated in the surroundings is also input.

In particular, outdoor noise may occur frequently. For example, various noises such as noise generated by people nearby, noise generated by public transportation such as taxis or buses, and noise generated at construction sites may be generated. There may be. In addition, the noise may occur indoors as well as the noise generated in the outdoors, for example, in a closed place such as karaoke, or in a place such as a call center for responding to inquiries from customers, the noise is essential.

When a voice call is made with the other party using a communication device such as a mobile communication terminal in a place where noise is generated indoors or outdoors, the receiver often cannot understand the sender's voice content due to the noise.

As such, in a communication device that receives a user's voice signal or a specific sound source through a microphone or a sensor, when noise generated from the surroundings is input together, the user's voice signal cannot be properly transmitted or only a specific sound source can not be received due to the noise. There was this.

Thus, various methods and devices have been proposed to solve this problem. FIG. 1 shows a schematic diagram of a noise reduction circuit introduced through a conventional microphone.

As shown in FIG. 1, as shown in FIG. 1, when a user's voice signal and a peripheral noise signal are input through a microphone 10, a conventional capacitor C2 is connected in series. Remove the noise signal. The signal from which the noise signal is removed is amplified by the amplifier 20 and output to the user through the speaker.

However, the noise canceling circuit introduced with the conventional microphone does not remove the non-linear noise, so that the noise is still not removed because it is synthesized and amplified with the input voice signal.

On the other hand, Japanese Patent Application Laid-Open No. 61-99451 (hereinafter referred to as "First Invention 1") shows that the performance of a telephone is improved by improving the performance of a telephone, as described in the publication 2 of the prior invention 1. As the phone amplifies and transmits even the smallest noise to the other party, the background of the invention is that the low level ambient noise, which was not the noise in the conventional phone, is heard by the other party and affects the call quality. That is, in the conventional non-sensitive phone, fine noise, which was not considered noise, is improved by using the improved phone, and the amplification performance is transmitted to the other party. The problem is to reduce these fine noises.

Therefore, in the preceding invention 1, the reference level is set to be smaller than the minimum sound of the caller's voice and higher than the ambient noise, and when the level of the input signal is lower than the reference level, the amplification gain is reduced, and the level of the input signal is higher than the reference level. In this case, a technique using an amplifier for increasing amplification gain is disclosed.

However, the reference level according to the preceding invention 1 cannot be applied in a variety of situations, and can only be used in a fixed manner. There was a problem that the reference level can only be determined at a lower level, that is, a sufficiently low level. That is, in order to remove the noise having a slightly larger level, the reference level should be raised a little higher, but in this case, there was a problem that the voice of the caller who speaks with a small voice is removed.

In addition, Japanese Laid-Open Patent Publication No. 2005-86361 (hereinafter referred to as "priority invention 2") discloses a technique for automatically setting a sign language volume in accordance with the ambient noise level. However, Prior Invention 2 is intended to solve the noise problem by simply increasing the transmission / receiving volume of both the noise and the voice, rather than removing the noise, and thus, a fundamental solution to the noise reduction has not been proposed.

The present invention has been made to solve the above-described problems, the reference current is set to the average value obtained by full-wave rectification of the effective sound source signal including the noise input through the microphone or sensor, and to the gain controlled by the set reference current Accordingly, it is an object of the present invention to provide an ambient noise removing device and method for amplifying an input current of an input sound source to amplify an effective sound source more and amplifying a smaller noise to remove ambient noise.

In addition, the present invention adjusts the level of the sound source signal including the noise input through the microphone or sensor based on a preset reference level, and exceeds the predetermined limit input level in the sound source signal including the adjusted input noise Another object of the present invention is to provide a peripheral noise canceling device and method for removing a sound source signal so that the level of the finally output sound source remains constant regardless of the separation distance between the sound source and the microphone.

In order to achieve the above object, the ambient noise removing apparatus according to an embodiment of the present invention, in the ambient noise removing apparatus for removing the noise from the effective sound source signal including the noise input through the microphone or sensor,

The gain is controlled by a reference current setting unit for setting a reference current to an average value obtained by full-wave rectification of the sound source signal and a reference current set in the reference current setting unit, and amplifies the input current of the input sound source signal according to the gain. Including a variable amplification unit,

And at least one of a reference level converging unit for converging the input level of the sound source signal to a preset reference level and an input level limiting unit for removing a sound source signal exceeding a predetermined limit input level from the sound source signal. It provides a peripheral noise removing device.

In addition, the ambient noise removal method according to another embodiment of the present invention in the ambient noise removal method for removing noise from the effective sound source signal including the noise input through the microphone or sensor,

(A) setting a reference current to an average value obtained by full-wave rectifying the sound source signal, and gain is controlled by the reference current set in step (a), and amplifying the input current of the input sound source signal according to the gain (B) the step of

(C) converging the input level of the sound source signal to a preset reference level, and removing (d) a sound source signal exceeding a predetermined limit input level from the sound source signal. Provides a method for removing ambient noise.

According to the apparatus and method for removing ambient noise of the present invention, the level of a sound source signal including noise input through a microphone or a sensor is adjusted to a predetermined value according to a preset reference level and obtained by full-wave rectification of the adjusted sound source signal. The reference current is set to the average value, and the input current of the input sound source is amplified according to the gain controlled by the set reference current so that the effective sound source is amplified louder while the noise is smaller. Even if it occurs to some extent, it is effective in removing ambient noise.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the ambient noise removing device and method according to a preferred embodiment of the present invention. In the following description of the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

First, to explain the principle of the ambient noise removing apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Figure 2 shows a graph showing the output level compared to the input level of the sound source input in the ambient noise removing device according to an embodiment of the present invention.

Referring to Figure 2, as shown in the ambient noise removing apparatus according to an embodiment of the present invention to look at the input level of 0 dBm, when the input level is +10 dBm, the corresponding output level is +20 dBm When the input level is -10 dBm, the corresponding output level is -20 dBm. That is, when an input level above a predetermined reference level is input, a higher output level is output. When an input level below a predetermined reference level is input, a lower output level is output.

On the other hand, at a point away from the microphone by a predetermined distance, the effective sound source such as the user's voice signal in terms of the mouth level input through the microphone is greater than the noise generated from the surrounding. This can be confirmed through experiments, for example, the sound pressure of the sound source near the mouth is about 102dB and the sound pressure is about 92dB at 8cm apart, whereas the noise is generally smaller than the sound pressure of the sound source within 8cm. have. Accordingly, the microphone is preferably present within 5 ~ 15cm from the user's mouth. Therefore, the separation distance means a distance within 5 ~ 15cm from the micro.

For example, in more detail, when talking to an external party using a mobile communication terminal in a place where a loud noise occurs, such as karaoke, the user of the mobile communication terminal, as well as those in the vicinity The noise generated by karaoke is felt louder than the voice of the user using the terminal.

However, at a point away from the microphone of the mobile communication terminal by a predetermined distance, the noise level generated in the karaoke is smaller than the voice level of the user using the mobile communication terminal in terms of the mouth level input through the microphone. This is because the user's voice is input through the microphone from a certain distance away from the microphone of the mobile communication terminal, but since the noise of karaoke is input through the microphone from a remote place, it is separated from the microphone by a predetermined distance away. There is attenuation to the point, whereby the noise level at the point away from the microphone of the mobile communication terminal by a predetermined distance is smaller than the voice level of the user using the mobile communication terminal.

An ambient noise removing apparatus according to an embodiment of the present invention using the above-described principles and characteristics will be described with reference to the accompanying drawings, and an example will be described for removing noise from a valid sound source including noise input through a microphone. .

Figure 3 shows a block diagram of a peripheral noise removing device according to an embodiment of the present invention.

As shown in FIG. 3, the ambient noise removing apparatus 100 of the present invention includes an ambient noise removing apparatus for removing noise from an effective sound source including noise input through the microphone 110.

A reference level converging unit 120 for converging the input level of the sound source signal input through the microphone 110 to a preset reference level;

An input level limiting unit 130 for removing a sound source signal exceeding a predetermined 'limiting input level' from the sound source signal input through the reference level converging unit 120; A reference current setting unit 140 for setting a reference current as an average value obtained by full-wave rectifying the sound source signal input through the input level limiting unit 130; A variable amplifying unit 150 having a gain controlled by the reference current set by the reference current setting unit 140 and amplifying the input current of the sound source input through the input level limiting unit 130 according to the corresponding gain; It includes an output level adjusting unit 170 for adjusting the output level of the sound source amplified by the variable amplification unit 150.

In addition, the peripheral noise removing apparatus 100 of the present invention includes a variable resistor unit for determining the amplification ratio so that the output level adjusting unit 170 can adjust the level of the sound source according to a predetermined amplification ratio in adjusting the level of the sound source ( 160, an output level limiting unit 180 for removing a sound source signal exceeding a predetermined 'limit output level' from a sound source signal input from the output level adjusting unit 170, and a sound source input through the output level adjusting unit 1700. The frequency limiter 190 may further include attenuating components having a predetermined frequency or more in the signal.

In the above-described configuration, the reference current setting unit 140 sets the reference current from the sound source input through the microphone 110. In detail, when a valid sound source including noise is input through the microphone 110, a predetermined voltage is applied as an electric signal corresponding to the input sound source, and a current is generated from the applied voltage. The reference current setting unit 140 receiving the generated current sets the reference current to an average value obtained by full-wave rectifying the input current.

Next, the variable amplifier 150 controls the gain by the reference current set by the reference current setting unit 140 and amplifies the input current of the input sound source according to the gain. In this case, the variable amplifier 150 uses a conventional operational amplifier, and the gain of the reference current set by the reference current setting unit 140 becomes the DC bias value so that the gain is variable to change the amplification degree. Since the gain variation of the operational amplifier is a well known technique, a detailed description thereof will be omitted. The variable amplification unit 150 receives a current of a valid sound source including noise through the microphone 110 similarly to the reference current setting unit 140, and converts the input current into a gain controlled by the set reference current. According to variable amplification.

On the other hand, the gain of the variable amplifier 150 is proportional to the voltage of the sound source input through the microphone, which amplifies the effective sound source larger than the reference current set by the reference current setting unit 140 to amplify a larger, reference current Less noise means less amplification.

In more detail, as described above, at a point away from the microphone 110 by a predetermined distance, the effective sound source has an input level larger than the noise. When a valid sound source including such noise is input through the microphone 110, the reference current setting unit 140 outputs an average value of input currents of the effective sound source including noise to set a reference current, and the variable amplifier unit. The variable 150 amplifies the effective sound source including the noise according to the gain controlled by the set reference current, but amplifies the effective sound source larger than the reference current, and amplifies the noise smaller than the reference current.

Next, the reference level converging unit 120 amplifies or attenuates the size of the effective sound source signal including the noise input from the microphone 110 based on a predetermined reference level. That is, as the distance between the sound source and the microphone 110 increases, the input level of the effective sound source input to the microphone 110 becomes smaller, and accordingly, the difference in the voltage level between the noise and the sound source is reduced. Even if the variable amplification unit 150 variably amplifies the noise and the sound source, the noise removal efficiency is reduced by that much. On the contrary, as the distance between the sound source and the microphone 110 gets closer, the input level of the effective sound source input to the microphone 110 becomes larger by that, and thus the sound source signal input through the microphone 110 is converted into a variable amplifier ( In 150, there is a possibility to be amplified more unnecessarily than the volume sufficient for the call.

Therefore, when the input level of the effective sound source including the noise input from the microphone 110 is smaller than the preset reference level, the reference level converging unit 120 amplifies the input level of the sound source to be larger by this reference level. When the input level of the effective sound source including the noise input from the microphone 110 is larger than the preset reference level, the input level of the sound source is attenuated by this reference level. Here, the reference level set by the reference level convergence unit 120 is determined by the separation distance between the sound source and the microphone 110, the separation distance is preferably 5cm.

Next, the input level limiting unit 130 removes a sound source signal exceeding a predetermined 'limit input level' from the sound source signal input through the microphone 110. That is, as the distance between the sound source and the microphone 110 increases, the input level of the effective sound source input to the microphone 110 becomes smaller, and accordingly, the difference between the voltage level between the noise and the sound source is reduced, and the air supply noise is noisy. Since the level is greater than that of the sound source, the variable amplifier 150 may amplify the noise louder than the sound source.

Therefore, the input level limiting unit 130 removes the sound source signal exceeding a predetermined limit input level, that is, noise, from the sound source signal whose level is adjusted through the reference level converging unit 120, that is, the variable amplifier 150 and the reference. Output to the current setting unit 140. Here, the above limit input level is a numerical value corresponding to a volume sufficient for communication, and the sound pressure is preferably 92 dB. On the other hand, the input level limiting unit 130 may be removed from the effective sound source, but may be preferable in terms of not amplifying a volume larger than the volume sufficient for the call.

Next, the variable resistor unit 130 is a variable resistor for determining the amplification ratio of the output level adjusting unit 170 to be described later.

Next, the output level adjusting unit 170 adjusts the level of the sound source amplified by the variable amplifier 150. The output level adjusting unit 170 may be implemented as an operational amplifier and adjusts the level of the sound source by finally amplifying the level of the sound source amplified by the variable amplifier 150 at a predetermined amplification ratio. The predetermined amplification ratio is determined through the variable resistor unit 130.

Next, the output level limiting unit 180 is to naturally make a voice output from the ambient noise removing device 100 without a sharp feeling, and the output level limiting unit preset in the sound source amplified by the output level adjusting unit 170, that is, Eliminate unnecessary sources above the level corresponding to the volume sufficient for the call.

Next, the general frequency response characteristic of the microphone has a bandwidth of 50 Hz to 20 kHz, while the range of the voice frequency is 300 Hz to 3.4 kHz, and the frequency limiter 190 uses the output level limiter 180. A component of a predetermined frequency, that is, 3.4 kHz or more, is attenuated and output from the input sound source signal. Therefore, in the system of the mobile communication terminal to which the ambient noise removing device 100 having the frequency limiter 190 is applied, a voice frequency having a bandwidth narrower than the bandwidth according to the frequency response characteristic of the microphone is modulated and transmitted / received. Accordingly, the efficiency of the base station is reduced, the call quality is improved and the efficiency of the frequency is used.

Next, the microphone 110 is preferably implemented as an electret condenser microphone (ECM), and in consideration of the attenuation ratio of the ambient noise, its sensitivity performance is preferably -40 dB or less at 1 kHz.

4 is a block diagram of an apparatus for removing ambient noise according to another embodiment of the present invention.

As shown in Figure 4, the ambient noise removing apparatus 400 of the present invention, in the ambient noise removing apparatus for removing the noise from the effective sound source including the noise input through the microphone 410,

A reference current setting unit 440 for setting a reference current to an average value obtained by full-wave rectifying the sound source signal input through the microphone 410; A variable amplifier 450 having a gain controlled by the reference current set by the reference current setting unit 440 and amplifying the input current of the sound source input through the microphone 410 according to the corresponding gain; A reference level converging unit 420 for converging the input level of the sound source signal input through the variable amplifier 450 to a preset reference level; An input level limiting unit 430 for removing a sound source signal exceeding a predetermined 'limiting input level' from the sound source signal input through the reference level converging unit 420; It includes an output level adjusting unit 470 for adjusting the output level of the sound source input through the input level limiting unit 430.

In addition, the ambient noise removing apparatus 400 of the present invention may further include a variable resistor unit 460, an output level limiter 480, and a frequency limiter 490.

Here, each component of the ambient noise removing apparatus 400 is different from each component of the peripheral noise removing apparatus 100 described with reference to FIG. 3 and the reference numerals thereof, the functions thereof are the same, and according to the function Since the effect is also the same, a detailed description thereof will be omitted. However, since the positions of the reference level converging unit 420 and the input level limiting unit 430 are different from those of FIG. 3, the reference level converging unit 420 may vary the amplified noise through the variable amplifier 450. If the input level of the effective sound source to be included is smaller than the preset reference level, the input level of the sound source is amplified by the reference level larger, while the input level of the effective sound source including the variable amplified noise from the variable amplifier 450 is amplified. If it is larger than this preset reference level, the input level of the sound source is attenuated by this reference level. By doing so, the level of the sound source finally output through the ambient noise removing device 400 is maintained constant regardless of the separation distance between the sound source and the microphone 410. The input level limiting unit 430 also removes a sound source signal exceeding a predetermined limit input level, that is, noise, from the sound source signal whose level is adjusted through the reference level converging unit 420.

Figure 5 is a block diagram of a peripheral noise removing device according to another embodiment of the present invention.

As shown in FIG. 5, the ambient noise removing apparatus 500 of the present invention includes an ambient noise removing apparatus for removing noise from an effective sound source including noise input through the microphone 510.

An extended reference current setting unit 540 for setting an 'extended reference current' for expanding the level of the sound source signal using an average value obtained by full-wave rectifying the sound source signal input through the microphone 510; A level expansion unit 450 having a gain controlled by the expansion reference current set by the expansion reference current setting unit 540 and extending the level of the sound source signal input through the microphone 410 according to the gain; A first level adjuster 570a for adjusting the level of the sound source input through the level expander 450; A level compressor 520 having a gain controlled by a predetermined 'compression reference current' and compressing the level of the sound source signal input through the first level adjuster 570a according to the corresponding gain; A compression reference current setting unit 530 for setting the compression reference current for compressing the level of the sound source signal using the average value obtained by full-wave rectifying the sound source signal output from the level compression unit 520; And a second level adjuster 570b for adjusting the level of the sound source input through the level compressor 520.

In addition, the peripheral noise removing apparatus 500 of the present invention may further include a first variable resistor unit 560a, a second variable resistor unit 560b, an output level limiter 580, and a frequency limiter 590. have.

Here, the level expansion unit 550 has the same function as the variable amplification unit 150 and the expansion reference current setting unit 540 with the reference current setting unit 140, and the effects appearing according to the function are also the same. Description is omitted. In addition, the first and second variable resistor units 560a and 560b include the variable resistor unit 160, the output level limiter 580, the output level limiter 180, and the frequency limiter 590, respectively. Since the function of the unit 190 is the same and the effects appearing according to the function are also the same, detailed description thereof will be omitted.

Meanwhile, the level compression unit 520 and the compression reference current setting unit 530 maintain a constant level of the sound source finally output through the ambient noise removing device 500 regardless of the separation distance between the sound source and the microphone 510. It is the same as the function of the reference level converging unit 420 described above as a component used in the above, and the effects appearing according to the function are also the same. That is, the level compressing unit 520 amplifies the louder sound when the effective sound source including the noise input through the first level adjusting unit 570a is smaller than the compression reference current, while inputting it through the first level adjusting unit 570a. If the effective sound source containing the noise is larger than the compressed reference current, it is attenuated smaller.

FIG. 6 is a circuit diagram of a level expansion unit and an extension reference current setting unit, which are components of FIG. 5, according to an embodiment of the present invention. As shown in FIG. 6, the level expansion unit 550 and the extension reference current setting unit 540. ) Preferably includes a rectifier for full-wave rectifying the input signal, a gain adjuster for adjusting the gain of the input signal according to the control of the rectifier, and an operational amplifier.

7 is a circuit diagram of a level compression unit and a compression reference current setting unit, which are components of FIG. 5, according to an embodiment of the present invention. The level compression unit 520 and the compression reference current setting unit as shown in FIG. 530 preferably includes the rectifier, gain regulator and operational amplifier described above, provided that the rectifier and gain regulator in FIG. 7 forms a feedback loop for the operational amplifier.

The ambient noise removing device having the above-described configuration can be controlled through a switch so that the operation is turned on or off by a user's operation. In addition, the apparatus for removing ambient noise may be applied to all communication devices including a general telephone, an electronic stethoscope, a radio, and a mobile communication terminal, and may be provided in a predetermined chip form. In particular, what is applied to the mobile communication terminal will be described later.

Hereinafter, an operation of the ambient noise removing device having the above-described configuration will be described with reference to the accompanying drawings, and a case in which the operation of the ambient noise removing device is turned on will be described by way of example.

8 is a flowchart illustrating a method for removing ambient noise according to an exemplary embodiment of the present invention, and is implemented in the ambient noise removing apparatus 100 described with reference to FIG. 3.

First, in step S11, the microphone 110 receives a valid sound source including ambient noise. In step S13, the reference level converging unit 120 adjusts the input level of the sound source signal input through the microphone 110 to a predetermined value according to a preset reference level. In operation S15, the input level limiting unit 130 removes the sound source signal exceeding a predetermined 'limit input level' from the sound source signal input from the reference level converging unit 120.

Next, a predetermined voltage is applied as an electrical signal corresponding to a valid sound source including ambient noise input from the input level limiting unit 130, a current is generated from the applied voltage, and the current is set as the reference current setting unit 140 and It is input to the variable amplifier 150.

Accordingly, the reference current setting unit 140 full-wave rectifies the input current in step S17, and sets the reference current using the average value obtained by full-wave rectification in step S19.

In operation S21, the variable amplifier 150 amplifies the input current according to a gain controlled by the reference current set by the reference current setting unit 140. Through this variable amplification process in step S21, the effective sound source is amplified more and the ambient noise is amplified smaller and consequently the ambient noise is removed.

Next, in step S23, the output level adjusting unit 170 finally amplifies the current amplified by the variable amplifier 150 according to a predetermined amplification ratio to adjust the output level of the sound source.

Next, in step S25, the output level limiting unit 180 removes unnecessary sound sources that are higher than or equal to the limit output level preset in the sound source finally amplified by the output level adjusting unit 170, that is, the volume sufficient for the call.

Next, in step S27, the frequency limiter 190 attenuates and outputs a predetermined frequency, that is, a component of 3.4 kHz or more, from the sound source signal input through the output level limiter 180.

9 is a flowchart illustrating a method for removing ambient noise according to another exemplary embodiment of the present invention, which is implemented in the ambient noise removing apparatus 400 described with reference to FIG. 4.

First, in step S31 the microphone 410 receives a valid sound source including the ambient noise. In step S33, the reference current setting unit 440 full-wave rectifies the sound source signal input through the microphone 410, and in step S35 sets the reference current to the average value obtained by full-wave rectification.

Next, in step S37, the variable amplifier 420 variably amplifies the input current according to a gain controlled by the reference current set by the reference current setting unit 440.

Next, in step S39, the reference level converging unit 420 adjusts the input level of the sound source signal amplified by the variable amplifier 450 based on the preset reference level to a predetermined value. In operation S41, the input level limiting unit 430 removes the sound source signal exceeding a predetermined 'limit input level' from the sound source signal input through the reference level converging unit 420.

Next, in step S43, the output level adjusting unit 470 finally amplifies the current amplified by the variable amplifier 450 according to a predetermined amplification ratio to adjust the output level of the sound source.

Next, in step S45, the output level limiting unit 480 removes unnecessary sound sources that are higher than or equal to the limit output level preset in the sound source finally amplified by the output level adjusting unit 470, that is, a volume sufficient for a call.

Next, in step S47, the frequency limiter 490 attenuates and outputs a predetermined frequency, i.e., 3.4 kHz or more, from the sound source signal input through the output level limiter 480.

FIG. 10 is a flowchart illustrating a method for removing ambient noise according to another exemplary embodiment of the present invention, and is implemented in the ambient noise removing apparatus 500 described with reference to FIG. 5.

First, in step S51 the microphone 510 receives a valid sound source including the ambient noise. Next, in step S53, the extended reference current setting unit 540 full-wave rectifies the sound source signal input through the microphone 510, and in step S55, sets the extended reference current to an average value obtained by full-wave rectification.

Next, in step S57, the level expansion unit 550 variably amplifies (level expansion) the input current according to the gain controlled by the expansion reference current set by the expansion reference current setting unit 540.

Next, in step S59, the first level adjustment unit 570a adjusts the level of the sound source input through the level expansion unit 550.

Next, in step S61, the compression reference current setting unit 530 full-wave rectifies the sound source signal input through the first level adjusting unit 570a, and sets the compression reference current to the average value obtained by full-wave rectification in step S63.

Next, in step S65, the level compression unit 520 variably amplifies (level compression) the input current according to the gain controlled by the compression reference current set by the compression reference current setting unit 530.

Next, in step S67, the second level adjusting unit 570b adjusts the level of the sound source input through the level compressing unit 520.

Next, in step S69, the output level limiting unit 580 removes unnecessary sound sources above the limit output level preset in the sound source finally amplified by the second level adjusting unit 570b, that is, a level corresponding to a volume sufficient for a call.

Next, in step S71, the frequency limiter 590 attenuates and outputs a predetermined frequency, that is, a component of 3.4kHz or more, from the sound source signal input through the output level limiter 580.

The circuit of the ambient noise removing apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings, and will be described with reference to an example of removing noise from a valid sound source including noise input through a microphone.

FIG. 11 is a circuit diagram illustrating an apparatus for removing ambient noise according to an exemplary embodiment of the present invention.

As shown in FIG. 11, the peripheral noise removing apparatus 200 of the present invention includes a preprocessing circuit unit 220 to which an input terminal is connected to a voice input input from the microphone 210; A full-wave rectifying circuit unit 240 having an input terminal connected to the voice input input from the preprocessing circuit unit 220 and an output terminal of the rectified current connected to a gain control terminal of the variable amplifier unit; An input terminal is connected to the voice input input from the preprocessing circuit unit 220, a gain control terminal is connected to the output terminal side of the full-wave rectifying circuit unit 240, and an output terminal of the amplified current is connected to the input terminal of the level adjusting unit through a resistor. It includes a variable amplification circuit unit 250 and the level conversion circuit unit 270 for receiving a current from the output terminal of the variable amplifier through the resistor and amplifies the signal according to a predetermined gain and outputs it through the output terminal. ,

The preprocessing circuit unit 220 includes a predetermined input level adjustment circuit unit 221 for converging the input level of the voice input input from the microphone 210 to a preset reference level and a voice input input from the input level adjustment circuit unit. At least one of the input level limit circuit unit 223 for removing the sound source signal exceeding the limit input level is included.

In addition, the peripheral noise removing apparatus 200 of the present invention includes a variable resistance circuit unit 260 and a level conversion circuit unit 270 for determining the gain in the level conversion circuit unit 270 to amplify a signal according to a predetermined gain. The post-processing circuit unit 230 is connected to the output terminal of the input terminal is further included,

The post-processing circuit unit 230 includes an output level limiting circuit unit 231 and an output level limiting circuit unit 231 for removing and outputting a sound source signal exceeding a predetermined 'limiting output level' from the current input from the level converting circuit unit 270. At least one of the frequency limiting circuit unit 233 which attenuates a predetermined frequency, that is, 3.4 kHz or more, from the current inputted from the terminal is included.

In the above-described configuration, the full-wave rectifying circuit unit 240 sets a reference current from a sound source input through an electronic condenser microphone (ECM: Electronic Condencer Mic) as shown. In detail, when a valid sound source including noise is input through the microphone, a predetermined voltage is applied as an electric signal corresponding to the input sound source, and a current is generated from the applied voltage. The full-wave rectifying circuit unit 240 receiving the generated current sets the reference current to an average value obtained by full-wave rectifying the input current.

Next, the variable amplifier circuit 250 has a gain controlled by the reference current set by the full-wave rectifier circuit 240, and amplifies the input current of the input sound source according to the gain. The variable amplifier circuit 250 receives a current of a valid sound source including noise through a microphone, like the full wave rectifier circuit 240, and variably amplifies the input current according to a gain controlled by a set reference current. will be.

Next, the input level adjustment circuit unit 220 amplifies or attenuates the magnitude of the current input from the microphone 210 based on a predetermined reference level. More specifically, when the level of the current input from the microphone 210 is smaller than the preset reference level, the input level adjusting circuit unit 220 amplifies the level larger by this reference level, while inputting from the microphone 210. If the level of the current is larger than the preset reference level, the level is amplified smaller by this reference level. 12 illustrates a detailed circuit diagram of the input level adjustment circuit unit shown in FIG. 11, wherein the input level adjustment circuit unit 220 includes a resistor, a diode, a transistor, and a transistor as shown in FIG. 12. It may be composed of a combination of capacitor elements.

Next, the input level limiting circuit unit 230 removes the sound source signal exceeding a predetermined 'limiting input level' from the current input from the output terminal of the input level adjusting circuit unit 220, thereby changing the variable amplifier circuit section 250 and full-wave rectification. Output to the circuit unit 240.

Next, the level conversion circuit unit 270 adjusts the level of the sound source by finally amplifying the level of the sound source amplified by the variable amplification circuit unit 250 at a predetermined amplification ratio.

Next, the frequency limiting circuit unit 290 is implemented by a predetermined low pass filter (LPF), it is preferable to be implemented by the LPF as shown in FIG. On the other hand, Figure 14 is a graph showing the frequency characteristics when applying a voltage of AC 1V to the input terminal of the frequency limit circuit unit 290, as shown in Figure 14 at 1kHz output voltage is 0.9V applied voltage While most of the output is confirmed, at 3.5kHz the output voltage is attenuated to 0.5V.

The output terminal of any one of the level converting circuit section 270, the output level limiting circuit section 231, and the frequency limiting circuit section 233 can be electrically connected to the microphone input terminal of the mobile communication terminal, and also has a hands-free having a predetermined connection standard. The mobile terminal may be connected to the mobile communication terminal through the connection terminal. When the peripheral noise removing apparatus 200 is connected through the connection terminal, the microphone of the mobile communication terminal itself may be automatically turned off.

Meanwhile, the preprocessing circuit unit 220 may be located between the variable amplifier circuit unit 250 and the variable resistance circuit unit 260 based on the peripheral noise removing apparatus 400 described with reference to FIG. 4. In addition, the ambient noise removing apparatus 200 is based on the ambient noise removing apparatus 500 described with reference to FIG. 5 without the preprocessing circuit unit 220 described above, and the level compression unit 520 and the compression reference current. A circuit corresponding to the setting unit 530 may be configured between the level conversion circuit unit 270 and the post processing circuit unit 230. In addition, the ambient noise removing device 200 according to the invention includes a switching switch for turning on or off the operation of the ambient noise removing device or a regulator for supplying power for driving the circuit. Since the resistors or capacitors that are not described elsewhere are used for driving and stability of the circuit, detailed descriptions thereof will be omitted.

FIG. 15 is a block diagram of a mobile communication terminal having an apparatus for removing ambient noise according to another embodiment of the present invention.

Referring to FIG. 15, as shown, the mobile communication terminal 300 incorporating the ambient noise removing device 310 according to another embodiment of the present invention includes a microphone 390 for receiving a sound source from the outside, and It includes a peripheral noise removing device 310 for removing noise from the sound source signal input through the microphone 390. The mobile communication terminal including the peripheral noise removing device 310 includes a wireless communication unit 330, a control unit 340, a key input unit 350, a display unit 360, and a memory, which are common components of the existing mobile communication terminal. 370 and the interface unit 380 is further included.

In the above-described configuration, the ambient noise removing device 310 is input through the reference level converging unit 311 or the microphone 390 to converge the input level of the sound source signal input through the microphone 390 to a preset reference level. An input level limiting unit 312 for removing a sound source signal exceeding a predetermined 'limiting input level' from the sound source signal; A reference current setting unit 313 for setting a reference current to an average value obtained by full-wave rectifying the sound source signal input through the reference level converging unit 311 or the input level limiting unit 312; A variable amplifier 314 having a gain controlled by the reference current set by the reference current setting unit 313 and amplifying the input current of the sound source input through the reference level converging unit 311 according to the corresponding gain; It includes an output level adjusting unit 316 for adjusting the output level of the sound source amplified by the variable amplifier 314.

In addition, the peripheral noise removing device 310 includes a variable resistor unit 315 for determining the amplification ratio so that the output level adjusting unit 316 can adjust the level of the sound source according to a predetermined amplification ratio in adjusting the level of the sound source. An output level limiting unit 317 for removing a sound source signal exceeding a predetermined 'limiting output level' from a sound source signal input from the output level adjusting unit 316, and a sound source signal input through the output level limiting unit 317. A frequency limiter 318 may be further included to attenuate and output a component having a predetermined frequency or more.

In the above-described configuration, the reference current setting unit 313 sets the reference current from the sound source input through the microphone 390. In detail, when a valid sound source including noise is input through the microphone 390, a predetermined voltage is applied as an electric signal corresponding to the input sound source, and a current is generated from the applied voltage. The reference current setting unit 313 which receives the generated current sets the reference current to an average value obtained by full-wave rectifying the input current.

Next, the variable amplifier 314 controls the gain by the reference current set by the reference current setting unit 313 and amplifies the input current of the input sound source according to the gain. The variable amplifier 314 receives a current of a valid sound source including noise through the microphone 390 similarly to the reference current setting unit 313, and converts the input current into a gain controlled by the set reference current. According to variable amplification.

Next, the reference level converging unit 311 amplifies or attenuates the magnitude of the effective sound source signal including the noise input from the microphone 390 based on a predetermined reference level. Specifically, when the input level of the effective sound source including the noise input from the microphone 390 is smaller than the preset reference level, the reference level converging unit 311 amplifies the input level of the sound source to be larger by this reference level. On the other hand, when the input level of the effective sound source including the noise input from the microphone 390 is larger than the preset reference level, the input level of the sound source is amplified smaller by this reference level.

Next, the input level limiting unit 312 removes a sound source signal exceeding a predetermined 'limit input level' from the sound source signal input through the microphone 390. In detail, the input level limiting unit 312 may remove the sound source signal exceeding a predetermined limit input level from the sound source signal whose level is adjusted through the reference level converging unit 311, that is, the noise and the variable amplifier 314. The reference current setting unit 313 outputs the result.

Next, the output level adjusting unit 316 adjusts the level of the sound source amplified by the variable amplifier 314. The output level adjusting unit 316 may be implemented as an operational amplifier, and finally adjusts the level of the sound source by amplifying the level of the sound source amplified by the variable amplifier 314 at a predetermined amplification ratio. The predetermined amplification ratio is determined through the variable resistor unit 312.

Next, the voice processing unit 320 processes a digital voice data into an analog voice signal or vice versa, and has a known configuration including an additional circuit such as an audio amplifying circuit or a filter. The signal source adjusted by) is received and signal processed. The voice processor 320 may be a voice codec.

The wireless communication unit 330 is configured to include an antenna and RF circuit for communication with the base station. In the present specification, the wireless communication unit 330 is interpreted to cover not only various versions of CDMA, but also existing methods such as cellular, GSM, W-CDMA, and WiBro, as well as mobile communication methods to be introduced in the future.

The controller 340 generally controls the operation of the mobile communication terminal. The key input unit 350 includes a plurality of numeric keys, character keys, and function keys, receives a user's command, and transmits the command to the controller 340. The display unit 360 operates as a whole. Display the status.

The memory 370 may be a nonvolatile memory such as an EEPROM or a flash memory, and stores data and programs necessary for driving the mobile communication terminal.

The interface unit 380 may be a communication port for connecting the mobile communication terminal with an external device, and is connected to the external device through a predetermined communication cable.

As described above, the peripheral noise removing device 310 may be included in the mobile communication terminal 300, but may be implemented as an integral part in an ear microphone provided with the mobile communication terminal 300. Depending on the operation, the operation may be turned on or off.

In addition, the peripheral noise removing device 310 may be provided in the form of a predetermined chip. Accordingly, even when the peripheral noise removing device 310 is connected to the interface unit 380 through a communication cable conforming to the connection standard of the input / output terminal, the audio signal is received. It can be implemented to be operated. At this time, when the peripheral noise removing device is connected through the interface unit 380 of the mobile communication terminal, the microphone of the mobile communication terminal itself can be implemented to be automatically turned off (OFF), the operation of the peripheral noise removing device is turned on (ON) In this case, the mobile terminal can receive and process the corresponding signal.

In addition, the connection standard includes a TTA24PIN, and even if the connection standard is revised later, the peripheral noise canceller may be provided to be accessible to the mobile communication terminal according to the revised connection standard. For reference, pin 7 of each pin of I / O terminal of TTA24PIN is used for AUDIO IN / PCM RX.

On the other hand, generally referred to as a vocoder (vocoder) is a technology that can use the frequency efficiently by varying the transmission rate of the voice data according to the speed of the voice. For example, when speech is fast, the speech signal is converted to a data rate of 8.6 Kbps, and when speech is slow, it is converted to 4.0 Kbps. If a person speaks little, it is converted to either 2.0 Kbps or 0.8 Kbps. Therefore, the peripheral noise device according to the present invention is equipped with a vocoder for processing the voice signal output from the above-described frequency limiting unit, in particular, a 13 Kbps QCELP (Qualcomm CELP) type EVRC (Enhanced Variable Rate Speech Codec) is installed. It may work together.

The apparatus and method for removing ambient noise of the present invention can be implemented in various modifications within the scope of the technical idea of the present invention, without being limited to the above-described embodiments.

1 is a circuit diagram of a noise reduction circuit introduced through a conventional microphone;

2 is a graph showing the output level of the input level of the sound source input from the ambient noise removing device according to an embodiment of the present invention,

3 is a block diagram of an apparatus for removing ambient noise according to an embodiment of the present invention;

Figure 4 is a block diagram of a peripheral noise removing device according to another embodiment of the present invention,

5 is a block diagram of an apparatus for removing ambient noise according to still another embodiment of the present invention;

6 is a circuit diagram of a level expansion unit and an extension reference current setting unit, which are components of FIG. 5, according to an embodiment of the present invention;

7 is a circuit diagram of a level compression unit and a compression reference current setting unit, which are components of FIG. 5, according to an embodiment of the present invention;

8 is a flowchart illustrating a method for removing ambient noise according to an embodiment of the present invention;

9 is a flowchart illustrating a method for removing ambient noise according to another embodiment of the present invention;

10 is a flowchart illustrating a method for removing ambient noise according to another embodiment of the present invention;

11 is a circuit diagram illustrating an ambient noise removing apparatus according to an embodiment of the present invention;

12 is a detailed circuit diagram of an input level adjusting circuit part shown in FIG. 11;

FIG. 13 is a detailed circuit diagram of the frequency limiting circuit part shown in FIG. 11;

14 is a graph showing frequency characteristics output from the circuit diagram of FIG. 13;

15 is a block diagram of a mobile communication terminal having an ambient noise removing device according to an embodiment of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

100, 200, 310, 400, 500: ambient noise canceller

300: mobile communication terminal

110, 210, 390, 410, 510: microphone

120, 311, 430: reference level converging unit 130, 312, 450: input level limiting unit

140, 313, 440: reference current setting unit 150, 314, 420: variable amplifier

160, 315, 460: variable resistors 170, 316, 470: output level adjusting unit

180, 317, 480, 580: Output level limit

190, 318, 490, 590: Frequency limit

220: preprocessing circuit section 221: input level adjustment circuit section

223: input level limit circuit 230: post processing unit

231: output level limiting circuit section 233: frequency limiting circuit section

240: full-wave rectifying circuit section 250: variable amplifier circuit section

260: variable resistance circuit portion 270: level conversion circuit portion

520: level compression unit 530: compression reference current setting unit

540: extension reference current setting unit 550: level expansion unit

Claims (9)

In the ambient noise removing device for removing noise from a valid sound source signal including the noise input through the microphone or sensor, A reference current setting unit which sets a reference current to an average value obtained by full-wave rectification of the sound source signal; The gain is controlled by the reference current set by the reference current setting unit, and includes a variable amplifier for amplifying the input current of the input sound source signal according to the gain proportional to the voltage of the sound source signal, And at least one of a reference level converging unit for converging the input level of the sound source signal to a preset reference level and an input level limiting unit for removing a sound source signal exceeding a predetermined limit input level from the sound source signal. Peripheral noise removing device. The method of claim 1, And a frequency limiting unit configured to attenuate components above a predetermined frequency in the sound source signal amplified by the variable amplifier. The method of claim 2, Ambient noise removing device, characterized in that the frequency of the sound source signal output from the frequency limiting unit is 300Hz ~ 3.4kHz. The method of claim 1, Peripheral noise removing device further comprises a vocoder for varying the transmission rate of the sound source signal amplified by the variable amplification unit. The method of claim 1, Sensitivity of the microphone is less than -40dB, characterized in that the ambient noise removing device. The method of claim 1, And a peripheral noise removing device connected to the mobile communication terminal. In the ambient noise removal method for removing noise from a valid sound source signal including the noise input through the microphone or sensor, (A) setting a reference current to an average value obtained by full-wave rectifying the sound source signal; and The gain is controlled by the reference current set in the step (a), and amplifying the input current of the input sound source signal according to the gain proportional to the voltage of the sound source signal, (C) converging the input level of the sound source signal to a preset reference level, and removing (d) a sound source signal exceeding a predetermined limit input level from the sound source signal. How to remove ambient noise. The method of claim 7, wherein And attenuating a component above a predetermined frequency in the sound source signal passed through step (b). The method of claim 8, In the step (f), the frequency is 300Hz ~ 3.4kHz characterized in that the ambient noise removing method.

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