JP2006072114A - Noise reduction device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem in which a conventional device which reduces noise over the entire audible frequency range and then causes its constitution to be complex resulting in cost increase. <P>SOLUTION: Noise is collected by a unidirectional microphone (40), its band is limited by a band-pass filter (50), and the noise is input to an amplifier (60), the amplifier (60) and a loudspeaker (70) are connected so that the sound collected by the unidirectional microphone (4) and sound outputted from the loudspeaker (70) are opposite in phase, thereby reducing the noise by making the output from the loudspeaker (70) cancel the noise. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a noise reduction device, and more particularly, to a device for reducing noise from indoors, such as talking voices from roads that enter the room from the outside during sleep, and automobiles.

  FIG. 4 shows an overall configuration diagram of a conventional silencer.

  In the conventional method, noise (10) is collected by a microphone (SM), and an output for canceling it is output from a speaker (S).

  FIG. 5 shows a block diagram of a configuration example of a conventional silencer.

As shown in FIG. 5, this method requires a frequency detector (23) because the delay time varies depending on the noise frequency. In the conventional silencer, a delay circuit (25) is required to obtain a delay time corresponding to the frequency. This delay circuit uses a method of A / D (analog / digital) conversion of the signal, D / A (digital / analog) conversion after delaying the signal, and requires a complicated configuration. Further ingenuity is required to cope with this frequency.
(For example, see Patent Document 1)

  FIG. 6 is a block diagram of another conventional silencer.

As shown in the block diagram of FIG. 6, the amplitude equivalent circuit 9 for flattening the sound pressure frequency characteristic of the speaker to be reproduced, the phase equivalent circuit 10 for flattening the phase frequency characteristic of the speaker, the circuit 12 for delaying the signal, etc. Is required.
(For example, see Patent Document 2)

JP-A-8-202373 JP 62-102290 A

  However, the conventional silencer has a problem that its configuration is complicated because it tries to reduce noise over a wide range of frequencies, and the cost is increased due to a device such as widening the spatial range for silence. .

  The present invention has been made in view of the above points, and is limited to a frequency range in which the sensitivity of the human ear is good, and has a simple configuration, and a silencing effect may be applied only to the vicinity of the head portion of the sleeping place. The purpose is to provide an inexpensive apparatus.

  The present invention relates to a noise reduction device for reducing noise by canceling noise from outside by collecting and collecting the noise from outside and processing the signal. A unidirectional microphone (40) for performing the signal, a bandpass filter (50) for band limiting the signal from the unidirectional microphone (40), and an output signal from the bandpass filter (50) Amplifier (60) and a speaker (70) for transmitting the output from the amplifier (60) to the space, and the sound collected by the unidirectional microphone (40) and output from the speaker (70) The speaker (70) and the amplifier (60) are connected so that the sound has an opposite phase.

  Further, the present invention is characterized by having signal detection means (80) for detecting an output signal from the bandpass filter (50).

  The present invention also has a timer means (90) for setting the time, and the unidirectional microphone (40), the bandpass filter (50), the amplifier (60), and the signal detection according to the set time. The power of the means (80) and the speaker (70) is controlled on and off.

  Further, according to the present invention, the unidirectional microphone (40) and the speaker (70) are installed in a room window, and the speaker (70) and the unidirectional microphone (40) are close to each other with a soundproof plate (130) therebetween. It is installed.

  Further, the present invention is characterized in that the unidirectional microphone (40) is installed in the vicinity of the human ear.

  In addition, the said reference symbol is attached | subjected only to make a specification easy to read, and a claim is not limited by this.

  ADVANTAGE OF THE INVENTION According to this invention, the noise from the outside can be reduced with a simple and low-cost apparatus, and there can exist an effect in the sleep etc. at the time of sleep.

  In addition, the amplifier operation of the noise reduction device can be operated only when noise is detected, and power consumption can be reduced.

  In addition, since it is possible to set a time for operating the noise reduction device such as during sleeping hours, power consumption can be reduced.

  Further, by installing the unidirectional microphone and the speaker close to each other, the phase difference between the speaker and the external noise is reduced, and external noise can be effectively reduced.

  In addition, by installing a unidirectional microphone in the vicinity of the human ear, it is possible to effectively work against noise in the vicinity of the ear.

  In this embodiment, the detailed operation of the noise reduction device will be described.

  FIG. 1 shows a block diagram of an embodiment of the present invention.

  The noise reduction apparatus according to the present embodiment is used to reduce the noise and make it possible to sleep well when sleep is disturbed by external noise or the like during sleep. The configuration includes a unidirectional microphone 40, a bandpass filter 50, an amplifier 60, a speaker 70, a signal detection circuit 80, and a timer 90.

  The output of the unidirectional microphone 40 is connected to the band pass filter 50. The output of the band pass filter 50 is connected to the amplifier 60 and the signal detection circuit 80. The output of the signal detection circuit is connected to the control terminal of the amplifier 60. The output of the amplifier 60 is connected to the speaker 70. The timer 90 is connected to control the power source of the unidirectional microphone 40, the band pass filter 50, the amplifier 60, the speaker 70, and the signal detection circuit 80. The phase relationship where the amplifier 60 and the speaker 70 are connected is such that the sound collected by the unidirectional microphone 40 and the sound output from the speaker 70 are in opposite phases.

  External noise is collected by the unidirectional microphone 40 and converted into an electrical signal. The converted electrical signal is input to the band pass filter 50. A signal from which frequency components in unnecessary regions have been removed by the band pass filter is output and input to the amplifier 60 and the signal detection circuit 80.

  When a signal of a predetermined level or higher is input to the signal detection circuit 80, the signal detection circuit 60 outputs a logic level signal “H” to the control terminal of the amplifier 60.

  When the “H” signal is received from the signal detection circuit 80, the amplifier 60 shifts the operation state from the standby state to the operation of amplifying the signal. Then, the signal from the bandpass filter 50 is amplified and the signal is output to the speaker 70.

  The speaker 70 receives an output signal from the amplifier 60 and converts the signal into air vibration.

  The timer 90 has a function of controlling the power supply of each part of the unidirectional microphone 40, the bandpass filter 50, the amplifier 60, the speaker 70, and the signal detection circuit 80. For example, when the time is set so as to work during sleep time. Based on the time set in the timer 90, the unidirectional microphone 40, the band pass filter 50, the amplifier 60, the speaker 70, and the signal detection circuit 80 are turned on and turned off at other times. It is possible to reduce power consumption by preventing the operation during non-sleeping hours.

  The bandpass filter 50 will be described.

  FIG. 7 is a characteristic diagram generally called a loudness curve, which is a sensitivity curve of sound pressure and frequency of a human ear. According to this, the frequency with the best sensitivity of the human ear is about 4 KHz. From the viewpoint of the minimum audible value characteristic, the frequency range when the sensitivity is lowered by 20 dB (1/100 times) from 4 KHz is about 200 to 8 KHz. At 10 dB (1/10 times), it is about 600 to 7 KHz, and at 5 dB (1/3 times), it is 2 K to 5.5 KHz.

  That is, considering the sensitivity characteristics of the human ear, there is a very good effect at about 200-8 KHz, a sufficient effect at about 600-7 KHz, and a large effect can be expected even at 2K-5.5 KHz. .

  Therefore, by using a band-pass filter, the noise is effectively and effectively reduced by limiting the frequency band to about 200 to 8 KHz, more preferably about 600 to 7 KHz, and still more preferably 2 K to 5.5 KHz. Can do.

  FIG. 8 shows an example of speaker characteristics.

  From the characteristic diagram of FIG. 8, a relatively flat characteristic is shown from 200 Hz to 8 KHz, and the frequency characteristic is generally attenuated in the low frequency range and the high frequency range. From this, it can be seen that if a silencing operation is performed in a low frequency range and a high frequency range, a circuit or the like for compensating this characteristic is required, which complicates the circuit and increases the cost.

  FIG. 2 shows the structure of an embodiment of the present invention.

  As shown in FIG. 2, a window 120 is formed between the walls 110-1 and 110-2. Noise from the outside enters through the window 120.

  A speaker 70 is installed in the window 120 so that a person can hear a sound obtained by adding the output of the speaker 70 and noise.

The unidirectional microphone 40 is installed in the vicinity of the speaker with a soundproof board 130 for reducing the influence of sound from the speaker 70. For example, if the distance between the unidirectional microphone 40 and the speaker 70 is X, and the noise frequency is 4 KHz, the speed of the sound is about 340 m / s. The length is 340 / 4000≈0.085 [m] = 8.5 [cm].
Since a great effect can be expected by suppressing the phase difference to 10% or less, it is desirable to set X to 8.5 mm or less. When the frequency is 8 KHz, the length is half of that, so X is more preferably 4.2 mm or less.

  Since the speaker 70 is configured to output a sound having an opposite phase to the sound collected by the unidirectional microphone 40, the noise reduction effect can be increased as the phase difference decreases.

  FIG. 3 is a diagram showing the structure of another embodiment of the present invention.

  Parts that are the same as those in FIG.

  In the case of this embodiment, the unidirectional microphone 40 is installed near the human ear. The output from the speaker 70 is controlled so that the external noise collected by the unidirectional microphone 40 and the added sound of the sound output from the speaker 70 cancel each other and become less. To do.

Configuration block diagram of one embodiment of the present invention The figure which shows the structure of one Example of this invention The figure which shows the structure of another Example of this invention Overall configuration diagram of conventional silencer Block diagram of a configuration example of a conventional silencer Block diagram of another conventional silencer Loudness curve characteristic diagram Example of speaker characteristics

Explanation of symbols

30 100 200 Noise reduction device 40 Unidirectional microphone 50 Band pass filter 60 Amplifier 70 Speaker 80 Signal detection circuit 90 Timer 110-1 110-2 Wall
120 Window 130 Soundproof board

Claims (5)

In a noise reduction device that reduces noise by collecting noise from outside, processing and outputting the signal, and canceling noise from outside,
The noise device is a unidirectional microphone for collecting noise from the outside,
A band-pass filter for band-limiting a signal from the unidirectional microphone;
An amplifier for amplifying an output signal from the bandpass filter;
A speaker for transmitting the output from the amplifier to the space;
A noise reduction apparatus, wherein the speaker and the amplifier are connected so that a sound collected by the unidirectional microphone and a sound output from the speaker are in opposite phases. 2. The noise reduction device according to claim 1, further comprising signal detection means for detecting an output signal from the band pass filter. Timer means for setting time is provided, and the unidirectional microphone, the band-pass filter, the amplifier, the signal detection means, and the speaker are turned on and off according to the set time. The noise reduction device according to claim 1 or 2, characterized in that 4. The noise according to claim 1, wherein the unidirectional microphone and the speaker are installed in a window of a room, and the speaker and the unidirectional microphone are installed close to each other with a soundproof plate interposed therebetween. Reduction device. 4. The noise reduction apparatus according to claim 1, wherein the unidirectional microphone is installed in the vicinity of a human ear.

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