JPH05207587A - Microphone device - Google Patents

Abstract

PURPOSE:To reduce a change in sound quality due to a change in a distance between a microphone and a talker (sound source). CONSTITUTION:Signals from a single directive microphone 1 used for sound collection and an unidirectional microphone 2 being a reference for distance detection are amplified by amplifiers 3, 4. Then signal levels subjected to band division by band pass filters 5, 6 are compared by plural comparators 7, 8, 9. Thus, plural high pass filters 10 are controlled by a comparison signal obtained in this way so as to vary the frequency characteristic of the sound signal from the single directivity microphone.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device used when the distance between a speaker and a microphone is not always constant at meetings, performances and the like.

[0002]

2. Description of the Related Art Conventionally, in a microphone device of this type, as shown in FIG. 2A, the voice of a speaker 19 is amplified by an amplifier 21 via a microphone 20 and is amplified by a speaker 22. It Therefore, as the distance between the speaker 19 and the microphone 20 gets closer to r3, r2, and r1, as shown in FIG.
As shown in (b), the proximity effect, which is a phenomenon in which the sound pressure in the low range becomes high, becomes remarkable. Therefore, the sound quality changes and the clarity deteriorates. In order to solve this problem, it is conceivable to use the omnidirectional microphone shown by the dotted line in FIG.

[0003]

However, when the omnidirectional microphone as described above is used, howling is likely to occur and the loudness level cannot be increased, so that the problem that the intelligibility is lowered cannot be solved. It was

In view of the above problems, it is an object of the present invention to provide a microphone device capable of suppressing a change in sound quality and a reduction in the loudness level regardless of the change in the distance between the speaker and the microphone.

[0005]

In order to achieve the above object, the present invention collects a sound of a sound source to generate a first sound signal and a sound according to a distance between the sound source and the sound collecting microphone. A distance detection microphone for generating a pressure level second audio signal, first and second amplifiers for amplifying the first and second audio signals, respectively, and an amplified first and second audio signal First and second band-pass filters that pass a predetermined low-frequency component to generate first and second low-frequency signals, and different sound pressure level differences between the first and second low-frequency signals. This is a configuration including a plurality of comparators that respectively compare with the level to generate comparison signals, and a plurality of high-pass filters that control the frequency characteristics of the first audio signal according to the plurality of comparison signals.

[0006]

According to the present invention, the cut-off frequency of the microphone for sound collection is controlled by the detection information of the change in the distance between the speaker and the microphone, so that the change in the sound quality and the decrease in the sound level can be reduced.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A microphone device according to an embodiment of the present invention will be described below with reference to FIG. In FIG.
Reference numeral 1 is a unidirectional microphone that collects sound from a sound source to generate a first sound signal, and 2 is omnidirectional that generates a second sound signal having a sound pressure level according to the distance from the sound source. Sex microphone. Reference numerals 3 and 4 are amplifiers for amplifying the audio signals obtained from the microphones 1 and 2, respectively.
Reference numerals 5 and 6 are bandpass filters that pass the frequency band that causes the proximity effect of the audio signals A1 and B1 amplified by the amplifiers 1 and 2. Reference numerals 7, 8 and 9 are comparators which receive the audio signals A2 and B2 from the band pass filters 5 and 6, respectively, and generate comparison signals C1, C2 and C3. Reference numeral 10 designates these comparison signals C1, C2 and C3 as a control input signal and switches a high pass filter composed of capacitors 11, 12 and 13 and a resistor 14 to cut off a low frequency component of the audio signal A1 from the amplifier 3. It is an analog switch. Reference numeral 15 is an output terminal for outputting the output signal D obtained from the analog switch 10.

Next, the operation of the above embodiment will be described.
In FIG. 1, the sound pressure level of the audio signal B2 obtained from the omnidirectional microphone 2 serving as the reference of the distance information through the amplifier 4 and the bandpass filter 6, and the unidirectional microphone 1 to the amplifier 3 and the bandpass filter 5 are shown. The sound pressure level of the audio signal A2 that has passed is compared by the comparators 7, 8 and 9. The change in the sound pressure level in the low frequency range of the audio signal A2 is larger than that of the audio signal B2 as shown in FIG. The sharper the directivity, the larger the level difference. On the other hand, the comparators 7, 8 and 9 have reference levels within different predetermined ranges and the input audio signal A2.
And a difference in sound pressure level of B2 are compared, and a comparison signal which is a binary signal indicating "1" or "0" is output. The predetermined range of these reference levels has a larger value in the order of the comparators 7, 8 and 9.

Therefore, when the distance between the speaker 19 shown in FIG. 1 and the sound collecting microphone 20 (which becomes the sound collecting unidirectional microphone 1 in FIG. 2) is r1, the difference in sound pressure level is large. Since it is large, the comparison signal C1 from the comparator 7 becomes "1", the capacitor 11 and the resistor 14 are connected by the analog switch 10, and the high-pass filter formed as a result is in the operating state, and the low frequency band of the audio signal A1. Shut off. Similarly, when the distance is r2 or r3, the comparison signal C2 or C3 from the comparator 8 or 9 becomes "1", and the capacitor 12 or 13 and the resistor 14 are connected, so that the high pass formed as a result. The filter is activated,
The low frequency band of the audio signal A1 is cut off. Speaker 19 shown in FIG.
And sound pickup microphone 20 (unidirectional microphone 1)
It is highest when the distance between and is r1, and becomes lower as it becomes r2 and r3.

As described above, the sound pressure level of the unidirectional microphone 1 which is a sound pickup microphone becomes higher in the low frequency range due to the proximity effect. , 9 has the effect that the high-pass filter composed of the capacitors 11, 12, 13 and the resistor 14 can be controlled, the change in the sound quality in the low frequency range can be reduced, and at the same time, the loudness is not impaired.

Although the high pass filter is controlled by the analog switch 10 in the above embodiment, the comparators 7, 8,
9 directly to capacitors 11, 12, and 13 and a resistor 14, respectively.
You may connect the high-pass filter which consists of. In this case, it can be realized at a low price without impairing the effect.

[0012]

The present invention is clear from the above embodiment,
The unidirectional microphone 1 which is a microphone for collecting sound has a high sound pressure level in the low range due to the proximity effect, and a sound pressure level difference with the omnidirectional microphone 2 is compared by the comparators 7, 8 and 9 to obtain a capacitor. At the cutoff frequency of the high-pass filter composed of 11, 12, 13 and the resistor 14,
This has the effect of being able to control changes in the sound quality in the low frequency range and at the same time not impairing the amount of loudspeaking.

[Brief description of drawings]

FIG. 1 is a block diagram of a microphone device according to an embodiment of the present invention.

2A is a general schematic diagram of a conventional sound pickup system, and FIG. 2B is a directional sound pressure-frequency characteristic of a general microphone.

[Explanation of symbols]

 1 Single Microphone 2 Omnidirectional Microphone 3,4 Amplifier 5,6 Bandpass Filter 7,8,9 Comparator 10 Analog Switch 11,12,13 Capacitor 14 Resistance 15 Output 19 Speaker 20 Sound Pickup Microphone 21 Amplifier 22 Speaker

Claims (2)

[Claims] 1. A sound pickup microphone that picks up sound from a sound source to generate a first sound signal, and distance detection that generates a second sound signal having a sound pressure level corresponding to the distance from the sound source. A microphone, first and second amplifiers for amplifying the first and second audio signals respectively, and the amplified first
And first and second band-pass filters that pass predetermined low-frequency components of the second and second audio signals to generate first and second low-frequency signals, and sounds of the first and second low-frequency signals. A plurality of comparators that compare the pressure level differences with different reference levels to generate comparison signals; and a plurality of high-pass filters that control the frequency characteristics of the first audio signal according to the plurality of comparison signals. Microphone device equipped with. 2. The microphone device according to claim 1, wherein the sound pickup microphone is a unidirectional microphone, and the distance detection microphone is an omnidirectional microphone.