JPH05207586A - Microphone device - Google Patents

Abstract

PURPOSE:To facilitate the adjustment by providing a microphone having a sound pipe in addition to a sound collection microphone to the device and taking a difference between sound signals of both the microphones so as to utilize a delay effect specific to a line microphone. CONSTITUTION:This microphone device is provided with a 1st microphone 1 of single directivity collecting a sound from a sound source and generating a 1st sound signal. Moreover, an unidirectional 2nd microphone 5d is provided at a position of a prescribed distance from the 1st microphone 1 opposite to the sound source. Then a sound pipe 5a of a prescribed length is connected to the 2nd microphone 5d to collect the sound from the sound source and the sound from the 1st microphone 1 to generate a 2nd sound signal. Then the delay effect specific to the line microphone is utilized by taking a difference between sound signals from both the microphones so as to facilitate the adjustment without taking the identity of the characteristics of both the microphones into account.

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 particularly for loudspeaking.

[0002]

2. Description of the Related Art Microphone devices used for loudspeaking have been well known. FIG. 15 shows such a conventional microphone device. In FIG. 15, 1 is a microphone unit, which has the highest sensitivity in the front direction, that is, in the direction of an angle of 0 degrees, the sensitivity decreases in the lateral direction, that is, in the direction of 90 degrees, and in the rear direction, that is, the direction of 180 degrees The lowest. In general, the directional pattern of sensitivity of the microphone unit 1 has a unidirectional pattern (first-order gradient type) shown in FIG.

FIG. 17 shows frequency sensitivity characteristics of the conventional microphone unit at 0 °, 90 °, 135 ° and 180 °. With such a characteristic, the howling margin is naturally limited, and in order to improve this, there is a microphone device having a super-directivity (secondary gradient type) configuration shown in FIG. In this figure, 1 and 2 are unidirectional microphone units having substantially the same characteristics and are arranged at intervals of a distance d. Reference numeral 3 is an adder circuit (or phase inversion circuit) that outputs the difference between the audio signals obtained from the two microphone units 1 and 2. Furthermore, 4
Is a low frequency correction circuit for correcting the low frequency component of the output signal of the adder circuit 3.

In the case of the configuration shown in FIG. 18, by adjusting the output level of the microphone unit 2, the audio signal obtained from the low-frequency correction circuit 4 has a directional characteristic as shown in FIG. It is possible to improve the howling margin as compared with those described above.

[0005]

However, in the above-described conventional microphone device, there is a problem that the two microphone units 1 and 2 are required to have characteristics that are relatively matched, and that adjustment is not easy.

The present invention solves the above problems,
It is an object of the present invention to provide an inexpensive microphone device that is easy to adjust and does not require a device having matching characteristics.

[0007]

In order to achieve the above-mentioned object, the present invention collects a sound from a sound source to generate a first audio signal, and a predetermined distance from the first microphone. From the sound source and the first microphone having an omnidirectional microphone arranged at the position of 1) and an acoustic tube of a predetermined length connecting the omnidirectional microphone to the terminal end. A second microphone that collects the emitted sound and generates a second audio signal;
And a synthesizing means for generating a synthesized signal which is the difference between the first and second audio signals.

[0008]

Therefore, according to the present invention, the difference between the sound signal from the first microphone for collecting the sound from the sound source and the sound signal from the second microphone with the acoustic tube is taken to obtain the first and The adjustment can be facilitated without considering the identity of the characteristics of the second microphone.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the first embodiment of the present invention.
Reference numeral 1 is a microphone unit as a first microphone that collects a sound from a sound source (not shown) and generates a first audio signal. Reference numeral 5 denotes a line microphone as a second microphone that collects not only the sound from the sound source but also the sound emitted from the microphone unit 1 to generate a second audio signal. ) 5a. The acoustic tube 5a is provided with a plurality of sound holes (or slits) 5b, and a resistance surface cloth 5c is attached to the outside of the tube in an annular shape. Further, an omnidirectional microphone 5d is provided at the end of the acoustic tube 5a. The distance between the microphone unit 1 and the omnidirectional microphone 5d is d. Reference numeral 3 denotes an adding circuit (phase shift inverting circuit) as a synthesizing unit that detects a difference between the first and second audio signals and outputs a synthesized signal.

Next, the operation of the above embodiment will be described. First, a case where the length 1 of the line tube 5a is 1 = 5 cm will be described with reference to FIGS. Figure 2
Shows the frequency characteristic of the omnidirectional microphone 5d alone, which is a substantially flat characteristic from 100 Hz to 10 kHz regardless of the direction. FIG. 3 shows a frequency characteristic of the microphone 5 incorporating the omnidirectional microphone 5d, which has different characteristics depending on the directions of 0 degree, 90 degrees, and 180 degrees, that is, a characteristic having directivity.

FIG. 4 shows an adding circuit 3 when the distance d between the microphone 1 and the omnidirectional microphone 5d is twice the line length l, that is, when d = 2l (= 10 cm).
0 degree, 90 degrees, 135 of the output signal of
FIG. 5 shows frequency characteristics in the directions of 180 degrees and 180 degrees.
FIG. 4 is a diagram showing the directivity pattern. As is apparent from FIG. 5, although it has a slight directivity to 180 degrees, that is, backward, the overall directivity is close to the superdirective of the secondary gradient type microphone shown in FIG. Note that FIG. 6 shows the adder circuit 3 when d = 3 l (= 15 cm).
Is the frequency characteristic of the output signal of. When the operation principle is analyzed from the characteristics of FIGS. 4 and 6, the output difference of the line microphone 5 is almost matched with the level of the unidirectional microphone 1 in the direction of 180 degrees. As the point where the directivity is the smallest,
It can be seen that it is near the frequency f (f = c / λ; c is the speed of sound) at which d ′ = λ / 6 (where d ′ = d−1 and λ is the wavelength).

Further, d is an effective variable range of the distance d.
> 1 and when d = 1 or d <l, the above-mentioned effective characteristics were not obtained. Considering the directivity of all frequency bands, the vicinity of d = 21 is optimal. k = 2
When πf / c is set, optimum characteristics are obtained in the vicinity of kl = 1. Since the line microphone 5 has a delay effect (delay time), it is considered that this delay characteristic works effectively to obtain the above characteristics. Further, even if the characteristics of the line microphones 5 vary, the adding circuit 3
Since it has little effect on the output signal of,
The cost increase can be suppressed.

FIG. 7 and FIG. 8 respectively show a line pipe length l.
Shows the frequency characteristics of the line microphone 5 in the case of 10 cm and 20 cm. In FIG. 9 and FIG.
It shows the frequency characteristics of the combined signal in the case of 10 cm and d = 2l and d = 3l. Also, FIG.
1 shows the frequency characteristic of the combined signal when l = 20 cm and when d = 21. 10 and 1
As is clear from 1, it is understood that the same result as in the case of l = 5 cm is obtained.

12 and 13 show a case where the line tube 5a in FIG. 1 is removed and d = 10 cm.
And the frequency characteristics of the synthesized signal by the unidirectional microphone 1 and the omnidirectional microphone 5d in the case of 20 cm. In this case, the characteristics in the low frequency region near d '= λ / 6 have the same characteristics as those in the above-mentioned embodiment, but the characteristics in the middle frequency region and the high frequency region are different from those in the above-mentioned embodiment and are effective. It can be seen that no significant improvement has been obtained.

In the case of the present invention, the line microphone 5
Is for obtaining a narrow directivity, and its level is adjusted to be low as in the above embodiment. Therefore, in the case of close proximity use such as speech, sound pressure input to the unidirectional microphone 1 is basically used, so that there is also an effect that sound quality deterioration is reduced.

Next, a second embodiment of the present invention will be described with reference to FIG. 14, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. 6 is a high-cut filter circuit as a first extracting means for removing high-frequency components,
Reference numeral 7 is a low-cut filter circuit as a second extracting means for removing low-frequency components, and 8 is an adding circuit as an adding means for adding signals in phase unlike the adding circuit 3.

In the operation of the second embodiment, the output signal of the line microphone 5 is divided into a low frequency component and a high frequency component,
As in the case of FIG. 1, the low-frequency component is a high-frequency component that is generated by the adding circuit 3 as a difference between the low-frequency component and the sound signal from the unidirectional microphone 1 and is passed through the low-cut filter circuit 7. And are further combined in the adder circuit 8.

The same effects as those of the first embodiment shown in FIG. 1 can be obtained in this second embodiment or in other embodiments in which the combination of the structures is changed.

[0019]

As is apparent from the above embodiment, the present invention provides a line microphone having an acoustic tube as a second microphone in addition to the first microphone for collecting sound, and outputs a voice signal from both microphones. By taking the difference between the two microphones, the delay effect peculiar to the line microphones can be utilized, and the effect of facilitating the adjustment can be obtained without considering the identity of the characteristics of both microphones.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a graph showing frequency characteristics of an omnidirectional microphone.

FIG. 3 is a graph showing frequency characteristics of a line microphone when the acoustic tube length 1 is 1 = 5 cm.

FIG. 4 is a graph showing frequency characteristics of a line microphone when l = 5 cm and the distance d between the microphones is d = 2l in FIG.

5 is a diagram showing a directivity pattern in FIG.

FIG. 6 is a graph showing frequency characteristics of the line microphone when l = 5 cm and d = 3 l in FIG.

FIG. 7 is a graph showing frequency characteristics of the line microphone when l = 10 cm in FIG.

FIG. 8 is a graph showing frequency characteristics of the line microphone when l = 20 cm in FIG.

9 is a graph showing frequency characteristics of the line microphone when l = 10 cm and d = 21 in FIG.

10 is a graph showing frequency characteristics of the line microphone when l = 10 cm and d = 3 l in FIG.

FIG. 11 is a graph showing the frequency characteristic of the line microphone when l = 20 cm and d = 21 in FIG.

FIG. 12 is a graph showing frequency characteristics of the line microphone when there is no acoustic tube and d = 10 cm in FIG.

FIG. 13 is a graph showing frequency characteristics of the line microphone in the case of d = 20 cm without the acoustic tube in FIG.

FIG. 14 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 15 is a diagram showing a first example of a conventional microphone device.

16 is a diagram showing a directivity pattern in FIG.

17 is a diagram showing frequency characteristics in FIG.

FIG. 18 is a diagram showing a second example of a conventional microphone device.

FIG. 19 is a diagram showing a directivity pattern in FIG.

[Explanation of symbols]

 1 Unidirectional Microphone 3 Addition Circuit (Phase Shift Inversion Circuit) 5 Line Microphone 5a Acoustic Tube 5b Sound Hole (or Slit) 5c Resistive Face Cloth 5d Omnidirectional Microphone

Claims (4)

[Claims] 1. A first microphone that picks up sound from a sound source to generate a first audio signal, and a first microphone that is arranged at a position at a predetermined distance from the first microphone and in a direction opposite to the sound source. Second sound by collecting the sound from the sound source and the sound emitted from the first microphone, the second sound having an omnidirectional microphone and a sound tube of a predetermined length for connecting the omnidirectional microphone to the end portion. A microphone device comprising: a second microphone that generates a signal; and a synthesizing unit that generates a synthetic signal that is a difference between the first and second audio signals. 2. A first extracting means for extracting a high frequency component of the second audio signal, a second extracting means for extracting a low frequency component of the synthesized signal, and the first and second extraction means. The microphone device according to claim 1, further comprising: an addition unit that adds signals output from the unit. 3. The microphone device according to claim 1, wherein the acoustic tube has a plurality of sound holes or slits on a side surface thereof and a resistance face cloth covering the side surface. 4. The microphone device according to claim 1, wherein the predetermined distance is an integral multiple of the length of the acoustic tube.