JP3106649B2 - Microphone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device, and more particularly to a microphone device used for loudspeakers.

[0002]

2. Description of the Related Art A microphone device used for loudspeaking is well known. FIG. 15 shows such a conventional microphone device. In FIG. 15, reference numeral 1 denotes a microphone unit, which has the highest sensitivity in the forward direction, that is, the direction at an angle of 0 degrees, decreases in sensitivity in the horizontal direction, that is, the direction of 90 degrees, and has the lower sensitivity in the direction of 180 degrees. Lowest. In general, a unidirectional (primary gradient type) pattern shown in FIG. 16 is used as the sensitivity directivity pattern of the microphone unit 1.

FIG. 17 shows frequency sensitivity characteristics of the conventional microphone unit at 0 °, 90 °, 135 ° and 180 °. With such characteristics, there is a limit in the howling margin, 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, reference numerals 1 and 2 denote microphone units having unidirectional characteristics having substantially the same characteristics, and are arranged at intervals of a distance d. Reference numeral 3 denotes an addition circuit (or a phase inversion circuit) that outputs a difference between audio signals obtained from the two microphone units 1 and 2. In addition, 4
Is a low-frequency correction circuit for correcting the low-frequency component of the output signal of the addition 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. The howling margin can be improved as compared with the case of

[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 relatively matching characteristics, and that adjustment is not easy.

[0006] The present invention is to solve 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 characteristics that match.

[0007]

SUMMARY OF THE INVENTION The present invention, in order to achieve the above object, a unidirectional microphone for generating a first sound signal picked up the sound from the sound source, the unidirectional Ma an omnidirectional microphone disposed at a position at a predetermined distance from the microphone and in a direction opposite to the sound source, and a sound tube of a predetermined length for connecting the omnidirectional microphone to a terminal portion, and Rainma Ikurohon that generates a second audio signal by picking up sound emitted from the sound and the unidirectional microphones <br/> Rohon from the sound source, the difference of the first and second audio signals And a composite signal for generating a certain composite signal.

[0008]

According to the present invention, the difference between the audio signal from the first microphone that picks up the sound from the sound source and the audio signal from the second microphone with the acoustic tube is obtained. Adjustment can be facilitated without considering the identity of the characteristics of the second microphone.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention,
Reference numeral 1 denotes a microphone unit as a first microphone that collects 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 annularly attached to the outside of the tube. 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, the case where the length 1 of the line tube 5a is 1 = 5 cm will be described with reference to FIGS. FIG.
Indicates the frequency characteristic of the omnidirectional microphone 5d alone, and is substantially flat from 100 Hz to 10 kHz regardless of the direction. FIG. 3 shows the frequency characteristics of the microphone 5 incorporating the omnidirectional microphone 5d. The characteristics are different depending on the directions of 0, 90, and 180 degrees, that is, characteristics having directivity.

FIG. 4 shows an adder 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 degrees, 90 degrees, 135
FIG. 5 shows frequency characteristics in degrees and 180 degrees.
Is a diagram showing the directivity pattern. As is clear from FIG. 5, although having a small directivity at 180 degrees, that is, at the rear, it has a directivity similar to the super directivity of the secondary gradient microphone shown in FIG. FIG. 6 shows the adder circuit 3 when d = 31 (= 15 cm).
7 shows the frequency characteristics of the output signal of FIG. When the operating principle is analyzed from the characteristics of FIGS. 4 and 6, the output level of the line microphone 5 is substantially equal to the level of the unidirectional microphone 1 in the direction of 180 degrees, and the output difference is particularly large. The point where the directivity becomes the smallest is
It can be seen that the frequency is near the frequency f (f = c / λ; c is the sound speed) where d ′ = λ / 6 (where d ′ = dl and λ is the wavelength).

The effective variable range of the distance d is d
> L, and when d = l or d <l, the above effective characteristics could not be obtained. Considering the directivity of the entire frequency band, the vicinity of d = 21 is optimal. k = 2
Assuming that πf / c, an optimum characteristic is obtained near 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-described characteristic. Further, even when the characteristics of the line microphone 5 vary, the addition circuit 3
Has little effect on the output signal of the
Cost increase can be suppressed.

FIGS. 7 and 8 show the line length l, respectively.
FIG. 9 shows the frequency characteristics of the line microphone 5 when 10 cm and 20 cm, and FIGS.
It shows the frequency characteristics of the synthesized signal when the distance is 10 cm and d = 2l and d = 3l. FIG.
Reference numeral 1 indicates the frequency characteristics of the composite signal when l = 20 cm and d = 2l. FIG. 10 and FIG.
As is clear from FIG. 1, the same result as in the case of l = 5 cm is obtained.

FIGS. 12 and 13 show the case where the line tube 5a in FIG. 1 is removed and d = 10 cm.
4 shows the frequency characteristics of the combined signal obtained by the unidirectional microphone 1 and the non-directional microphone 5d in the case of 20 cm and 20 cm. In this case, the characteristics in the low-frequency portion near d '= λ / 6 show the same characteristics as those in the above-described embodiment. 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 the level thereof is also adjusted to be low as in the above embodiment. Therefore, in the case of close use of speech or the like, since sound pressure input to the unidirectional microphone 1 is fundamental, there is also an effect that deterioration of sound quality 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 denoted by the same reference numerals, and the description thereof will be omitted. Only components different from those in FIG. 1 will be described. 6 is a high cut filter circuit as first extracting means for removing high frequency components,
Reference numeral 7 denotes a low-cut filter circuit as second extracting means for removing low-frequency components, and reference numeral 8 denotes an adding circuit, which is different from the adding circuit 3 and serves as adding means for adding in-phase signals.

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 for the low-frequency component, as in the case of FIG. 1, the addition circuit 3 generates a composite signal that is the difference between the audio signal from the unidirectional microphone 1 and the high-frequency component that has passed through the low-cut filter circuit 7. Are further combined by the adder circuit 8.

The same effects as those of the first embodiment shown in FIG. 1 can be obtained in the second embodiment or another embodiment in which the combination of the configurations is changed.

[0019]

According to the present invention, as is apparent from the above embodiment, a line microphone having an acoustic tube is provided as a second microphone in addition to the first microphone for sound collection having unidirectionality . By taking the difference between the audio signals from both microphones, it is possible to utilize the delay effect peculiar to the line microphone, and to obtain an effect of easily adjusting the characteristics of both microphones without considering the sameness. Ma
Even if the length of the acoustic tube is short, similar characteristics can be obtained.
it can.

[Brief description of the drawings]

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

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

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

FIG. 4 is a graph showing frequency characteristics of a line microphone when l = 5 cm and a distance d between microphones is d = 21 in FIG. 1;

FIG. 5 is a diagram showing a directivity pattern in FIG. 4;

FIG. 6 is a graph showing frequency characteristics of the line microphone when l = 5 cm and d = 31 in FIG. 1;

FIG. 7 is a graph showing the frequency characteristics of the line microphone when l = 10 cm in FIG. 1;

FIG. 8 is a graph showing frequency characteristics of a line microphone when l = 20 cm in FIG. 1;

FIG. 9 is a graph showing the frequency characteristics of a line microphone when l = 10 cm and d = 2l in FIG. 1;

FIG. 10 is a graph showing the frequency characteristics of the line microphone when l = 10 cm and d = 31 in FIG. 1;

11 is a graph showing frequency characteristics of the line microphone when l = 20 cm and d = 2l in FIG. 1;

FIG. 12 is a graph showing frequency characteristics of a line microphone when d = 10 cm without the acoustic tube in FIG. 1;

FIG. 13 is a graph showing the frequency characteristics of the line microphone when d = 20 cm without the acoustic tube in FIG. 1;

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.

FIG. 16 is a diagram showing a directivity pattern in FIG. 15;

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. 18;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Unidirectional microphone 3 Addition circuit (phase shift inversion circuit) 5 Line microphone 5a Sound tube 5b Sound hole (or slit) 5c Resistive surface cloth 5d Non-directional microphone

Claims (4)

(57) [Claims] 1. A unidirectional microphone that collects sound from a sound source to generate a first audio signal, and that is located at a predetermined distance from the unidirectional microphone and relative to the sound source. And a sound tube of a predetermined length for connecting the omnidirectional microphone to the end portion thereof, and a sound from the sound source and the unidirectional microphone. and Rainma Ikurohon the sound emitted that generates a second audio signal picked up from a microphone device that includes a combined signal to generate a composite signal which 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 synthesizing means, and the first and second extracting means. 2. The microphone device according to claim 1, further comprising an adding unit for adding a signal output from the unit. 3. The sound tube has a plurality of sound holes or slits on a side surface of the sound tube, and a resistance surface cloth covering the side surface.
DOO microphone device according to claim 1 or 2, wherein the having. 4. The apparatus according to claim 1, wherein the predetermined distance is an integral multiple of the length of the acoustic tube .
Microphone device as claimed in.