JPS60219894A - Microphone device - Google Patents

Abstract

PURPOSE:To obtain a narrow directivity in a wide band by disposing differential microphones on the top and near to the trailing end of a line microphone, fetching the output difference and synthesizing it with an output of the line microphone. CONSTITUTION:An interval of differential microphones 5 and 6 is assumed to be L. The output difference between both microphones 5 and 6 can be obtained by a subtractor circuit 7 whose outputs are level-adjusted by a volume 8. These differential microphones 5 and 6 and the subtractor circuit 7 comprise a secondary gradient-type microphone, which has the directivity in directions of 0 deg. and 180 deg. and is constituted in such a way that an output will not be produced in the direction of 90 deg. irrespective of frequency. By adding the output difference between the differential microphones 5 and 6 to an output of a line microphone, such sharing can be possible that a low frequency range is for outputs of the secondary gradient-type microphone while a high frequency range is for outputs of the line microphone. As a result the microphone having the narrow directivity in a wide band can be accomplished.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a microphone device.

Conventional configuration and its problems FIG. 1 shows a conventional microphone device.

In FIG. 1, reference numeral 1 denotes an acoustic tube having a plurality of sound holes 2, and a resistance surface cloth 3 is provided on the acoustic tube 1 so as to cover the sound holes 2.
is attached, and an omnidirectional microphone 4 is attached to the terminal end thereof, and these constitute a line microphone.

Next, its operation will be briefly explained. In FIG. 1, a row wave enters the sound tube 1 from each sound hole 2, passes through this sound tube 1, and reaches the omnidirectional microphone 4 provided at the end. The resistance surface cloth 3 is adjusted so that the phase is not canceled in the O0 direction, which is the longitudinal direction, and the phase is canceled in the other directions. In other words, since this microphone device utilizes the wave effect of sound waves, the directivity becomes sharp in proportion to the frequency above the frequency where the length of the sound tube 1 and the wavelength of the wave are approximately the same. Therefore, in order to provide directivity to the low frequency range, the length of the acoustic tube 1 must be increased.

Figure 2 shows the frequency characteristics when the acoustic tube length l is about 2ocIn.As can be seen from the figure, the directivity is sharp in the high range, but the omnidirectional microphone U7'' in the low range.
The characteristics are almost the same as the single unit.

As described above, in conventional microphone devices, when using an omnidirectional microphone, it is necessary to increase the length of the acoustic tube in order to achieve directivity in the low frequency range, and the directivity in the high frequency range The disadvantage is that it becomes too sharp.

OBJECTS OF THE INVENTION The present invention eliminates the above-mentioned conventional drawbacks, and aims to provide a microphone device that can provide directivity over the entire band and has a high housing margin.

Structure of the Invention In order to achieve the above-mentioned object, the present invention provides a quadratic gradient type microphone in which four differential type microphones are arranged near the front end and rear end of a line microphone, and the output difference thereof is taken out; This is a microphone device that synthesizes the output of a phycrophon and is capable of obtaining narrow directivity over a wide band.Description of an EmbodimentThe configuration of an embodiment of the present invention will be explained below with reference to drawings. .

FIG. 3 shows an embodiment of the present invention, and the -S portions as in FIG. 1 are indicated by the same numbers. In Figure 3, reference numerals 5 and 6 are two differential microphones with unidirectionality and relatively similar characteristics; It is located near the tip on the e-j axis, and its output is coupled to one input terminal of the subtraction circuit 7. Similarly, the differential microphone 6 is located near the rear end on a substantially parallel axis, and its output passes through the volume 8 and is sent to the subtraction circuit 7.
is connected to the other input terminal of the differential microphone 5゜6, and is configured to take out the output difference of the differential microphone 5゜6 from the output terminal.
Further, the output is combined with the output of the omnidirectional microphone 4 by a combining section 9. Note that the same effect can be obtained even if the volume 8 is configured on the differential microphone 5 side.

Next, the operation of the Saturday hC embodiment will be explained. In FIG. 3, L is the interval between the differential microphones 6.6, each output is appropriately level-adjusted by the volume 8, and the output difference is obtained by the subtraction circuit 7. Single differential microphone 5, 6. ! :The M3E circuit 8 constitutes a quadratic gradient type microphone, and Fig. 4 shows an example of the characteristics in the case of L-20 accuracy. Therefore, in the range kL≦2, the frequency f is proportional to the frequency, reaches a maximum at the frequency where the wavelength λ is 2L (approximately the point kL-π), and the frequency f where λ=L. It is lowest at the point n times h.

(k=-, ω=2πf+ c: speed of sound, j: frequency.

(n: positive integer) The same applies to 1800, but since the differential microphone itself has directivity with respect to 00, the same degree of directivity as the differential microphone alone can be obtained. On the other hand, in the 90' direction, since there is no acoustic phase difference of 1, the output is theoretically low regardless of the frequency.

As can be seen from the above, this quadratic gradient microphone exhibits narrow directivity. However, in the case of this one microphone, the bass range is about +66B10ct relative to the frequency, so if you try to widen the required playback band, you will inevitably shorten L and increase the amount of correction in the bass range, which will easily lead to S/1 (deterioration). However, in the case of the present invention, L is made large and the frequency kL-1 is configured to be in the low range, so it is practical enough even without correction in the low range, and even if it is corrected, the correction is small. Since only a small amount is required, S/N deterioration does not occur at all.

On the other hand, the output of a line microphone is as shown in Figure 2, and has directivity at frequencies of ke≧1 or more, and kd≧
Since π exhibits narrow directivity, with the configuration of this embodiment, the low frequency range can be divided into the output of the quadratic tilt type microphone, and the high frequency range can be divided into the output of the line microphone], and this can be divided into 414 For example, by using an acoustic filter, it is possible to create a microphone with narrow directivity over a wide band, thereby providing a microphone with a high housing margin. Also, if you are using a quadratic tilt type microphone.
There is little S/N deterioration, and since the line microphone uses an omnidirectional unit, the S/N is very good, so there is an advantage that the overall S/N can be made good.

In reality, there is a possibility that the respective outputs of the line microphone and the quadratic gradient type microphone will give an image of J&MI in a frequency range that is not required. Therefore, in order to further improve the synthesis characteristics, the embodiment shown in FIG. 5 can be considered.

In FIG. 6, numeral 10 is a low-cut filter circuit, which cuts the low frequency range of the output of the line microphone 4. Reference numeral 11 denotes a high-cut filter circuit, which cuts the high frequency range of the output of the secondary gradient microphone. In other words,
Each of the filter circuits 10 and 11 is designed to cut out unnecessary bands and prevent them from having an adverse effect. Reference numeral 12 denotes a low frequency correction circuit, which corrects the low frequency range of the synthesized output in order to widen the playback band as necessary. It should be noted that the gist of the present invention is the same even if this correction is performed on the output of the quadratic tilt type microphone, that is, before synthesis, in addition to this embodiment.

Since low frequency correction causes S/N deterioration, it is desirable to reduce it as much as possible. In addition, if L (l is set well, a sufficient practical reproduction band can be obtained without correction. Also, the cutoff frequency (crossover) of the filter circuits 10 and 11 is kl = 4
When considering the synthesis of frequency characteristics and directional characteristics, it is preferable to make the vicinity approximately coincident with the front and rear, but in the case of the embodiments shown in FIGS. 3 and 6, L! Although we have explained the case where -il is set, the gist of the present invention is the same even when L>β and e. This is an example of characteristics when configured as in the embodiment shown in FIG. However, this is the case where l=20 cm, l=, L, the crossover frequency is 4=4, and there is no low frequency correction. As shown in Figure 6, it is possible to obtain narrow directivity characteristics in a wide frequency range, and it is possible to provide a microphone device with a high howling margin. It is most desirable to configure the differential microphones 6 in the same manner in view of deterioration of sound quality.

Effects of the Invention As described above, according to the present invention, the high frequency range is generated by the line microphone and the low frequency range is generated by the quadratic tilt type microphone, so that +J is generated. Has a wide reproduction band, has little S/N deterioration, and has good sound throughout the entire range from bass to treble] B I: JJ 4
'! The microphone can be placed in the
This has the advantage that it is possible to provide a microphone device with a high overall housing margin.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a conventional microphone device, FIG. 2 is a characteristic diagram in FIG. 1, FIG. 3 is a configuration diagram of a microphone device in an embodiment of the present invention, and FIG. FIG. 5 is a configuration diagram showing another embodiment of the present invention, and FIG. 6 is a characteristic diagram of the embodiment shown in FIG. 6. 1...Acoustic tube, 2...Omnidirectional microphone, 6.6...Differential microphone, 7...
...MW circuit, 9...Synthesis section. Name of agent Toshio Nakao, Physician, and one other person Figure 1 p Figure 2 1! □ Surrounding liquid (text, (th) Bottle bL 41- Figure 3 4m 曾

Claims (1)

[Scope of Claims] (1) A line microphone in which a resistance surface cloth is attached to the sound hole portion of a sound tube having a plurality of tags, and a microphone is provided at the terminal end of the sound tube, and a tip portion of the line microphone. 2 placed near and near the rear end, respectively.
A second-order gradient microphone configured with two differential microphones, a subtraction circuit that extracts the output difference between the two differential microphones, and a synthesizer that mutually synthesizes the output of the line microphone and the output of the second-order gradient microphone. (2) Connect a low frequency filter circuit to the output side of the line microphone and a high frequency filter circuit to the output side of the quadratic slope microphone, and set the cutoff frequency of these filter circuits. The microphone device according to claim 1, characterized in that the distances are substantially the same. (3) The microphone device according to claim 1 or 2, characterized in that a low frequency correction circuit is connected to the output side of the quadratic gradient type microphone. (4) A low frequency correction circuit is connected to the output side of a synthesis section that mutually synthesizes the output of a line microphone and the output of a quadratic gradient microphone. Microphone device as described in section.