JPS5888995A - Secondary sound pressure gradient type unidirectional microphone - Google Patents

Abstract

PURPOSE:To decrease the entire length of a microphone and to attain the small sized microphone, by arranging an HPF, an LPF, an adder and a subtractor at a space part between a full band microphone unit and a low frequency microphone unit, in a band split type microphone. CONSTITUTION:In a secondary sound pressure gradient type unidirectional microphone consisting of a high band unidirectional microphone unit Mh, a full band unidirectional microphone unit Ma and a low frequency unidirectional microphone unit Ml, an electric circuit component 5 comprising all or a part of an HPF, an LPF, an adder ADD and a subtractor SUB is arranged at the space between the unit Ma and Ml. Thus, the length of the unit PTU such as the mechanism part can be shortened by using the space of the microphone unit MHU, allowing to decrease the entire length of the microphone without deteriorating the characteristics of microphones.

Description

[Detailed Description of the Invention] Conventional methods for giving a microphone sharp unidirectional characteristics (directivity) include adding an acoustic tube in front of the microphone, and placing the microphone at the focal point of a parabolic reflector. There are other methods such as arranging multiple unidirectional microphone units in a plane perpendicular to the sound source and calculating the output from each microphone unit. As shown in Fig. 1, a method is known in which microphone units with unidirectionality are arranged in the front and back direction, and the output from each microphone unit is processed to obtain the desired output. However, according to the construction principle shown in FIG. 1 described above, the 5 sound pressure gradient type unidirectional microphone p-phone can be constructed to be smaller than the unidirectional microphone according to the other methods described above. It has the following characteristics.

In FIG. 1, S is a sound source, MI, pigeon is a microphone unit with unidirectionality, SUB is a subtracter, EQ is an initializer, 0 is an output terminal, and the above-mentioned Ml, M2
In this case, a unidirectional microphone unit for all bands is used, and one microphone unit and one microphone unit M2 are arranged in the front and back direction with a distance d apart, and the output signal from each microphone unit Mt I M2 is sent to a subtracter SUB. Subtract with .

The output from the subtractor SUB is maximum when 1/2 of the wavelength of the sound wave is equal to the distance d between the two microphone units Mt + M2, and becomes O when the wavelength of the sound wave is an integer fraction of the above-mentioned distance. Become.

FIG. 2 is a frequency characteristic curve diagram of the output signal of the subtractor SUB in the sound pressure gradient type unidirectional microphone shown in FIG. The output increases with the octave slope. Therefore, it is necessary to correct the frequency characteristics of the output signal of the subtracter SUB by the equalizer circuit EQ and send it to the output terminal O to flatten the frequency characteristics in the used band.

FIG. 3 is a curve diagram showing an example of the equalizer characteristics of the equalizer circuit EQ, and FIG. 4 is a curve diagram showing an example of the equalizer characteristics of the equalizer circuit EQ.
The output signal sent to the output terminal O from the
FIG. 3 is a side view of a front frequency characteristic curve of the sound pressure gradient type unidirectional microphone having the illustrated configuration.

In order to make the sound pressure gradient type unidirectional microphone having the configuration shown in FIG. 1 flat as shown in FIG. 4, an equalizer circuit EQK is required.
For example, as shown in Figure 3, the equalizer characteristics must be such that no significant correction can be made in the low frequency band; If significant reinforcement is performed, problems arise in that the SA deteriorates and the system becomes vulnerable to wind noise and so-called blowing.

As a means to solve the above problems, a secondary sound pressure gradient type unidirectional microphone .mu.phone having a band-divided configuration as shown in FIG. 5 was attempted. That is, in FIG. 5, S is a sound source, Ml, Mh, Ma, etc. are microphone units each having unidirectionality, LPF is a low-pass filter, I (PF is a high-pass filter, S
UB is a subtracter, ADD is an adder, and 0 is an output terminal. A microphone unit Ma is placed at a distance dl from the microphone unit, and a microphone unit Mh is placed at a distance dh in front of the microphone unit Mg. A signal obtained by passing the output signal of the microphone unit Mt through a low-pass filter LPF and a signal obtained by passing the output signal of the microphone unit Mh through a high-pass filter IFF are added by an adder ADD. Subtractor SUB from
The output signal of the adder ADD is subtracted by the subtracter SUB from the output signal of the microphone unit Ma for all bands, and the output terminal OvC microphone output is sent out. The secondary sound pressure gradient type unidirectional microphone having the configuration shown in FIG. A usable frequency characteristic can be obtained, and the secondary sound pressure gradient type unidirectional microphone having the configuration shown in Fig. 5 overcomes the drawbacks of the conventional microphone explained with reference to Fig. 1. It will be resolved in .

However, the secondary sound pressure gradient type unidirectional microphone having the configuration shown in Figure 5 can obtain good frequency characteristics when the distance between the microphone and the sound source is more than a certain distance. When the sound source and microphone are close to each other, the output of signal components in the low frequency band becomes abnormally high.
When a microphone is used with a sound source close to the microphone, the recorded sound has an abnormally emphasized low frequency range, and an improvement has been desired.

FIG. 6 shows a secondary sound pressure gradient type unidirectional microphone p-phone which is band-divided as shown in FIG. FIG. 6 is a pull diagram showing the configuration of the microphone P-phone, in which S is a sound source, Mh is a high frequency unidirectional microphone unit, Ma is a full band unidirectional microphone unit, and ML is a unidirectional microphone unit for all bands. is a unidirectional microphone unit for low frequencies, HPF is a high-pass filter, LPF is a low-pass filter, A
DD is an adder, SUB is a subtracter, and O is an output terminal.

The high-frequency microphone unit Mh is located closer to the sound source S than the full-band microphone unit Ma.
The low-frequency microphone unit ML is arranged so that the distance from the microphone unit Ma for all bands is dh, and the microphone unit ML for low frequencies is located closer to the sound source S than the microphone unit Ma for all bands. It is arranged so that the distance from the above-mentioned all-band microphone unit Ma on the far side is dz.

The high frequency microphone unit) Mh and the low frequency microphone unit Mt have almost the same characteristics as the microphone unit for all bands) Ma.
The high-frequency microphone unit Mh is a high-pass filter HPF.
The band of the low-frequency microphone unit (MZ) is limited by a low-pass filter LPF.

The output signal from the high-frequency microphone unit (Mh) that has passed through the high-pass filter HPF and the output signal from the low-frequency microphone unit ML that has passed through the low-pass filter LPF are added by an adder ADD. The subtracter SUB Ic is supplied as a subtraction signal from the subtractor SUBI
An output signal from a microphone (p-phone unit) Ma for all bands is given to B. The output signal from the subtracter SUB is sent to the output terminal O as a microphone output signal.

The secondary sound pressure gradient type unidirectional microphone p-phone shown in FIG. As for the arrangement of the microphone unit (pphone units) Ma, a high-frequency microphone unit Mh is placed closest to the sound source S, and a full-band microphone unit Mh is placed at a distance dh from the high-frequency microphone unit Mh. A microphone p-phone unit) Ma is arranged, and further, a distance dz from the microphone p-phone unit) Ma for all bands, that is, from a position of the high-frequency microphone unit) Mh,
By arranging the low-frequency microphone unit (MZ) at a distance of 1 (dh+dz), no matter how close the sound source S is to the microphone, the distance between the sound source S and the low-frequency microphone unit ML is at least (dh+dz). dt) Since the above is done, the sound source S is close to the microphone and -
However, the output signal level does not rise abnormally in the low frequency range, and the problems with the secondary sound pressure gradient type unidirectional microphone having the configuration shown in FIG. be.

Now, the secondary sound pressure gradient type unidirectional microphone ρ-phone having the configuration shown in FIGS. Usually, the distance dz between the low-frequency microphone unit ML and the full-band microphone unit Ma is the same as the distance between the high-frequency microphone unit Mh and the full-band microphone unit p. ) It is necessary to make the interval approximately 3 to 5 times the interval dh from Ma.

By the way, since the above-described interval dh is selected to be about 10 to 15 LM when the microphone is used in a normal voice band, the secondary sound pressure gradient having the configuration shown in FIGS. 5 and 6 described above is In the type unidirectional microphone P-phone, the arrangement part of the three microphone units described above (
The length of the microphone unit section) accounts for a large proportion of the total length of the microphone. In particular, the microphone having the configuration shown in FIG.
dz + dh), so if the microphone is divided into a microphone unit part and a circuit, battery, mechanical unit, etc., as is the case with a normal microphone, the total length of the microphone will be considerably large, p, approximately The total length is approximately 70-80% of the total length of a narrow-form directional microphone with the same performance, such as a so-called gun microphone that uses an acoustic tube, and the above-mentioned feature of being able to be made smaller is diminished. .

The present invention has been made for the purpose of solving the above-mentioned problems and providing a stable secondary sound pressure gradient type unidirectional microbon. The specific contents of the secondary sound pressure gradient type directional microphone-phone will be explained in detail.

First, FIG. 7 shows a secondary sound pressure gradient type unidirectional microphone as shown in FIG. 7 is a vertical cross-sectional side view of a microphone, showing for reference a microphone formed by arranging unit parts p'ru such as A microphone transformer 3, a battery 4, an electric circuit section 5, etc. are provided in the housing l to which the switch SW 2 is fixed.
is installed and configured.

The microphone unit parts are connected and fixed to the other end of the unit part PTU, such as the above-mentioned mechanical parts. It is configured by attaching a range microphone unit Mh, an all-band microphone unit Ma, and a low-range microphone unit Ml. Reference numeral 7 denotes a wire mesh portion provided on the outer periphery of the microphone unit portion (1), and this wire mesh portion 7 is connected and supported by an exterior portion 8 that fits around the outer periphery of the housing 1.

FIG. 8 is a longitudinal sectional side view of one embodiment of the secondary sound pressure gradient type unidirectional microphone of the present invention, which has already been described in FIG. The same drawing numerals as those used in FIG. 7 are used for corresponding components in the microphone shown in FIG.

In the microphone of the present invention shown in FIG. 8, the microphone unit M for all bands in the microphone unit section
Between a and the low-frequency microphone unit Mt are the circuit elements shown in FIG. 6, namely, a high-pass filter HPF, a low-pass filter LPF, an adder ADD, and a subtracter SU.
An electric circuit section 5 consisting of all or part of B is arranged and housed.

In this way, the secondary sound pressure gradient type unit according to the present invention shown in FIG.
In the case of a directional microphone (p-phone), units such as mechanical parts in the microphone of the normal configuration shown in Figure 7)
The electric circuit section 5 that was housed in the PTU was replaced with a microphone (P-phone unit) for all bands between the microphone unit sections.
Since the space between Ma and the low-frequency microphone unit is used for storage, the overall length of the microphone can be made shorter than that of the microphone having the configuration shown in FIG.

If the space between the multiple microphone units that make up the band-splitting type secondary sound pressure gradient type unidirectional microphone is acoustically transparent, the desired characteristics cannot be obtained. In the secondary sound pressure gradient type unidirectional microphone according to one embodiment of the present invention shown in FIG. This is a space between the low-frequency microphone unit Mt, and an electric circuit portion 5 whose size is negligible compared to the wavelength of the sound wave in the frequency band handled by the low-frequency microphone unit Mt is arranged there. Even if the microphone is retracted, the characteristics of the microphone may deteriorate. Good unidirectivity can be obtained even if the electric circuit section 5 is arranged and housed in the space between the unit Ma and the bass microphone (p-phone unit) Mt.

Note that the band division type 2 of the configuration shown in FIG.
Like a next-order sound pressure gradient type unidirectional microphone, from the one closest to the sound source to the one farthest away, there is a microphone p-phone unit Mt for the low range, a microphone p-phone unit Mh for the high range, and a microphone for the entire band. In the case where the support (support) Ma is arranged, the distance between the microphone units is the largest in the space between the low-frequency microphone unit Mt and the high-frequency microphone (p) Mh. When the electric circuit portion 5 is placed and housed in the space, the dimensions of the electric circuit portion 50 placed and housed in the space are negligible compared to the wavelength of the sound wave in the frequency band handled by the high-frequency microphone unit. Unless the electric circuit portion 5 is small, the presence of the electric circuit portion 5 arranged and housed in the above-mentioned space will cause the high frequency microphone p
(Honunits)) This will have an adverse effect on Mh and worsen the directional characteristics.

As is clear from the detailed explanation above, in the second-order sound pressure gradient type unidirectional microphone P-phone of the present invention, the microphone unit section including three microphone units can be used for all bands. Microphone unit M
The space between the microphone unit (a) and the bass microphone unit (Mt) is effectively used for arranging and storing the electric circuit section 5, thereby shortening the overall length of the microphone, and improving the characteristics of this type of microphone unit. A small directional microphone that is said to be
This made it possible to easily provide phones.

[Brief explanation of the drawing]

Figures 1, 5, and 6 are block diagrams showing the construction principle of a sound pressure gradient type unidirectional microphone, Figures 2 to 4, and 9 are characteristic curve side views, and Figure 7 is a block diagram showing the principle of construction of a sound pressure gradient type unidirectional microphone. FIG. 8 is a vertical side view of an embodiment of a second-order sound pressure gradient type unidirectional microphone p-phone according to the present invention. ML...Low frequency microphone unit, Ma...
・Microphone unit for all bands, Mh-...Microphone unit for high range, HPF...High-pass filter, L
PF...low-pass filter, M le...adder, SUB...
・Subtractor, SW...switch, 1...casing, 2...
・Connector, 3...Microphone transformer, 4...
Battery, 5... Electric circuit part, 6... Microphone support, 7... Wire mesh part, 8... Exterior part, MHU ・-
・Microphone unit, PTU...Unit parts such as mechanical parts Patent applicant Akira Japan Victor Co., Ltd. 2 Figure f → Akira 3 Notebook 4 Leap

Claims (1)

[Claims] A unidirectional high-frequency microphone unit,
A unidirectional all-band microphone unit and a unidirectional low-frequency microphone unit are placed at predetermined intervals, and the output signals from each microphone unit are processed. In a band-splitting type secondary sound pressure gradient type unidirectional microphone P-phone, which is designed to obtain an output using A secondary sound pressure gradient type unidirectional microphone that houses at least some of the electric circuit components such as a subtractor, a subtractor, and a filter.