JP3270495B2 - Directional microphone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional microphone.

[0002]

2. Description of the Related Art Conventionally, as a method of obtaining a single directivity of a microphone, first, there is a method of combining an omnidirectional pressure microphone and a bidirectional pressure gradient microphone. And hypercardioid microphones (for example, Masao Nishinomaki "Electroacoustic Oscillations", (1990. 1. 20.), Corona, p. 174).

[0003] Second, there is a method in which microphones are arranged in an array to obtain directivity by combining outputs (for example, Takashi Nishi et al., "Multi-directional simultaneous sound pickup device", December 19, 1988, Information and Communication Society Research Report Material EA88-65).

Further, there is a third method using a line microphone or a parabolic reflector (for example, translated by Masao Nishimaki, HF Olson "Acoustic Engineering", (12.8 of 1977), Kindai Kagakusha, pp. 369-372).

[0005]

The prior art 1 can be realized with a single microphone capsule and is small in size. However, the attenuation in the other directions with respect to the main axis of directivity is small, and considering the multi-channel sound pickup, the recorded sound is difficult. The level connection with the adjacent channel becomes worse. Here, the adjacent channels are, for example, the recording channel in the front three channels of L (left), C (center), and R (right). If attention is paid to the R channel, the C channel is the adjacent channel.

The prior art 2 is not practical in view of the fact that the prior art 2 is large and requires a signal processing device and is mounted on a television camera.

Further, considering multi-channel sound collection in the prior art 3, the microphone has a narrow directivity, and there is no problem in connection of recording sound levels with adjacent channels, but the microphone is directed in the direction of the channel to be picked up. It has to be large and the shape is large, resulting in poor operability.

Accordingly, an object of the present invention is to provide a directional microphone which eliminates the above-mentioned drawbacks, has a directional characteristic in a single direction, is small, and has a large attenuation of directional sensitivity in the direction of an adjacent channel. Is what you do.

[0009]

In order to achieve this object, a directional microphone according to the present invention comprises at least two directional microphones whose main axes are oriented in a predetermined sound collecting direction while being parallel to each other, and are arranged at intervals d. Microphone capsules, and an adder circuit for calculating the sum of the outputs of the two microphone capsules. The output of the adder circuit is used for the predetermined sound collection direction constituted by the two microphone capsules. While being used as the output of the microphone system, it is possible to obtain a directivity at a desired frequency such that the sensitivity of the microphone system in the direction in which the microphone capsule is arranged is smaller than the sensitivity of the microphone capsule alone in the direction. In this manner, the interval d is set. As in the present configuration, by adding the outputs of the two microphone capsules arranged at the interval d, the directional characteristics of the microphone capsule alone (in this case, the hypercardiod characteristics) are added to the dipole characteristics (that is, the donut-shaped directional characteristics). ) Can be obtained at a desired frequency at c / 2d (c is a sound speed of 340 m / s). Further, by setting the interval d, the donut-shaped directional characteristics are changed so that the sensitivity of the microphone system in the direction in which the adjacent channel, that is, the microphone capsule is arranged, is smaller than the sensitivity of the microphone capsule alone in the direction. A high directivity can be realized at a desired frequency. That is, the sensitivity of the microphone capsule pair in the direction adjacent to the intended sound collection direction, particularly the sensitivity in the microphone axial direction (that is, the direction in which the microphone capsule is arranged) can be reduced to zero.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. In the first embodiment, L (left) and R (right) 2 of one-point sound collecting microphones of a 3-1 system 4-channel stereo (4 channels of front L, C, R and rear S) are used.
This is an example in which the present invention is applied for channel sound collection.

FIG. 1 is a configuration diagram of the microphone. Block 15 is a microphone receiving section, and element 1
-14 are directional microphone capsules. Elements 1-6
Is a capsule for the R channel, elements 7 to 12 are capsules for the L channel, element 13 is a capsule for the C channel,
Element 14 is an S-channel capsule. Block 16 is a synthesis circuit. The L and R channels provide the present invention in three places, namely the elements (1, 6, 1).
7), used for a set of elements (2, 5, 18) and elements (3, 4, 19) (hereinafter referred to as application), since the L and R channels have the same circuit configuration, Inside, R
Only the channel circuit is shown in the block diagram. In this figure, elements 17 to 20 are addition circuits, element 21 is a low-pass filter (LPF), element 22 is a band-pass filter (BPF), and element 23 is a high-pass filter (HPF). The C channel uses a narrow directional microphone capsule 13, and the S channel is a single capsule.

Since the microphone capsule of the L channel is arranged at a position symmetrical to the microphone capsule of the R channel with respect to the axis A of the microphone, the directivity pattern in the horizontal plane is symmetrical with respect to A. The description is the same as that of the R channel except for the above. Then, R
Only the channel will be described below.

The capsules for the R channels of the capsules 1 to 6 have their main axes directed in the R direction by φ with respect to the center direction of the microphone. In order to maintain a directional characteristic similar to a wide frequency range, sound is collected by dividing into three frequency bands. Capsules 1 and 6 are low-frequency capsules, capsules 2 and 5 are middle-frequency capsules, Capsules 3 and 4 are high frequency capsules. Capsules 1 and 6
Are added by an adder 17 and band-limited by an LPF 21. The outputs of capsules 2 and 5 are added by
The band is limited at F22, and the outputs of the capsules 3 and 4 are added at the adder 19 and band-limited at the HPF 23. Next, these three signals are added by the adder circuit 25 and output as the R channel.

Here, the directivity coefficient of the R channel is DC × [DLP × cos ｛(k × d ₁ × cos θ) / 2｝ + DBP × cos ｛(k × d ₂ × cos θ) / 2｝ + DHP × cos ｛ (K × d ₃ × cos θ) / 2}]. In this equation, DC is the directivity coefficient of the microphone capsule alone, DLP is the coefficient of the low-pass filter,
DBP is a coefficient of a band-pass filter, and DHP is a coefficient of a high-pass filter. Also, k = ω / c, ω is an angular frequency of 2πf (f is a frequency), and c is a sound speed.

Next, specific numerical examples will be shown. Hypercardioid directional characteristics (DC =
0.25 + 0.75 × cos (θ−φ)), the filter slope is 6 dB / oct, and the cutoff frequency is 500 H for DLP.
z, DBP is 500 Hz, 2000 Hz, DHP is 2000 Hz, d ₁ = 0.4 m, d ₂ = 0.1 m, d ₃ = 0.025 m, φ
= 60 degrees and the calculation result at f = 1000 Hz is shown by the solid line 25 in FIG.
Shown in A broken line 26 is a directivity pattern of a hypercardioid with the main axis directed at 60 degrees.

Embodiment 2 is an example in which the present invention is applied to two-channel stereo. The configuration diagram is shown in FIG. In the figure, element 31 is a narrow directional microphone capsule, elements 32-35 are directional microphone capsules, elements 32 and 33 are microphone capsules for the R channel whose main axis is oriented in the R direction φ degrees, and elements 34 and 35 are L directions. This is a microphone capsule for the L channel whose main axis is oriented at φ degrees. Elements 36 and 37 are addition circuits, and element 38 is a distribution circuit.

First, the sound in the R direction is received by the microphone capsules of the capsules 32 and 33, and the respective outputs are added to an adder circuit.
The result is added at 36 to become an R channel output. The sound in the L direction is received by the microphone capsules of the capsules 34 and 35 and is added by the adding circuit 37 to become the output of the L channel. The sound in the C direction is received by the narrow directional microphone capsule 31, and is equally distributed and added to L and R by the element 38, respectively.

The first embodiment is an example in which the present invention is applied to multi-channel sound pickup. Its directional characteristic is a combined directional pattern indicated by a solid line 25 shown in FIG.
The sensitivity in the 0-degree direction is attenuated by about 4 dB compared to the hypercardioid characteristic indicated by the broken line 26 in the degree direction, and sound collection with a good connection between the C channel and the recorded sound can be achieved. Further, as shown in the numerical example, the shape is about 40 cm in length, and the width is about 4 cm when the diameter of the capsule is 1 cm. Thus, a relatively small size and good operability can be realized even when attached to a TV camera.

Synthetic Directivity Pattern FIG. 2 The solid line 25 in FIG. 2 shows the combined directional characteristics of the capsules for the R channels of the capsules 1 to 6, wherein the data is calculated at f = 1000 Hz.
Filter cutoff frequency is 500H for each DLP
Considering that z, DBP are 500 Hz and 2000 Hz, and DHP is 2000 Hz, it can be considered that this combined directional pattern shows the characteristics of the capsules 2 and 5 and the adder circuit 18 and the two microphone capsules Depending on the arrangement, the arrangement direction connecting the two microphone capsules (0 ° in FIG. 2)
It can be said that the object of the present invention has been achieved because the sensitivity of the microphone system constituted by the two microphone capsules (direction) is lower (about -4 dB) than the sensitivity of the microphone capsule alone.

The second embodiment is intended for use in news gathering, drama dialogue, and the like. The present invention applied to the L and R channels collects attenuated sound in the center direction, and Is clearly taken by a narrow directional microphone arranged at the center, distributed to the L and R channels, added and used as respective outputs. This method makes it possible to clearly capture the necessary sound without deteriorating the stereo effect as much as possible.

Although several embodiments to which the present invention is applied have been described above, it is obvious that the present invention is not limited to these application examples and various modifications and changes can be made within the gist of the present invention. Will.

[0022]

By using the directional microphone of the present invention, the directional microphone has a single directivity, and the sensitivity in the direction in which the microphone capsule is arranged is attenuated as compared with the case of using a single microphone, thereby affecting adjacent channels. It is possible to form a directional pattern with a small size in a small shape, and to configure a microphone with good operability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment to which the present invention is applied.

FIG. 2 is an example of directivity characteristics of the microphone according to the first embodiment.

FIG. 3 is a configuration diagram of a second embodiment to which the present invention is applied.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshiro Haraga 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Keiji Imanaga 2-8-8 Ogikubo, Suginami-ku, Tokyo No. Sanken Microphone Co., Ltd. (56) References Real Opening Sho 59-114696 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 1/40 320 H04R 3/00 320

Claims (1)

(57) [Claims] 1. At least two microphone capsules which are oriented in a predetermined sound collecting direction while their main axes are kept parallel to each other and are arranged at an interval d, and the output sum of the two microphone capsules is obtained. The output of the addition circuit is used as the output of the microphone system for the predetermined sound collection direction constituted by the two microphone capsules, and is used in the direction in which the microphone capsules are arranged. The distance d is set so that a directivity such that the sensitivity of the microphone system is smaller than the sensitivity of the microphone capsule alone in the direction can be obtained at a desired frequency.
The directional microphone is characterized in that a directional microphone is set.