JP2006108986A - Sound collecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a gain and an SN ratio of a sound collecting device by receiving sound by a plurality of microphones different in distances from a focal position of a sound collecting board and canceling noise based on the output of the microphones. <P>SOLUTION: An acoustic wave is collected to a focus by the parabolic sound collecting board 10, an omnidirectional microphone 11 is disposed in the focal position, and an omnidirectional microphone 12 is disposed in a position except for a focus. The microphone 11 and the microphone 12 constitute a differential microphone. Thus, direct sound reaching the microphone 11 and the microphone 12 is canceled. Reflected sound (acoustic wave reached from a distant place in a target direction) reflected in the parabolic sound collecting board 10 is selectively collected. Thus, the parabolic sound collecting device 1 with directivity, the high gain and the high SN ratio is provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sound collecting device that collects sound using a sound collecting plate, and more particularly to a sound collecting device with improved gain and SN ratio.

  Conventionally, for the purpose of improving the gain of a microphone, a method of collecting sound by installing a microphone at the focal position of a sound collecting plate has been widely used. Such a technique is called parabolic sound collection when the sound collection plate has a paraboloid of revolution, and is called mirror-type sound collection when the sound collection plate has a rotation ellipsoid.

  In such a sound collecting method, the gain corresponding to the magnification of the opening area of the sound collecting plate with respect to the sound receiving portion area of the microphone can be increased, and the SN ratio can be improved by improving the directivity.

  Here, an omnidirectional microphone is often used as the microphone. This is because the omnidirectional microphone is suitable for collecting the reflected sound from the sound collecting plate without leaking. However, if an omnidirectional microphone is used, not only the reflected sound from the sound collecting plate but also the direct sound is collected, so that the S / N ratio which is an advantage of using the sound collecting plate is impaired. In addition, although a technique using an omnidirectional microphone has been attempted, sufficient hemispherical characteristics have not been obtained.

  Therefore, various ideas have been taken in recent years in order to further improve the gain and SN ratio at the time of sound collection using a reflector. For example, Patent Document 1 discloses a technique for collecting sound while suppressing a specific frequency component by making the sound collecting position of a microphone equal to or less than the focal length of a sound collecting plate in parabolic sound collecting. Disclosure.

  Further, in Patent Document 2, the target sound is separated from the surrounding noise to realize high-S / N ratio sound collection, so that the distance between the apex and the aperture is 10 times or more the distance between the apex and the focal point. The sound collector provided with the sound-collecting board of the rotating paraboloid which is is disclosed.

  Further, Patent Document 3 is configured to effectively collect only a sound source from a distant place using a super-directional microphone and a microphone having a sub-cardioid characteristic, and prevent picking up unnecessary sounds from the side and the back. Is disclosed.

JP 7-210180 A JP-A-7-231495 JP-A-10-224882

  However, the above-described conventional technique has a problem in that the sound collector is increased in size and configuration is complicated. Further, even with the above-described conventional technology, there is a problem in that a sufficient gain and SN ratio are not necessarily obtained.

  The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a sound collector capable of realizing a high gain and a high SN ratio with a small and simple configuration. To do.

  In order to solve the above-described problems and achieve the object, the sound collecting device according to the invention of claim 1 is a sound collecting plate having a paraboloid of revolution or an ellipsoid of rotation, and a distance from the focal position of the sound collecting plate. And a plurality of different microphones.

  According to a second aspect of the present invention, in the sound collecting device according to the first aspect, the plurality of microphones include a first microphone and a second microphone connected in reverse phase to the first microphone. It is a differential microphone.

  According to a third aspect of the present invention, there is provided a sound collecting device according to the second aspect, wherein the first microphone is disposed at the focal point of the sound collecting plate, and the second microphone is disposed at a position other than the focal point. And

  According to a fourth aspect of the present invention, there is provided a sound collecting device according to the first, second or third aspect, wherein a plurality of microphones are arranged perpendicular to the sound collecting plate.

  According to the first aspect of the present invention, the sound collecting device receives sound by a plurality of microphones having different distances from the focal position of the sound collecting plate having a paraboloid of revolution or an ellipsoid of rotation, and based on the output of each microphone. Since noise cancellation is performed, there is an effect that it is possible to obtain a sound collector that achieves a high gain and a high SN ratio.

  According to the second aspect of the present invention, since the sound collecting device forms a differential microphone with the first microphone and the second microphone to perform noise cancellation, a high gain and a high SN ratio can be achieved with a small and simple configuration. It is possible to obtain a sound collecting device that achieves the above.

  Further, according to the invention of claim 3, since the sound collecting device arranges the first microphone at the focal point of the sound collecting plate and arranges the second microphone at a position other than the focal point to form a differential microphone. There is an effect that it is possible to obtain a sound collector that cancels the direct sound from the reflected sound and realizes a high gain and a high S / N ratio.

  According to the fourth aspect of the present invention, since the sound collecting device is provided with a plurality of microphones perpendicular to the sound collecting plate and performs noise cancellation based on the output of each microphone, the sound collecting device is biased from the high sound range to the low sound range. There is an effect that it is possible to obtain a sound collecting device that collects sound with a high gain and a high SN ratio.

  Exemplary embodiments of a sound collecting device according to the present invention will be described below with reference to the accompanying drawings.

  First, an outline of a sound collecting device according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration when the present invention is applied to a parabolic sound collector. As shown in the figure, the parabolic sound collector 1 has a microphone 11 disposed at a focal point 13 of a parabolic sound collecting plate 10 having a paraboloid of revolution, and a microphone 12 disposed at a position away from the focal point 13. . Here, the microphone 11 and the microphone 12 are preferably omnidirectional microphones.

  If comprised in this way, the microphone 11 and the microphone 12 will receive the direct sound of the substantially the same level, and also the microphone 11 will receive the reflected sound from the parabolic sound collection board 10 in addition to a direct sound strongly. Become. Therefore, when the microphone 11 and the microphone 12 are connected in reverse phase to form a differential microphone (noise canceling microphone), the direct sound received by the microphone 11 and the microphone 12 is canceled out and reflected as a difference sound. Only sound can be collected selectively.

  Similarly, the present invention can be used in a mirror type sound collector. FIG. 2 is a diagram showing a schematic configuration when the present invention is applied to a mirror type sound collector. As shown in the figure, in the mirror type sound collector 2, a microphone 21 is disposed at a focal point 23 of a mirror sound collecting plate 20 having a spheroid surface, and a microphone 22 is disposed at a position out of focus.

  Then, by forming a differential microphone by connecting the microphone 21 and the microphone 22 in reverse phase, it is possible to selectively collect only the reflected sound as in the parabolic sound collector 1 shown in FIG. it can. The difference between the parabolic sound collector 1 and the mirror sound collector 2 is that the parabolic sound collector 1 collects a plane wave at the focal point 13, whereas the mirror type sound collector 2 collects a spherical wave at the focal point 23. It is. Therefore, the mirror type sound collecting device 2 is preferably used when the distance to the sound source is fixed.

  Next, a specific configuration example of the parabolic sound collector 1 will be described. FIG. 3 is a configuration diagram showing a configuration example of the parabolic sound collector 1. In the figure, the microphone 11 and the microphone 12 and the difference circuit 14 are connected, and the output of the microphone 12 is subtracted from the output of the microphone 11 in the difference circuit 14. Then, the output of the difference circuit 14 is amplified by the amplifier 15 and used for input to an audio device or the like.

  Further, as shown in FIG. 4, the output of the microphone 11 may be subtracted from the output of the microphone 11 by the difference circuit 18 after the output of the microphone 11 is amplified by the amplifier 16 and the output of the microphone 12 is amplified by the amplifier 17. .

  The configurations shown in FIGS. 3 and 4 can be applied not only to the parabolic sound collector 1 but also to the mirror sound collector 2. 3 and 4 are merely examples of the configuration, and various modifications can be made.

  Next, the sound collecting ability of the parabolic sound collecting device 1 will be described. As shown in FIG. 5A, a microphone is installed at a focal position, and a sound source is provided at a vertical distance of 130 cm and horizontal distances of 0 cm, 25 cm, 50 cm, 75 cm, 100 cm, 150 cm, 200 cm, 250 cm, and 300 cm from the focal point.

  Then, pink noise (1 / f noise) is reproduced from each sound source, and the result of plotting the sound pressure at the microphone position is shown in FIG. As shown in the figure, the S / N ratio is improved by about 13 dB when a differential microphone is constituted by the microphone 11 and the microphone 12 as compared with the case where an omnidirectional microphone is disposed alone at the focal position. . In addition, although the SN ratio improvement of the parabolic sound collector 1 has been described here, it goes without saying that the same effect can be obtained with the mirror sound collector 2.

  In this way, the differential microphone is composed of the first microphone (mic 11, microphone 21) installed at the focal position of the sound collecting plate and the second microphone (mic 12, microphone 22) installed at a position other than the focal position. By configuring, it is possible to achieve both a high gain and a high S / N ratio even with sound collection far from the target sound source.

  In order to achieve a high S / N ratio with the conventional technology, the sound collecting plate is designed deeply so that the focal point is located inside the parabolic (or mirror type) sound collecting plate, and the microphone is hidden inside the sound collecting plate. However, in the sound collecting device according to the present invention, the S / N ratio can be improved without depending on the shape of the sound collecting plate. A high signal-to-noise ratio can be achieved even outside the sound collector.

  In the present invention, the gain is increased by the distance difference between the microphones (the microphone 11 and the microphone 12 or the microphone 21 and the microphone 22). The distance between the microphones affects the cancelable frequency. Specifically, if the distance between the microphones is increased, the cancellation capability in the high sound range is reduced. Therefore, the distance between the microphones, that is, the installation position of the microphone is set in balance with the gain.

  The sound waves are distributed in order from the high sound range to the low sound range from the focal point toward the sound collecting plate. Therefore, the microphone 11 and the microphone 12 (or the microphone 21 and the microphone 22) are perpendicular to the sound collecting plate, and the microphone 12 (the microphone 22) is collected with the installation position (that is, the focal position) of the microphone 11 (the microphone 21). By installing it between the sound plates, it is possible to collect sound from the high sound range to the low sound range without deviation.

  As described above, in the parabolic sound collector 1 and the mirror sound collector 2 according to the present embodiment, the first microphone is provided at the focal position of the sound collecting plate having a rotating paraboloid or a rotating ellipsoid. By providing a second microphone at a position other than the focal point and forming a differential microphone with the first microphone and the second microphone, a high gain and a high SN ratio can be realized with a small and simple configuration. .

  As described above, the sound collecting device according to the present invention is useful for a sound collecting device that collects sound using a sound collecting plate, and is particularly suitable for improving gain and SN ratio.

It is explanatory drawing explaining the outline | summary of the parabolic sound collector to which this invention is applied. It is explanatory drawing explaining the outline | summary of the mirror type sound collector to which this invention is applied. It is a block diagram which shows the structural example of the parabolic sound collector concerning a present Example. (Part 1) It is a block diagram which shows the structural example of the parabolic sound collector concerning a present Example. (Part 2) It is explanatory drawing explaining the verification method of the sound collection capability of the parabolic sound collector shown in FIG. It is explanatory drawing explaining the sound collection capability of the parabolic sound collector shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Parabola type sound collector 2 Mirror type sound collector 10 Parabola sound collector 11, 12, 21, 22 Microphone 14, 18 Difference circuit 15, 16, 17 Amplifier 20 Mirror sound collector

Claims (4)

A sound collecting plate having a rotating paraboloid or a rotating ellipsoid;
A plurality of microphones having different distances from the focal position of the sound collecting plate;
A sound collecting device comprising:   The sound collecting device according to claim 1, wherein the plurality of microphones are differential microphones having a first microphone and a second microphone connected in reverse phase to the first microphone.   The sound collecting device according to claim 2, wherein the first microphone is disposed at a focal point of the sound collecting plate, and the second microphone is disposed at a position other than the focal point.   4. The sound collecting device according to claim 1, wherein the plurality of microphones are arranged perpendicular to the sound collecting plate.

Images