JP2010272926A - Sound pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound pick-up device which can raise operating frequency of a sub-woofer. <P>SOLUTION: A recording device 1 includes: a microphone M1 for a front side; a microphone M2 for a left front side; a microphone M3 for a right front side; a microphone M4 for a left back side; a microphone M5 for a right back side; and a microphone M6 for a sub-woofer. These microphones are unidirectional microphones. The microphone M1 to the microphone M5 are arranged in the same plane, and the microphone M6 is arranged in a different position of the plane where the microphone M1 to the microphone M5 are arranged. The recording device 1 arranges the microphone M6 for the sub-woofer inside of the device, and arranges other microphones M1 to M5 around. Moreover, the recording device 1 arranges front directions of directional axes of the microphone M1 to the microphone M5 to directions of respective loudspeakers installed when respectively reproducing in a surround sound. The recording device 1 arranges a directional axis of the microphone M6 for a LFE channel so as to be perpendicular to directional axes of the other microphone M1 to the microphone M5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a sound collection device that collects multi-channel sound.

  Conventionally, when recording a multi-channel audio source, various means for generating a low-frequency channel audio signal have been proposed (see, for example, Non-Patent Document 1).

  The recording device of Non-Patent Document 1 generates eight multi-channel audio signals by arranging eight microphones inside a rugby ball-shaped casing. These microphones are omnidirectional condenser microphones, and are arranged on the front side, right side, left side, upper side, right rear side, left rear side, rear side, and inside of the housing, respectively. These microphones collect audio signals of different channels. A microphone arranged inside the housing picks up a low frequency channel.

  In addition, in a live recording such as classical music, a low frequency channel audio signal is often not recorded. When recording is not performed, the audio signals of other channels are often synthesized, and only the low frequency is obtained from the synthesized audio signal to generate a low frequency channel audio signal.

  Further, in the creation of content such as a movie, the audio signal of the low frequency channel is generated by processing from some sound material such as a separately recorded sound and is used to reinforce the low frequency effect. However, it is rare that a low-frequency channel audio signal is prepared when creating a content for live recording.

“H2-PRO Surround Sound Microphone User Guide”, Rising Sun Products Ltd.

  However, the recording device of Non-Patent Document 1 generates an audio signal of each channel using an omnidirectional microphone that collects sound with the same sensitivity around the entire periphery of the recording apparatus. In this recording device, other microphones are placed around the internal microphone (microphone for low frequency channel), and each microphone picks up the entire circumference of the microphone with the same sensitivity. An audio signal having the same waveform component is included in other channels. For this reason, when a multi-channel audio signal recorded by this recording device is played back, there is a problem that the audio signal of the low-frequency channel and the audio signal of the other channel cancel each other or become extremely strong. There is.

  Also, when playing live recorded classics, etc., when synthesizing the audio signals of all channels and generating the audio signal of the low frequency channel, the audio signals of the same waveform component are naturally included, so the audio signals may be canceled out. , The problem of being extremely strong arises.

  Further, when playing back live-recorded content, a low-frequency channel audio signal is often not output under normal settings. For this reason, the usage frequency of the owned subwoofer falls, and a user will feel unnecessarily.

  Therefore, the present invention provides a sound collection device capable of collecting a low-frequency channel audio signal that does not cancel or extremely strengthen the audio signal during reproduction.

  The sound collection device according to the present invention includes a plurality of microphones, sound collection means different from the plurality of microphones, and acquisition means for obtaining only a low frequency of the audio signal collected by the sound collection means. The plurality of microphones are arranged such that the direction of a speaker installed during surround sound reproduction is set as the sound collection direction, and collects a multi-channel audio signal. The sound collecting means is arranged to pick up a sound signal having a low correlation with the sound signals picked up by the plurality of microphones. For example, a vibration sensor is used as sound collection means. Since the vibration sensor collects sound by a propagation method different from that of the plurality of microphones, it can collect an audio signal (vibration) having a low correlation.

  As a result, the sound collecting device can pick up the sound signal of the low-frequency channel that does not cancel the sound signals at the time of reproduction or does not extremely strengthen at the same time as collecting the surround sound.

  Moreover, the unidirectional microphone may be sufficient as the some microphone with which the sound collection device of this invention is provided, and a sound collection means. In this case, the plurality of microphones are arranged so that each of them is directed radially outward (so that the respective directivity axes overlap). That is, the plurality of microphones are arranged such that the direction of the maximum sensitivity (the direction in which the sensitivity is maximum) is directed radially outward. The sound collecting means is arranged so that the direction perpendicular to the directional axes of the plurality of microphones is the directional axis. At this time, since the direction of the sensitivity maximum of the plurality of microphones and the directivity axis of the plurality of microphones are perpendicular to each other, the sound collection unit can collect a sound signal having a low correlation with the sound signals collected by the plurality of microphones. .

  Furthermore, since the sound collecting apparatus arranges the plurality of microphones on the same plane and arranges the plurality of microphones radially, the directivity axes of the plurality of microphones overlap at one point, and thus the directivity axes of the plurality of microphones overlap. The sound collection means may be arranged at a position (that is, a position surrounded by a plurality of microphones) and on a plane on which the plurality of microphones are arranged. In this case, since the sound collecting means is arranged in the direction of the minimum sensitivity of the plurality of microphones (the direction in which the sensitivity is minimum), compared to the case where the sound collecting means is arranged at a position different from the plane on which the plurality of microphones are arranged, A sound signal having a lower correlation with the sound signals picked up by a plurality of microphones can be picked up.

  The sound collecting device according to the present invention can pick up a sound signal of a low-frequency channel that does not cancel out or extremely strengthen the sound signals at the same time as reproducing the surround sound.

It is a figure which shows arrangement | positioning of the microphone which a recording device has. It is a block diagram which shows the function and structure of a recording device. It is a figure which shows the other example of arrangement | positioning of the microphone which a recording device has. It is a block diagram which shows the function and structure of the recording device which concern on other embodiment.

  The recording device 1 of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an arrangement of microphones included in a recording apparatus. 1A shows a perspective view, and FIG. 1B shows a plan view. FIG. 2 is a block diagram showing the function and configuration of the recording apparatus.

  As shown in FIG. 1A, the recording apparatus 1 includes a front microphone M1, a left front microphone M2, a right front microphone M3, a left rear microphone M4, a right rear microphone M5, a subwoofer microphone M6, and an LPF. A unit 11 (see FIG. 2) and a storage unit 12 (see FIG. 2) are provided. The microphones M1 to M6 are unidirectional microphones.

  A unidirectional microphone has a directional axis in the direction perpendicular to the diaphragm, and the sensitivity in the front direction of the diaphragm (front direction of the directional axis) is maximized (hereinafter referred to as the maximum sensitivity), and the direction of the rear surface of the diaphragm The sensitivity in the back direction of the directional axis is minimized (hereinafter referred to as sensitivity minimum).

  The recording apparatus 1 arranges the microphones M1 to M5 on the same plane on the outer peripheral surface of the recording apparatus 1. The recording apparatus 1 arranges the directivity axes in the front direction of the microphones M1 to M5 radially toward the direction of each speaker installed when reproducing the surround sound (so that the directivity axes overlap). . Moreover, the recording apparatus 1 arrange | positions the microphone M6 for subwoofers in the position different from the plane in which the microphone M1-microphone M5 was arrange | positioned inside an own apparatus. The recording apparatus 1 arranges the directivity axis of the microphone M6 for the LFE channel so as to be perpendicular to the directivity axes of the other microphones M1 to M5.

  Specifically, as shown in FIG. 1B, the front microphone M1 has the front direction of the directional axis (direction of maximum sensitivity) as the + Y direction, and the + Y direction side from the reference point (for example, the center of the apparatus). Is arranged. Then, the left front microphone M2 is arranged at a position rotated in a direction of 30 degrees in the -X direction (hereinafter referred to as the L direction) from the front microphone M1, and the L direction from the reference point is the front direction of the directional axis. And The right front microphone M3 is disposed at a position rotated from the front microphone M1 in the direction of 30 degrees in the + X direction (hereinafter referred to as the R direction), and the R direction from the reference point is the front direction of the directional axis. The left rear microphone M4 is arranged at a position rotated from the front microphone M1 in the direction of 100 degrees to 120 degrees in the -X direction (hereinafter referred to as the SL direction), and the SL direction from the reference point is located in front of the directional axis. The direction. The right rear microphone M5 is disposed at a position rotated from the front microphone M1 in the direction of 100 degrees to 120 degrees in the + X direction (hereinafter referred to as SR direction), and the SR direction from the reference point is the front direction of the directional axis. And In this way, the microphones M1 to M5 are arranged on the same plane so that the respective directivity axes are arranged such that the direction of the sensitivity maximum is radially outward. Further, the directivity axes of the microphones M1 to M5 overlap at the reference point.

  On the other hand, as shown in FIG. 1A, the subwoofer microphone M6 is arranged in the −Z direction from the reference point and points in the −Z direction (direction perpendicular to the directivity axis of the microphones M1 to M5). The front direction of the shaft (the direction of maximum sensitivity of the microphone M6) is assumed. Thus, the directivity axis of the subwoofer microphone M6 passes through the position where the directivity axes of the microphones M1 to M5 overlap, and is perpendicular to the plane shared by the directions of maximum sensitivity of the microphones M1 to M5.

  After installing the recording device 1 at the listening point, the user starts sound emission of the sound to be recorded (for example, start of music performance or start of movie shooting) and starts recording. At this time, the user installs the recording apparatus 1 with the front microphone M1 facing the front direction from the listening point and the subwoofer microphone M6 facing the downward direction from the listening point.

  From the above, the front microphone M1 picks up the audio signal (C channel audio signal) from the front direction (+ Y direction). The left front microphone M2 collects an audio signal (L channel audio signal) from the left front direction (L direction). The right front microphone M3 collects an audio signal (R channel audio signal) from the front right direction (R direction). The left rear microphone M4 collects an audio signal (SL channel audio signal) from the left rear direction (SL direction). The right rear microphone M5 collects an audio signal (SR channel audio signal) from the right rear direction (SR direction). Then, the subwoofer microphone M6 collects an audio signal from the lower direction (−Z direction) (an audio signal used for the LFE channel).

  At this time, the subwoofer microphone M6 has a low correlation with the sound signal collected by the microphones M1 to M5 because the plane in which the sensitivity maximum directions of the microphones M1 to M5 share and the directivity axis of the subwoofer are vertical. Audio signals can be collected, and audio signals that do not cancel each other during reproduction or are not excessively strong can be collected.

  Next, the function, configuration, and processing of the recording device 1 will be described. As illustrated in FIG. 2, the LPF unit 11 is a low-pass filter that acquires only a low frequency of an input audio signal. The storage unit 12 is a storage unit that stores an audio signal of each channel. The recording device 1 stores the audio signals picked up by the microphones M1 to M6 in the storage unit 12, respectively. At this time, the audio signal collected by the subwoofer microphone M6 is stored in the storage unit 12 after passing through the LPF unit 11. As a result, the recording apparatus 1 can generate an LFE channel audio signal (low frequency channel audio signal) consisting of only the low frequency audio signal.

  As described above, the recording apparatus 1 can record the audio signal of the LFE channel that hardly includes the audio signal having the same waveform component as the audio signal of the other channel and has a low correlation with the audio signal of the other channel. Therefore, when the multi-channel audio signal generated using the recording device 1 is reproduced, the surround sound is not canceled or extremely strengthened between the LFE channel audio signal and the other channel audio signal. Can be realized.

  For example, the recording apparatus 1 can record the audio signal of the LFE channel that does not cancel or extremely strengthen the audio signal of the other channel at the time of reproduction even when the performance of classical music or the like is recorded live. .

  In the above-described embodiment, the subwoofer microphone M6 is disposed downward. However, the present invention is not limited to this, and for example, the subwoofer microphone M6 may be disposed upward. The subwoofer microphone M6 only needs to collect an audio signal having a low correlation with other audio signals, and may collect the audio signal from above. The subwoofer microphone M6 is preferably picked up from the lower direction because the sound picked up from the lower direction can pick up low-pitched sounds such as earth sounds and vibrations.

  In the above-described embodiment, the microphones M1 to M5 are arranged on the same plane, and the subwoofer microphone M6 is arranged at a position different from this plane. However, as shown in FIG. 3, the microphones M1 to M6 may be arranged on the same plane. FIG. 3 is a diagram illustrating another example of the arrangement of microphones included in the recording apparatus.

  In this case, the recording apparatus 1 radiates the directivity axes in the front direction of the microphones M <b> 1 to M <b> 5 toward the respective speakers installed when playing the surround sound, so that the directivity axes overlap each other. )Deploy. The recording apparatus 1 arranges the subwoofer microphone M6 at a position where the directivity axes of the microphones M1 to M5 overlap so that the directivity axis of the subwoofer microphone M6 and the directivity axis of the microphones M1 to M5 are vertical. That is, the directivity axis of the subwoofer microphone M6 is perpendicular to a plane shared by the directions of the maximum sensitivity of the microphones M1 to M5. The subwoofer microphone M6 is arranged in the direction of the minimum sensitivity of the microphones M1 to M6.

  For this reason, the subwoofer microphone M6 is a voice signal that is picked up by the microphones M1 to M5 when arranged on the same plane as compared to the case where the microphones M1 to M5 are arranged at different positions. The sound signal having a lower correlation with the sound signal can be picked up, and the sound signal that cancels out the sound signals during reproduction or is extremely strong is not picked up.

  When the subwoofer microphone M6 is arranged on the same plane as the microphones M1 to M5, the subwoofer microphone may be a bidirectional microphone. A bi-directional microphone has a theoretically zero sensitivity in the direction parallel to the diaphragm, and a three-dimensionally low sensitivity surface (hereinafter referred to as a NULL surface) because the direction in which the sensitivity is zero is rotationally symmetric. .). In this case, since the NULL surface of the subwoofer microphone M6 and the directivity axis of the microphones M1 to M6 coincide with each other, the recording apparatus 1 uses a bidirectional microphone rather than a unidirectional microphone as the subwoofer microphone M6. However, the correlation between the audio signals collected by the subwoofer microphone M6 and the microphones M1 to M5 can be further reduced.

  In the above-described embodiment, the microphones M1 to M5 are arranged on the same plane, but they may be arranged on different planes.

  The subwoofer microphone M6 is preferably a microphone having a low frequency characteristic superior to the high frequency characteristic compared to the other microphones M1 to M5.

  Note that the recording device 1 may be a sound collection device that is provided with an external output terminal instead of the storage unit 12 and stores an audio signal in the external storage device.

  In the above embodiment, the 5.1 channel has been described as an example. However, any recording device capable of recording a multi-channel audio signal including the LFE channel such as the 2.1 channel and the 7.1 channel. Good.

  Next, a recording apparatus 2 according to another embodiment will be described with reference to FIG. FIG. 4 is a block diagram illustrating functions and configurations of a recording apparatus according to another embodiment. The recording apparatus 2 is different from the recording apparatus 1 of the first embodiment in the method of generating an LFE channel audio signal. Only differences from the first embodiment will be described below.

  The recording device 2 includes a measurement mode for measuring stationary noise and a recording mode for recording an audio signal. Stationary noise refers to vibrations that occur during normal times (when nothing is done) (for example, vibrations that occur due to air flow or the like). In the measurement mode, no sound is picked up by the microphones M1 to M5, and a signal picked up by the vibration sensor 21 is stored in the memory of the removing unit 23 as stationary noise through a process described later. In the recording mode, the signals picked up by the microphones M1 to M5 are stored in the storage unit 12, and the signals acquired by the vibration sensor 21 are stored in the storage unit as audio signals of the LFE channel through processing to be described later. 12 is stored. When the user installs the recording device 2 at the listening point, the user executes the measurement mode, measures the stationary noise, and then executes the recording mode to record the audio signal.

  Next, the function, configuration, and processing of the recording device 2 will be described. As shown in FIG. 4, the recording device 2 includes a vibration sensor 21, an amplitude conversion unit 22, a removal unit 23, and an amplifier 24 instead of the subwoofer microphone M <b> 6 of the recording device 1.

  The vibration sensor 21 is an acceleration sensor (for example, a sensor of a piezoelectric type, a capacitance type, a piezoresistive type, etc.) that acquires vibration. The vibration sensor 21 converts the acquired vibration into an electrical signal. The amplitude converter 22 performs second-order integration of the input electrical signal and converts acceleration information into amplitude. The removal unit 23 includes a memory that is controlled based on an operation of an operation unit (not shown) and stores stationary noise. When the measurement mode is selected, the removal unit 23 stores the input amplitude in the memory as stationary noise. Further, when the recording mode is selected, the removing unit 23 removes stationary noise stored in the memory from the input amplitude. The amplifier 24 amplifies the input amplitude.

  In the measurement mode, the vibration acquired by the vibration sensor 21 is stored in the memory of the removal unit 23 via the amplitude conversion unit 22. As a result, the recording device 2 can measure the amplitude based on the vibration acquired by the vibration sensor 21 as stationary noise.

  In the recording mode, the vibration acquired by the vibration sensor 21 is stored in the storage unit 12 via the vibration sensor 21, the amplitude conversion unit 22, the removal unit 23, the amplifier 24, and the LPF unit 11. As a result, the recording device 2 can record the sound obtained by removing the stationary noise from the vibration acquired by the vibration sensor 21 as an audio signal of the LFE channel.

  As described above, the recording device 2 records the vibration itself at the place where the recording device 2 is installed as an audio signal of the LFE channel. By reproducing the recorded audio signal of the LFE channel, it is possible to convey a sense of realism during recording. For example, an automobile equipped with the recording device 2 is driven to record an audio signal of the LFE channel. By reproducing the recorded audio signal of the LFE channel, it is possible to convey a sense of presence as if the user is in the car.

  For example, in the production of live-recorded content (for example, content such as a documentary or a treasure), the recording device 2 reinforces the low frequency effect of the LFE channel audio signal (the vibration itself at the place where the device is installed). Can be recorded as an effect. Further, since the recording device 2 can generate an effect only by recording, even a slight vibration can be generated as an audio signal of the LFE channel. For this reason, compared with the case where the signal is processed and generated from some material, the output audio signal of the LFE channel is increased, and the frequency of using the owned subwoofer is increased, so the user does not feel it unnecessarily.

  Further, since the recording apparatus 2 collects the LFE channel audio signal by a propagation method different from that of the other channel audio signal, the recording device 2 may generate an LFE channel audio signal having a low correlation with the other channel audio signal. it can.

  In the above-described embodiment, an acceleration sensor is used as the vibration sensor 21. However, a speed sensor or a displacement sensor may be used. At this time, the amplitude converter 22 changes the conversion method according to the type of sensor.

  DESCRIPTION OF SYMBOLS 1, 2 ... Recording apparatus, 11 ... LPF part, 12 ... Memory | storage part, 21 ... Vibration sensor, 22 ... Amplitude conversion part, 23 ... Removal part, 24 ... Amplifier, M1-M6 ... Microphone

Claims (3)

A sound collecting device for collecting multi-channel audio signals in surround sound,
A plurality of microphones arranged for each of the multi-channel channels, each of which is set as a sound collection direction of a speaker installed at the time of reproducing the surround sound,
Sound collecting means arranged to pick up sound signals having low correlation with sound signals picked up by the plurality of microphones;
A sound collection device comprising: an acquisition unit that acquires only a low frequency from an audio signal generated by the sound collection unit. The plurality of microphones and the sound collection means are unidirectional microphones,
The plurality of microphones are arranged so that each faces radially outward,
The sound collecting device according to claim 1, wherein the sound collecting means uses a direction perpendicular to a directivity axis of the plurality of microphones as a directivity axis. The plurality of microphones are arranged on the same plane,
The sound collection device according to claim 2, wherein the sound collection unit is arranged on the plane at a position where the directivity axes of the plurality of microphones intersect.

Images