JP2007300513A - Microphone device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microphone device having flat frequency response characteristics to a proximity sound source. <P>SOLUTION: The microphone device is constituted such that a first microphone 7 and a second microphone 8 which form a set are arranged in a spherical wave acoustic field generated by the proximity sound source 9, the first microphone 7 is set at a position close to the proximity sound source 9 and the second microphone 8 is set at a remote place in comparison with distance between the microphone 7 and the proximity sound source 9. With the above structure, the flat frequency response characteristics are obtained to the proximity sound source and a noise suppression effect in a low frequency area is sufficiently secured. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a microphone device that improves frequency response to a close sound source.

  Headsets enable hands-free calls to speakers, and are widely used not only for call center operators but also as mobile phone options and voice communication terminals via personal computers (PCs). .

  As shown in FIG. 13, the headset used in the call center is a microphone attached to the tip of an arm 23 extending from the receiver 22 by the speaker 20 using the headband 21 to contact the receiver 22 with the ear of the speaker 20. 24 is positioned near the mouth, the voice information of the speaker 20 is picked up by the microphone 24, and used when the speaker has a conversation with the other party. The environment in which the headset shown in FIG. 13 is used is often an environment in which the influence of ambient noise is large. In particular, in call centers, many operators are often placed relatively adjacent to each other in a non-partitioned room, and the microphones of a specific speaker's headset pick up the voices of the operators on the front, back, left, and right. Arise. In order to solve this problem, in many cases, a microphone for a headset uses a close-talking microphone capsule to reduce the influence of ambient noise due to the directivity and proximity effect of the microphone.

  An example of the close-talking microphone capsule is schematically shown in FIG. As shown in FIG. 14, in the close-talking microphone capsule, the case 25 is divided into two front and rear chambers by a vibration film 26, a front sound hole 27 is opened in front of the vibration film 26, and the rear of the vibration film 26. The rear sound hole 28 is open.

  A sound wave of wavelength λ coming from the front side of the case 25 is drawn into the case 25 from the front sound hole 27 of the case 25, and the sound pressure P 1 of the sound wave is applied to the front surface of the vibration film 26. Further, the sound wave having the wavelength λ coming from the front side of the case 25 is diverted to the outside of the case 25 and drawn into the case 25 from the back sound hole 28 of the case 25, and the sound pressure P2 of the sound wave is applied to the vibration film 26. It acts on the back. The vibrating membrane 26 outputs an output signal proportional to the difference between the sound pressures P1 and P2 acting on the front surface and the back surface.

  In the close-talking microphone capsule shown in FIG. 14, the frequency response of the far field located at a distance of L = 1 m shows the response characteristic shown by the solid line in FIG. On the other hand, the frequency response of the microphone capsule located at a distance of L = 2.5 cm shows the response characteristic indicated by the dotted line in FIG. 15, and exhibits the noise suppression effect in the low frequency band.

  However, the sound environment of a call center is quite different, and the current situation is that the use of a close-talking microphone capsule is not always effective. Further, when the close-talking microphone capsule is used alone, as shown in FIG. 15, the output level of the sound pressure in the low frequency range is insufficient as compared with the high frequency range, and the frequency response shows a form in which the high range is raised. Therefore, there is a problem in terms of sound quality.

  Further, when considering microphone devices that collect sound using a plurality of microphones that have been developed conventionally, they are classified into a type shown in FIG. 16 and a type shown in FIG. As representative examples of the prior art belonging to each type, the types shown in FIG. 16 include microphone devices disclosed in Japanese Patent Application Laid-Open Nos. 8-213936, 9-327084, and 5-256776. included. The type shown in FIG. 17 includes a microphone device disclosed in Japanese Patent No. 2897230. However, the microphone devices disclosed in these publications are only a part, and the microphone devices disclosed in many publications have been developed.

  A microphone device of the type shown in FIG. 16 has been developed to collect sound information from a sound source located far away, and combines a first microphone 30 and a second microphone 31.

  The microphone device of the type shown in FIG. 16 is used for a video tape recorder or the like. As an environment surrounding the microphone device, there is a noise source emitted from the video tape recorder at a short distance, and the sound is picked up at a long distance. There is a sound source to be picked up by a person to be photographed.

  The microphone device of the type shown in FIG. 16 is attached as an accessory such as a video tape recorder, and the video tape recorder is downsized to the palm of the photographer. Therefore, the size of the microphone device is required to be reduced in size corresponding to the size of the video tape recorder, and the interval d between the first microphone 30 and the second microphone 31 is set as narrow as possible. Yes. Incidentally, the distance d is set to about 10 mm.

  Furthermore, the microphone device of the type shown in FIG. 16 is required to pick up sound information emitted by a person or the like in a far field, and suppresses noise generated from a video tape recorder in a near field. Is required. Therefore, as shown in FIG. 16, the sound information collected by the second microphone 31 is subtracted from the sound information collected by the first microphone 30, and only the sound information from the sound source in the far field is collected. It is impossible to do.

  Therefore, as shown in FIG. 16, a directivity formation / frequency characteristic correction circuit 32 is provided on the output side of the first microphone 30 and the second microphone 31. The directivity formation / frequency characteristic correction circuit 32 collects sound information from a sound source in a far-distance sound field and forms directivity so as not to pick up noise in a short-distance sound field. Further, in order to improve the voice quality of the sound information collected by the directivity formation / frequency characteristic correction circuit 32, the frequency characteristic is corrected.

  As described above, the microphone device of the type shown in FIG. 16 is limited in size reduction because of the presence of the directivity formation / frequency characteristic correction circuit 32. In order to reduce the size of the microphone device, it is necessary to set the distance d between the first microphone 30 and the second microphone 31 as narrow as possible.

  However, since the interval d between the first microphone 30 and the second microphone 31 is determined by the upper limit value of the frequency range in which sound can be collected, setting the interval d to be narrow means Sensitivity in the main frequency band where energy is concentrated is lowered, and as a result, sound quality of sound information to be collected is deteriorated.

  A microphone device of the type shown in FIG. 17 combines a first microphone 40 and a second microphone 41, sets the first microphone 40 at the mouth of a speaker 42 with a headset, and the second microphone 41. Is set to a position where noise should be picked up.

  The microphone device of the type shown in FIG. 17 is installed by bringing the first microphone 40 close to the sound source to be picked up, and the second microphone 41 is separated from the sound source to be picked up and close to the noise source. Therefore, the transfer function simulation circuit 43 estimates a transfer function of a path through which the noise passes when the noise is transmitted to the first microphone in consideration of a process in which the noise is transmitted to the first microphone 40. The noise information collected by the second microphone 41 is delayed by a time corresponding to the transfer function estimated by the transfer function simulation circuit 43, and the noise information of the noise is input to the subtractor 44. A subtraction process is performed between the sound information picked up by the first microphone 40 and the sound information of the noise picked up by the second microphone 41, thereby suppressing the noise. It is necessary to secure.

  As described above, the microphone device of the type shown in FIG. 17 includes the transfer function simulation circuit 43 and the subtractor 44, and therefore there is a limit in reducing the size. Furthermore, since the first microphone 40 and the second microphone 41 need to be installed close to the sound source to be picked up and the noise sound source having different characteristics, respectively, the first microphone 40 and the second microphone 41 need to be installed. The distance d between the two microphones 41 must be extremely wide, and there is a limit to the reduction in size from this point.

As described above, when examining the characteristics of various microphone devices that have been developed in the past, it is not possible to obtain a flat frequency response characteristic even for a nearby sound source, that is, the sound quality of sound information is difficult, and the low frequency There is a problem that the noise suppression effect in the area is insufficient.
JP-A-8-213936 JP-A-9-327084 Japanese Patent Laid-Open No. 5-256776 Japanese Patent No. 2897230

  An object of the present invention is to provide a microphone device that can obtain a flat frequency response characteristic with respect to a proximity sound source and that can sufficiently ensure a noise suppression effect in a low frequency range.

  In order to achieve the above object, a microphone device according to the present invention includes a first microphone and a second microphone forming a pair arranged in a spherical wave sound field generated by a proximity sound source, and the microphone device for the proximity sound source. The frequency response is greatly improved.

Specifically, in the microphone device according to the present invention, the first microphone and the second microphone forming a pair are arranged in a spherical wave sound field generated by a proximity sound source,
Set the first microphone close to the proximity sound source,
The second microphone is set farther than a distance between the microphone and the close sound source.

  According to the present invention, the first microphone and the second microphone that form a pair are arranged in a spherical wave sound field generated by a proximity sound source, and therefore need to be considered in the case of the microphone device shown in FIG. In addition, it is not necessary to estimate a transfer coefficient of a path through which noise passes, a transfer function simulation circuit becomes unnecessary, and the structure of the microphone device can be simplified. Furthermore, a noise suppression effect can be obtained only by subtracting sound information output from the first microphone and the second microphone.

  Further, the first microphone is set at a position approaching a close sound source, and the second microphone is set farther than the distance between the microphone and the close sound source, thereby the first microphone. Therefore, it is possible to ensure a relatively wide distance between the acoustic terminals, which is the distance between the second microphone and the second microphone, and the frequency response of the microphone device with respect to the proximity sound source is improved.

  In general, since the frequency range in which a microphone can collect sound is defined by a response to a plane wave, in the present invention, the distance between the acoustic terminals between the first microphone and the second microphone is the sound pressure of the plane wave. What is necessary is just to determine based on the upper limit of the frequency range which can collect sound.

  In setting the distance between the acoustic terminals, in addition to the determination based on the upper limit value of the frequency range that can be picked up by the sound pressure of the plane wave as described above, the determination is made in consideration of the noise suppression amount. When the amount of noise suppression at 100 Hz is set to 30 dB or more, it is preferable to set the distance d between the first microphone and the second microphone to a range of about 30 mm <d <50 mm. Is.

  Regarding the microphone arrangement, the first microphone is arranged in front of the proximity sound source, and the second microphone is arranged at a position shifted laterally with respect to the position of the first microphone. Is also good. The first microphone and the second microphone may be arranged on a straight line with respect to the proximity sound source.

  The microphone may be either omnidirectional or directional. However, in terms of simplifying the configuration of the microphone device, the first microphone and the second microphone are omnidirectional. It is desirable to have sound collection characteristics.

  As described above, according to the present invention, since the first microphone and the second microphone forming a pair are arranged in a spherical wave sound field generated by a close sound source, transmission of a path through which noise passes as in the related art. There is no need to estimate the coefficient, and no transfer function simulation circuit is required, and the structure of the microphone device can be simplified. Furthermore, a noise suppression effect can be obtained simply by subtracting sound information output from the first microphone and the second microphone.

  Further, the first microphone is set at a position approaching a close sound source, and the second microphone is set farther than the distance between the microphone and the close sound source, thereby the first microphone. The distance between the sound terminals, which is the distance between the second microphone and the second microphone, can be secured relatively wide, and the frequency response of the microphone device with respect to the proximity sound source can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Next, an example in which the microphone device according to the present invention is applied to a microphone device of a headset will be described as an embodiment.

  Considering a headset used in a call center or the like, as shown in FIG. 1, the headset is an arm extending from the receiver 3 by the speaker 1 using the head hand 2 to reach the receiver 3 to the ear of the speaker 1. The microphone device 5 attached to the tip of 4 is positioned near the mouth 1a, the voice information of the speaker 1 is picked up by the microphone device 5, and the speaker and the other party are used when talking.

  In an environment in which the headset shown in FIG. 1 is used, there are many noise sources 6 that become noise for the microphone device 5 of the speaker 1, and the influence of noise is often large. In particular, in a call center, many operators are often placed relatively adjacent to each other in an unpartitioned room, and the voices of the operators placed on the front, back, left and right of the microphone device 5 of the headset of a specific speaker are often found. Becomes a noise source 6 and the microphone device 5 of the headset of the specific speaker picks up the voice of another operator.

  The present invention specializes in a spherical wave sound field generated by a proximity sound source, and obtains a flat frequency response with respect to the proximity sound source and sufficiently ensures a noise suppression effect in a low frequency range. It is.

  The basic concept of ambient noise reduction in the present invention will be described. An omnidirectional microphone generally used for a mobile phone or the like outputs a voltage proportional to the sound pressure received by a sound hole provided on the front surface, and is classified as a pressure type as a transducer type. The sound pressure sensitivity of the omnidirectional microphone does not depend on the arrival direction of the sound wave and the distance from the sound source of the microphone, and therefore has no effect from the viewpoint of reducing ambient noise.

  On the other hand, the close-talking microphone has two sound holes before and after the microphone capsule, and is proportional to the difference in sound pressure received by these sound holes. being classified.

  The close-talking microphone mechanically realizes the operation of taking the difference between the sound pressure received at the front sound hole and the sound pressure received at the back sound hole. When the sound wave received by the microphone can be treated as a plane wave (hereinafter referred to as a far-field sound field), the output of the pressure gradient microphone is proportional to the phase difference of the sound wave at the front and rear sound hole positions. On the other hand, when the microphone is close to the sound source and the sound wave received by the microphone is a spherical wave (hereinafter referred to as a near field (spherical wave sound field)), in addition to the above phase difference, The difference in the amplitude of the sound wave also becomes the pressure gradient.

  Therefore, as the amplitude difference contributes to the output of the microphone, the sound pressure sensitivity of the close-talking microphone is larger in the near field than in the far field, and this is called a proximity effect. That is, if the close-talking microphone is used while being placed at the speaker's mouth, it is difficult to pick up sound waves emitted from a sound source far from the speaker, and ambient noise can be reduced by the proximity effect of the microphone. Assuming that the distance between the front and rear sound holes in the close-talking microphone is a simple distance between acoustic terminals, the effect of reducing ambient noise due to the proximity effect depends on the distance between acoustic terminals.

  However, as described in the section of the prior art, the conventional close-talking microphone improves the frequency response to a sound source that generates a far-field sound field, and is intended to reduce the size. The distance between them is about 10 mm at the longest, and it is the actual situation that the microphone capsule alone cannot be expected to reduce the ambient noise beyond the distance between the sound terminals.

  The present invention realizes a configuration in which two omnidirectional microphones are combined to realize the frequency responsiveness possessed by a close-talking microphone and to ensure a relatively long distance between acoustic terminals.

  In the embodiment of the present invention, as shown in FIGS. 2 and 3, the omnidirectional first microphone 7 and the second microphone 8 constituting the microphone device 5 are placed in the spherical wave sound field generated by the proximity sound source 9. It is installed. Here, when applied as a microphone device of the headset shown in FIGS. 2 and 3, the proximity sound source 9 is a sound (sound source) emitted by the speaker 1, and the spherical wave sound field is a sound of the speaker 1. Is a sound field generated by the propagation of.

  Since the first microphone 7 and the second microphone 8 are omnidirectional, the sound pressure sensitivity of the microphones 7 and 8 is the sound wave from the proximity sound source 9 when placed in the spherical wave sound field. It does not depend on the arrival direction of the microphone and the distance from the sound source 9 of the microphone. Therefore, the microphones 7 and 8 output a large voltage signal when the sound level from the proximity sound source 9 is high, and output a small voltage signal when the sound level is low.

  Further, the microphones 7 and 8 will be mainly considered. The microphone device 5 of the headset includes a spherical wave sound field (near field) generated at a short distance with respect to the near sound source 9 and a diagram different from the near sound source 9 at a far position with respect to the near sound source 9. 1 and the far field generated by the noise source 6 shown in FIG. In the near field, there is a great difference in the sound pressure level picked up by the microphones 7 and 8.

  On the other hand, in the far field, the level difference between the sound information reaching the microphones 7 and 8 is extremely small.

  In the embodiment of the present invention, in order to improve the noise suppression effect using the characteristics described above, the positional relationship between the first microphone 7 and the second microphone ophone 8 arranged in the spherical wave sound field is regulated. is doing. Specifically, as shown in FIGS. 2 and 3, the first microphone 7 is set at a position A that approaches the proximity sound source 9 in the spherical wave sound field. On the other hand, the second microphone 8 is set at a position B far from the distance between the microphone 7 and the close sound source 9 in the spherical wave sound field.

  Since the first microphone 7 and the second microphone 8 are set in the positional relationship shown in FIGS. 2 and 3, the output signal differs depending on the positional relationship. That is, since the first microphone 7 is set at a position approaching the proximity sound source 9, the sound pressure level of the sound information from the proximity sound source 9 is set so that the second microphone 8 Since it is larger than the sound pressure level of the sound information to be picked up, a large voltage signal is output corresponding to the sound information from the close sound source 9.

  Since the first microphones 7 and 8 are non-directional, they pick up not only the sound information from the spherical wave sound field but also the sound information from the far field. However, since the far field is generated at a position far away from the spherical wave field, when the microphones 7 and 8 pick up sound information coming from the far field, There is almost no difference in the level of sound information picked up by the microphones 7 and 8.

  Therefore, as shown in FIG. 6B, the first microphone 7 has a voltage signal S1 having a large output value P1 corresponding to sound information from the close sound source 9, and sound from the long distance noise source 6. A voltage signal N1 having an output value P2 corresponding to the information is output. Further, as shown in FIG. 6C, the second microphone 8 has a voltage signal S2 having a relatively small output value P3 (P1 >> P3) corresponding to the sound information from the proximity sound source 9, and the distance A voltage signal N2 having an output value P4 (P2≈P4) corresponding to sound information from the noise source 6 is output.

  Accordingly, as shown in FIG. 6A, when the subtracter 10 subtracts the voltage signals S2 and N2 output from the second microphone 8 from the voltage signals S1 and N1 output from the first microphone 7. As shown in FIG. 7B, the S / N ratio is greatly improved, a flat response characteristic is obtained with respect to the adjacent sound source 8, and a sufficient noise suppression effect in the low frequency range can be secured. it can. For reference, in the case of a conventional close-talking microphone, the output level with respect to a proximity sound source is around −10 dB. It can be seen that the output level in the embodiment of the present invention is greatly improved.

  Next, the distance d between acoustic terminals between the first microphone 7 and the second microphone 8 will be described.

  In general, since the frequency range in which a microphone can collect sound is defined by a response to a plane wave, in the present invention, the distance between the acoustic terminals between the first microphone 7 and the second microphone 8 is the sound of a plane wave. It is determined based on the upper limit of the frequency range where sound can be collected with pressure. Furthermore, when setting the distance between the sound terminals, in addition to the determination based on the upper limit value of the frequency range that can be picked up by the sound pressure of the plane wave as described above, the determination is made in consideration of the amount of noise suppression. When the amount of noise suppression at 100 Hz is set to 30 dB or more, it is preferable to set the distance d between the first microphone and the second microphone to a range of about 30 mm <d <50 mm. Is. The basis for this will be described.

  In microphone characteristic measurement, in the microphone and the microphone device according to the embodiment of the present invention, the midpoint of the line segment connecting the first microphone 7 and the second microphone 8 is defined as the microphone position. FIG. 12 is a characteristic diagram showing the relationship between the distance d between acoustic terminals, which is the distance between the first microphone 7 and the second microphone 8, and the amount of noise suppression. In FIG. 12, the noise suppression amount is shown by the sensitivity difference of the microphone device at 100 Hz when the distance from the close sound source to the microphone is 25 cm and 1 m. It can be seen that if the desired noise suppression amount is 30 dB or more, the distance between the sound terminals is set to at least about 30 mm. Further, according to the definition of the microphone device, when the distance d between the acoustic terminals is 50 mm or more, the first microphone 7 and the adjacent sound source are in the same position, so the upper limit of the distance d between the acoustic terminals is less than 50 mm.

  An example of the distance d between the acoustic terminals is shown. If the frequency band picked up by the microphones 7 and 8 is the telephone voice band, that is, 300 Hz to 3.4 KHz, and the upper limit value of the frequency that can be picked up by the sound pressure of the plane wave is about 4 KHz, the obtained distance d between the acoustic terminals is 42. 5 mm. The distance d between the acoustic terminals is calculated by simulation. The above numerical value is an example, and if the upper limit value of the frequency that can be picked up by the sound pressure of the plane wave changes, it changes accordingly, based on the upper limit value of the frequency for the microphone device to pick up sound. Set as appropriate. The distance d between the acoustic terminals listed as an example in the embodiment of the present invention is 42.5 mm, and the distance between the acoustic terminals of the conventional close-talking microphone is 10 mm. I understand that.

  Next, the arrangement relationship between the first microphone 7 and the second microphone 8 will be described.

  As shown in FIG. 2, the first microphone 7 is disposed in front of the proximity sound source 9, and the second microphone 8 is on a straight line connecting the proximity sound source 9 and the first microphone 7. To place. In this case, the first microphone 7 and the second microphone 8 are installed with a distance d between the acoustic terminals.

  In addition, as shown in FIG. 3, the first microphone 7 is disposed in front of the proximity sound source 9, and the second microphone 8 is shifted laterally with respect to the position of the first microphone 7. It may be arranged at a position. Similarly, in the case of FIG. 3, the first microphone 7 and the second microphone 8 are separated from each other by the distance d between the acoustic terminals. In the example of FIG. 3, the second microphone 8 is installed while being shifted in the horizontal direction, so that it has an advantage that it does not get in the way for the speaker 1 when worn on the headset and the usability is good. is doing.

  In the case of the arrangement relationship between the microphones 7 and 8 shown in FIGS. 2 and 3, when the frequency response is examined in relation to the proximity sound source 9 shown in FIGS. 5A and 5B, it is shown in FIG. 5C. Thus, it is confirmed that there is no difference in their frequency responsiveness.

  This will be specifically described. The microphone device 5 including the microphones 7 and 8 shown in FIG. 2 is set at the front position of the proximity sound source 9, and the distance between the proximity sound source 9 and the first microphone 7 is set to L. In this case, the second microphone 8 is disposed farther than the first microphone 7 with respect to the proximity sound source 9. In this state, the signal was output from the proximity sound source 9 while changing the frequency in the range of 20 Hz to 20 KHz, and the frequency responsiveness of the microphones 7 and 8 to the signal was evaluated. The evaluation result is shown as case 1 in FIG.

  Further, the microphone device 5 including the microphones 7 and 8 shown in FIG. In this case, the second microphone 8 is disposed laterally with respect to the first microphone 7, and the distance between the proximity sound source 9 and the first microphones 7 and 8 is set to L, respectively. In this state, the pseudo sound was output from the proximity sound source 9 while changing the frequency in the range of 20 Hz to 20 KHz, and the frequency response when the pseudo sound was reproduced by the microphones 7 and 8 was evaluated. The evaluation result is shown as case 2 with a solid line in FIG.

  As is apparent from the evaluation results shown in FIG. 5C, the first microphone 7 and the second microphone 8 are arranged in a straight line as shown in FIG. 2, and the second microphone as shown in FIG. In the case of the configuration in which the microphone 8 is arranged laterally with respect to the first microphone 7, the respective frequency responsiveness is approximate. Therefore, it can be seen that the arrangement relationship between the first microphone 7 and the second microphone 8 may be selected as one of the arrangement relationships shown in FIG. 2 or FIG. 3 depending on the object to which the microphone device 5 is applied. . In this case, the frequency response does not change.

  Next, a structure when the microphone device 5 according to the embodiment of the present invention is attached to a headset will be described. The microphone mounting structure shown in FIG. 4 corresponds to FIG.

  As shown in FIG. 4, a substantially S-shaped piece 11 is attached to the tip of the arm 4 of the headset. Flat pieces 11 a and 11 b having an angle θ with respect to the axis of the arm 4 are formed back-to-back on the piece 1. Of the flat surfaces 11a and 11b of the piece 1, the flat surface 11a on the tip side is the mouth of the speaker 1 as shown by an arrow when the speaker 1 wears a headset as shown in FIGS. It is formed to face the 1a side. The flat surface 11b on the front side is formed toward the outer side opposite to the mouth 1a of the speaker 1.

  The first microphone 7 is incorporated in the piece 11, and the pressure receiving portion of the first microphone 7 is opened in the flat surface 11a. Therefore, the first microphone 7 receives the sound pressure mainly from the voice from the speaker 1 at the pressure receiving unit and outputs a voltage signal as sound information.

  The second microphone 8 is incorporated in the piece 11, and the pressure receiving portion of the second microphone 8 is opened in the flat surface 11b. Therefore, since the second microphone 8 is set outward with respect to the mouth 1a of the speaker 1, the second microphone 8 can be used in addition to the voice from the speaker 1 in the long-distance sound field. The sound pressure due to noise generated from the noise source 6 is received by the pressure receiving unit, and a voltage signal as sound information is output.

  According to the microphone mounting structure shown in FIG. 4, when the speaker 1 wears a headset, only the first microphone 7 is set in the mouth 1a of the speaker 1, and the second microphone 8 is the first microphone. This is set on the arm 4 side away from the microphone 7 and does not give the speaker a sense of incongruity.

  Next, the result of the characteristic evaluation of the microphone device 5 according to the embodiment of the present invention will be described. This evaluation was performed in order to evaluate the difference from the frequency response of the conventional close-talking microphone shown in FIG.

  The evaluation was performed as follows. That is, a pseudo proximity sound source 9 was prepared as shown in FIG. Moreover, the microphone device 5 shown in FIG. 2 was used as the microphone device 5. The microphone device 5 was set at the front position of the proximity sound source 9 and the distance between the proximity sound source 9 and the first microphone 7 was set to L. In this case, the second microphone 8 is disposed farther than the first microphone 7 with respect to the proximity sound source 9. In this state, signals were output from the proximity sound source 9 while changing the frequency in the range of 20 Hz to 20 KHz, and the frequency responsiveness of the microphones 7 and 8 was evaluated.

  Furthermore, the distance between the center position between the first microphone 7 and the second microphone 8 and the proximity sound source 9 was changed to L1 and L2. When the distance is L1, it means that the first microphone 7 and the second microphone 8 of the microphone device 5 according to the embodiment of the present invention are set in the spherical wave sound field generated by the proximity sound source 9. . When the distance is L2, the first microphone 7 and the second microphone 8 of the microphone device 5 according to the embodiment of the present invention are generated by the noise source 6 that is located far from the proximity sound source 9. It means that it is set in the far field. The distance L1 was set to 2.5 cm, and the distance L2 was set to 1 m.

  In FIG. 7B, when the distance between the center position between the first microphone 7 and the second microphone 8 and the proximity sound source 9 is set to L2, as shown by the solid line, The response is extremely deteriorated and shows a characteristic that gradually improves as the frequency shifts to a high frequency range. Furthermore, large peaks and dips occur in the region exceeding 8 KHZ. It can be seen that such a frequency response is inaccurate as a microphone device that requires a flat frequency response with respect to a nearby sound source.

  In FIG. 7B, when the distance between the central position between the first microphone 7 and the second microphone 8 and the proximity sound source 9 is set to L1, that is, the first microphone 7 and the second microphone When the microphone 8 is set in the spherical wave sound field generated by the proximity sound source 9, it can be seen that the frequency response is flat from the low frequency range to the high frequency range, as indicated by a dashed line. It can also be seen that the damping phenomenon in the high frequency range is suppressed to a very small level.

  Furthermore, in the microphone device 5 according to the embodiment of the present invention, the following should be noted. That is, the noise suppression effect in the low frequency range is extremely large, and the output level in frequency response is greatly improved to around 18 dB. Moreover, the output level of about 18 dB is maintained from the low frequency range to the high frequency range, as is apparent from FIG. 7B. Furthermore, the upper limit of the high frequency region is extended to about 20 KHz, the frequency response is flat in the vicinity, and the output level is greatly improved.

  The evaluation result shown in FIG. 7B shows that the first microphone 7 and the second microphone 8 forming a pair are arranged in a spherical wave sound field generated by the proximity sound source 9 in the embodiment of the present invention. One microphone 7 is set at a position approaching the proximity sound source 9, and the second microphone 8 is based on a configuration in which the second microphone 8 is set farther than the distance between the microphone 7 and the proximity sound source 9. It is believed that there is. Further, the distance d between the acoustic terminals between the first microphone 7 and the second microphone 8 is determined based on the upper limit value of the frequency range in which sound can be collected with the sound pressure of the plane wave, and the evaluation result is shown in FIG. Since it is the result shown in b), it is proved that the distance d between the acoustic terminals between the first microphone 7 and the second microphone 8 is relatively wide.

  As described above, according to the embodiment of the sound invention, it is possible to obtain a flat response characteristic with respect to a close sound source, and to sufficiently ensure a noise suppression effect in a low frequency region. Furthermore, since the noise suppression effect can be obtained by simply subtracting the output signals from the first microphone and the second microphone, an extra circuit other than the microphone is not required, and the size can be reduced.

  In the embodiment of the present invention, the case where the present invention is applied to a microphone device of a headset used in a call center has been described. However, the present invention is not limited to this. The present invention can be similarly applied not only to a call center but also to a voice device in a noisy environment, for example, a microphone device used in a store / game room, office, factory / outdoor work place, and the like.

  In the embodiment of the present invention, non-directional microphones are used for the first microphone and the second microphone. However, these microphones have directivity, and the frequency response is corrected by the circuit configuration. It may be made to do.

  In the above description, the case where ambient noise suppression is turned on is described, but the present invention is not limited to this. When it is desired to convey the surrounding atmosphere to the other party, or when the wind is very strong and the wind noise level is high and conversation using the microphone device is difficult, as shown in FIG. 8, the first microphone near the sound source is used. The operation of the microphone 8 may be switched off by the switch 12 so that only the sound picked up at 7 is output and the output of the second microphone 8 is not supplied to the subtractor 10.

  Next, an embodiment in which the microphone device according to the present invention is incorporated in a portable terminal will be described. In this embodiment, the microphone device according to the present invention is incorporated in a mobile phone which is one of mobile terminals. The mobile terminal is not limited to a mobile phone, and the microphone device according to the present invention may be incorporated in a mobile terminal other than the mobile phone.

  The mobile phone 13 shown in FIG. 9 is used when the user needs to carry it. When used in a crowded environment, the microphone of the mobile phone 13 picks up the surrounding speech, The other party's voice is difficult to hear.

  Therefore, in the embodiment of the present invention, the microphone of the mobile phone 13 is used as the first microphone 7, the second microphone 8 is attached to the arm 14, and the arm 14 is attached to the mobile phone 13 so as to be extended.

  When the mobile phone 13 shown in FIG. 9 is used, the voice uttered by the user becomes a proximity sound source. As a configuration for extending the arm 14 from the mobile phone 13 shown in FIG. 9, a configuration in which the arm 14 is drawn linearly along a slide groove (not shown) formed in the mobile phone 13 as shown in FIG. As shown in (b), one end of the arm 14 is pivotally supported and attached so as to be rotatable, and the arm 14 is rotated so that the second microphone 8 is drawn out of the mobile phone 13.

  As shown in FIG. 10 (a) or 10 (b), when the second microphone 8 is pulled out and set to the outside of the mobile phone 13 when the mobile phone 13 is used, the second microphone 8 is The distance between the first microphone 7 and the second microphone 8 is set to the above-described distance d between the acoustic terminals.

  According to the embodiment of the present invention shown in FIGS. 10 (a) and 10 (b), as described above, the first microphone 7 and the second microphone 8 that form a pair include a proximity sound source (user's voice). Therefore, it is not necessary to estimate the transfer coefficient of the path through which the noise passes, which is necessary to be considered in the case of the microphone device shown in FIG. It becomes unnecessary, and the structure of the microphone device can be simplified. Furthermore, a noise suppression effect can be obtained only by subtracting sound information output from the first microphone 7 and the second microphone 8.

  Furthermore, by setting the first microphone 7 at a position approaching a proximity sound source, and setting the second microphone 8 farther than the distance between the microphone 7 and the proximity sound source, The distance d between the acoustic terminals, which is the distance between the first microphone 7 and the second microphone 8, can be secured relatively wide, and the frequency response of the microphone device with respect to the proximity sound source is improved.

  In the embodiment shown in FIGS. 10A and 10B, the arm 14 to which the second microphone 8 is attached is folded in the mobile phone 13, and the second microphone 8 is shown in FIG. If the switch 12 is disconnected from the circuit and the arm 14 is pulled out and the second microphone 8 is set at a fixed position, the second microphone 8 may be connected to the circuit by the switch 12. It is.

  In the embodiment shown in FIGS. 9 and 10, the arm 14 to which the second microphone 8 is attached is attached to the mobile phone 13 so that it can be pulled out to the outside, but this is not a limitation. The arm 24 to which the second microphone 8 is attached is detachably attached to the mobile phone 13, and when the second microphone 8 is used, the arm 24 is attached to the mobile phone 13 and the second microphone 8 is attached to the first phone. The distance between the microphone 7 and the proximity sound source may be set far away.

  As shown in FIG. 11, the first microphone 7 is fixed to the mobile phone 13 at a position where the user's voice as a proximity sound source is picked up, and the second microphone 8 is connected to the first microphone 7 and the proximity sound source. It may be set at a distance compared to the distance between and fixed to the mobile phone 13. Also in this case, when the second microphone 8 is not used, the second microphone 8 is disconnected from the circuit by the switch 12 as shown in FIG. 8, and conversely, when the second microphone 8 is used, The two microphones 8 may be connected to the circuit by the switch 12. Even in this case, the distance between the first microphone 7 and the second microphone 8 is set to the above-described distance d between acoustic terminals.

  In the case of the embodiment shown in FIG. 11, when the user holds the mobile phone 13, the openings of the first microphone 7 and the second microphone 8 may be covered with the user's hand. Therefore, as shown in FIG. 11, one end of the first sound guide 15 that guides the sound from the proximity sound source is connected to the first microphone 7, and the other end of the sound guide 15 cannot be blocked by the user's hand. Open to position. Similarly, one end of the second sound guide 16 is connected to the second microphone 8 and the other end of the sound guide 15 is opened at a position where it cannot be blocked by the user's hand.

  According to the embodiment shown in FIG. 11, the first microphone 7 and the second microphone 8 are incorporated in the mobile phone 13, and these microphones 7 and 8 do not protrude outside the mobile phone 13. Can be used without any sense of incongruity. In addition, the first microphone 7 and the second microphone 8 can reliably pick up sound information due to the presence of the sound guides 15 and 16, and the noise suppression effect by the first microphone 7 and the second microphone 8 is sufficient. Can be demonstrated.

  As described above, according to the present invention, it is most suitable as a microphone device used not only in a call center but also in voice communication under a noisy environment, for example, in a store / game room, office, factory / outdoor work place, etc.

It is a figure which shows an example environment where the microphone apparatus which concerns on embodiment of this invention is used. It is a figure which shows the arrangement | positioning relationship of the microphone in embodiment of this invention. It is a figure which shows the arrangement | positioning relationship of the microphone in embodiment of this invention. It is a figure which shows the attachment state of the microphone in embodiment of this invention, Comprising: (a) is a top view, (b) is the figure seen from the front side, (c) is the figure seen from the speaker side. (A) And (b) is a figure which shows the arrangement | positioning relationship for evaluating the difference in the characteristic of the microphone apparatus shown in FIG.2 and FIG.3, (c) is a characteristic view which shows an evaluation result. (A) is a circuit diagram which shows the case where a subtraction process is performed with respect to the signal which a 1st microphone and a 2nd microphone output, (b) and (c) are output by a 1st and 2nd microphone. It is a wave form diagram which shows an example of a signal. (A) is a figure which shows the state which evaluates the microphone apparatus based on embodiment of this invention, (b) is a characteristic view which shows an evaluation result. It is a circuit diagram which shows the microphone apparatus which concerns on another embodiment of this invention. 1 is a front view showing a state in which a microphone device according to the present invention is incorporated in a mobile phone and the microphone device is folded. (A) is embodiment which incorporated the microphone apparatus based on this invention in a mobile telephone, Comprising: The front view which shows the structure which extends | stretches an arm linearly and pulls out the 2nd microphone to the exterior of a mobile telephone. FIG. 4 is a front view showing a configuration in which an arm is rotated to pull out a second microphone to the outside of the mobile phone. (A) is a front view which shows the state which folded another embodiment which incorporated the microphone apparatus based on this invention in the mobile phone, (b) is the same side view. It is a characteristic view which shows the relationship between the distance between acoustic terminals which is the space | interval of a 1st microphone and a 2nd microphone, and a noise suppression amount. It is a figure which shows the microphone apparatus integrated in the conventional headset. It is sectional drawing which shows the conventional close-talking microphone. It is a characteristic view which shows the frequency response by the close-talking microphone shown in FIG. It is a figure which shows the conventional microphone apparatus. It is a figure which shows the conventional microphone apparatus.

Explanation of symbols

5 Microphone device 6 Noise source (long-distance sound source)
7 First microphone 8 Second microphone 9 Proximity sound source 12 Switch

Claims (12)

The first microphone and the second microphone forming a pair are arranged in a spherical wave sound field generated by a proximity sound source,
Set the first microphone close to the proximity sound source,
The microphone device, wherein the second microphone is set farther than a distance between the first microphone and the proximity sound source.   2. The distance between acoustic terminals between the first microphone and the second microphone is determined based on an upper limit value of a frequency range in which sound can be collected with sound pressure of a plane wave. Microphone device. The distance d between acoustic terminals between the first microphone and the second microphone is
3. The microphone device according to claim 2, wherein the range is set in the vicinity of 30 mm <d <50 mm. The first microphone is disposed in front of the proximity sound source,
The microphone device according to claim 1, wherein the second microphone is disposed at a position shifted laterally with respect to the position of the first microphone.   The microphone device according to claim 1, wherein the first microphone and the second microphone are arranged in a straight line with respect to the proximity sound source.   The microphone device according to claim 1, wherein the first microphone and the second microphone have a non-directional sound collection characteristic.   2. The microphone device according to claim 1, wherein the operation of the second microphone can be switched on and off.   The microphone device according to claim 1, wherein the first microphone and the second microphone are microphones mounted on a portable terminal.   9. The microphone according to claim 8, wherein the second microphone is extended from the portable terminal and set farther than a distance between the first microphone and the proximity sound source. apparatus.   The said 2nd microphone is attached to the said portable terminal so that attachment or detachment is possible, and is set in the distance compared with the distance between the said 1st microphone and the said proximity sound source. Microphone device.   The microphone device according to claim 8, wherein the first microphone and the second microphone are fixedly attached to the portable terminal.   The microphone device according to claim 8, wherein the operation of the second microphone can be switched on and off.

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