JP2014096732A - Voice collection device, and telephone set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simplified and small-sized voice collection device capable of improving the quality of collected voice signals.SOLUTION: The present invention relates to a voice collection device for forming a voice signal to be outputted from a voice signal from a bone conduction microphone which converts bone conduction voice vibration into an electric signal and a voice signal from an air conduction microphone which converts air voice vibration into an electric signal. The voice collection device comprises: equalizer means for equalizing frequency characteristics, which are not flat, included in the voice signal from the bone conduction microphone and converting the voice signal into a voice signal including flat frequency characteristics; band limit means for extracting a frequency component so as to exclude a frequency component included in the voice signal from the bone conduction microphone, from the voice signal from the air conduction microphone; and mix means for mixing the voice signal outputted from the equalizer means and the voice signal outputted from the band limit means.

Description

  The present invention relates to a sound collection device and a telephone, and can be applied to, for example, a highway telephone set beside an expressway.

  For example, in a large noise environment such as traffic noise, a telephone using a bone conduction microphone (hereinafter referred to as a microphone) having good noise resistance is installed.

  Conventionally, there is a telephone described in Patent Document 1 as a telephone to which such a bone conduction microphone is applied. The technology described in Patent Document 1 captures the air sound vibration from the user's mouth and the bone conduction sound vibration by separate microphones, and adds the sound signals from these two microphones to obtain a synthesized sound signal. The user can freely adjust the mixing ratio of the audio signals from the two microphones.

  However, in the technique described in Patent Document 1, since the frequency bands of the two microphones overlap even if the mixing ratio is adjusted, a microphone (hereinafter referred to as an electric signal) that converts air sound vibration in the synthesized sound signal. The sound signal component from the air conduction microphone includes ambient noise, and the characteristic of the bone conduction microphone that it is difficult to input the ambient noise is negated.

  The technique described in Patent Document 2 solves such inconvenience. The technology described in Patent Document 2 includes an air conduction microphone and a bone conduction microphone, and each frequency component is obtained by a high-pass filter and a low-pass filter for the air conduction microphone and a low-pass filter for the bone conduction microphone. The transmission state detection unit detects whether or not the transmission state is detected by comparing the output levels of the two low-pass filters. On the other hand, the ambient noise level is detected from the output of the air conduction microphone. Based on the result, the mixing ratio of the low frequency and high frequency components of the audio signal of the air conduction microphone and the low frequency component of the audio signal of the bone conduction microphone is changed, and the two audio signals are synthesized by the mixing circuit, Output.

JP-A-6-30490 Japanese Patent Laid-Open No. 10-23122

  However, in the technique described in Patent Document 2, since the sound collecting device is composed of many components, the device is complicated, large, expensive, and difficult to commercialize. For example, when many components are to be realized by LSI or DSP in order to eliminate the complexity of the configuration, the LSI or DSP is operated in addition to the transmitter power supply (power supply voltage) applied to a normal telephone. Since a power supply voltage is required, the configuration of the power supply unit becomes complicated, and the meaning of applying LSI or DSP is lost.

  Therefore, there is a demand for a simple and small sound collection device and telephone that can improve the sound quality of the collected sound signal.

  The first aspect of the present invention forms an audio signal output from an audio signal from a bone conduction microphone that converts bone conduction sound vibration into an electric signal and an audio signal from an air conduction microphone that converts air sound vibration into an electric signal. (1) equalizer means for equalizing a non-flat frequency characteristic of the audio signal from the bone conduction microphone and converting it to an audio signal having a flat frequency characteristic; and (2) from the air conduction microphone. Band limiting means for extracting a frequency component from the audio signal so as to exclude the frequency component of the audio signal from the bone conduction microphone, (3) the audio signal output from the equalizer means, and the band limiting means And a mixing means for mixing the audio signal output from.

  The telephone of the second aspect of the present invention is characterized in that the sound collecting device of the first aspect of the present invention is applied as a transmission signal forming unit.

  ADVANTAGE OF THE INVENTION According to this invention, the simple and small-sized sound collection apparatus and telephone which can improve the sound quality of the collected sound signal are realizable.

It is a block diagram which shows the structure of the sound collection device of embodiment. It is explanatory drawing which shows the frequency characteristic of the bone conduction microphone in the sound collection device of embodiment. It is explanatory drawing of the equivalent process of the equalizer circuit in the sound collection device of embodiment. It is explanatory drawing which shows the frequency characteristic of the air-conduction microphone in the sound collection device of embodiment. It is explanatory drawing which shows the frequency characteristic of the bandpass filter in the sound collection device of embodiment. It is explanatory drawing which shows the frequency characteristic of the output signal from the mix circuit in the sound collection device of embodiment. It is explanatory drawing of the mixing ratio which the sound collection device of embodiment can respond.

(A) Main Embodiment Hereinafter, an embodiment in which a sound collecting device and a telephone according to the present invention are applied to a road telephone will be described in detail with reference to the drawings.

(A-1) Configuration of Embodiment FIG. 1 is a block diagram illustrating a configuration of a sound collection device of the embodiment.

  In FIG. 1, the sound collection device 10 according to the embodiment includes a bone conduction microphone 1, an air conduction microphone 2, a bone conduction microphone amplifier 3, an air conduction microphone amplifier 4, an equalizer circuit 5, a band pass filter (BPF) 6, a mix. A circuit (mixer) 7, a transmission signal output terminal 8, and a mixing ratio variable switch 9 are provided. The sound collecting device 10 is incorporated in a telephone handset (a handset) 11. Although not shown in FIG. 1, the handset 11 also has a reception signal processing configuration.

  The bone conduction microphone 1 is provided, for example, in the vicinity of a reception signal speaker unit (not shown) of the handset 11. When the user presses the speaker unit for the received signal against the right or left ear and the handset 11 is positioned so that the air conduction microphone 2 of the handset 11 is positioned at the mouth, the bone conduction microphone 1 removes the skin or the like. The bone conduction microphone 1 is provided on the handset 11 so as to contact the cheekbone. When the user utters voice, the vocal cords vibrate, and this voice vibration is conducted through the skull. The bone conduction microphone 1 captures this bone conduction voice vibration and converts it into an electrical signal. For example, a frequency component that can be captured by a commercially available bone conduction microphone 1 is 300 Hz to 2 kHz. The skull is rarely vibrated by ambient noise (air vibration), and the bone conduction microphone 1 has a characteristic that it is difficult to capture ambient noise even if the ambient noise has a frequency component of 300 Hz to 2 kHz. doing.

  The bone conduction microphone amplifier 3 amplifies the audio signal from the bone conduction microphone 1 and supplies it to the equalizer circuit 5. The bone conduction microphone amplifier 3 amplifies the bone conduction microphone 1 so as to maintain the frequency characteristic curve of the bone conduction microphone 1.

  The equalizer circuit 5 performs an equalization process on the audio signal supplied from the bone conduction microphone amplifier 3 and supplies the audio signal S1 after the equalization process to the mix circuit 7.

  FIG. 2 is a characteristic curve diagram showing the frequency characteristics of the bone conduction microphone 1. As described above, the bone conduction microphone 1 has a band in which 300 Hz to 2 kHz can be captured. On the high frequency side of this band (for example, 1 kHz to 2 kHz), as shown in FIG. Have The equalizer circuit 5 raises the high frequency range so that it can be easily heard, and flattens the frequency characteristics as shown in FIG.

  Incidentally, if the high frequency side is included in the transmission signal with the characteristic of lowering to the right, the sound quality is low and the sound quality becomes low, and the intelligibility of the conversation is poor. By interposing, such a problem can be prevented beforehand.

  The air conduction microphone 2 converts air sound vibration generated when a user emits sound into an electric signal. Since the air conduction microphone 2 captures air vibrations, it also captures air vibrations of ambient noise. In general, the band that can be captured by the air conduction microphone 2 is a wide range of 100 Hz to 8 kHz so that not only voice but also sound can be captured. As a result, ambient noise can be easily captured. FIG. 4 shows the frequency characteristics of the air conduction microphone 2.

  The air conduction microphone amplifier 4 amplifies the audio signal from the air conduction microphone 2 and supplies it to the band pass filter 6. The air-conduction microphone amplifier 4 amplifies with the same gain, for example, at least in the band range of 2 kHz to 3.4 kHz.

  Between the gain of the bone conduction microphone amplifier 3 and the gain of the bone conduction microphone amplifier 3, the frequency of the signal after mixing by the mix circuit 7 when the mixing ratio in the mix circuit 7 to be described later is 10:10 The characteristic is determined to be flat (see FIG. 6 described later and R1 in FIG. 7 described later).

  The band pass filter 6 passes (filters) frequency components belonging to the band 2 kHz to 3.4 kHz among the frequency components of the audio signal output from the air conduction microphone amplifier 4, and mixes the filtered audio signal S <b> 2. This is given to the circuit 7. The band 2 kHz to 3.4 kHz is a band obtained by excluding the band 300 Hz to 2 kHz of the audio signal related to bone conduction output from the equalizer circuit 5 from the pass band 300 Hz to 3.4 kHz according to the legacy telephone. The band 100 Hz to 8 kHz that can be captured by the air conduction microphone 2 is too wide from the necessary band as a telephone, and a lot of ambient noise is mixed. For this reason, the bandpass filter 6 is used to limit the band while considering the band 300 Hz to 2 kHz of the audio signal related to bone conduction.

  If the sound collection device 10 of the embodiment is applied to a broadband telephone such as an IP telephone, a high-pass filter with a cutoff frequency of 2 kHz may be applied instead of the band-pass filter 6. good.

  The mix circuit 7 mixes (synthesizes) the audio signal S1 related to bone conduction output from the equalizer circuit 5 and the audio signal S2 related to air conduction output from the band-pass filter 6, and transmits a speech signal output terminal. 8 is given. As described above and as shown in FIG. 6, the audio signal S1 related to bone conduction output from the equalizer circuit 5 has a band of approximately 300 Hz to 2 kHz, and the air conduction output from the bandpass filter 6 is Since the audio signal S2 generally has a band of 2 kHz to 3.4 kHz, the synthesized audio signal output from the mix circuit 7 has a band of 300 Hz to 3.4 kHz.

  The transmission signal output terminal 8 is an output terminal of a transmission signal in the handset 11, and the voice signal (synthesized voice signal) output from the transmission signal output terminal 8 is given to the telephone body. For example, in the case of a soft phone, the audio signal (synthesized audio signal) output from the transmission signal output terminal 8 is given to the personal computer.

  The mixing ratio variable switch 9 is a switch (or a switch for switching the mixing ratio between the audio signal S1 related to bone conduction output from the equalizer circuit 5 and the audio signal S2 related to air conduction output from the bandpass filter 6 (or The mix circuit 7 mixes (synthesizes) the two audio signals S1 and S2 at the mixing ratio instructed by the mixing ratio variable switch 9.

  FIG. 7 is an explanatory diagram of a mixing ratio that can be accommodated by the sound collection device 10 according to the embodiment. FIG. 7 shows a case where three types of mixing ratios R1 to R3 can be handled, and any one of the mixing ratios R1 to R3 is made effective by operating the mixing ratio variable switch 9. For example, the mixing ratio R1 is a mixing ratio when the audio signals S1 and S2 are mixed at 10:10, and the mixing ratio R2 is a mixing ratio when the audio signals S1 and S2 are mixed at 10: 9. R3 is a mixing ratio when the audio signals S1 and S2 are mixed at 10: 8. Since the audio signal S2 also includes ambient noise components, when the ambient noise is high, the user selects a mixing ratio in which the ratio of the audio signal S2 is relatively smaller than the ratio of the audio signal S1, and synthesizes it. What is necessary is just to make it relatively reduce the component of the ambient noise mixed in the audio signal.

  Although a specific circuit of the mix circuit 7 is not limited, for example, a two-input adder circuit configuration using an operational amplifier can be applied. In this case, when the audio signal S2 is input to the operational amplifier via the input resistance, the mixing ratio can be switched by the mixing ratio variable switch 9 by changing the input resistance by turning on and off the switch. .

(A-2) Operation | movement of embodiment Next, operation | movement of the sound collection device 10 of embodiment is demonstrated, referring drawing already mentioned.

  When the user of the sound collection device 10 according to the embodiment puts the handset 11 in a position for calling and pronounces it, sound vibration caused by the sound conducts through the skull and also conducts through the air as air vibration. The sound vibration conducted through the skull is captured by the bone conduction microphone 1 and converted into an electrical signal (sound signal), while the air sound vibration conducted through the air is captured by the air conduction microphone 2 and is an electrical signal. (Audio signal).

  The audio signal output from the bone conduction microphone 1 is amplified by the bone conduction microphone amplifier 3 and supplied to the equalizer circuit 5. The audio signal output from the bone conduction microphone amplifier 3 has a frequency component of 300 Hz to 2 kHz depending on the frequency characteristics of the bone conduction microphone 1, and the frequency characteristics are 1 kHz to 2 as shown in FIG. It has a downward-sloping characteristic on the high frequency side of 2 kHz. The audio signal output from the bone conduction microphone amplifier 3 is equalized by the equalizer circuit 5 so as to have a flat frequency characteristic in the range of 300 Hz to 2 kHz, as shown in FIG. S1 is applied to the mix circuit 7.

  The audio signal output from the air conduction microphone 2 is amplified by the air conduction microphone amplifier 4 and applied to the band pass filter 6. The audio signal output from the air conduction microphone amplifier 4 has a frequency component of 100 Hz to 8 kHz due to the frequency characteristics of the air conduction microphone 2, but passes through the band pass filter 6, so that the band 2 kHz to 3 Only 4 kHz is filtered and the filtered audio signal S2 is applied to the mix circuit 7.

  The audio signal S1 related to bone conduction output from the equalizer circuit 5 and the audio signal S2 related to air conduction output from the band-pass filter 6 are instructed via the mixing ratio variable switch 9 in the mixing circuit 7. The synthesized voice signal obtained by mixing (synthesizing) at the mixing ratio is applied to the transmission signal output terminal 8.

(A-3) Effects of the Embodiment According to the above embodiment, a simple and small sound collection device or telephone that can improve the sound quality of the collected sound signal (synthesized sound signal) can be realized. Hereinafter, this effect will be described in detail.

  In the synthesized speech signal to be output, the band of 300 Hz to 2 kHz includes only the information of the speech signal captured by the bone conduction microphone 1 (since it does not include the information of the speech signal captured by the air conduction microphone 2). The influence of ambient noise can be eliminated and the sound quality of the synthesized speech signal can be improved. Further, the frequency characteristics of the bone conduction microphone 1 are not flat, but the equalizer circuit 5 compensates for the non-flat frequency characteristics, so that in this respect as well, the sound quality of the synthesized speech signal can be improved, An easy-to-hear synthesized speech signal can be realized.

  Incidentally, when the sound collection device 10 of the embodiment is applied to an emergency telephone for a tunnel on a highway, since the peak frequency of the noise in the tunnel is 700 Hz to 1 kHz, the noise resistance characteristic of the bone conduction microphone 1 is the most. Effectively utilized.

  The frequency characteristic of the air-conduction microphone 2 is 100 Hz to 8 kHz, which is too wide for a telephone, and ambient noise is easily mixed. However, since the band is limited to 2 kHz to 3.4 kHz by the band pass filter 4, The influence can be suppressed to the minimum, and the sound quality of the synthesized speech signal can be improved.

  Even if the band is limited to 2 kHz to 3.4 kHz and the influence of the ambient noise is minimized, if the ambient noise is anxious, the influence of the ambient noise can be further suppressed by selecting the mixing ratio. And the sound quality of the synthesized speech signal can be improved.

  Since the circuit included in the sound collection device 10 of the embodiment is the bone conduction microphone amplifier 3, the air conduction microphone amplifier 4, the equalizer circuit 5, the band pass filter 6, the mix circuit 7, and the like, the sound collection device 10 is simplified. Can be small. That is, the apparatus can be made inexpensive and suitable for commercialization.

  Since the amplifiers 3 and 4, the equalizer circuit 5, the band pass filter 6, the mix circuit 7, and the like can be configured by analog operational amplifier technology, the sound collection device 10 can be realized in a small size with a simple and inexpensive circuit. When configured with analog operational amplifier technology, it can operate with low power consumption, and can also operate with a power supply for transmission signals of a normal telephone (a dedicated power supply is required when configured with an LSI or DSP). Therefore, commercialization is easy also in this aspect.

(B) Other Embodiments In the description of the above-described embodiment, the modified embodiment is referred to. However, the modified embodiment as exemplified below can be given.

  In the above-described embodiment, the case where the sound collection device is applied to a handset of a road telephone with heavy traffic noise has been described. The sound collecting device of the present invention can be applied to a telephone.

  The device to which the sound collecting device of the present invention is applicable is not limited to a telephone. The sound collection device of the present invention can be applied to a communication device (for example, a transceiver) having a sound capturing function.

  In the above-described embodiment, the entire sound collection device is incorporated in the handset. However, only a part of the sound collection device may be incorporated in the handset. For example, the bone conduction microphone 1, the air conduction microphone 2, the bone conduction microphone amplifier 3 and the air conduction microphone amplifier 4 are incorporated in the handset, and the equalizer circuit 5, the band pass filter 6, the mix circuit 7 and the mixing ratio variable switch 9 are telephone sets. You may make it incorporate in a main body side.

Moreover, you may make it apply the sound collection apparatus of this invention to the other attachment body which attached the microphone and the speaker instead of a handset. For example, the bone conduction microphone 1 or the bone conduction microphone amplifier 3 may be added to the headset, and the processing circuit may be provided in the telephone body. In the above embodiment, the mixture ratio can be changed stepwise. However, the mixing ratio may be continuously changed using a volume (variable resistance).

  In the above-described embodiment, the mixing circuit 7 realizes the function of changing the mixing ratio between the audio signal related to bone conduction and the audio signal related to air conduction. However, the audio signal related to bone conduction is achieved by another method. And the mixing ratio of the sound signal related to conduction in the air may be changed. For example, applying a mix circuit that does not have a variable mixing ratio function and applying an amplifier for an air conduction microphone that can change the gain according to a command from an external switch, etc., can be used for audio signals related to bone conduction and in-air conduction. The mixing ratio with the audio signal may be changed.

  In the above description, the examples in which the amplifiers 3 and 4, the equalizer circuit 5, the band pass filter 6, the mix circuit 7, and the like are configured by the analog operational amplifier technology are mentioned, but it is needless to say that they may be configured by other technologies. Further, an analog / digital conversion circuit may be inserted at any position, and a desired circuit may be configured by a digital circuit in subsequent processing stages. Furthermore, instead of the digital circuit, a desired circuit function may be realized by software processing.

  The various bands mentioned in the description of the above embodiment are examples, and the present invention is not limited to the above bands. For example, if the frequency component that can be captured by the bone conduction microphone 1 to be applied is 300 Hz to 2.2 kHz, the pass band of the band pass filter 6 may be selected to 2.2 kHz to 3.4 kHz. Further, for example, a frequency component lower than the band of the audio signal from the bone conduction microphone 1 may be mixed into the synthesized audio signal. For example, in addition to the band pass filter 6, a band pass filter that extracts a band of 100 Hz to 300 Hz of the audio signal from the air conduction microphone amplifier 4 is provided, and the output audio signal from the newly provided band pass filter is also mixed. You may do it.

  DESCRIPTION OF SYMBOLS 1 ... Bone conduction microphone, 2 ... Air conduction microphone, 3 ... Bone conduction microphone amplifier, 4 ... Air conduction microphone amplifier, 5 ... Equalizer circuit, 6 ... Band pass filter (BPF), 7 ... Mix circuit, 8 ... Sending Talk signal output terminal, 9 ... mixing ratio variable switch, 10 ... sound collecting device.

Claims (6)

In a sound collecting device that forms an audio signal output from an audio signal from a bone conduction microphone that converts bone conduction audio vibration into an electric signal and an audio signal from an air conduction microphone that converts air audio vibration into an electric signal,
Equalizer means for equalizing the non-flat frequency characteristic of the audio signal from the bone conduction microphone and converting it to an audio signal having a flat frequency characteristic;
Band limiting means for extracting a frequency component from the audio signal from the air conduction microphone so as to exclude the frequency component of the audio signal from the bone conduction microphone;
A sound collecting apparatus comprising: a mixing unit that mixes the audio signal output from the equalizer unit and the audio signal output from the band limiting unit.   2. The sound collection device according to claim 1, further comprising a mixing ratio switching unit that switches a mixing ratio between the audio signal output from the equalizer unit and the audio signal output from the band limiting unit.   The band limiting means comprises a band pass filter having an upper limit frequency component of an audio signal from the bone conduction microphone as a lower limit of the pass band and an upper limit of the telephone band as an upper limit of the pass band. The sound collection device according to 1 or 2.   4. The sound collecting apparatus according to claim 1, wherein each of the equalizer means, the band limiting means, and the mixing means is constituted by an analog signal processing circuit to which an operational amplifier is applied.   5. A telephone set, wherein the sound collecting device according to claim 1 is applied as a transmission signal forming unit.   6. The telephone according to claim 5, wherein the sound collecting device is incorporated in a handset.

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