Bone conduction microphone speaker device

Abstract

To provide a bone conduction microphone speaker device that can suppress the occurrence of howling without causing switching noise.SOLUTION: In a bone conduction microphone speaker device 10 including a bone conduction microphone speaker element 11, a speaker signal input terminal SPIN, and a microphone signal output terminal MIC, a signal separation circuit SSC includes a first A / D conversion circuit 12A and a first D / A conversion circuit 13A connected in series between a terminal BC of the bone conduction microphone speaker element 11 and the microphone signal output terminal MIC, a second A / D conversion circuit 12B and a second D / A conversion circuit 13B connected in series between the speaker signal input terminal SPIN and the terminal BC of the bone conduction microphone speaker element 11, and a controller 14 that alternately operates the first A / D conversion circuit 12A and the first D / A conversion circuit 13A and the second A / D conversion circuit 12B and the second D / A conversion circuit 13B.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bone conduction microphone speaker device, and particularly to a technique effective for suppressing howling in a communication system using a bone conduction microphone speaker device.

Background Art

[0002] A bone conduction microphone has a function of extracting the sound of a person's voice transmitted through the bone and outputting it as an audio signal. Therefore, it is suitable for transmitting only the audio of a person's voice without picking up external noise. Also, a bone conduction speaker has a function of transmitting a received signal as vibrations to a person's bone (bone conduction sound), which is transmitted to the cochlea of the ear and recognized as sound, and has the advantage that the surrounding sound can be heard because the ear is not blocked.

[0003] On the other hand, in construction work, etc., workers may talk to each other using a radio (transceiver). However, during work, both hands may be occupied with work, so in that case, it is not possible to switch the transmission and reception of the radio using the hands. Therefore, for conversations between workers during work, a radio equipped with a headset having a microphone and a speaker is used. However, in an environment where the noise is extremely large, such as in tunnel construction, there is a problem that a headset equipped with a general microphone and speaker cannot be used for conversations.

[0004] Therefore, in the above situation, a device (unit) that integrates the functions of a bone conduction speaker and a bone conduction microphone is effective. As an invention related to a communication system using a bone conduction speaker and microphone, for example, there is an invention described in Patent Document 1. However, since a person's bone has good sound conductivity, when multiple people make a call at the same time, the voice of the other party emitted from the bone conduction speaker is transmitted to the bone conduction microphone and returns to the other party, overlapping the voice of the other party speaking and being input to the microphone, causing howling.

[0005] Also, as a technology for preventing howling, in a system using a speaker microphone unit for meetings, an invention in which a controller switches between a microphone and a speaker used according to acoustic conditions is described in Patent Document 2. However, this invention does not relate to a bone conduction microphone speaker and does not use an A / D conversion circuit or a D / A conversion circuit.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] Since the bone conduction microphone speaker is physically one device, in order to prevent howling, it is necessary to prevent the output signal from the voice output terminal of the wireless device from leaking into the microphone input terminal. Therefore, the inventor conceived and studied the technology as described below. As shown in FIG. 3, the technology under consideration is to provide a switch SW1 and an amplifier AMP in series between the bone conduction microphone speaker 11 and the microphone input terminal MC of the wireless device 20, and to provide a switch SW2 between the bone conduction microphone speaker 11 and the speaker voice output terminal SP of the wireless device 20. Then, according to the timing shown in FIG. 4, the switches SW1 and SW2 are alternately turned on to switch between transmission and reception in a time-division manner.

[0008] As a result, in the technology of switching between transmission and reception in a time-division manner using switch elements, although it is possible to prevent the voice signal from leaking from the speaker voice output terminal SP to the microphone voice input terminal MC, it was found that there is an adverse effect due to the switching noise generated when the switches SW1 and SW2 are turned on and off.

[0009] Before describing the present invention, a system examined by the present inventor and shown in FIG. 3 will be described first. It is generally known that in systems equipped with switching elements, switching noise occurs when the switching element is turned on and off. Therefore, when switching elements are used in a voice communication system, the switching noise is carried over to the voice signal and can be heard as noise. On the other hand, the frequency band of the voice signal transmitted through the radio can be a maximum of 3 kHz. Therefore, the inventors decided to set the switching frequency of the switches SW1 and SW2 to more than double that, initially setting it at 20 kHz.

[0010] As a result, it was confirmed that setting the above conditions makes it possible to prevent the audio signal from being transmitted from the speaker audio output terminal to the microphone audio input terminal, but it was found that there was a problem in that it was not possible to sufficiently suppress howling. Therefore, the inventor speculated that, since the period of 20 kHz is 50 μS, and the impedance from the radio's speaker audio output terminal SP to the microphone input terminal MC is 4.7 Ω and 1.52 mH, when the signal transmitted from the speaker audio output terminal SP to the bone conduction microphone speaker's input / output terminal (BC) is cut, reverberation occurs as a reaction caused by the inductor inside the microphone speaker, and measured the reverberation by applying a 1 kHz square wave to BC. The results are shown in Figure 5.

[0011] From Figure 5, we can see that reverberation remains for about 160μS from the turning point of the square wave. Therefore, we adjusted the timing and added a pause when switching between switches SW1 and SW2, and created a switch signal so that SW1 and SW2 turn on and off at the timing shown in Figure 6. After trial and error, we decided to set the on period MC→BC of switch SW1 to 125μS and the on period SP→BC of SW2 to 100μS, insert a 45μS pause when switching from SW1 to SW2, and insert a 160μS pause when switching from SW2 to SW1. The reason we inserted a 45μS pause when switching from SW1 to SW2 is to eliminate noise when switching the switches.

[0012] With the above settings, it has been found that howling is suppressed and the voice during a simultaneous call is improved. However, in the above settings, the switching frequency is given by the following formula 1 / (125 + 45 + 100 + 160) x 106 = 2.3 KHz and it has been found that this value is not preferable because it enters the audible range. Therefore, the inventor of the present invention has adopted a new method that is not a time-division method using a switching element, and as a result of intensive studies, has arrived at the idea of the present invention.

[0013] The present invention has been made under the above background, and an object thereof is to provide a bone conduction microphone speaker device that can suppress the occurrence of howling without generating switching noise when a system capable of simultaneous calling is configured via a wireless device using a bone conduction microphone speaker.

Means for Solving the Problems

[0014] In order to solve the above problems, the invention according to the present application a bone conduction microphone speaker element, a speaker signal input terminal to which a signal supplied to operate the bone conduction microphone speaker element as a speaker is input, a microphone signal output terminal for outputting a signal generated by the bone conduction microphone speaker element functioning as a microphone, and a bone conduction microphone speaker device comprising: a first A / D conversion circuit and a first D / A conversion circuit connected in series between the terminal of the bone conduction microphone speaker element and the microphone signal output terminal; a second A / D conversion circuit and a second D / A conversion circuit connected in series between the speaker signal input terminal and the terminal of the bone conduction microphone speaker element; A controller that controls the operations of the first A / D conversion circuit, the first D / A conversion circuit, the second A / D conversion circuit, and the second D / A conversion circuit, The controller is configured to alternately operate the first A / D conversion circuit and the first D / A conversion circuit, and the second A / D conversion circuit and the second D / A conversion circuit.

[0015] According to the above configuration, since the circuit of the output system of the microphone audio signal having the first A / D conversion circuit and the first D / A conversion circuit and the circuit of the input system of the speaker audio signal having the second A / D conversion circuit and the second D / A conversion circuit operate in a time-division manner, the signal from the speaker audio input terminal does not leak into the circuit on the microphone audio output side. Therefore, when a system capable of simultaneous communication is configured via a wireless device using the bone conduction microphone speaker device of the present invention, howling can be suppressed. In addition, since an A / D conversion circuit or a D / A conversion circuit is used instead of a switch element for switching transmission and reception, switching noise is not generated.

[0016] Here, preferably, a predetermined interval period is provided from the stop of the operation of the second A / D conversion circuit and the second D / A conversion circuit to the start of the operation of the first A / D conversion circuit and the first D / A conversion circuit. The controller is configured to control the second D / A conversion circuit so as to drop the output of the second D / A conversion circuit to the ground potential during the interval period. Alternatively, during the interval period, the controller is configured to send a signal or data obtained by inverting the phase of the immediately preceding signal in the first A / D conversion circuit to the second D / A conversion circuit. According to the above configuration, reverberation generated immediately after the stop of the operation of the A / D conversion circuit and the D / A conversion circuit of the input system of the speaker audio signal can be quickly suppressed.

[0017] Also, preferably, a latch means for latching the output of the first A / D conversion circuit or a sample hold circuit capable of holding the input signal of the first A / D conversion circuit is provided. The controller Causes the latch means or the sample hold circuit to hold the output data or the input signal immediately before stopping the operation of the first A / D conversion circuit. During the period when the operation of the first A / D conversion circuit is stopped and the second A / D conversion circuit and the second D / A conversion circuit are operating, the data or signal held by the latch means or the sample hold circuit is used to continuously transmit the voice frequency signal at the time of stopping the operation of the first A / D conversion circuit to the first D / A conversion circuit. According to such a configuration, it is possible to reduce the discomfort (abnormal sound) during the operation of the bone conduction microphone speaker element as a speaker.

[0018] Furthermore, preferably, the bone conduction microphone speaker element, the first A / D conversion circuit, the first D / A conversion circuit, the second A / D conversion circuit, the second D / A conversion circuit, and the controller are constituted by one or more LSIs or ICs, and are housed in one package. A connector to which the speaker signal input terminal, the microphone signal output terminal, and the ground terminal are connected is provided on the side surface of the package. According to such a configuration, the bone conduction microphone speaker device and the radio can be connected by a single cord. By wearing the bone conduction microphone speaker device from the vicinity of the head, particularly from near the temples to near the cheekbones, it is possible to make a call with the radio even when both hands are occupied, and it is possible to effectively reduce the howling generated during the call.

Effect of the Invention

[0019] According to the bone conduction microphone speaker device of the present invention, when a system that enables simultaneous calls via a wireless device is configured, there is an effect that howling can be suppressed without generating switching noise.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit configuration diagram of an embodiment of the bone conduction microphone speaker device according to the present invention. As shown in FIG. 1, the bone conduction microphone speaker device 10 of the present embodiment includes a bone conduction microphone speaker element (hereinafter referred to as a bone conduction microphone) 11, a microphone audio output terminal MIC connected to the microphone input terminal MC of the radio 20 via a signal transmission line L1, an audio signal input terminal SPIN connected to the speaker audio output terminal SP of the radio 20 via a signal transmission line L2, and a ground terminal GND to which a reference fixed potential such as a ground potential is applied.

[0022] Between the terminal of the bone conduction microphone speaker 11 and the microphone audio output terminal MIC, an A / D conversion circuit 12A that converts the audio analog signal from the bone conduction microphone speaker 11 into a digital signal and a D / A conversion circuit 13A that converts the converted digital signal back into the original analog signal are connected in series. Also, between the audio signal input terminal SPIN and the terminal of the bone conduction microphone speaker 11, an A / D conversion circuit 12B that converts the audio analog signal from the radio 20 into a digital signal and a D / A conversion circuit 13B that converts the converted digital signal back into the original analog signal are connected in series.

[0023] The microphone audio output terminal MIC, the audio signal input terminal SPIN, and the ground terminal GND are connected to connector terminals (not shown), and are connected to the radio 20 by a cord via the connector terminals. Also, although not shown, a power supply for operating the internal circuit is supplied from the radio 20 to the bone conduction microphone speaker device 10. Also, although not shown, an amplifier for amplifying the microphone audio signal may be provided in the subsequent stage of the A / D conversion circuit 12B or in the microphone audio input section of the radio 20.

[0024] Furthermore, the bone conduction microphone speaker device 10 is provided with a controller 14 that controls the operation timings of the A / D conversion circuits 12A and 12B and the D / A conversion circuits 13A and 13B. The controller 14 can be constituted by a microcontroller LSI having a CPU, a memory, and an I / O port. In this specification, the circuit constituted by the A / D conversion circuits 12A and 12B, the D / A conversion circuits 13A and 13B, and the controller 14 is referred to as a signal separation circuit SSC. Then, the bone conduction microphone speaker 11 and the IC (semiconductor integrated circuit) and LSI (large-scale semiconductor integrated circuit) constituting the signal separation circuit SSC are housed in one package to constitute the bone conduction microphone speaker device 10.

[0025] Also, there is an LSI called a PIC (Peripheral Interface Controller) built into the microcontroller LSI, which has a plurality of A / D conversion circuits and D / A conversion circuits and allows the user to freely configure the internal logic. Therefore, such an LSI may be used. In that case, the bone conduction microphone speaker device 10 in FIG. 1 can be constituted by two devices, namely, the bone conduction microphone speaker 11 and the controller LSI.

[0026] FIG. 2 shows an example of the control timings of the A / D conversion circuits 12A and 12B and the D / A conversion circuits 13A and 13B by the controller 14. In FIG. 2, (A) shows the operation timings of the A / D conversion circuit 12A and the D / A conversion circuit 13A on the path from the bone conduction microphone speaker (BC) to the microphone audio output terminal MIC, and (B) shows the operation timings of the A / D conversion circuit 12B and the D / A conversion circuit 13B on the path from the audio signal input terminal SPIN to the bone conduction microphone speaker (BC). Note that in FIG. 2, the period of the low level of each waveform is the period during which the circuit is activated.

[0027] As shown in Fig. 2(A), in the bone conduction microphone speaker device 10 of the present embodiment, the A / D conversion circuit 12A and the D / A conversion circuit 13A on the path from the bone conduction microphone (BC) to the microphone audio output terminal MIC operate in the odd-numbered periods T1, T3, T5,.... On the other hand, the A / D conversion circuit 12B and the D / A conversion circuit 13B on the path from the audio signal input terminal SPIN to the bone conduction microphone (BC) operate in the even-numbered periods T2, T4,.... The controller 14 generates a control signal and supplies it to each circuit so that the A / D conversion circuits 12A, 12B and the D / A conversion circuits 13A, 13B operate at the above timings.

[0028] However, as shown in Fig. 2(B), the operation periods of the A / D conversion circuit 12B and the D / A conversion circuit 13B are not the entire periods T2, T4,...., but are shorter periods T2', T4',... from the timings t2, t4,... when the operations of the A / D conversion circuit 12A and the D / A conversion circuit 13A stop. Also, immediately after the end timings t2', t4,... of the periods T2', T4,... there are provided interval periods Ti1, Ti2,... during which the operations of the circuits on both the input side and the output side paths stop simultaneously. The preferred time for the above periods T1, T3, T5,... is 80 μS or less, the preferred time for the periods T2', T4,... is 30 μS or less, and the preferred time for the interval periods Ti1, Ti2,... is about 10 μS.

[0029] As described above, in the bone conduction microphone speaker device 10 of the present embodiment, the output system of the microphone audio and the input system of the speaker audio are separated, and the A / D and D / A conversion circuits of the output system and the A / D and D / A conversion circuits of the input system are operated in a time-division manner. Therefore, the crosstalk of signals from the input system to the output system is prevented, and howling can be suppressed. Also, since the bone conduction microphone speaker device 10 of the present embodiment does not use a switch element as shown in Fig. 3, generation of noise due to on / off control signals of frequencies in the audible range can also be prevented.

[0030] Furthermore, since the A / D conversion circuit 12A and the D / A conversion circuit 13A are provided, by appropriately setting the reference voltage of the comparator constituting the D / A conversion circuit 13A, the output dynamic range of the D / A conversion circuit can be expanded to amplify the signal. Therefore, it is also possible to omit the aforementioned amplifier for amplifying the microphone audio signal. Note that there are also circuits of a type that incorporate switch elements in the A / D conversion circuit and the D / A conversion circuit. However, generally, the A / D conversion circuit and the D / A conversion circuit are turned on and off at frequencies much higher than the audible range, so there is no influence on the call due to switching noise.

[0031] Furthermore, in the case of the time-division method using a switch element, as described above, there is reverberation (160 μS shown in FIG. 3) when the signal transmitted from the speaker audio output terminal SP of the wireless device to the bone conduction microphone speaker (BC) is cut. In the bone conduction microphone speaker device 10 of the present embodiment, a signal is sent from the controller 14 to the D / A conversion circuit 13B so that the output of the D / A conversion circuit 13B is dropped to the ground potential immediately after the operation of the D / A conversion circuit 13B is stopped. Thereby, unnecessary signals can be absorbed and reverberation can be suppressed.

[0032] Alternatively, immediately after the operation of the D / A conversion circuit 13B is stopped, a signal (or data) obtained by inverting the phase of the previous signal is sent from the A / D conversion circuit 12A on the microphone audio output path to the D / A conversion circuit 13B on the audio input path, and the D / A conversion circuit 13B is made to function as a damper for a short time, so that the signal can be canceled and the reverberation can be made as close to zero as possible.

[0033] Here, as a specific means of sending a signal with reversed phase from the A / D conversion circuit 12A, for example, a memory using the FILO (Fast In Last Out) method is used, and data is read out from the most recently stored data in the reverse order of the storage order and sent to the D / A conversion circuit 13B. When sending data with the immediately previous signal phase-reversed from the A / D conversion circuit 12A to the D / A conversion circuit 13B, in the output system, it is advisable to operate only the A / D conversion circuit 12A with the operation of the D / A conversion circuit 13A stopped for a time corresponding to the above short time.

[0034] Furthermore, in the bone conduction microphone speaker device 10 of the present embodiment, when shifting from the microphone voice output to the speaker drive by stopping the operation of the A / D conversion circuit 12A in the output system, the last output of the A / D conversion circuit 12A is latched, and the last voice frequency signal of the A / D conversion circuit 12A is continuously transmitted to the D / A conversion circuit 13A. Thereby, it is possible to reduce the discomfort (abnormal sound) during the operation of the circuit in the voice input system and driving the speaker. Instead of latching the last output of the A / D conversion circuit 12A, the microphone voice signal immediately before the operation stop of the A / D conversion circuit 12A may be held in a sample and hold circuit provided at the entrance of the A / D conversion circuit 12A, and the voice frequency signal immediately before the stop may be continuously transmitted to the D / A conversion circuit 13A during the speaker drive.

[0035] FIG. 7 shows a configuration example of a communication system to which the bone conduction microphone speaker device according to the present invention is applied. In the communication system of FIG. 7, a bone conduction microphone speaker 11 and a signal separation circuit SSC having a configuration as shown in FIG. 1 are housed in one package and configured as a microphone speaker device 10.

[0036] In addition, on the side surface of the package 15 of the above-described microphone speaker device 10, a connector terminal 16 to which a microphone audio output terminal MIC, a speaker audio input terminal SPIN, and a ground terminal GND are connected is provided. Then, the microphone speaker device 10 and a wireless device (transceiver) 20 are connected so as to be capable of signal transmission by a cord 30 having one end connected to the connector terminal 16.

[0037] Note that the microphone speaker device 10 constituting the communication system shown in FIG. 7 may be mounted, for example, when an operator wears a dust mask, so as to be sandwiched between the dust mask and the side portion of the operator's face. Further, when an operator or a driver of a motorcycle wears a helmet and makes a call, it may be mounted so as to be sandwiched between the helmet or a tightening belt and the side portion of the face of the operator or the driver. By doing so, even when both hands are occupied, a call can be made by the wireless device, and by using the bone conduction microphone speaker device of the above-described embodiment, howling generated during the call can be effectively reduced.

[0038] Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments. For example, in the bone conduction microphone speaker device 10 of the above-described embodiment, the operation timings of the A / D conversion circuits 12A and 12B and the D / A conversion circuits 13A and 13B may be appropriately changed according to the specifications and characteristics of the bone conduction microphone speaker 11 to be used.

Explanation of Reference Numerals

[0039] 10 Bone conduction microphone speaker device 11 Bone conduction microphone speaker 12A, 12B A / D conversion circuit 13A, 13B D / A conversion circuit 14 Controller 15 Package 16 Connector terminal 20 Wireless device 30 Cord SSC Signal separation circuit

Claims

1. A bone conduction microphone speaker element, a speaker signal input terminal to which a signal supplied to operate the bone conduction microphone speaker element as a speaker is input, a bone conduction microphone speaker device comprising a microphone signal output terminal for outputting a signal generated when the bone conduction microphone speaker element functions as a microphone, a first A / D conversion circuit and a first D / A conversion circuit connected in series between a terminal of the bone conduction microphone speaker element and the microphone signal output terminal, a second A / D conversion circuit and a second D / A conversion circuit connected in series between the speaker signal input terminal and the terminal of the bone conduction microphone speaker element, a controller for controlling operations of the first A / D conversion circuit and the first D / A conversion circuit and the second A / D conversion circuit and the second D / A conversion circuit, wherein the controller alternately operates the first A / D conversion circuit and the first D / A conversion circuit and the second A / D conversion circuit and the second D / A conversion circuit. The bone conduction microphone speaker device is characterized by this.

2. A predetermined interval period is provided from the stop of operation of the second A / D conversion circuit and the second D / A conversion circuit to the start of operation of the first A / D conversion circuit and the first D / A conversion circuit, wherein the controller controls the second D / A conversion circuit so as to drop the output of the second D / A conversion circuit to a ground potential during the interval period. The bone conduction microphone speaker device according to claim 1 is characterized by this.

3. A predetermined interval period is provided from the stop of operation of the second A / D conversion circuit and the second D / A conversion circuit to the start of operation of the first A / D conversion circuit and the first D / A conversion circuit, wherein during the interval period, it is configured to send a signal or data obtained by inverting the phase of the immediately preceding signal in the first A / D conversion circuit to the second D / A conversion circuit. The bone conduction microphone speaker device according to claim 1 is characterized by this.

4. It comprises latch means for latching the output of the first A / D conversion circuit or a sample and hold circuit capable of holding an input signal of the first A / D conversion circuit, The controller, The output data or input signal immediately before stopping the operation of the first A / D conversion circuit is held by the latch means or the sample and hold circuit. During the period when the operation of the first A / D conversion circuit is stopped and the second A / D conversion circuit and the second D / A conversion circuit are operating, the data or signal held by the latch means or the sample and hold circuit is used to continuously transmit a voice frequency signal at the time of stopping the operation of the first A / D conversion circuit to the first D / A conversion circuit. The bone conduction microphone speaker device according to claim 2 or 3, characterized in that it is configured as such.

5. The bone conduction microphone speaker element, the first A / D conversion circuit, the first D / A conversion circuit, the second A / D conversion circuit, the second D / A conversion circuit, and one or more LSIs or ICs constituting the controller are housed in one package. The bone conduction microphone speaker device according to claim 4, characterized in that a connector to which the speaker signal input terminal, the microphone signal output terminal, and the ground terminal are connected is provided on a side surface of the package.

Images