WO2006007441A1

WO2006007441A1 - Wireless communication headset with microphone switching system

Info

Publication number: WO2006007441A1
Application number: PCT/US2005/021536
Authority: WO
Inventors: Abraham Glezerman
Original assignee: Cardo Systems Inc
Current assignee: Cardo Systems Inc
Priority date: 2004-06-16
Filing date: 2005-06-16
Publication date: 2006-01-19
Anticipated expiration: 2006-12-16

Abstract

An improvement in the use of a wind screened microphone for wireless communication headsets including a microphone switching system (240) for such headsets. The wireless communication headset has a housing including a communication circuit (200), a speaker, first (170A) and second (170W) microphones and a switch (240). The communication circuit includes a local signal output, a local signal input, and a wireless output to a local device. The speaker is connected to the local signal output and is operable to deliver audible signals received at the local device from the remote connection. The first and second microphones (17A, 170W) are configured to receive sound waves from the local party and generate local party signals. One of the first and second microphones (17A, 170W) includes a wind screen and a switch (240) operatively connected so as to convey the local party signals from one of the first and second microphones, through the communication circuit (200) and to the wireless output.

Description

Wireless Communication Headset with Microphone Switching System

Field of the Invention The present invention relates to improvements in the use of wind screened microphones for wireless communication headsets, and, more particularly, to a microphone switching system for such headsets.

Background of the Invention Hands-free headsets for use with cellular phones and traditional land-line phones are known. One major problem with traditional headsets is wind noise associated with the environment can be picked up by the headset's microphone and transmitted along with the user's voice. Several filtering, cancellation and microphone switching techniques for eliminating or reducing wind noise are known. One such device, described in U.S. Patent No. 5,058,171 (hereinafter "the '171 patent"), is directed to a microphone arrangement comprising two individual microphones wherein wind pressure is continuously measured during the sound recording by one of the microphones and depending on the measured wind pressure the microphone least sensitive to the noises caused by the wind can be selected and used for recording. Another device for use with hearing aids, described in U.S. Patent No. 6,327,370 (hereinafter "the '370 patent"), is directed to a manual or automatic switching function which can switch from a omnidirectional microphone to a directional microphone whenever the ambient noise level rises above a certain predetermined value. To effect switching, the '370 patent, like the '171 patent, evaluates the ambient noise measured in dB above a reference pressure level. Further improvements in the design of communication headsets are still needed and the present invention addresses that need.

Summary of the Invention The invention described herein provides an improvement over prior-art communication headsets. The present invention is a wireless communication headset permitting bidirectional communication between a local party and a remote connection. The headset has a housing including a communication circuit, a speaker, first and second microphones and a switch. The communication circuit includes a local signal output, a local signal input, and a wireless output to a local device. The speaker is connected to the local signal output and is operable to deliver audible signals received at the local device from the remote connection. The first and second microphones are configured to receive sound waves from the local party and generate local party signals. One of the first and second microphones includes a wind screen. The headset also includes a switch operatively connected so as to convey the local party signals from one of the first and second microphones, through the communication circuit and to the wireless output.

According to one aspect of the invention, the switch is part of the communication circuit, and the first and second microphones are both electrically connected to respective local communication signal inputs with the switch operative to convey at any given time the local party signals from one of the first and second microphones to the wireless output.

Optionally, in accordance with another aspect of the invention, the switch is manually actuatable and the communication headset is provided with a handle operative to move the switch from a first state to a second state, wherein one of the first and second microphones is communicatively connected to the wireless output of the headset when the switch is in the first state and the other of the first and second microphones is communicatively connected to the wireless output of the headset when the switch is in the second state.

In accordance with further aspects of the invention that can be included in one or more different embodiments, one of the first and second microphones is a directional microphone and the other of the first and second microphones is a omnidirectional microphone and the switch uses the output of a wind estimator circuit to effect automated switching of the microphones.

These and further aspects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments of the present invention.

Brief Description of the Drawings

FIG. 1 is a perspective view of a communication headset in accordance with the present invention;

FIG. 2 is a cutaway view of one embodiment of a communication headset of the invention having a switch for switching between microphones wherein the switch is external to a communication circuit;

FIG. 3 is a cutaway view of another embodiment of a communication headset of the invention having a switch for switching between microphones wherein the switch is internal to a communication circuit;

FIG. 4 is a schematic diagram of a communication circuit of the communication headset of the invention in relation to a local device;

FIG. 5 is a schematic circuit diagram of the communication headset including manual switching between microphones; FIG. 6 is a schematic diagram of a communication headset including automatic wind- noise-level dependent switching between microphones; and

FIG. 7 shows one possible relationship between detection signals supplied by a signal-pattern detector and an estimated wind-probability signal.

Detailed Description of Preferred Embodiments

With reference to FIG. 1, a preferred embodiment of the communication headset 110 is illustrated. The communication headset 110 has a housing 100, microphones 170A and

170W, a speaker 160, a socket for a power source 150 (shown covered by a lid), internal communications circuitry 200 (see FIG. 2) and an optional mount 180. Speaker 160 can rest within a user's ear or can be configured to rest proximate to the user's ear by way of an attachment as described in U.S. Patent Application Serial No. 10/605,667, filed October 16,

2003, entitled Wireless Communication Headset with Exchangeable Attachments, the entirety of which is hereby incorporated by reference. The power source is preferably a rechargeable battery but can also be any of a variety of standard power sources.

Communication headset 110 can be used with any land-line or cellular telephone and with a conventional cellular service provided by a cellular service provider. Headset 110 can also be used with a cellular telephone employing Bluetooth, Wifi, or other wireless technology and, in this case, headset 110 communicates directly with the wireless communication chip in the phone. Bluetooth wireless technology is presently the preferred protocol for wireless communication between the cellular phone and the headset 110. Alternatively, the headset 110 can be used with cellular phones that are not equipped with Bluetooth circuitry by interposing an adapter between the phone and the headset, as described in the aforementioned, co-pending application. Referring to FIG. 2, the communications circuitry 200 receives sound from a local user's spoken voice at one of microphones 170A and 170W and outputs sound from a remote conversant' s spoken voice through speaker 160 to enable a conversation between a local user of the headset 110 and the remote conversant at a remote connection over a cellular network. Microphones 170A and 170W generate local party signals (electrical signals) which correspond to the received audible signals of the local user. Communication circuit 200 includes a wireless transceiver 230 for providing wireless communication between headset 110 and a local device 260 (e.g., a cell phone). Wireless transceiver 230 transmits local party signals to the local device 260 and receives remote party signals from the local device 260 through a wireless port 250 that includes a wireless output to transmit remote party signals originated by the remote party to headset 110 and a wireless input to receive local party signals originated by the local user from headset 110. Communication circuit 200 also includes a local communication signal output 210 for transmitting received remote party signals from wireless transceiver 230 to speaker 160 and a local communication signal input 220 for transmitting received local party signals from microphones 170A and 170W to wireless transceiver 230. Accordingly, audible signals picked up by microphones 170A and 170W are sent as local party signals to signal input 220 of communication circuit 200 and wirelessly transmitted to local device 260 by wireless transceiver 230. A respective transceiver 250 in communication with local device 260 is provided to wirelessly transmit and receive local and remote party signals to and from transceiver 230 of communication circuit 200. Thus, remote party signals at local device 260 can be communicated wirelessly to communication circuit 200 for output by speaker 160. Communication circuit 200 can comprise a custom integrated circuit or can comprise multiple circuits that operate together, as described below. Referring to FIGS. 1-3, microphone 170W is shown including a windscreen to act as a physical wind barrier and is disposed about axis A-W along side a non-windscreened microphone 170A. With the air inlets of Microphones 170A and 170W similarly disposed relative to the A-W axis, incoming sound waves in the vicinity of this axis can be picked up equally well by either microphone. The windscreen should preferably be of sufficient porosity or of a multiply perforate molded housing to allow sound pressure waves to transfer through the particular material, without degrading its frequencies, or bouncing around inside. Accordingly, a windscreen possessing at least several of the following qualities is preferred: a smooth, soft and highly contoured surface, a sufficient porosity and depth to slow wind velocity to a crawl (no more than about one or two m.p.h.) so that the microphone is essentially surrounded with nonmoving "dead" air.

Referring to FIG. 4, communication circuit 200 further includes a processor 400 and memory 410. Processor 400 provides electronic control functions of the communications headset 110. Local communication takes place between communication headset 110 and local device 260 (e.g., cell phone) and can be accomplished wirelessly by employing Bluetooth or other wireless technology and, in the illustrated case, headset 110 communicates directly with the phone's circuitry. Communication between local device 260 and a remote user can be accomplished through a conventional cellular network and remote signals received by local device 260 are transmitted locally to headset 110 for output to speaker 160. Similarly, local signals generated by microphones 170A, 170W are transmitted locally to local device 260 for transmission to a remote party over a cellular network in the preferred embodiment.

Microphone selection, as accomplished by communication headset 110, allows optimization of the signal-to-noise ratio of the headset as a function of background and wind noise conditions. As will be set forth in more detail below, such selection can be done either manually or automatically.

FIG. 5 shows a circuit diagram of a preferred embodiment of the communication headset 110 of FIG. 2 where switch 240 is manually controlled by the user. Windscreened microphone 170W can be a directional microphone of at least the first order while microphone 170A can be a omnidirectional microphone. The output of directional microphone 170W is AC coupled to the input of an equalizer circuit 520 through capacitor 530. The equalizer circuit 520 at least partially equalizes the amplitude of the low frequency components of the electrical signal output from the directional microphone 170W with the amplitude of the mid and high frequency components of the electrical signal output. This equalization serves to compensate for the decreased sensitivity that a directional microphone provides at lower frequencies, and s provided if such a microphone is used. The equalizer circuit 520 provides the equalized signal output line 540. The equalized electrical signal output from the equalizer circuit 520 and the electrical signal output from the omnidirectional microphone 170A are supplied to opposite terminals of switch 240 that has its pole terminal connected to signal input 220 of communication circuit 200. The electrical signal output from omnidirectional microphone 170A is AC coupled through capacitor 550. If the microphone 170W is switched off at the circuit path, the equalizer circuit 520 can be simultaneously powered off. Referring again to FIGS. 2 and 5, a switch 240, operatively connected between microphones 170A, 170W and communication circuit 200, is provided to selectively convey the local party signals from one of microphones 170A and 170W to the communication circuit 200. Switch 240, while shown separately connected with communication circuit 200 via signal input 220, can alternatively be incorporated as part of communication circuit 200 (see FIG. 3), in which case microphones 170A and 170W are both electrically connected to respective local communication signal inputs 270 and 280 and the switch 240 is operative to convey the local party signals from one of microphones 170A and 170W to wireless transceiver 230 at any given time. Switch 240 includes at least two switching states. In a first switching state, local party signals from microphone 170A are passed by switch 240 to signal input 220 of communication circuit 200 to the exclusion of the local party signals from microphone 170W. In a second switching state, local party signals from microphone 170W are passed by switch 240 to signal input 220 of communication circuit 200 to the exclusion of the local party signals from microphone 170A. In the embodiment of FIG. 3, switching is accomplished directly by electronic circuitry included in the communication circuit 200 and thus the first and second switching states described above are accomplished by the communication circuit 200. A hybrid approach might have both microphones active to a certain degree with the switch effecting the proportion of the contribution of each microphone.

Housing 100 includes a user-operable control 120 providing a user of the headset 110 the ability to control the state of switch 240 and thus, manually effect switching between microphone 170A and 170W. Control 120 can be configured as a push-button, a handle pivotable between a first and second position, or any conventional switching means known in the art. According to a preferred arrangement control 120 is a push-button configured to control the state of switch 240. When control 120 is pressed switch 240 switches between first and second switching states, thereby permitting local party signals to flow from one or the other-of microphones 170A and 170W.

FIG. 6 shows a circuit diagram of an embodiment of the communication headset 110 including automatic wind-noise-level dependent switching between microphones 170W and 170A. A signal discrimination circuit 690 includes an input for receiving the local party signals from one of the first and second microphones and an output for supplying a probability indication signal Vp which is indicative of the probability that the local party signal is dominated by wind noise. The signal discrimination circuit 690 includes a signal pattern detector 600 configured to detect characteristic patterns in the local party signals picked up by the microphone 170A, for example wind-characteristic patterns having a probability of occurrence in speech signals. Signal pattern detector 600 detects at least first and second signal patterns, S-voice and S-wind, respectively, in the occurrence of a sample portion of the local party signal based on successive changes in frequency. The detection signals indicate that a detected pattern in the local party signal is likely to be indicative of the presence or absence of wind signals (wind-characteristic patterns). S-voice having a probability that the sample portion is predominately a speech signal and S-wind having a probability that the sample portion is predominately a wind signal. The signal pattern detector 600 supplies S-voice and S-wind signals to an estimator circuit 610. Utilizing these detection signals the estimator circuit 610 derives a probability indication signal Vp in dependence on one or more of the detection signals. The indication signal Vp is indicative of the probability that the local party signals picked up by microphone 170A is dominated by wind noise.

A suitable criterion for deriving the probability indication signal Vp can be, for example, a criterion providing a distinct relationship between the frequency in detected speech verses known wind characteristics. Thus, it is possible, for example, to determine, in successive time intervals, the difference between the number of detected speech-characteristic patterns and the number of detected wind-characteristic patterns. Different weighting factors may then be allocated to patterns of different types. It is to be noted that the reliability of the probability indication signal Vp increases as a larger number of different types of characteristic patterns are detected. However, in principle, it is adequate to detect characteristic patterns of one type. One approach to deriving the probability signal Vp is described with reference to FIG. 7. This figure shows a detection signal S-voice and a detection signal S-wind output by signal pattern detector 600 and an associated probability indication signal Vp as a function of the time t as calculated by estimator circuit 610. Each pulse in the detection signal S-voice indicates that a speech-characteristic pattern of a given type has been detected by the detector 600. Each pulse in the signal S-wind indicates that a wind-characteristic pattern of a given type has been detected by detector 600.

In deriving the probability signal Vp, the value of the probability signal Vp is incremented by a given first value in response to each pulse in the detection signal S-voice. In response to each pulse in the detection signal S-wind, the value of the probability signal Vp is decremented by a given second value. In the present example, the second value is equal to the first value. It will be evident that the first and the second value need not be equal to one another. In the present example, it has been assumed that the number of detectable speech-characteristic patterns that occurs per unit of time during reception of a speech signal, is larger than the number of detectable wind-characteristic patterns which occurs per unit of time during reception of a speech signal, hi order to compensate for this, the value of the probability signal Vp decreases gradually in the absence of pulses in the detection signals.

If a large number of speech-characteristic patterns and no (or hardly any) wind- characteristic patterns are detected, it may be assumed that the probability that the received signal is a speech signal free of wind noise is high, hi that case, the value of the probability signal Vp will be high. Conversely, if a large number of wind-characteristic patterns -and consequently fewer speech-characteristic patterns are detected, the probability that the received audio signal is a wind signal will be high. In that case, the value of the probability signal Vp will be low. Consequently, the signal Vp is indicative of the probability that the received audio signal contains wind noise. In the case that the reception of a speech signal for which a very large number of speech-characteristic patterns are detected is followed by the reception of a wind signal, it may take a substantial time for the probability signal Vp to drop. This can be precluded by limiting the maximum value of the probability signal Vp. For similar reasons it is also advantageous to limit the minimum value of the probability signal Vp.

The signal pattern detector 600 and the estimator circuit 610 may be incorporated on communication circuit 200 and constructed as hard-coded modules. It is also possible to construct the signal pattern detector and the estimator circuit by means of a so-called program-controlled circuit, for example, a microcomputer loaded with a suitable program. Referring to FIG. 6, The probability indication signal Vp is supplied to the positive input of comparator 640 for comparison to reference signal Vref that is supplied to the negative input of the comparator 640. The output of comparator 640 is a binary signal and is supplied as a control signal to FET switch 470. The output of the comparator is also supplied to the input of logic inverter 480, the output of which is supplied as a control signal to FET switch 490.

In operation, the signal Vref is set to a magnitude representative of a reference wind- noise probability level at which the communication headset 110 is to switch between non- windscreened microphone 170A and windscreened microphone 170W. For example, the signal Vref can be set to a level representative of a 70 percent probability that wind-noise is effecting the transmission. When the calculated probability indication signal Vp thus rises above the voltage level indicative of 70 percent, FET switch 470 will have a low series pass resistance level and will connect the equalized output signal at line 540 to the input of the communication circuit 200 while FET switch 490 will have a high series pass resistance and will effectively disconnect the electrical signal output of microphone 170A from the input of communication circuit 200. Thus, when the probability of detected wind-noise is high communication headset 110 will switch to windscreened microphone 170W. When the calculated probability indication signal Vp drops below the voltage level representing 70 percent, FET switch 490 will have a low series pass resistance level and will connect the electrical signal output of microphone 170W at line 270 to the input of the communication circuit 200 while FET switch 470 will have a high series pass resistance and will effectively disconnect the equalized signal output on line 540 from the input of the communication circuit 200. Thus, when the probability of detected wind noise is low communication headset 110 will switch to non- windscreened microphone 170A. To avoid excessive switching at probability levels near Vref, the comparator 640 may be designed to have a certain degree of hysteresis.

According to an additional aspect of the present invention, the reference signal Vref may be variable and may be set to a level that is optimized for a particular headset user. To this end, reference signal Vref may be supplied from a voltage divider having a trimmer pot as one of its resistive components (not shown). The trimmer pot may be adjusted to set the optimal Vref value.

Claims

I Claim:

1. A wireless communication headset permitting bidirectional communication between a local party and a remote connection, comprising: a housing, the housing including: a communication circuit having a local communication signal output, a local communication signal input, and a wireless output to a local device; a speaker which is connected to the local communication signal output so as to deliver audible signals received at the local device from the remote connection; first and second microphones each configured to receive sound waves from the local party and generate local party signals, one of the first and second microphones including a wind screen; and a switch operatively connected so as to convey the local party signals from one of the first and second microphones, through the communication circuit and to the wireless output.

2. The wireless communication headset of claim 1, wherein the switch selectively connects one of the first and second microphones to the local communication signal input.

3. The wireless communication headset of claim 1, wherein the switch is part of the communication circuit, and wherein the first and second microphones are both electrically connected to respective local communication signal inputs with the switch being operative to convey, at any given time, the local party signals from one of the first and second microphones to the wireless output.

4. The wireless communication headset of claim 1, wherein the switch is manually actuatable.

5. The wireless communication headset of claim 4, further comprising one of a handle and a button operative to move the switch from a first state to a second state, wherein one of the first and second microphones is communicatively connected to the wireless output of the headset when the switch is in the first state and the other of the first and second microphones is communicatively connected to the wireless output of the headset when the switch is in the second state.

6. The wireless communication headset of claim 1, wherein one of the first and second microphones is a directional microphone and the other of the first and second microphones is an omnidirectional microphone.

7. The wireless communication headset of claim 6, further comprising an equalization amplifier connected to receive the local party signal from the directional microphone and configured to at least partially equalize the amplitude of the signal.

8. The wireless communication headset of claim 1, further comprising: a signal discrimination circuit having an input for receiving the local party signals from one of the first and second microphones and an output for supplying a probability indication signal which is indicative of the probability that the local party signal is dominated by wind noise; a comparison means for detecting whether the probability indication signal is above or below a predetermined threshold; and the switch configured to switch between one of the first and second microphones dependent upon the output of the comparison means.

9. The wireless communication headset of claim 8, wherein the signal discrimination circuit comprises: a signal pattern detector for detecting first and second signal patterns in the occurrence of a sample portion of the local party signal based on successive changes in frequency, said first signal pattern having a probability that the sample portion is predominately a speech signal and said second signal pattern having a probability that the sample portion is predominately a wind signal; and an estimation means for deriving the probability indication signal dependent upon the detection of the first and second signal patterns.

10. The wireless communication headset of claim 9, wherein the estimation means increases the value of the probability indication signal for a given period of time for each first signal pattern detected by the signal pattern detector and decreases the value of the probability indication signal for a given period of time for each second signal pattern detected by the signal pattern detector.