Abstract:
A wireless communication headset for reducing wind-induced noise and providing improved microphone performance under a variety of different ambient noise conditions includes a housing defining a cavity and first and second apertures in communication with the cavity. A microphone disposed within the cavity has a transducer oriented along an axis, whereby the first and second apertures are located on opposite sides of the axis. A baffle surrounds the transducer and is oriented along the axial direction. Optionally, a shroud at a forward end of the baffle defines an air space ahead of the transducer. Further still, a liner such as a foam layer or swatch of fabric is disposed within the cavity, providing a diffuse acoustic path between the first and second apertures and the transducer so as to prevent wind flow from directly impinging upon the microphone.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to arrangements for housing microphones used in communication headsets and, more particularly, to a headset case and microphone arrangement configured for eliminating or reducing wind noise.  
       BACKGROUND OF THE INVENTION  
       [0002]     Hands-free headsets for use with cellular phones and traditional land-line phones are known. One major problem with traditional communication headsets is ambient noise associated with the environment that can be picked up by the headset&#39;s microphone and transmitted along with the user&#39;s voice. It has long been desired to provide improved microphone performance in devices such as communication headsets that operate under a variety of different ambient noise conditions. It is well-known that wind flow over a microphone will induce significant amounts of low frequency noise. Wind-induced noise is a particular problem for communication headsets, such as those used in connection with cellular phones, when used, for example, outdoors or near an open window in a vehicle.  
         [0003]     Although there are several devices in the prior art that attempt to eliminate or reduce wind-induced noise in microphone arrangements, they generally are not acceptable for applications such as communication headsets. As communication headsets become increasingly compact and the parts contained therein more miniaturized, there is less and less space available to accommodate prior art solutions.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention overcomes the disadvantages of the prior art by providing a wireless communication headset which reduces wind-induced noise and provides improved microphone performance under a variety of different ambient noise conditions. The communication headset includes a housing defining a cavity and first and second apertures in communication with the cavity. A microphone disposed within the cavity has a transducer oriented along an axis, whereby the first and second apertures are located on opposite sides of the axis. A baffle surrounds the transducer and is oriented along the axial direction. Further still, a liner disposed within the cavity provides a diffuse acoustic path between the first and second apertures and the transducer so as to prevent wind flow from directly impinging upon the microphone.  
         [0005]     In accordance with one aspect of the invention, the housing is free of any aperture which is oriented along the axial direction of the transducer and in communication with the cavity. That is to say, there is no opening in the case which directly faces the transducer of the microphone. Additionally, the apertures have an elongated length which is longer than the elongated baffle.  
         [0006]     In accordance with yet another aspect of the invention, the liner can comprise a foam layer that extends substantially between the first and second apertures and provides the diffuse acoustic path for substantially all air paths therebetween. The foam layer has an acoustic resistivity of at least 2 acoustic Ω/cm 2 . Furthermore, air paths between the first and second apertures flow in a direction that is perpendicular to the transducer. Alternatively, the liner can comprise one or more fabric swatches, or layers of swatches that overlie the first and second apertures to diffuse air flowing into the cavity.  
         [0007]     A communication headset in accordance with further aspects of the present invention includes the foregoing headset components as well as a communication circuit for processing acoustic signals coupled by the transducer.  
         [0008]     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, a preferred embodiment of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of a communication headset in accordance with a preferred embodiment of the present invention;  
         [0010]      FIG. 2  is an exploded view of a communication headset in accordance with the preferred embodiment of the present invention; and  
         [0011]      FIG. 3  is an exploded view of a partially assembled communication headset in accordance with the preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0012]     With reference to  FIG. 1 , a preferred embodiment of the communication headset  10  is illustrated. Communication headset  10  includes a housing  80  having a first portion  24   a  connected to an earphone  12  for providing audio signals to a user&#39;s ear and a second portion  24   b  connected to a microphone assembly disposed near the user&#39;s mouth. Referring to  FIGS. 1-3 , communication headset  10  includes microphone  16 , user operable switches  13 ,  150 , internal communications circuitry  18  and an optional mount  180 . Earphone  12  can rest within a user&#39;s ear or can be configured to rest proximate to the user&#39;s ear by way of an attachment as described in U.S. patent application Ser. No. 10/605,667, filed Oct. 16, 2003, entitled Wireless Communication Headset with Exchangeable Attachments, the entirety of which is hereby incorporated by reference. The power source (not shown) is preferably a rechargeable battery but can also be any of a variety of standard power sources.  
         [0013]     Communication headset  10  can be used with any land-line or cellular telephone and with a conventional cellular service provided by a cellular service provider. Headset  10  can also be used with a cellular telephone employing Bluetooth, Wifi, or other wireless technology and, in this case, headset  10  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  10 . Alternatively, the headset  10  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.  
         [0014]     Referring to  FIGS. 2 and 3 , microphone  16  includes a transducer and has a body disposed in a molded, plastic baffle  14  which is secured within the second portion  24   b  of the headset  10 . Baffle  14  can be arranged to include a shroud that is aligned with an axis of the transducer and leads to a forward port  52 . The shroud of baffle  14  provides optimum microphone sensitivity by defining an air space ahead of the microphone  16  transducer and funneling sound waves through port  52  to the microphone  16  while shielding the microphone&#39;s transducer from the direct flow of sound waves through the housing. This has the effect of essentially increasing the effective length of the microphone  16  and allowing sound waves to be picked up by the microphone more efficiently. Accordingly, the larger the length Z, the greater the sensitivity of microphone  16 . According to a preferred embodiment, length Z is adjusted to achieve optimum microphone sensitivity. Electrical lines  17  are supplied to the microphone by port  50  to transfer power and audio signals to a communication circuit  18 . The forward port  52  collects sound waves (i.e., voice signals) from the user to deliver them to microphone  16 . A coaxial cable, such as twisted pair or shielded conductors, electrically connects microphone  16  and a speaker  13  of earphone  12  to communication circuitry  18 . Communication circuitry  18  provides electronic control functions of communication headset  10  such as processing acoustic signals coupled by the transducer and physically connects and supports the microphone  16  and the speaker  13 .  
         [0015]     To provide the headset  10  assembly with an improved acoustic response, a liner disposed on an inside surface of the headset housing within a cavity is provided. The liner can comprise an acoustic foam layer  20  that encases the shroud of the baffle, and preferably the entire microphone  16 . The liner can alternatively comprise a fabric such as a cloth or an expanded PTFE material (e.g., GOR-TEX brand fabric swatch), and preferably overlies aperture pairs  41  in the housing to thereby diffuse air that flows into the cavity and prevent wind flow from directly impinging upon the microphone, but can be otherwise disposed within the cavity so as to prevent wind flow from directly impinging upon the transducer of the microphone, such as around the transducer and upon the shroud so that a “dead” space of air is available forward of the transducer element. In either arrangement, the impact of wind is buffered more effectively than in conventional case arrangements in which the microphone&#39;s transducer is oriented in a direct line of sight with an aperture that couples sound waves from the exterior of the case to an interior region.  
         [0016]     Referring to  FIG. 2 , the headset assembly of  FIG. 1  is shown to include an upper and lower housing  24  and  26 , respectively, provided from molded plastic. Housings  24  and  26  define a space for housing the components of headset  10 , such as, baffle  14 , communication circuitry  18 , foam layer  20  and speaker  13 , and provide second portion  24   b  with aperture pairs  41  for allowing audible signals to enter headset  10  therethrough. While aperture pairs  41  are shown only appearing on upper housing  24 , the apertures can be on either upper or lower housings, or both. According to a salient aspect of the present invention, apertures  41  are located on opposing sides of the microphone&#39;s axis (C-axis), e.g., at longitudinal ends of the second portion  24   b  of headset  10 , and can be generally parallel to one another so as to create a substantially parallel airflow through second portion  24   b , or can comprise circular openings or non-parallel slots. What is important is that at least one aperture of a pair is displaced on either side of axis C that includes the microphone&#39;s transducer.  
         [0017]     As illustrated in  FIG. 3 , the center axis C of microphone  16  is oriented at an angle of about 90° with respect to the axis L in which sound waves are received by the apertures  41 .  
         [0018]     As illustrated, the liner comprises an acoustic foam layer  20  ( 20   a  and  20   b ), here provided from polyester urethane, a hydrophobic material or any other similar material selected to improve the acoustic properties of the microphone  16  and to match the acoustic properties of baffle  14  to the microphone  16  is disposed in the space created by the housings  24 ,  26 . Referring to  FIG. 2 , the acoustic foam layer  20  is provided which can seat the baffle  14 , e.g., regions  27   a ,  27   b . The foam layer  20  can engage sidewall regions  24   c ,  26   c  in housings  24  and  26 , respectively, to seal foam layer  20  within headset  10 , thereby sealing microphone  16  and baffle  14  in cavity regions  27   a  and  27   b  and preventing its movement within. Foam layer  20  provides a diffuse acoustic path between the first and second apertures  41  and the shroud so as to prevent wind flow from directly impinging upon the microphone  16 . Preferably, the foam layer  20  provides a diffuse acoustic path for substantially all of the air paths between the aperture pairs  41 .  
         [0019]     In an alternative arrangement, a diffuse air flow path is achieved by disposing a fabric swatch over the aperture pairs  41 . A presently preferred fabric includes an expanded PTFE membrane, such as 100% expanded PTFE, and is available from W. L. Gore &amp; Associates, Inc. in a variety of different forms, but all of their fabrics rated for outerwear are suitable for use as the liner, including their line of WINDSTOPPER(R) fabric. The fabric is selected in thickness and material so as to permit acoustic waves to enter into the housing, yet provide a controlled air-space cavity in front of the microphone&#39;s transducer. The fabric liner need not engage or contact the baffle or the shroud, yet will still provide a diffuse acoustic path between the first and second apertures  41  and the shroud so as to prevent wind flow from directly impinging upon the microphone  16 . Preferably, the fabric liner, if used, provides a diffuse acoustic path for substantially all of the air paths between the aperture pairs  41 .  
         [0020]     According to a salient aspect of the present invention housing  80  is free of any aperture which is orientated along the axial direction (C) and in communication with the cavity. Additionally, air paths between the first and second apertures flow in a direction that is perpendicular to the transducer.  
         [0021]     Baffle  14 , as shown in  FIG. 2 , has a generally cylindrical shape, but of course could have other cross-sectional geometries, such as rectangular or circular, and the size, shape and location of forward port  52  may be altered so as to adjust the directionality of the microphone. The acoustic resistivity of acoustic foam layer  20 , if used as the liner, may be varied to also vary the directionality and polarity of microphone  16 . Specifically, the acoustic resistivity of foam layer  20  may be increased to at least about 1 acoustic Ω/cm 2  and preferably has an acoustic resistivity of at least about 2 acoustic Ω/cm 2 .  
         [0022]     Referring to  FIG. 3 , the liner in the form of the foam layer  20  acts as an acoustic wind diffuser between apertures  41  and the shroud of the baffle  14 . Air apertures  41  are similarly disposed on opposing sidewall regions  24   c ,  26   c , such that incoming sound waves in the vicinity of apertures  41  can be directed to microphone  16 . The foam layer should preferably be of sufficient porosity or be multiply perforate to allow sound pressure waves to transfer through the particular material, without degrading its frequencies, or bouncing around inside. Foam layer  20  should not decrease the sensitivity of microphone  16  by an appreciable amount and sound essentially passes through the foam layer  20  unobstructed however wind does not. Accordingly, a foam layer 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. A “dead” air cavity can be achieved using a fabric liner as previously described, instead of or in addition to the foam layer.  
         [0023]     The effect of the liner (e.g., the fabric or acoustic foam layer  20 ) and the baffle  14  in the communication headset  10  is to alter the polar patterns that can be plotted as compared to plots for a headset assembly without the foam  20  and baffle  14 . Specifically, a rear lobe that would be present when the liner and baffle are not provided is effectively eliminated by adding the liner and baffle.  
         [0024]     While it has been typical in conventional microphone assemblies to minimize the acoustic resistivity of acoustic foam layers in conventional wind screens by increasing the porosity of the foam layer, the microphone assembly of the present invention advantageously can utilize a foam layer with a higher acoustic resistivity by decreasing the porosity of foam layer and yet obtaining not only better wind-isolation properties, but also improved acoustic characteristics for the microphone assembly. The reduction of the rear lobe of the polar pattern of the microphone assembly is particularly advantageous when communication headset  10  is used outdoors in particular windy environments with substantially no direct air path along the axis of the microphone&#39;s transducer.  
         [0025]     While the invention has been described with reference to several embodiments thereof, the invention is more broadly defined and limited only by the recitations in the claims appended hereto and their legal equivalents.