Abstract:
A microphone shield system is disclosed. The microphone shield system includes an impervious elastic membrane stretched over and covering a microphone on substantially all sides. The impervious elastic membrane is adapted to pass a selected acoustical frequency range. The selected acoustical frequency range excludes a frequency range of noise from environmental effects, such as wind and rain.

Description:
TECHNICAL FIELD 
     This invention relates to microphone shields, and more particularly to shielding a microphone from environmental effects. 
     BACKGROUND 
     High-quality reproduction of sound using available sound recording techniques and equipment is desirable in variety of applications. For example, high-quality, low-noise sound reproductions are important in television and movie industry, radio communication, and wireless telephone devices. Clean voice and dialog reproduction may be desired in the presence of ambient and background noise levels of moderate to high amplitude. 
     One frequently encountered source of undesirable background noise is caused by air or liquid moving relative to a sound-transducing device, such as a microphone. This type of noise may occur due to environmental conditions. For example, wind may cause distortion of the microphone-sensing membrane. Rain may also cause impact noise as drops of rain land on the microphone. Further, the combination of wind and rain may degrade the structure of the microphone with heat and moisture. 
     There are several prior art designs that have used open cell foam or cloth, known as a “wind sock” in the recording industry, to reduce the effect of wind noise on microphones. For example, in some embodiments, Drever (U.S. Pat. No. 4,600,077) and McCormick (U.S. Pat. No. 5,808,243). use “wind sock” designs that provide alternate layers of foam  102  and air spaces  104  to improve the microphone  100  performance (see FIG.  1 ). However, these techniques are often ineffective in wind conditions above approximately 10 kph. 
     Electronic filtering techniques have also been used to filter out wind noise. However, electronic filtering also attenuates desired audio frequencies, thereby substantially degrading sound quality. 
     SUMMARY 
     In recognition of the above-described problems with the prior designs, the inventors have developed a system that enables relatively low-noise microphone sensing in wind speeds of up to 80 kph, and in some cases, even beyond 80 kph. The inventors recognized that high wind conditions, above a wind speed threshold of about 10 kph, cause pressure imbalances between the front and rear sides of the microphone-sensing element. 
     The present invention includes a microphone shield system including an impervious elastic membrane stretched over and covering a microphone on at least one side. The impervious elastic membrane is adapted to pass a selected acoustical frequency range. The selected acoustical frequency range excludes a frequency range of noise from environmental effects, such as wind and rain. 
     The system also includes an opening to allow a plurality of wires to pass through the impervious-elastic membrane. The plurality of wires provides connections to the microphone. 
     The present invention also includes a method for shielding a microphone from noise created by environmental effects, such as wind and rain. The method includes stretching an impervious elastic membrane over the microphone to form an enclosure, and passing a plurality of wires through the impervious elastic membrane to provide connections to the microphone. 
     The present invention further includes a wireless telephone device. The device includes housing and communication electronics within the housing. The communication electronics provides transmission and reception of electronic signals. The device also includes a microphone and an impervious elastic membrane stretched over and covering the microphone on at least one side. The impervious elastic membrane is adapted to pass a selected acoustical frequency range, where the selected acoustical frequency range excludes a frequency range of noise from environmental effects, such as wind and rain. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     DESCRIPTION OF DRAWINGS 
     Different embodiments of the disclosure will be described in reference to the accompanying drawing wherein: 
     FIG. 1 shows an embodiment of a prior art microphone shield design; 
     FIG. 2 shows a microphone shield system in accordance with an embodiment of the present invention; 
     FIG. 3 shows a microphone shield system in accordance with another embodiment of the present invention; 
     FIG. 4 shows a microphone shield system in accordance with yet another embodiment of the present invention; 
     FIG. 5 shows a microphone shield system in accordance with yet another embodiment of the present invention; 
     FIG. 6 is a flowchart of a method for providing a relatively low-noise microphone sensing in a high wind condition; and 
     FIG. 7 is a front view of a wireless telephone device according to an embodiment of the present invention. 
     Like reference symbols in the various drawings indicate like elements. 
    
    
     DETAILED DESCRIPTION 
     Throughout this description, the embodiments and examples shown should be considered as examples rather than as limitations of the invention. 
     The present invention includes system and methods for achieving this improvement in wind noise immunity. For one embodiment, the present invention also provides physical isolation of the microphone from moisture to protect the microphone from the effects of rain and other moisture. In this embodiment, the system substantially reduces the sound of wind and raindrops striking the microphone. 
     An embodiment of the present system  200  is illustrated in FIG.  2 . The system  200  includes an impervious elastic membrane  202  enclosing a microphone  204 . This membrane  202  may include elastic material such as latex or synthetic rubber. In this embodiment, the latex or synthetic rubber membrane  202  is stretched over the microphone  204 . The stretched membrane  202  may be supported over a frame or inflated with gas such as air. In some embodiments, the membrane  202  may be stretched over the microphone  204  by a pressure induced by gas such as air. 
     Sound waves pressing against the membrane  202  may cause the membrane  202  to vibrate. The vibration of the membrane  202  then transmits energy to the air inside the enclosure  206 . Thus, the membrane  202  functions as a band-pass filter. This membrane  202  filters out unwanted noise from the acoustical signal reaching the microphone  204 . The desired acoustical band may be selected by varying the thickness of the membrane  202 . 
     For example, a balloon may be fully inflated to achieve a 100 Hz to 10 KHz band-pass. This band filters out unwanted low-frequency noise below 100 Hz. This membrane may be used in outdoor microphone sensing of ordinary speech and singing. If only ordinary speech were to be sensed, then a thicker and/or less stretched membrane may be used to pass frequencies from 300 Hz to 5 KHz. Thus, the frequency band of the filter is a function of both the thickness of the membrane and the tightness of the stretching. 
     In some embodiments, the use of the membrane  202  as a band-pass filter substantially reduces the low-frequency vibration from reaching the microphone  204 . However, the vibration may create a resonance within the enclosure  206 . Therefore, a layer of open-cell foam  208  or other porous material may be used to acoustically dampen the membrane&#39;s natural resonances. The foam  208  may be provided on the outside or the inside of the membrane  202 . 
     The enclosure  206 , formed by the membrane  202  and the foam  208 , may further operate to reduce sub-sonic variations of air pressure. In particular, the sub-sonic variations between the front  210  and back  212  of the microphone&#39;s sensing element  214  may be substantially reduced. The reduction in air-pressure variations may reduce acoustical distortion caused by wind or rain noise at the microphone&#39;s sensing element  214 . In addition, the membrane  202  may form a sealed enclosure  206  to protect the microphone  204  from environmental effects such as wind and/or rain. 
     For some embodiments, the membrane  202  forms an airtight or air-pressurized enclosure  206 . Wires  216  from the microphone-sensing element  214  may be guided through the enclosure  206  for processing of the acoustical signal. 
     FIG. 3 illustrates another embodiment of the present system. The system  300  includes an impervious elastic membrane  302  stretched over a chamber  304 . The membrane  302  may include elastic material such as latex or synthetic rubber. This stretched membrane  302  may be supported over a frame above the chamber  304  or inflated with gas. 
     For one embodiment, this chamber  304  may include hard and rigid material for robustness in providing weather protection for a microphone  306 . The chamber  304  may be cylindrical or spherical in shape. In some embodiments, the chamber  304  is pressurized with gas  308  above atmospheric pressure. Again, the membrane  302  and the chamber  304  may be lined with foam  310  to dampen the acoustical resonances. 
     Further embodiments of the present system are shown in FIGS. 4 and 5. The embodiment  400  is designed for a chamber  402  with smaller opening  404  than the embodiment  300 . For this embodiment  400 , the membrane  406  is stretched over the top of the chamber  402 . T 
     he embodiment  500  is designed for a chamber  502  with a neck  504 , which provides an opening.  506 . For this embodiment  500 , the membrane  508  is stretched just over the opening  506 . Again, the chamber  502  may be pressurized with gas above the atmospheric pressure. 
     A flowchart of a method for providing a relatively low-noise microphone sensing in a high wind condition is shown in FIG.  6 . The method includes stretching an impervious elastic membrane over a microphone to form an enclosure at step  600 . At step  602 , the membrane may be lined with open-cell foam. Finally, the wire leads are passed through the enclosure to provide electrical connection to the microphone at step  604 . 
     Several embodiments of the microphone shield system have been discussed above. Such a shield system is contemplated for use in wireless telephone communications and radio communication equipment. In addition, the microphone shield system is also contemplated for use in connection with other technologies utilizing audio recording such as outdoor movie and news recording, and other applications. 
     FIG. 7 shows a front view of a wireless telephone device  700 . The wireless device  700  uses a microphone  702  enclosed with an impervious elastic membrane to filter out unwanted noise from the acoustical signal reaching the microphone  702 . The wireless device  700  further includes a key pad.  704 , various other buttons  706 , a speaker  708 , an antenna  710 , a display  712 , and communication electronics contained within a housing  714 . 
     While specific embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications may be made without sacrificing the advantages provided by the principles disclosed herein. For example, even though the impervious elastic membrane has been described in terms of latex or synthetic rubber, other elastic material may be used as membrane. Accordingly, the invention may be embodied in other specific forms without departing from its spirit or essential characteristics.