AACAA
`US005268965A
`(11) Patent Number:
`5,268,965
`p19)
`United States Patent
`Badieetal.
`[45] Date of Patent:
`Dec. 7, 1993
`
`
`[54] USER SELECTABLE NOISE CANCELING
`FOR PORTABLE MICROPHONES
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`.
`Inventors: Merhdad Badie, Sunrise; William R.
`Williams, N. Lauderdale, both of Fla.
`
`3,114,105 12/1963 Neumiller ......cssssssssecsseeees 381/91
`wee 455/89
`3,370,236 2/1968 Walker.....
`
`4,051,330 9/1977 Cole ceecscsccsscssssscsssccsscseccseees 381/68.1
`
`[73] Assignee: Motorola, Inc., Schaumburg, Ill.
`
`[21] Appl. No.: 41,921
`
`[22] Filed:
`
`Apr. 2, 1993
`
`Primary Examiner—Forester W. Isen
`Attorney, Agent, or Firm—M. Mansour Ghomeshi
`[57]
`ABSTRACT
`Briefly, according to the invention, a noise-cancelling
`microphone apparatus 302 is disclosed. The micro-
`phone comprises a housing 510 and a sound transducer
`502 mounted within the housing 510. The housing has
`first 514 and second sides 512 and the transducer 502 has
`first 304 and second soundports 308 coupledto the first
`Related U.S. Application Data
`514 and second sides 512 of the housing respectively.
`ae
`[63] Continuation of Ser. No. 793,966, Nov.18, 1991, aban-=The microphone 302 also includes a mounting clip310
`coupled to one side of the housing §12 in the proximity
`.
`of one of the sound ports 308. The mounting clip 310is
`SU] Unt, C1 eeecceceeseseeseeecesessssensserscere HO4R 1/02_—intended for mounting the microphone 302 to a user so
`[52] U.S. Ch. eececsecsssseseseceteseereees 381/91; 381/122;
`as to substantially close the sound port 308 when micro-
`381/169
`phone 302 is attached.
`[58]. Field of Search................. 381/169, 170, 122, 91;
`455/100
`
`
`
`10 Claims, 3 Drawing Sheets
`
`302
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`514
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`U.S. Patent
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`Dec. 7, 1993
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`U.S. Patent
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`Dec. 7, 1993
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`Sheet 20f3 -
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`5,268,965
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`U.S. Patent
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`Dec. 7, 1993
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`Sheet 30f 3 5,268,965
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`1
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`5,268,965
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`USER SELECTABLE NOISE CANCELING FOR
`PORTABLE MICROPHONES
`
`This is a continuation of application Ser.. No.
`07/793,966, filed on Nov. 18, 1991 and now abandoned.
`
`TECHNICAL FIELD
`This invention relates generally to microphones and
`more particularly to directional microphone.
`BACKGROUND
`
`A directional microphoneutilizes front and rear port-
`ing to sense the difference between the instantaneousair
`pressures which impinge on its two surfaces. If an un-
`wanted sound arrives from front of the user, who is
`talking directly into front of the microphone,it will pass
`the rear inlet first and with a distance delay reaches the
`frontinlet (facing the user). An internal delay at the rear
`inlet to.the diaphragm is optimally designed to time to
`cancel the distance delay, thus allowing the unwanted
`sound to reach the diaphragm from bothinlets simulta-
`neously and therefore being cancelled. Directional mi-
`crophones havetraditionally been used with portable
`units. In many applicationsdirectional microphonesare
`remotely located, either attached to ones clothing or to
`a strap belt, both for hands free operation. Referring to
`FIG.1, an example ofthe attachment of a microphone
`102 to the clothing of an operator 106 is shown. The
`microphone 102 includes a front port 104 and a rear
`port 108 (in the back, not shown). Since the operator
`can no longer speak directly into the front port 104 his
`voice waves reachthe rear port 108 out of timing sync
`with those reaching the front port 104. This timing
`corruption, essential to the operation of the directional
`microphone102,results in a reduction of the level of the
`electrical signal produced by the microphone 102 in
`response to the voice waves. In manysituations this
`problem is so significant that the operator is forced to
`Tremove the microphoneanduseit in a hands on manner
`defeating the purpose of the remoteness of the micro-
`phone.It is therefore clear that a need exists for a direc-
`tional microphone that can also be used in hands free
`applications where the operator does not directly talk
`into the microphone.
`
`SUMMARYOF THE INVENTION
`
`Briefly, according to the invention, a noise-cancelling
`microphone apparatus is disclosed. The microphone
`comprises a housing and a sound transducer mounted
`within the housing. The housing hasfirst and second
`sides and the transducer has first and second sound
`ports coupled to the first and second sides of the hous-
`ing respectively. The microphone also includes a
`mounting means coupled to one side of the housing in
`the proximity of one of the sound ports. The mounting
`means is intended for mounting the microphone to a
`user so as to substantially close the sound port when
`microphoneis attached.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG.1 is a diagram of the attachment of a micro-
`phoneto the clothing of an operator in accordance with
`the present invention.
`FIG. 2a and 20 are perspective viewsofa directional
`microphone showing the attachmentof a hook and loop
`fastener in accordance with the present invention.
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`2
`FIG.3a and 30 are perspective viewsof a directional
`microphone showinga clip on fastener in accordance
`with the present invention.
`FIG.4 is a block diagram of a transmitter in accor-
`dance with the present invention.
`FIG. 5 is a diagram of the internal elements of a mi-
`crophone in accordance with the present invention.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`Referring to FIG. 2a, a perspective view of a micro-
`phone 202 is shown in accordance with the present
`invention. The microphone 202 includes a rear port 204
`and a front port (not shown). These two ports are con-
`nected to a directional transducer included in the elec-
`tronics of the microphone 202. The front and rear ports
`204 channel the available sound waves to the transducer
`which produces a proportional electrical signal. The
`available sound waves include waves from ambient
`noise signals. The front and rear ports 204 along with
`the directional transducer work together to render the
`microphone 202 directional. The operation of direc-
`tional. microphones is well known in the art. Sound
`waves directed at the front port are properly converted
`to electrical signals. However, noise waves not directed
`at any particular port are cancelled. The rear port 204 is
`surrounded with a hook and loop fastener such as a
`velcro piece 216 whichis used to attach the microphone
`202 to a stand or to an operator’s clothing. Volume
`control and channel selections are provided via 212 and
`214 respectively and are notrelated to this invention. A
`screw on connector 206 is provided to connect the
`microphone202 to a device it is meant to operate with,
`such as a communication device. The connection be-
`tween the hand held microphone 202 and the connector
`206 is provided via the cable 210. A piece of velcro
`patch 208 comprising hook and loop fastener meansis
`used by the operator to attach the microphone 202 to
`his clothing or his belt strap. The velcro patch 208is
`placed and attached to an operator’s clothing or his
`strap using adhesives, a safety pin, orit is simply sowed
`on. Later when the operator wishes to use his micro-
`phone 202 hands free, he proceeds with attaching the
`two velcro pieces 208 and 216 together.
`FIG. 2b shows the microphone 202 with its velcro
`piece 216 attached to the velcro patch 208. The attach-
`ment of the microphone 202 to the velcro patch 208
`results in the obstruction of the rear port 204. This
`obstruction greatly reduces the flow of soundsignals to
`the rear port 204 leaving only the front port as the
`means of receiving sound signals. With only one port
`operating, the microphone 202 is rendered omni-direc-
`tional. That meansthat the effects of the ambient noise
`cancelling port are substantially minimized. As de-
`scribed, the conversion of the directional microphone
`202 to omni-directional is entirely selective and auto-
`matic.That is as the operator removes the microphone
`202 form his shirt or his strap, the obstruction of the rear
`port 204 is removed which results in the microphone
`202 returning to its directional mode of operation. This
`generally happens when the operator intends to hold
`the microphone 202 andtalk intoit.
`In summary a directional microphone 202 having a
`front and rear port 204 is rendered omni-directionalas it
`is attached to the clothing of an operatorvia a hook and
`loop fastener such as velcro patch 208. As the velcro
`patch 208 attaches to the velcro piece 216 the rear port
`204 is blocked. The blocking of the rear port 204 mini-
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`3
`mizes the effects of the noise cancelling that is inherent
`to the directional microphone 202.
`Referring to FIG. 3a, a side view of an alternative
`embodiment of the present invention is shown. A mi-
`crophone apparatus 302 is shownto include a front port
`304 and a rear port 308. These two ports 304 and 308
`render the microphone 302 directional in regular hand
`held operation and as the operator speaks directly into
`the front port 304. Internal to the microphone 302,there
`is a transducerintended for producingelectrical signals
`in response to sound waves. Ambient noise is greatly
`eliminated from being convertedtoelectrical signal by
`the cancelling features of the microphone 302. A clip
`310 is used to clip the microphone 302 to an operator’s
`shirt or his strap belt and provides the mounting means
`for the microphone 302. A cable 306 provides electrical
`connection between the microphone 302 and an elec-
`tronic device the microphone302is intended to operate
`with. As can be seen in FIG. 3a, the rear port 308 is
`open indicating that the operation of the microphone
`302 is directional.
`Referring to FIG. 36 now, the microphone 302 is
`shownattached to the operator; either on his clothing
`orto his strap belt. A portion of the clothing or the strap
`is shown by 312. It can be seen that strap 312 is being
`pushed in by a pad 314 and therefore blocking the rear
`port 308. The material used for the pad 314 is preferably
`rubber. This blockage of the rear port 308 greatly re-
`duces the entrance ofthe sound waves to the transducer
`of the microphone 302. Since the directional operation
`of the microphone 302 is dependent on the rear port
`308, the result is an omni-directional microphone. With
`the microphone 302 omni-directional, the position of
`the operator’s mouth andthe location of the two ports
`304 and 308 is not significant from a noise cancelling
`stand point. Onceagain it is evident that the conversion
`from directional to omni-directional is user selectable
`and doesnot require any additional actions taken by the
`operator. Furthermore, the blocking of the rear port
`308 may be accomplished by a switch, preferably me-
`chanical. The operator activates a mechanical switch
`whichresults in the rear port 308 being blocked. Micro-
`phonesnot intended for remote operation can take spe-
`cial advantage of such a switch.
`In summary, a directional microphone 302 is con-
`verted to an omni-directional microphonevia the action
`of clipping the microphoneto the clothing of the opera-
`tor. By clipping the microphone 302 to the clothing of
`the operator, the rear port 308, providing noise cancel-
`ling to the microphone 302, is blocked. This blockage
`reducesthe effects of the noise cancelling operation of
`the microphone 302.
`Referring to FIG.4, a block diagram of a transmitter
`is shown in accordance with the present invention. A
`transmitter 402 is coupled to the microphone 202 via the
`microphonecable 210. The audio signals from the mi-
`crophone202 are routed to the transmitter 402 for trans-
`mission via an antenna 406. The microphone 202 is
`attached to a person’s clothing via the velcro patch 208
`which dampensthe soundlevels reaching the rear port
`204. Such dampeningofthe soundlevelsat the rear port
`204 reduces the effects of noise cancellation which is
`inherent in directional microphones.
`Referring now toFIG.5, the internals of microphone
`302 are shown. The microphone 302 includes a housing
`510 which has a front side 514 and a back side 512. The
`front port 304 and the rear port 308 are coupled to front
`side 514 and rear side 512 respectively. A microphone
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`element 502 is shownas the transducer means for con-
`verting sound waves to electrical signals. The front port
`304 and the rear port 308 are coupled to the front and
`rear inlets 506 and 508 respectively via extension tub-
`ings. A diaphragm 504 senses the difference between
`the instantaneousair pressure which impinges on its two
`surfaces. This pressure difference at the diaphragm 504
`causes it to move, and this mechanical movement is
`converted to an electrical output signal by the micro-
`phoneelement 502. Theclip 340is placed in close prox-
`imity to the rear port 308 so as to block it when the
`microphone302is attached to the person’s clothing 312.
`To summarize, as is known, the operation ofa direc-
`tional microphone is hampered when the user of these
`microphones doesn’t speak directly into them.It is fur-
`ther known that most of remote microphonesare in-
`tended for attachmentto the clothing of the user. Such
`attachments greatly hamper the direct path of sound
`waves, generated by theuser, to the microphoneresult-
`ing in performance degradation. This invention mini-
`mizes performance degradation of directional micro-
`phones when used remotely. A directional microphone
`302 having a front port 304 and a rear port 308is at-
`tached to a user’s clothing. The mounting of the micro-
`phone 302 results in the pad 314 pushing a portion of the
`clothing of the user against the rear port 308 resulting in
`its blockage. This blocking results in the removal of the
`contribution of the rear port 308 to the operation of the
`directional microphone 302. Consequently,
`the user
`doesn’t have to directly speak into the microphone 302
`in order to achieve acceptable performance.
`Whatis claimedis:
`1. A noise cancelling microphone, comprising:
`a housing having first and secondsides;
`a sound transducer mounted within the housing, the
`transducer having first and second sound ports
`coupledto the first and second sides of the housing
`respectively; and
`‘
`mounting means coupled to one side of the housingin
`the proximity of the second sound port for mount-
`ing the microphoneto a user so as to selectively
`and substantially close the second sound port when
`the microphoneis attached to the user.
`2. The noise cancelling microphone of claim 1,
`wherein the mounting means includes hook and loop
`fastener means.
`3. The noise cancelling microphone of claim 1,
`wherein the mounting means includesa clip.
`4. The noise cancelling microphone of claim 3,
`wherein the clip includes a pressure pad.
`5. The noise cancelling microphone of claim 1,
`wherein the sound transducer includes a directional
`transducer.
`6. A portable microphone apparatus adapted to be
`mounted on a person’s clothing, comprising:
`a microphoneelement for converting sound wavesto
`electrical signals, the microphone element having a
`first and a second port operating in combination to
`substantially prevent the ambient noise from being
`converted to electrical signals; and
`fastening means attached to the portable microphone
`for fastening the portable microphone totheper-
`son’s clothing so as to selectively and substantially
`block the second port.
`7. A communication device, comprising:
`transmitter meansfor transmitting a signal;
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`5
`microphone means coupled to the transmitter means
`for converting sound wavesto electrical signals,
`the microphone means including:
`a housing having a first and a second side;
`a transducer means mounted within the housing and
`having a first and a second port coupled to thefirst
`and second sides of the housing respectively for
`substantially cancelling ambient noise;
`fastening means attached to the second side of the
`microphone means, substantially close to the sec-
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`5,268,965
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`ond port ofthe transducer,for fastening the micro-
`phone means to a person’s clothing so as to selec-
`tively block the second port.
`8. The communication deviceof claim 7, wherein the
`fastening means includes hook and loop fastener means.
`9. The communication device of claim 7, wherein the
`fastening means includesa clip.
`10. The communication device of claim 7, wherein
`the transducer means includes a directional transducer.
`*
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