Patent Publication Number: US-2003223590-A1

Title: Assembly for eliminating noise for microphones and method for making the same

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to an assembly and a method for eliminating a noise by overlapping two reverse signals caused by the noise.  
       BACKGROUND OF THE INVENTION  
       [0002] A conventional cordless microphone  1  is shown in FIG. 1 and generally includes head  12  and a shank  11 . The head  12  includes a casing  121  with a plurality of apertures  122  defined therethrough and enclosing a chamber  123  in the head  12 . A sound picking device  124  is received in the casing  121  and connected to a switch  13  which is connected to an amplifier  111  received in the shank  11 . A signal emitting member  2  is connected to the bottom of the shank  11  so as to emit a signal to a regulator to transfer the signal into sound. There is an inherent problem for the conventional microphone and that is the microphone could generate a huge noise especially when the microphone is hit or scraped unintentionally, or the moment when the switch  13  is pushed. This is because the sound caused by the impact to the microphone is picked by the sound picking device  124  and is amplified by the amplifier  111 . Although some manufacturers mount a spring or a rubber pad connected to the sound picking device to reduce the vibration to reduce noise, it is not satisfied by the users.  
       SUMMARY OF THE INVENTION  
       [0003] In accordance with one aspect of the present invention, there is provided a method for eliminating noise for microphones. The method comprising a sound picking process, a phases reversing process, and an eliminating process. Two sound picking members are used to pick the same sound entering the microphone and respectively send a first signal and a second signal. The phases reversing process transfers the first signal and the second signal into two signals that have reverse phases. The eliminating process overlaps the two signals with reverse phases so as to eliminate the two signals.  
       [0004] The present invention provides a noise eliminating device for a microphone and comprises two sound picking members, a phases reversing unit, and a overlapping unit. The two sound picking members receive the same sound and send two respective signals. The phases reversing unit is connected to an output port of the first sound picking member and reverses the phase of the signal coming from the first sound picking member. The overlapping unit is connected to an output port of the second sound picking member. The signal and the reverse signal are overlapped and eliminated.  
       [0005] The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0006]FIG. 1 shows a conventional microphone which shows a sound picking device;  
     [0007]FIG. 2 shows the circuit used in the method and the device for eliminating noise of a microphone of the present invention;  
     [0008]FIG. 3 shows three processes of the method for eliminating noise of a microphone of the present invention, and  
     [0009]FIG. 4 shows the wave patterns of different sounds treated in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0010] Referring to FIG. 2, the method for eliminating noise for microphones comprises a sound picking process  31 , a phases reversing process  32  and an eliminating process  33 . The sound picking process  31  uses a first sound picking member and a second sound picking member to respectively picking the same sound entering the microphone and respectively sent a first signal and a second signal transferred from the sound. The two signals have the same phase.  
     [0011] The phases reversing process  32  transfers the first signal and the second signal into two signals that have reverse phases. The first signal in the phases reversing process is rotated 180 degrees so that the reversed first signal has 180 degrees of phase difference with respect to the second signal.  
     [0012] The eliminating process  33  overlaps the two signals with reverse phases so as to eliminate the two signals. By this way, there will be no noise being generated from the microphone.  
     [0013] As shown in FIG. 3, the noise eliminating device  5  for a microphone is connected to an amplify circuit  4  of the microphone and includes a first sound picking member  51  and a second sound picking member  52 . The first sound picking member  51  is a capacitor-type or coil-type sound picking member and is isolated from outside of the microphone so that the sound outside cannot enter the first sound picking member  51  and only the sound caused by hitting or scraping the microphone can be received by the first sound picking member  51 . The second sound picking member  52  is a coil-type or capacitor-type sound picking member and communicates with outside of the microphone so that the second sound picking member  52  can receive the sound coming from the outside of the microphone and the sound caused by hitting or scraping the microphone.  
     [0014] The phases reversing unit  53  includes a capacitor C 1  and a reverse amplify circuit  531  which is connected to the capacitor C 1  and the voltage source VCC. The reverse amplify circuit  531  includes a reverse amplifier U 1  and a resistor R 2  which is connected between the capacitor C 1  and the negative output terminal of the reverse amplifier U 1 , a feed-back resistor R 3  is connected between the capacitor C 1  and the positive output terminal of the reverse amplifier U 1 , two resistors R 4 , R 5  are connected between the voltage source VCC and the positive output terminal of the reverse amplifier U 1 , and a capacitor C 2 . The reverse amplify circuit  531  employs the two resistors R 4 , R 5  and the capacitor C 2  to divide the voltage source VCC to be a direct current reference voltage for the reverse amplifier U 1 . The signal entering the reverse amplify circuit  531  is reversed 180 degrees and amplified by the rate of R 3 /R 2 . The feed-back resistor R 3  is a variable resistor so that the rate of amplify can be adjusted by adjusting the resistance of the feed-back resistor R 3 .  
     [0015] The overlapping unit  54  includes a capacitor C 3  which is connected to the second sound picking member  52 , a summing member  541  connected to the capacitor C 3  and the reverse amplify circuit  531 . The output terminal of the summing member  541  is connected to the amplify circuit  4  of the microphone.  
     [0016] Referring FIGS. 2, 3 and  4 , when a noise sound is applied to the microphone by hitting or scraping the microphone, the sound picking process  31  is activated and the noise sound is received by the first and the second sound picking member  51 ,  52  and a signal S 1  is sent by the two sound picking members  51 ,  52 . In the phases reversing process  32 , the signal sent by the first sound picking member  51  is reaches the capacitor C 1  and the reverse amplify circuit  531  and amplified at the rate of the value of R 3 /R 2  and a reverse signal S 2  is sent. There is a phase difference of 180 degrees between the signal S 2  and the signals S 1 , S 3 . The S 2  is the value of R 3 /R 2  times of the S 1 . By adjusting the value of R 3 , the reverse phase signal S 2  output from the point A of the reverse amplify circuit  531  I has the same pattern as the signal S 3  coming from the second sound picking member  52 . Besides, in the eliminating process  33 , the signal S 3  of the second sound picking member  52  is connected to the summing member  541  via the capacitor C 3 . Therefore, the reverse phase signal S 2  coming from the reverse amplify circuit  531  is overlapped with the signal S 3  coming from the second sound picking member  52  by the summing member  541 . The S 2  and S 3  are eliminated to each other at the output terminal of the summing member  541 , so that no noise is sent to the amplify circuit  4  of the microphone.  
     [0017] A sound coming from outside of the microphone can only be received by the second sound picking member  52  and a signal is sent by the second sound picking member  52  to the summing unit  54 . There is no signal sent by the first sound picking member  51  which is isolated from the outside of the microphone. The phases reversing unit  53  has no signal being sent to the summing unit  54  so that the signal sent by the second sound picking member  52  can be output after being amplified by the amplify circuit  4 . The present invention can be used on any type of microphones.  
     [0018] While we have shown and described the embodiment in accordance with the present invention, it should be clear to those skilled in the art that further embodiments may be made without departing from the scope of the present invention.