Abstract:
A system and method for reducing or entirely canceling background or ambient noise from a voice transmission from a communications device. A communications device, such as a mobile telephone, is configured with an ambient noise compensation signal generator that is connected between a microphone and a mixer. The original output of the microphone and a compensation signal generated by the ambient noise compensation signal generator are mixed together prior to being passed to a transmitter. In one embodiment a buffer is provided between the microphone and the mixer to help synchronize the timing of the signals to be mixed. In another embodiment a second microphone is employed to detect ambient noise.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to voice communication and, more specifically, to automated control to compensate for variable ambient noise levels. 
         [0003]    2. Background of the Invention 
         [0004]    Voice communication devices such as mobile telephones have become ubiquitous; they show up in almost every environment. They are used in the home, at the office, in the car, on a train, at the airport, at the beach, at restaurants and bars, on the street, and almost any other imaginable venue. As might be expected, these diverse environments have relatively higher and lower levels of background or ambient noise. For example, there is generally less noise in a quiet home than there is in a crowded bar. 
         [0005]    Significantly, in an on-going telephone call from an environment having relatively higher ambient noise, it is sometimes difficult for the party at the other end of the connection to hear what the party in the noisy environment is saying. That is, the ambient noise in the environment often “drowns out” the mobile telephone user&#39;s voice, whereby the other party cannot hear what is being said. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a novel system and method for monitoring the ambient noise in the environment in which a voice communications device or mobile telephone is operating and canceling the ambient noise before the ambient noise is transmitted to the other party so that the party at the other end of the voice communication link can more easily hear what the mobile telephone user is transmitting. 
         [0007]    The present invention preferably employs noise cancellation technology that is operable to attenuate or even eliminate pre-selected portions of an audio spectrum. By monitoring the ambient noise in the location in which the mobile telephone is operating and applying noise cancellation protocols at the appropriate time, it is possible to significantly reduce the background noise to which a party to a telephone call might be subjected. 
         [0008]    It is therefore an object of the present invention to provide a system and method that enhances the convenience of using a mobile communications device, even in a location having relatively loud ambient noise. 
         [0009]    It is also an object of the present invention to provide a system and method for canceling ambient noise before the ambient noise is transmitted to another party. 
         [0010]    It is yet another object of the present invention to monitor ambient noise via a second microphone associated with a mobile telephone and thereafter cancel the monitored ambient noise. 
         [0011]    It is still another object of the present invention to provide an enable/disable switch on a mobile communications device to enable/disable the noise cancellation features of the invention. 
         [0012]    These and other objects of the present invention will become apparent upon reading the following detailed description in conjunction with the associated drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates an exemplary mobile telephone including an optional second microphone for sampling ambient noise and an enable/disable button in accordance with the present invention. 
           [0014]      FIG. 2  illustrates an exemplary embodiment of the present invention. 
           [0015]      FIG. 3  illustrates a second exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention provides a unique background noise or ambient noise cancellation feature for a communications device such as a mobile (or cellular) telephone or even a conventional wire line telephone. While the present invention has applicability to at least these types of communications devices, the principles of the present invention are particularly applicable to all types of communications devices. For simplicity, the following description employs the term “mobile telephone” as an umbrella term to describe the embodiments of the present invention, but those skilled in the art will appreciate that the use of such term is not to be considered limiting to the scope of the invention, which is set forth by the claims appearing at the end of this description. 
         [0017]      FIG. 1  illustrates an exemplary mobile telephone  10  that comprises a microphone  11 , a speaker  12 , a display screen  13 , a keypad  14  and an antenna  15 . Optionally, a second microphone  16  for sampling ambient noise level and an ambient noise compensation enable/disable button  17  may also be provided. These latter two elements will be described more fully below. Those skilled in the art will appreciate that speaker  12  could be replaced by an ear piece (not shown) that is worn by the mobile telephone user in the conventional manner. Speaker  12  is used herein to mean the device by which sound is transferred from the mobile telephone to the user. Also, display screen  13  could be a touch screen display, which might incorporate keypad  14  as well as enable/disable button  17 . 
         [0018]      FIG. 2  illustrates an exemplary embodiment of the present invention including microphone  11 , ambient noise compensation signal generator  20 , a mixer  22 , transmitter  24  and antenna  15 . 
         [0019]    In accordance with the present invention, ambient noise or background noise is cancelled before being the combined with the intended voice communication picked up at microphone  11  and sent to transmitter  24  and antenna  15 . More specifically, in a first embodiment, microphone  11  picks up both ambient noise as well as the intended voice communication (together, the “combined signal”). As is well known in the art of noise cancellation, it is possible (e.g., via filtering and digital signal processing (DSP) techniques) to attenuate or even cancel-out pre-selected portions of an audio signal or pre-selected bands of a frequency spectrum. 
         [0020]    As shown in  FIG. 2 , ambient noise compensation signal generator  20  is connected to microphone  11  and monitors the combined signal. Then, ambient noise cancellation generator, in accordance with well-known techniques, generates compensation signals that are operable to attenuate or altogether cancel background noise that is not intended or desirable to be transmitted to another party. These compensation signals are fed into mixer  22  where these signals are mixed with the combined signal coming directly from microphone  11 . The result is that the ambient noise or background noise is eliminated, or at least substantially reduced, before the combined signal (ambient noise plus voice signal) is passed to transmitter  24  (which, e.g., includes a radio frequency modulator, etc.) and ultimately to antenna  15 . 
         [0021]    Optionally, a buffer  28  is provided to slow the progress of the combined signal emanating from microphone  11  so that when the combined signal reaches mixer  22  the arrival time of the combined signal and the compensation signals generated by ambient noise cancellation generator is synchronized. 
         [0022]    In another embodiment, as shown in  FIG. 3 , a second microphone  16  is provided for the principal purpose of sampling ambient noise. That is, microphone  16  is dedicated substantially to picking up ambient noise rather than a voice signal. A second microphone, especially one that is located away from mobile telephone user&#39;s mouth would be less affected by the user&#39;s own voice when taking the ambient noise level measurement and, thus, might be more desirable in certain implementations of the present invention. 
         [0023]    More specifically, it is often the case that microphone  11 , which is used primarily for receiving voice signals from a user, is arranged to have directional characteristics, wherein the microphone is more sensitive to sound coming from predetermined directions. In contrast, second microphone  16  is preferably omni-directional such that the microphone is equally sensitive to sound emanating from any direction. A more accurate detection of ambient noise level can be obtained using such an omni-directional microphone. Also, although not shown expressly in the drawings, microphone  16  could be arranged spatially distant from mobile telephone  10 . For example, second microphone  16  could be arranged to hang from a wire that is connected to mobile telephone  10 , whereby there would be even less chance for the mobile telephone user&#39;s voice to interfere with noise cancellation signal generation. 
         [0024]    Optionally, in the dual microphone embodiment, microphone  11  is also in communication with ambient noise cancellation signal generator  20  to provide additional signal information to generator  20  to aid in distinguishing more easily between ambient noise and voice signals. 
         [0025]    Further in accordance with the present invention there is provided an enable/disable switch  17  ( FIG. 1 ) that is preferably operable to enable/disable ambient noise compensation signal generator  20 . For example, depending on the nature of the ambient noise in a particular environment, known noise cancellation techniques might also inadvertently attenuate the voice signal that is intended to be transmitted. In such a case, it is preferable that the noise cancellation features of the present invention be disabled, at least for a limited period, until the ambient noise is such that it can be more effectively distinguished from the voice signal and attenuated independently. For example, a mobile telephone user may want to call a friend from a noisy public event (e.g., a concert or sporting event) for the main purpose of letting the friend hear the background noise. In such a case, the switch  17  is preferably manipulated to disable the noise cancellation features of the present invention. 
         [0026]    The foregoing disclosure of the preferred embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be obvious to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
         [0027]    Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.