Abstract:
Disclosed embodiments include means and methods of enhancing the quality of an audio signal by estimations and manipulations of voice attributes. Disclosed embodiments include means and methods of estimating a pitch period of an input audio signal, converting the audio signal into the frequency domain using a FFT, decreasing the pitch estimation value based on a fundamental frequency of the signal based on a first predefined condition and increasing the fundamental frequency of the audio signal based upon a second predefined condition.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of U.S. non-provisional application Ser. No. 13/161,937 filed on or about Jun. 16, 2011, which was a U.S. non-provisional application of a U.S. provisional application Ser. No. 61/356,240 and filed on or about Jun. 18, 2010. The entire teachings and contents of the related patent applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to signal processing and more specifically the invention relates to methods and systems for reducing noise in a signal at a communication device. 
       PRIOR ART 
       [0003]    U.S. Pat. No. 8,315,862 by Kim et al and issued on Nov. 20, 2012 describes a pitch calculating unit used to extract a pitch period of an audio signal. However, Kim teaches away from the present invention failing to suggest subsequent adjustments to either a pitch estimation or fundamental frequency of an audio signal by use of predefined conditions or other parameters. 
       BACKGROUND 
       [0004]    Various communication devices such as a cell phone, a mobile phone, a Personal Desktop Assistant (PDA) or a wireless telephone may be used for communication over telecommunication network or the Internet. The communication devices may be used at home, office, inside a car, train, airport, beach, restaurants and bars, street, and almost any other venue that may have variable levels of environmental noise. The environmental noise may be picked up from a microphone of a communication device and may degrade quality of speech signals transmitted or received at the communication device. As a result, in an ongoing call the speech of a caller may be unintelligible to a receiver. Further, the communication device may use more bandwidth or network capacity when there is noise in environment, especially during non-speech segments in a two-way conversation when a user is not speaking. Consequently, noise reduction and improvement in Signal-to-Noise Ratio (SNR) may be performed prior to transmitting the signals from the communication device. 
         [0005]    Pitch of a signal such as speech signal is an acoustic parameter for speech recognition, compression, and synthesis. The pitch plays a significant role in both production and perception of the speech. Generally, the pitch is perceived with great accuracy at a fundamental frequency that characterizes the vibrations of speaker&#39;s vocal chords. The speech signal is a quasi-periodic or a virtually periodic signal. Therefore, harmonic components of the speech signal are present at integer multiples of the fundamental frequency. 
         [0006]    Various techniques for noise reduction employ Pitch Detection Algorithm (PDA) to estimate the pitch or the fundamental frequency of the speech signal. PDA may be used in the time domain to estimate the period of the quasi-periodic signal, and then invert that value to generate the frequency of the signal. One approach for pitch estimation may be to measure the distance between zero crossing points of the signal (i.e. the Zero Crossing Rate). However, this technique may not be effective in case of complex waveforms including multiple sine waves with differing periods. However, zero-crossing techniques may be in some cases, for example in speech applications where a single source of sound is considered. This technique is simple and inexpensive, however, it may be inaccurate and generate noisy signals. 
         [0007]    Further, PDA may be used in frequency domain for polyphonic detection. The Fast Fourier Transform (FFT) may be used to convert the signal to a frequency spectrum. Various frequency domain algorithms include the harmonic product spectrum, cepstral analysis, or maximum likelihood which attempt to match the frequency domain characteristics of the signal to pre-defined frequency maps. The FFT algorithm is efficient and can be applied in various scenarios. However, processing power required increases with the desired accuracy of the signal. The frequency domain based PDA may be less expensive, resistant to noise, and adjustable to different kind of inputs as compared to time domain based analysis. However, in this case, low pitches may be tracked less accurately than high pitches. 
         [0008]    Pitch of a signal is a perceptive parameter and not a physical parameter. For a single sinusoid, below mentioned Equation 1 defines the relation between the frequency ‘F’ and the pitch ‘P’ of the signal in the harmonic scale: 
         [0000]    
       
         
           
             
               
                 
                   
                     P 
                      
                     
                       ( 
                       F 
                       ) 
                     
                   
                   = 
                   
                     
                       P 
                       ref 
                     
                     + 
                     
                       O 
                        
                       
                           
                       
                        
                       
                         
                           log 
                           2 
                         
                          
                         
                           ( 
                           
                             F 
                             
                               F 
                               ref 
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   1 
                 
               
             
           
         
       
     
         [0000]    where ‘P ref ’ and ‘F ref ’ are the pitch and the corresponding frequency respectively of a tone of reference. The constant ‘O’ is the division of the octave. For example, a value of O as 12 leads to the classic dodecaphonic musical scale. This technique is computationally inexpensive, reasonably resistant to noise, adjustable to different kind of inputs. However, low pitches may be tracked less accurately than high pitches. 
         [0009]    Various techniques are available for noise reduction. In case of multi-microphone techniques, more than two microphones results in effective noise reduction. However, the communication devices pose spatial restrictions on use of multiple microphones. Further, under a stationary noise environment such as fan or motor noise, a spectral subtraction method may be utilized for the noise reduction. In this technique, noise spectrum to be subtracted is obtained during non-speech activity. Therefore, non-stationary noise may not be removed. In monaural approach, the noise reduction is based on discrimination between properties of the voice and the noise. The spectrum of voiced sounds include harmonic components that are integer multiples of the fundamental frequency. An existing technology such as comb filter method may be used for the noise reduction. However, in case of comb filter method, a detection error in the fundamental frequency may degrade the quality of the filtered voice. 
         [0010]    A true fundamental frequency of the signal may be determined from several possible frequencies using time continuity. Another existing technique uses time continuity property of both power spectrum envelopes (PSE) and the fundamental frequency to estimate the true fundamental frequency. Further, the reliable fundamental frequency may be determined by using continuity of power spectrum envelopes due to quasi stationary characteristics of the human voice. However, the fundamental frequency extracted from the noisy signal may include fluctuations because of noise interference. Therefore, the fundamental frequency is adopted from both the latest frequency and the predicted frequency so as to keep the continuity in the frequency. Moreover, the comb filtering for continuous speech with noise often generates strange sounds because the harmonic structure at higher frequency is disturbed by the noise. 
         [0011]    Another existing technique as disclosed in U.S. Pat. No. 6,415,034 uses multiple microphones for noise cancellation. However, noise may leak past an ear capsule of the microphone and enter into a speech microphone. Further, the technique requires complex, power consuming and expensive digital circuitry, which may not be suitable for portable, battery powered devices such as mobile phones. 
         [0012]    Another existing technique for reducing noise as disclosed in U.S. Pat. No. 5,969,838 utilizes two fiber optic microphones placed side-by-side to each other. However, the technology uses light guides and other relatively expensive and/or fragile components that may not be suitable for communication devices. Yet another technique as disclosed in U.S. Pat. No. 5,406,622 uses two adaptive filters for noise reduction. One of the adaptive filters is driven by a transmitter of the communication device to subtract speech signal from a reference value to produce an enhanced reference signal. Another adaptive filter is driven by the enhanced reference signal to subtract noise from a transmitter of the communication device. However, the technique requires accurate detection of speech and non-speech regions in the speech signal. Therefore, an incorrect detection of the speech and the non-speech region may degrade the performance of noise reduction. 
         [0013]    Another technique for noise cancellation includes passive expander circuits that are used in the electret-type telephonic microphone. However, only low level noise that occurs during periods when speech is not present may be reduced. Further, passive noise-canceling microphones may be used to reduce the background noise. However, passive noise-canceling microphones have a tendency to attenuate and distort the speech signal when the microphone is not in close proximity to the user&#39;s mouth. Moreover, such microphones are effective only in a frequency range up to about 1 kHz. 
         [0014]    Active noise-cancellation circuitry may be used to reduce background noise. In this case, a noise-detecting reference microphone and adaptive cancellation circuitry are used to generate a continuous replica of the background noise signal that is subtracted from the total background noise signal. However, this technique may be susceptible to cancellation degradation because of a lack of coherence between the noise signal received by the reference microphone and the noise signal impinging on the transmit microphone. Further, the performance may vary based on the directionality of the noise and may tend to attenuate or distort the speech. 
         [0015]    Therefore, techniques for noise reduction of a speech signal at a communication device are desired. 
       SUMMARY 
       [0016]    Embodiments of the invention provide a communication device for generating enhanced audio signals. The communication device comprising at least one microphone and a noise processor. The at least one microphone is configured to acquire an audio signal, wherein the audio signal comprises at least one speech signal and at least one noise signal. The noise processor is configured to: detect a pitch estimation of the audio signal, initialize a plurality of processing parameters for the audio signal, and process the audio signal based on the pitch estimation and the processing parameters, wherein the audio signal is processed to reduce the at least one noise signal and generate an enhanced audio signal. 
         [0017]    Embodiments of the invention provide a method for generating enhanced audio signals at a communication device. The method comprising: acquiring by one or more microphones of the communication device an audio signal, wherein the audio signal comprises at least one speech signal and at least one noise signal. Further, the method comprises detecting, at a noise processor, a pitch estimation of the audio signal, initializing, at a noise processor, a plurality of processing parameters for the audio signal, and processing, at the noise processor, the audio signal based on the pitch estimation and the processing parameters, wherein the audio signal is processed to reduce the at least one noise signal and generate an enhanced audio signal. 
         [0018]    Embodiments of the invention further provide a communication device for transmitting enhanced audio signals. The communication device comprising at least one microphone configured to acquire an audio signal, wherein the audio signal comprises at least one speech signal and at least one noise signal; and a noise processor configured to: detect a pitch estimation of the audio signal, initialize a plurality of indices for a Fast Fourier Transform (FFT) of the audio signal, decrease the pitch estimation value based on a fundamental frequency of the audio signal based on a first predefined condition, and multiplying the pitch estimation value with at least one of the plurality of processing parameters to generate an enhanced audio signal, and a transmitter configured to transmit the enhances audio signal over a communication channel. 
         [0019]    In one aspect of the invention, an enhanced experience is provided for using a cellular telephone or other wireless communications devices, even at a location with high background or environmental noise. 
         [0020]    In another aspect of the invention, the background noise is reduced before the being transmitted to a second party over the communication channel. 
         [0021]    In another aspect of the invention, there is a difference between a “pitch” of an audio signal and a “pitch estimate” of an audio signal. The “pitch” of an audio signal sometimes refers to the fundamental frequency of the audio signal. The “pitch estimate” is sometimes a value that is related to the pitch, which varies with frequency. Sometimes, the “pitch” of an audio signal represents a single fundamental frequency; and sometimes the “pitch estimate” is a function that varies with frequency. 
         [0022]    In still another aspect of the invention, the communication device comprises a switch to enable and/or disable the noise reduction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
           [0024]      FIG. 1  illustrates an environment where various embodiments of the invention function; 
           [0025]      FIG. 2  illustrates components of a communication device for reducing noise in communication signals, in accordance with an embodiment of the invention; 
           [0026]      FIG. 3  is an exemplary graph of pitch for a signal having noise, in accordance with an embodiment of the invention; 
           [0027]      FIG. 4  illustrates an exemplary graph for the pitch corresponding to the frequency of a clear voice signal, in accordance with an embodiment of the invention; 
           [0028]      FIG. 5  illustrates a flowchart for reduction of noise in a signal, in accordance with an embodiment of the invention; 
           [0029]      FIGS. 6A and 6B  comprise flowcharts for reduction of noise in a signal, in accordance with an embodiment of the invention; 
           [0030]      FIG. 7  is an exemplary diagram illustrating amplitude corresponding to samples of a speech signal mixed with a noise signal; 
           [0031]      FIG. 8  is an exemplary diagram illustrating a data rate of the noisy speech signal corresponding to the number of frames; 
           [0032]      FIG. 9  is an exemplary diagram illustrating the pitch of the signal corresponding to the number of frames; 
           [0033]      FIG. 10  is an exemplary diagram illustrating the value of pitch estimator corresponding to the number of frames, in accordance with an embodiment of the invention; 
           [0034]      FIG. 11  is an exemplary diagram illustrating a spectrogram of the noisy speech signal before noise reduction; and 
           [0035]      FIG. 12  is an exemplary diagram illustrating the spectrogram of the noisy speech signal after noise reduction, in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be embodied in a multitude of different ways as defined and covered by the claims and their equivalents. In this description, reference is made to the drawings wherein like parts are designated with like numerals throughout. Unless otherwise noted in this specification or in the claims, all of the terms used in the specification and the claims will have the meanings normally ascribed to these terms by workers in the art. 
         [0037]    The present invention provides systems and methods to improve the intelligibility in noisy environments experienced in communication devices such as a cellular telephone, wireless telephone, cordless telephone, and so forth. 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, as well as other devices that process speech in noisy environments such as voice recorders, dictation systems, voice command and control systems, and the like. For simplicity, the following description may employ the terms “telephone” or “cellular 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. 
         [0038]      FIG. 1  illustrates an environment  100  where various embodiment of the invention function. As shown, environment  100  includes communication devices  102  and  104  which may communicate over a network  106 . Examples of communication devices  102  and  104  include, but are not limited to, a mobile phone, a smart phone, a Personal Desktop Assistant (PDA), a laptop, a tablet computer (PC), and so forth. Network  106  may be for example, a Public Switched Telephone Network (PSTN), mobile network, the Internet, the Ethernet, Bluetooth network, and so forth. 
         [0039]    Communication device  102  may be used in a noisy environment such as a hotel, a train, on a highway, an industrial setting and so forth. As shown, the noisy environment may have a background noise or noise signal  108  that may be sent along with the user speech signal  110  as a voice signal from communication device  102  to communication device  104 . Background noise  108  may be reduced from the voice signal to achieve high Signal-to-Noise Ratio (SNR) based on detection of acoustic characteristics of the signals. Examples of acoustic characteristics of a signal include, but are not limited to, amplitude, period, loudness, fundamental frequency, pitch and so forth. 
         [0040]    Sometimes, a pitch of a signal is a perceptual property characterizing vibration of vocal chords of a speaker. Further, the pitch may ascend or descend monotonically with frequency and may be used as parameter for signal representation and processing. Therefore, the pitch may be derived by calculation of a fundamental frequency of the voice signal. Typically, the fundamental frequency of a signal is inverse of a signal period that is a smallest repeating unit of the signal. 
         [0041]      FIG. 2  illustrates components of communication device  102  for reducing noise in the communication signals, in accordance with an embodiment of the invention. Communication device  102  includes a receiver  202  for receiving signals from communication device  104  over network  106 . Further, communication device  102  includes a transmitter  204  for transmitting signals to communication device  104  over network  106  through a communication channel. A person skilled in the art will appreciate that the functionality and circuitry of receiver  202  and transmitter  204  can be provided on a single physical component or housing. 
         [0042]    Microphone  206  of communication device  102  picks sound signals generated at communication device  102 . In an embodiment of the invention, communication device  102  may include multiple microphones  206  to pick the sound signals. Further, communication device  102  may include speakers  210  for outputting sounds. The sound signals picked by microphone  206  may be processed by a noise processor  208  to reduce and/or suppress background noise  108 . In an embodiment of the invention, communication device  102  may include a button, a switch or a function to enable or disable noise processor  208 . In an embodiment of the invention, noise processor  208  may be a processor that includes instructions set for processing the sound signals. The signals processed by noise processor  208  may be sent to transmitter  204  for communicating with communication device  104 . A person skilled in the art will appreciate that more than one communication device  104  may be in communication with communication device  102 . Therefore, transmitter  204  may transmit the signals to multiple communication device  104 . Noise processor  208  may use detect the pitch in the signals to identify noise and reduce it. The pitch detection scheme implemented by noise processor  208  is explained in detail in conjunction with  FIGS. 3 and 4 . 
         [0043]    In an embodiment of the invention, noise processor  208  may process the signals received from receiver  202  to reduce and/or suppress the noise in the signals. For example, in case the signals received from communication device  104  include noise, then noise processor  208  may process the received signals to output a clear signal through speakers  210 . Although not shown, communication device  102  may have other components such as a display screen, one or more buttons, a memory, a processor and so forth. 
         [0044]      FIG. 3  is an exemplary graph  300  of pitch versus frequency for a signal having noise, in accordance with an embodiment of the invention. As shown, f 0  is the fundamental frequency of the speech signal, and f 1  and f 2  are multiples of the fundamental frequency (f 0 ). And the other frequencies  304  may be due to noise in the signal. Noise processor  208  uses a pitch estimation function to estimate the pitch of the signal. The pitch estimation is illustrated as a pitch estimator  302  in  FIG. 3 . 
         [0045]    The pitch estimation may be performed by varying a value of pitch between the frequencies. For example, as show, pitch estimator  302  decreases up to a frequency of (f 0 +f 1 )/2 and then increases after (f 0 +f 1 )/2. A same process is used for pitch between the frequencies f 1  and f 2 . 
         [0046]    For a single sinusoid, the following equation gives the relation between a frequency ‘F’ and the pitch ‘P’ in the harmonic scale (Equation (A)): 
         [0000]    
       
         
           
             
               
                 
                   
                     P 
                      
                     
                       ( 
                       F 
                       ) 
                     
                   
                   = 
                   
                     
                       P 
                       ref 
                     
                     + 
                     
                       O 
                        
                       
                           
                       
                        
                       
                         
                           log 
                           2 
                         
                          
                         
                           ( 
                           
                             F 
                             
                               F 
                               ref 
                             
                           
                           ) 
                         
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     A 
                     ) 
                   
                 
               
             
           
         
       
     
         [0000]    where ‘P ref ’ and ‘F ref ’ are the pitch and the corresponding frequency respectively of a tone of reference and the constant ‘0’ is the division of the octave. 
         [0047]      FIG. 4  illustrates an exemplary graph  400  for the pitch corresponding to the frequency of a clear voice signal, in accordance with an embodiment of the invention. Graph  400  may be used to define the equations for the calculation of pitch. Further, a fundamental frequency  402  of the pure or clear voice signal is shown in graph  400 . The equation for the decreasing pitch estimator is calculated as follows. The slope of the equation for pitch estimation is given by: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       
                         Y 
                          
                         
                             
                         
                          
                         2 
                       
                     
                     
                       
                         X 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         X 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                   = 
                   
                     
                       
                         Y 
                          
                         
                             
                         
                          
                         1 
                       
                       - 
                       Y 
                     
                     
                       X 
                       - 
                       
                         X 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
       
     
         [0048]    When Y 1 =1, Y 2 =α, X 1 =pitch of pure voice signal, and X 2 =1.5*of pure voice signal, the above equation can be rewritten as 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       
                         1 
                         - 
                         α 
                       
                       
                         ( 
                         
                           
                             1.5 
                              
                             
                                 
                             
                              
                             pitch 
                           
                           - 
                           pitch 
                         
                         ) 
                       
                     
                     = 
                     
                       
                         1 
                         - 
                         Y 
                       
                       
                         X 
                         - 
                         pitch 
                       
                     
                   
                    
                   
                     
 
                   
                    
                   
                     
                       
                         2 
                          
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                       
                       pitch 
                     
                     = 
                     
                       
                         1 
                         - 
                         Y 
                       
                       
                         X 
                         - 
                         pitch 
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
       
     
         [0049]    The parameter a may be a smoothing factor to avoid abrupt changes in the equation value. In an embodiment of the invention, the value of a may range from 0.125 to 0.500. 
         [0050]    Rearranging the above equation, we get 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       2 
                        
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                        
                       
                         ( 
                         
                           X 
                           - 
                           pitch 
                         
                         ) 
                       
                     
                     pitch 
                   
                   = 
                   
                     1 
                     - 
                     Y 
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
       
     
         [0051]    Solving for Y, we get 
         [0000]    
       
         
           
             
               
                 
                   Y 
                   = 
                   
                     1 
                     - 
                     
                       
                         2 
                          
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                          
                         X 
                       
                       pitch 
                     
                     + 
                     
                       2 
                        
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
       
     
         [0052]    For nth fundamental frequency, the above equation becomes 
         [0000]    
       
         
           
             
               
                 
                   Y 
                   = 
                   
                     1 
                     - 
                     
                       
                         2 
                          
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                          
                         X 
                       
                       pitch 
                     
                     + 
                     
                       2 
                        
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                        
                       n 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
       
     
         [0053]    The Equation (5) is hereafter referred to as a first predefined condition. 
         [0054]    Similarly, the equation for increasing pitch estimator is obtained as follows: 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       2 
                        
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                     
                     pitch 
                   
                   = 
                   
                     
                       1 
                       - 
                       Y 
                     
                     
                       
                         
                           ( 
                           n 
                           ) 
                         
                          
                         
                           ( 
                           pitch 
                           ) 
                         
                       
                       - 
                       X 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
       
     
         [0055]    Rearranging the above equation, we get 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       2 
                        
                       
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                          
                         
                           [ 
                           
                             
                               
                                 ( 
                                 n 
                                 ) 
                               
                                
                               
                                 ( 
                                 pitch 
                                 ) 
                               
                             
                             - 
                             X 
                           
                           ] 
                         
                       
                     
                     pitch 
                   
                   = 
                   
                     1 
                     - 
                     Y 
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     7 
                     ) 
                   
                 
               
             
           
         
       
     
         [0056]    Solving for Y, we get 
         [0000]    
       
         
           
             
               
                 
                   Y 
                   = 
                   
                     1 
                     - 
                     
                       
                         2 
                          
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                          
                         
                           { 
                           
                             
                               [ 
                               
                                 
                                   ( 
                                   n 
                                   ) 
                                 
                                  
                                 
                                   ( 
                                   pitch 
                                   ) 
                                 
                               
                               ] 
                             
                             - 
                             X 
                           
                           } 
                         
                       
                       pitch 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     8 
                     ) 
                   
                 
               
             
           
         
       
     
         [0057]    Therefore, Y can be derived as 
         [0000]    
       
         
           
             
               
                 
                   Y 
                   = 
                   
                     1 
                     + 
                     
                       
                         2 
                          
                         
                           ( 
                           
                             1 
                             - 
                             α 
                           
                           ) 
                         
                          
                         X 
                       
                       pitch 
                     
                     - 
                     
                       2 
                        
                       
                         ( 
                         
                           1 
                           - 
                           α 
                         
                         ) 
                       
                        
                       n 
                     
                   
                 
               
               
                 
                   Equation 
                    
                   
                       
                   
                    
                   
                     ( 
                     9 
                     ) 
                   
                 
               
             
           
         
       
     
         [0058]    The Equation (5) is hereafter referred to as a second predefined condition. Therefore, the value of ‘Y’ represents the pitch of the signal at a reference frequency. 
         [0059]      FIG. 5  illustrates a flowchart for reduction of noise in a signal, in accordance with an embodiment of the invention. A signal may be processed by noise processor  208  of communication device  102  to remove noise. At step  502 , a pitch of the signal is determined. In an embodiment of the invention, the pitch of the signal is determined by using Equation (A). Thereafter, at step  504 , processing parameters of indices for Fast Fourier Transform (FFT) may be initialized. In an embodiment of the invention, the initialization of the indices for FFT may be used to define the various parameters such as bins of the FFT. At step  506 , resolution of the FFT may be calculated. Typically, ‘N’ point FFT provided ‘N’ frequency or FFT bins. The resolution of the FFT is given by: F s /N where is N is the FFT size and F s  is the sampling frequency. In an exemplary instance, in case the sampling frequency (F s ) is 8000 Hz a 256 (N) point FFT is used, then the resolution is 8000/256=31.25. 
         [0060]    Thereafter, at step  508 , the FFT resolution is compared with the pitch of the signal. Subsequently, at step  510 , a noise free signal or a clear signal is generated by multiplying the pitch with the FFT bins. In an embodiment of the invention, the multiplication is performed if the FFT resolution matches the pitch of the signal. N another embodiment of the invention, the pitch may be varied to match the resolution and remove the noise. The variation and comparison of the pitch is explained in detail in conjunction with  FIG. 6 . Therefore, a noise free clear signal is generated from noise processor  208 , which can be sent by transmitter  204  or outputted by speakers  210 . 
         [0061]      FIG. 6  illustrates another flowchart for reduction of noise in a signal, in accordance with an embodiment of the invention. Noise processor  208  may process the signal to remove noise based on the various parameters of the signal. At step  602 , a pitch of the signal is determined by noise processor  208  of communication device  102 . In an embodiment of the invention, the pitch is calculated by using Equation (A). In another embodiment of the invention, the pitch is calculated by using Equations (5) or (9). At step  604 , the indices for FFT are initialized, such as bins and resolution (hereafter referred to as ‘res’). Further, counters ‘k’ and ‘n’ are initialized to a specified value. In an embodiment of the invention, k and n have an initial value of 1. However, a person skilled in the art will appreciate that other values may also be selected. 
         [0062]    At step  606 , a comparison is performed between the ‘res’ and pitch. In case, k*res is more than n*pitch and less than (n*pitch+pitch/2), then pitch estimator (Y)  302  may be decreased, else the process is forwarded to step  616 . In an embodiment of the invention, pitch estimator  302  may be decreased by using Equation 5, at step  608 . Subsequently, at step  610  the value of bin of the FFT is calculated by multiplying Y with the original value of bin, i.e. bin(k)=Y*bin (k). As a result, the noise in the signal at the particular bin (or frequency) is removed. Thereafter, at step  612 , the value of k is incremented. In an embodiment of the invention, the value of k is incremented by 1. However, a person skilled in the art will appreciate that other increment values are also possible. At step  614 , the value of k is compared with a predefined number. In an embodiment of the invention, the predefined number is 128. In case, the value of k is less than the predefined number then the process continues at step  604 . 
         [0063]    At step  604 , in case the comparison is not satisfied then another comparison is performed at step  616 . At step  616 , in case, k*res is more than n*pitch and less than (n+1)*pitch, then pitch estimator  302  may be increased. At step  618 , pitch estimator  302  may be increased. In an embodiment of the invention, pitch estimator  302  may be increased by using Equation 9. Thereafter, the process continues at step  612  as discussed above. In case, the condition at step  616 , are not met than process continues to step  612 . Therefore, each of the bins of the FFT for the signal are processed based on the estimated pitch to remove noise from the signal. 
         [0064]      FIG. 7  is an exemplary diagram illustrating amplitude corresponding to samples of a speech signal mixed with a noise signal. As shown, the white noise is present in the signal. Further, in this example the Signal-to-Noise Ratio (SNR) may be 6 dB. 
         [0065]      FIG. 8  is an exemplary diagram illustrating a data rate of the noisy speech signal corresponding to the number of frames. As shown, in  FIG. 8 , the data rate is mostly active only when the speaker is speaking. 
         [0066]      FIG. 9  is an exemplary diagram illustrating the pitch of the signal corresponding to the number of frames. Further, the diagram illustrates that the pitch exists only when the speaker is speaking. 
         [0067]      FIG. 10  is an exemplary diagram illustrating the value of pitch estimator corresponding to the number of frames, in accordance with an embodiment of the invention. In an embodiment of the invention, the higher value of the pitch estimator results in higher pitch detection and subsequently may be used to remove noise from the signal. 
         [0068]      FIG. 11  is an exemplary diagram illustrating a spectrogram of the noisy speech signal before noise reduction. A region  1102  illustrates noise in the high frequency regions of the signal. 
         [0069]      FIG. 12  is an exemplary diagram illustrating the spectrogram of the noisy speech signal after noise reduction, in accordance with an embodiment of the invention. The noise may be reduced by noise processor  208  and a noise reduced portion is shown by a region  1202 . In an embodiment of the invention, the noise in the high frequency regions which mask the speech signal may be reduced to generate an enhanced or clear signal. 
         [0070]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope the invention is defined in the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 
         [0071]    Disclosed embodiments include, but are not limited to the following items: 
         [0072]    Item 1. A method of enhancing the quality of an input audio signal, the method comprising the steps of: 
         [0000]    a) estimating a pitch estimation value of the input audio signal;
 
b) decreasing the pitch estimation value based upon a fundamental frequency of the audio signal, based upon a first predefined condition;
 
c) increasing the pitch estimation value based upon a fundamental frequency of the input audio signal based upon a second predefined condition; and
 
d) multiplying the resulting pitch estimation value by one or more FFT bins to enhance the input signal.
 
         [0073]    Item 2. The method of item 1 wherein the FFT bins are derived by using the fast Fourier transformation applied to the pitch estimation. 
         [0074]    Item 3. The method of item 1 wherein the resulting pitch estimation value is multiplied by one or more processing parameters used upon the input audio signal. 
         [0075]    Item 4. The method of item 1 using a noise processor to perform pitch estimation. 
         [0076]    Item 5. The method of item 1 using a noise processor to adjust the pitch estimation. 
         [0077]    Item 6. The method of item 1 wherein the input audio signal includes both a noise component and a voice component. 
         [0078]    Item 7. A system for enhancing the quality of an input audio signal, the system comprising; 
         [0000]    a processor configured to:
 
a) estimate a pitch estimation value of the input audio signal;
 
b) initialize a plurality of processing parameters for the input audio signal;
 
c) decrease the pitch estimation value based upon a fundamental frequency of the input audio signal and a first predefined condition; and
 
d) enhance the input audio signal by multiplying the pitch estimation by one or more of the processing parameters.
 
         [0079]    Item 8. The system of item 7 wherein the processor is configured to decrease the pitch estimation value based upon a fundamental frequency of the input audio signal and a second predefined condition. 
         [0080]    Item 9. The system of item 7 wherein the input audio signal contains both noise and voice signals. 
         [0081]    Item 10. A system for enhancing the quality of an input audio signal, the system comprising; 
         [0000]    a) one or more microphones configured to acquire an input audio signal;
 
b) a processor configured to estimate a pitch estimation value of the input audio signal;
 
c) the processor further configured to initialize a plurality of indices for a Fast Fourier Transform (FFT) of the input audio signal; and
 
d) the processor further configured to enhance the input audio signal by multiplying the pitch estimation value by one or more of the indices of the FFT.
 
         [0082]    Item 11. The system of item 10 wherein the processor is further configured to decrease the pitch estimation value based upon a fundamental frequency of the input audio signal based on a first predefined condition. 
         [0083]    Item 12. The system of item 10 wherein the processor if further configured to decrease the pitch estimation value based upon a fundamental frequency of the input audio signal based on a second predefined condition. 
         [0084]    Item 13. The system of item 10 wherein the processor is further configured to initialize a plurality of processing parameters for the input audio signal. 
         [0085]    Item 14. The system of item 13 wherein the processor is further configured to enhance the input audio signal my multiplying the pitch estimation value by one or more of the processing parameters. 
         [0086]    Item 15. A method of enhancing the quality of an input audio signal, the method comprising the steps of: 
         [0000]    a) estimating a spectrum pitch value of an input audio signal; and
 
b) mathematically manipulating the spectrum pitch value by one or more spectral bins to enhance the input audio signal.
 
         [0087]    Item 16. The method of item 15 wherein the estimated spectrum pitch value is one or more FTT bins that are derived by using the fast Fourier transformation applied to said estimation. 
         [0088]    Item 17. The method of item 15 including the step of decreasing the spectrum pitch estimation value based upon the spectrum pitch of the input audio signal. 
         [0089]    Item 18. The method of item 15 including the step of increasing the spectrum pitch estimation value based upon the pitch of the input audio signal. 
         [0090]    Item 19. The method of item 15 wherein the resulting spectrum pitch estimation value is multiplied by one or more processing parameters used upon the input audio signal. 
         [0091]    Item 20. The method of item 15 using a processor to perform the spectrum pitch estimation. 
         [0092]    Item 21. The method of item 15 using a processor to adjust the spectrum pitch estimation. 
         [0093]    Item 22. The method of item 15 wherein the input audio signal includes both a noise component and a voice component. 
         [0094]    Item 23. A system for enhancing the quality of an input audio signal, the system comprising; 
         [0000]    a processor configured to:
 
a) identify a pitch estimation value of an input audio signal;
 
b) initialize a plurality of processing parameters for the input audio signal;
 
c) decrease said value based on a fundamental frequency spectrum of the input audio signal and a first predefined condition; and
 
d) enhance the input audio signal by mathematically manipulating the estimation by one or more of the processing parameters.
 
         [0095]    Item 24. The system of item 23 wherein the processor is configured to decrease the pitch estimation value based upon a fundamental frequency of the input audio signal and a second predefined condition. 
         [0096]    Item 25. The system of item 23 wherein the input audio signal contains both noise and voice signals. 
         [0097]    Item 26. A system for enhancing the quality of an input audio signal, the system comprising; 
         [0000]    a) one or more microphones configured to acquire an input audio signal;
 
b) a processor configured to estimate a pitch value of the input audio signal;
 
c) the processor further configured to initialize a plurality of indices for a Fast Fourier Transform (FFT) of the input audio signal; and
 
d) the processor further configured to enhance the input audio signal by multiplying the pitch estimation value by one or more of the indices of the FFT.
 
         [0098]    Item 27. The system of item 26 wherein the processor is further configured to decrease the pitch estimation value based upon a fundamental frequency of the input audio signal based on a first predefined condition. 
         [0099]    Item 28. The system of item 26 wherein the processor if further configured to increase the pitch estimation value based upon a fundamental frequency of the input audio signal based on a second predefined condition. 
         [0100]    Item 29. The system of item 26 wherein the processor is further configured to initialize a plurality of processing parameters for the input audio signal. 
         [0101]    Item 30. The system of item 26 wherein the processor is further configured to enhance the input audio signal my multiplying the pitch estimation value by one or more of the processing parameters. 
         [0102]    Item 31. The system of item 26 wherein the input audio signal contains a noise component and a voice component.