TH42304A - Noise suppression in mobile communication systems. - Google Patents

Abstract

DC60 (15/12/42) Methods and devices are disclosed for suppressing honey-like noise in mobile communication systems where the digital processor associated with the speech encoder in a mobile phone receives an incoming speech sample stream and performs a Fast Fourier Transform on that stream. Inferential knowledge of the frequency spectrum points where honey-like noise occurs is used to determine which speech samples in the Fast Fourier Transform result have increased noise. The noise at these frequencies is then suppressed by approximating the interval between two adjacent frequency samples to suppress the noise in those samples in between, for example. And by performing a Fast Fourier Transform on the incoming speech stream, inferential knowledge about the frequency spectrum points where the buzzing noise occurs is used to determine which speech samples in the Fast Fourier Transform have increased noise. Subsequently, the noise at these frequencies is suppressed by approximating the interval between two adjacent frequency samples to suppress the noise in that sample, for example.

Claims (9)

1. Methods for suppressing noise in mobile television include the following steps: obtaining a signal sample from a microphone; performing a Fast Fourier transform on this sample; determining a number of frequency positions associated with the Fast Fourier transform where the noise occurs; and suppressing the noise at one or more of these frequency positions. 2. The method of claim 1, in which the suspension procedure includes estimation of the range between a certain number of frequencies adjacent to one or more such frequency positions. 3. The method of claim number 1, which states that the mobile radio includes digital mobile radios. 4. The method of claim number 1, in which the radiotelephone shall include a GSM mobile phone. 5. Methods for suppressing noise in mobile communication systems, which include the following steps: determining whether the incoming sample from the microphone contains no speech; if so, performing a Fourier transform on the incoming sample by derivative of the first expression Xnew(n) = (X(n-1) + X(n+1) ) / 2 and the second expression N(n) = X(n)-Xnew(n) for n multiplied by the access rate of the system and divided by the sampling rate, which is further divided by a number of points relating to the aforementioned fast Fourier transform, where n is set to equal a predetermined series of numbers; estimating the noise signal N(n) for each noise frequency of a certain number of noise frequencies relating to a certain number of points; and suppressing the noise at one or more of those points. 6. A mobile phone, which includes a converter for converting a number of analog signals from a microphone into a sample signal, which is then converted into a series of digits, and a digital processor connected to such converter. This digital processor will be able to: perform a Fast Fourier transform on the aforementioned digitized sample signal; determine a number of frequency positions associated with the occurrence of the Fast Fourier transform noise; and suppress such noise at one or more of those frequency positions. 7. A mobile phone under claim 6, whose digital processor is capable of performing the function of suppressing such interference by estimating it over a range between a number of frequencies adjacent to one or more such frequency positions. 8. Mobile phones under claim number 6, including digital mobile radiophones. 9. Mobile phones under claim number 6, including GSM mobile phones.