Adaptive filters are the filters that can change its transfer function corresponding to the error feedback so that it can work on noisy environment.ie these type of filters can distinguish the input and the noise and can able to change its transfer function accordingly.
Many types of algorithems are there to implement these type of filters.The widely used algorithems are Least Mean Squares (LMS) and Recursive Least Squares (RLS).
Recursive least squares (RLS) algorithm is used in adaptive filters to find the filter coefficients that relate to recursively producing the least squares (minimum of the sum of the absolute squared) of the error signal (difference between the desired and the actual signal).Least mean squares (LMS) algorithms are used in adaptive filters to find the filter coefficients that relate to producing the least mean squares of the error signal (difference between the desired and the actual signal).

FIR filters are widely used in speech compression applications in mobile phones.

why we are using filters ? to get desired frequency of signals. For some applications, adaptive coefficients are required since some parameters of the desired processing operation (for instance, the properties of some noise signal) are not known in advance. In these situations it is common to employ an adaptive filter, which uses feedback to refine the values of the filter coefficients and hence its frequency response.

From my knowledge , answer is yes, i think the question is about the separation of voice from noise.For that it need an adaptive controller and an adaptive filter. The adaptive controller performs adaptive control to identify an impulse response of the communication system including the speaker and the microphone , and passes the identified impulse response to the adaptive filter . The transmission characteristics of the communication system determined by adaptive control are copied to the filter. The loudness-compensation-based gain determining unit determines the optimum gain be added to the voice-navigation signal based on the voice-navigation signal output from the filter and the noise signal .

However, a simple adaptive filter that gets the noisy speech and a reference noise is not generally a workable solution. Instead, with an array of microphones one can reinforce the signal coming from a certain direction and damp the others

• Written by Prakash.
• In category Engineering.
• 15 years ago.

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