Here we eliminate noise using an adaptive filter which is a system with a linear filter that has a transfer function controlled by variable parameters and a means to adjust those parameters according to an optimization algorithm.
An adaptive filter is a system with a linear filter that has a transfer function controlled by variable parameters and a means to adjust those parameters according to an optimization algorithm. Because of the complexity of the optimization algorithms, almost all adaptive filters are digital filters. The closed loop adaptive filter uses feedback in the form of an error signal to refine its transfer function.
As the power of digital signal processors has increased, adaptive filters have become much more common and are now routinely used in devices such as
• mobile phones
• digital cameras
• medical monitoring equipment
An adaptive filter is required when either the fixed specifications are unknown or the specifications cannot be satisfied by time-invariant filters. The adaptive filters are time-varying since their parameters are continually changing in order to meet a performance requirement. Adaptive filters are considered nonlinear systems; therefore their behavior analysis is more complicated than for fixed filters.
Various approaches are used for noise removal in signal processing.
• ANFIS method is being used for removal of noise from audio speech signals. An audio signal contaminated with noise is taken and inspected with eight types of membership functions: bell MF, triangle MF, Gaussian MF, two-sided MF, pi-shaped MF, product of two sigmoid MF, difference of two sigmoid MF and trapezoidal MF. Finally using ANFIS, the original audio speech signal is restored. The major advantage of this system is its ease of implementation and faster convergence rate.
• The number of different applications in which adaptive techniques are being successfully used has increased enormously during the last two decades. Some examples are echo cancellation, equalization of dispersive channels, system identification, signal enhancement, adaptive beam-forming, noise cancelling, and control.