Noise and Echo Cancellation
One of the key requirements in most real-life applications involving speech signals is that the speech should be devoid of unwanted noise and other interferences. Most embedded applications operate in nonideal acoustic environments. Ambient noise can often severely impair the quality of the speech signal, to the point that a person hearing it may not even be able to understand the content of the speech. If the speech is further processed by processing algorithms such as speech compression, these algorithms could potentially provide suboptimal performance when the input speech is noisy. Tasks such as speech recognition have even more stringent requirements for the quality of the speech input, and are particularly sensitive to background noise interference. To some extent such noise can be filtered using regular digital filtering techniques, but in many cases the noise does not follow a deterministic frequency profile and might even change dynamically. Such situations call for more advanced algorithms that can adapt to the noise and remove it. Besides noise, echo generated due to various electrical and acoustic reasons can also be a significant cause of signal corruption and must be eliminated. This chapter explores various techniques to reduce or eliminate noise and echo from speech signals, and looks at real-life applications where such algorithms are critical.
KeywordsSpeech Signal Little Mean Square Adaptive Filter Noise Suppression Noise Cancellation
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