Transient noise pulses differ from short duration impulsive noise, in that they have a longer duration, a relatively higher proportion of low-frequency energy content, and usually occur less frequently than impulsive noise. The sources of transient noise pulses are varied and may be electronic, acoustic, or due to physical defects in the recording medium. Examples of transient noise pulses include switching noise in telephony, noise pulses due to adverse radio transmission environments, scratches and defects on damaged records, click sounds from a computer keyboard etc. The noise pulse removal methods considered in this chapter are based on the observation that transient noise pulses can be regarded as the response of the communication channel, or the playback system, to an impulse. In this chapter we study the characteristics of transient noise pulses and consider a template-based method, a linear predictive model, and a hidden Markov model for the modelling and removal of transient noise pulses. The subject of this chapter closely follows that of Chapter 11 on impulsive noise.
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