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Summary: ××
AM-DEMODULATION OF SPEECH SPECTRA AND ITS APPLICATION TO
NOISE ROBUST SPEECH RECOGNITION
Qifeng Zhu and Abeer Alwan
Department of Electrical Engineering, UCLA
Los Angeles, CA 90095
ABSTRACT
In this paper, a novel algorithm that resembles amplitude
demodulation in the frequency domain is introduced, and its
application to automatic speech recognition (ASR) is studied.
Speech production can be regarded as a result of amplitude
modulation (AM) with the source (excitation) spectrum being
the carrier and the vocal tract transfer function (VTTF) being
the modulating signal. From this point of view, the VTTF can
be recovered by amplitude demodulation. Amplitude
demodulation of the speech spectrum is achieved by a novel
nonlinear technique, which effectively performs envelope
detection by using amplitudes of the harmonics and discarding
inter-harmonic valleys. The technique is noise robust since
frequency bands of low energy are discarded. The same
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