Application of Time-domain Pitch Synchronous Overlap and Add to Simulate the Frequency Shifting Function in Hearing Aids
Date Issued
2010
Date
2010
Author(s)
Han, Shin-Ru
Abstract
Many listeners with medium-severe hearing loss present audiograms with high frequency loss descending profiles. These patients can resolve spectral cues normally for lower frequency signals, but they often show less ability to use high frequency information. Frequency shifting hearing aids, which transpose the high frequency components of input sounds to the low frequency region, are known to be beneficial for sensorineural severe-to-profound hearing impaired listeners with residual hearing in the low frequency region. Early studies with frequency-lowering technology reported mostly unfavorable results, and the devices never gained clinical popularity. However, as hearing aid technology becomes ever more sophisticated, it is appropriate to reconsider whether frequency-lowering hearing aids should be an amplification choice in those with high-frequency hearing loss. Slow playback is the earliest method of implementing frequency-lowering in hearing aids, while resulting in longer output signals. This can cause the input and output signals to be desynchronized in time. In this research, time-scale modification and slow playback are combined to simulate frequency-shifted speech. Time-scale modification can change signal length without changing the spectrum characters and let output signal the same length with input. The time-scaling algorithms used in this paper are LSEE-MSTFTM, SOLA and TD-PSOLA. In the analysis process, the time frequency analysis diagram and the pitch contour diagram are utilized to compare simulation result. G&L method has more steady result, but it costs too much time. SOLA method is faster while the frame length will affect the output result. For the affricatives in speech ,TD-PSOLA method tend to has incorrect speech length, On the whole, TD-PSOLA method has the best result in three methods.
Subjects
Frequency shifting hearing aids
Time-scale modification
LSEE-MSTFTM
SOLA
TD-PSOLA
SDGs
Type
thesis
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