One of the types of objects in Praat.
A Harmonicity object represents the degree of acoustic periodicity, also called Harmonics-to-Noise Ratio (HNR). Harmonicity is expressed in dB: if 99% of the energy of the signal is in the periodic part, and 1% is noise, the HNR is 10*log10(99/1) = 20 dB. A HNR of 0 dB means that there is equal energy in the harmonics and in the noise.
Harmonicity can be used as a measure for:
The signal-to-noise ratio of anything that generates a periodic signal.
Voice quality. For instance, a healthy speaker can produce a sustained [a] or [i] with a harmonicity of around 20 dB, and an [u] at around 40 dB; the difference comes from the high frequencies in [a] and [i], versus low frequencies in [u], resulting in a much higher sensitivity of HNR to jitter in [a] and [i] than in [u]. Hoarse speakers will have an [a] with a harmonicity much lower than 20 dB. We know of a pathological case where a speaker had an HNR of 40 dB for [i], because his voice let down above 2000 Hz.
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© ppgb, June 10, 2003