I I T B o m b a y p c p a n d e y @ e e . i i t b . a c . i n I C A 2 0 0 4 , K y o t o , J a p a n , A p r i l 4 - 9 , 2 0 0 4 • Introdn • HNM •Methodology •Results •Conclusions 1 ICA 2004, Kyoto, April 4-9, 2004 / Session: SPP02, Paper No 00574 (Th.P3.17) Harmonic Plus Noise Model Based Speech Synthesis in Hindi and Pitch Modification By P.K. Lehana P.C. Pandey
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ABSTRACTIn harmonic plus noise model (HNM), each segment of speech is modeled as two bands: a lower "harmonic" part represented as amplitudes and phases of the harmonics of a fundamental and an upper noise part using an all-pole filter excited by random white noise, with dynamically varying band boundary. HNM based synthesis can be used for good quality output with relatively small number of parameters and it permits pitch and time scaling without explicit estimation of vocal tract parameters. We have investigated its use for synthesis in Hindi which has aspirated stops and lacks voiced fricatives. It was found that good quality synthesis could be carried out, including those of aspirated stops. The upper band of HNM was needed only for the palatal and alveolar fricatives. Sensitivity of output quality to the errors in glottal closure instants was studied and random perturbations exceeding 4% of the local pitch period resulted in noticeable degradation. Synthesis with pitch scaling showed that the frequency scale of the amplitudes and phases of the harmonics of the original signal needed to be modified by a speaker dependent warping function, obtained by studying the relationship between pitch frequency and formant frequencies for the three cardinal vowels spoken with different pitches.
Material: 2-channel recording of vowels for male and female speakers• Speech signal • EGG from imp. glottograph
Processing: – Estimation of pitch periods from• speech signal • EGG – Analysis of vowels for HNM parameters– Resynthesis, with 0 - 20 % perturbation in GCIs – Assessment of quality of resynthesized vowels
Material: Sustained vowels at different notes by male and female speakers
Processing:• Study of F0 & formants in cardinal vowels• Formant synthesis after interchanging the notes• Scaling of HNM parameters by pitch-scaling factor