Nasalized Vowel Detection Based on a Threshold of an Acoustic Parameter

In this paper, a threshold based approach using an acoustic parameter derived from the modified group delay function is presented for the detection of nasalized vowels from the mixture of oral and nasalized vowels of normal speakers. It is shown through acoustic analysis on the modified group delay spectrum that during the event of nasalization additional formants (resonances) at various frequency locations are introduced. Also, it is found that the introduction of a new formant in low frequency region around 250Hz remains consistent irrespective of female or male speakers. By verifying this fact on the band-limited modified group delay spectrum that is capable of resolving two closely spaced formants, an acoustic parameter RMGD is formed. Utilizing RMGD, the idea of detection of nasalized and oral vowels is formulated as a two-class problem and solved based on a threshold based scheme .Simulation results on TIMIT database show that the proposed method detect nasalized vowel from the mixture of oral and nasalized vowel with 92% average accuracy.