Investigations of the Quality of Speech Imitated by Alexandrine Parrot ( $$\varvec{ Psittacula~eupatria}$$ P s i t t a c u l a e u p a t r i a )

Abstract

Speech is an important means of communication. Like human beings, birds also use sounds to communicate their emotions. Harmonic plus noise model (HNM) has widely been used for high-quality analysis/synthesis of human speech. Some species of parrots, particularly, Alexandrine parrots, have been reported as possessing the capability of imitating the human speech. The objective of this paper is to investigate the quality of the speech imitated by Alexandrine parrots using HNM as an analysis/synthesis platform. Spectrographic analysis of the phrases recorded from human speakers and Alexandrine parrots showed that parrot's vocal tract does not remain stable during the production of longer phrases. For fricatives, the parrot's sounds are relatively weak in high-frequency content. The duration of noise burst is slightly larger for parrot sounds as compared to that of human beings. For the laughing sound, the formants of the parrot vocal tract are relatively clearer. The parrots are not able to produce the liquid sound /r/. The parrot is able to imitate most of the vowels to some extent, and imitated consonants are not intelligible. Perceptual evaluation of speech quality scores of the phrases imitated by parrots were around 2.2, when the percentage of voice part was fixed in the range 30---50 and noise part in the range 20---40. These investigations would be useful for extracting the information from their calls, behavior study of the endangered birds, safeguarding the crashes with aero planes, and defense-related activities.