Hugh B. Morgenbesser
John Buck
Dept. of Elec. Eng. and Comput. Sci., MIT, 77 Massachusetts Ave., Cambridge, MA 02139
Peter Tyack
Woods Hole Oceanogr. Inst., Woods Hole, MA 02543
A digital system was developed for analysis, modification, and synthesis of dolphin signature whistles. These whistles are modeled as frequency modulated signals with harmonically related frequency components. This system provides control over specific acoustic features which may be used in playback experiments. The analysis subsystem breaks the signal up into short overlapping blocks of time and estimates the fundamental frequency for each block. The system outputs frequencies and energies for the first three harmonics. The modification subsystem facilitates the following user-specified alterations to these features: Exclusion of one or more harmonic, variation of the energy envelopes, shifts and scalings of the frequency contours, and time dilation. The synthesis subsystem reconstructs each harmonic separately and then sums them to create the synthetic signal. Three different approaches for making smooth transitions between consecutive time blocks are compared.