Framewise heterodyne chirp analysis of birdsong

Harmonic birdsong is often highly nonstationary, which suggests that standard FFT representations may be of limited suitability. Wavelet and chirplet techniques exist in the literature, but are not often applied to signals such as bird vocalisations, perhaps due to analysis complexity. In this paper we develop a single-scale chirp analysis (computationally accelerated using FFT) which can be treated as an ordinary time-series. We then study a sinusoidal representation simply derived from the peak bins of this time-series. We show that it can lead to improved species classification from birdsong.