Unsupervised acoustic classification of individual gibbon females and the implications for passive acoustic monitoring

The dataset is comprised of 933 calls (range: 2- 46 calls per female) collected from 66 different individual Bornean gibbon (Hylobates funereus) females from five different sites in Malaysian Borneo: Maliau Basin Conservation Area, Deramakot Forest Reserve, Imbak Canyon Conservation Area, Danum Valley Conservation Area and Kalabakan Forest Reserve using a Marantz PMD 660 flash recorder (Marantz, Kawasaki, Kanagawa Prefecture, Japan) equipped with a Røde NTG-2 directional condenser microphone (Røde Microphones, Sydney, Australia). For each call we calculated MFCCs over a standardized number of windows (8) for each call, and the size of time windows we used to calculate MFCCs varied depending on the total duration of the call. For each of the 8 windows, we calculated 12 Mel-filters (or bandpass filters; Davis & Mermelstein, 1980)) between 500 and 1500 Hz, which corresponds with the frequency range of Bornean gibbon female great calls. The first MFCC for each time window corresponds to the amplitude or loudness of the signal; this will vary depending on the recording distance to the calling animal and is therefore not appropriate for discriminative tasks so we only used 11 MFCCs for each time window. MFCCs describe the spectral envelope at particular points in time, but do not capture temporal variation in the signal. Therefore, we also calculated delta-cepstral coefficients which provide a measure of change from one frame the next, and provide information about the temporal dynamics of the signal. As we estimated 11 MFCCs for each time window, we also had 11 delta coefficients. We also included duration, which resulted in a final feature vector of 177 parameters describing each call.