Low frequency vocalizations attributed to sei whales (Balaenoptera borealis)

Abstract

Low frequency ͑Ͻ100 Hz͒ downsweep vocalizations were repeatedly recorded from ocean gliders east of Cape Cod, MA in May 2005. To identify the species responsible for this call, arrays of acoustic recorders were deployed in this same area during 2006 and 2007. 70 h of collocated visual observations at the center of each array were used to compare the localized occurrence of this call to the occurrence of three baleen whale species: right, humpback, and sei whales. The low frequency call was significantly associated only with the occurrence of sei whales. On average, the call swept from 82 to 34 Hz over 1.4 s and was most often produced as a single call, although pairs and ͑more rarely͒ triplets were occasionally detected. Individual calls comprising the pairs were localized to within tens of meters of one another and were more similar to one another than to contemporaneous calls by other whales, suggesting that paired calls may be produced by the same animal. A synthetic kernel was developed to facilitate automatic detection of this call using spectrogram-correlation methods. The optimal kernel missed 14% of calls, and of all the calls that were automatically detected, 15% were false positives.

Vocalization Source Level Distributions and Pulse Compression Gains of Diverse Baleen Whale Species in the Gulf of Maine

“…The sei whales were identified from their downsweep calls [9][10][11], hypothesized to be long-range contact calls potentially enabling coordinated activities, such as feeding [1,10] or breeding [10]. They usually occur singly or as doublets with approximately a 4-s separation ( Figure 1D) and sometimes as triplets.…”

“…From the beamformed spectrograms, the time-frequency characteristics of each baleen whale vocalization were extracted via pitch tracking [1,10,65,66] and applied for species classification. A pitch track describes the time-variation of the fundamental frequency in the vocalization signal.…”

“…The four baleen whale species analyzed here are fin whale (Balaenoptera physalus), sei whale (Balaenoptera borealis), minke whale (Balaenoptera acutorostrata) and an Unidentified Baleen Whale Species (UBWS) . Each baleen whale species was identified from its characteristic vocalization type: the fin whales were identified from their short duration 20-Hz center frequency calls [5][6][7][8]; the sei whales from their downsweep chirps occurring singly or as doublets with roughly a 4-s separation or sometimes as triplets [9][10][11]; and the minke whales were identified from their pulse trains [12][13][14] comprised of a series of click sequences (see Figure 1 here and also the Extended Data Figures 1-4 of [1]). The unidentified baleen whale species vocalized downsweep signals in the 30-60 Hz frequency range over a 2-3-second duration (see Figure 1J here and the Extended Data Figures 1B and 3A of [1]).…”

Using feature vectors to detect frog calls in wireless sensor networks

“…This ensures that the cross correlation of the kernel and white noise is 0. To achieve this, each kernel frame was constructed as a "Mexican hat" wavelet as described by Mellinger and Clark (2000) and Baumgartner et al (2008). However, since the frequency distribution of the M. iteratus call is asymmetric [see Fig.…”

“…This work presents a simple yet effective and computationally efficient method of accurately detecting M. iteratus calls in noisy recordings using both temporal and frequency features. Since no current work specifically addresses M. iteratus detection, our proposed technique is compared with spectrogram correlation used by Baumgartner et al (2008) to identify instances of sei whale calls in noisy underwater recordings. The performance of the two methods are evaluated using audio recorded from the remote WSN and the results are compared.…”