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A decrease in the frequency of two southeast Pacific blue whale song types was examined over decades, using acoustic data from several different sources in the eastern Pacific Ocean ranging between the Equator and Chilean Patagonia. The pulse rate of the song units as well as their peak frequency were measured using two different methods (summed auto-correlation and Fourier transform). The sources of error associated with each measurement were assessed. There was a linear decline in both parameters for the more common song type (southeast Pacific song type n.2) between 1997 to 2017. An abbreviated analysis, also showed a frequency decline in the scarcer southeast Pacific song type n.1 between 1970 to 2014, revealing that both song types are declining at similar rates. We discussed the use of measuring both pulse rate and peak frequency to examine the frequency decline. Finally, a comparison of the rates of frequency decline with other song types reported in the literature and a discussion on the reasons of the frequency shift are presented. [ABSTRACT FROM AUTHOR]

Male fin whales, Balaenoptera physalus, produce a song consisting of 20 Hz notes at regularly spaced time intervals. Previous studies identified regional differences in fin whale internote intervals (INI), but seasonal changes within populations have not been closely examined. To understand the patterns of fin whale song in the western North Atlantic, the seasonal abundance and acoustic features of fin whale song are measured from two years of archival passive acoustic recordings at two representative locations: Massachusetts Bay and New York Bight. Fin whale 20 Hz notes are detected on 99% of recorded days. In both regions, INI varies significantly throughout the year as two distinct periods: a 'short-INI' season in September-January (9.6 s) and a 'long-INI' season in March-May (15.1 s). February and June-August are transitional-INI months, with higher variability. Note abundance decreases with increasing INI, where note abundance is significantly lower in April-August than in September-January. Short-INI and high note abundance correspond to the fin whale reproductive season. The temporal variability of INI may be a mechanism by which fin whale individuals encode and communicate a variety of behaviorally relevant information. [ABSTRACT FROM AUTHOR]

In this paper, the problem of detecting and recognizing North Atlantic right whale (NARW), Eubalaena glacialis, contact calls in the presence of ambient noise is considered. A proposed solution is based on a multistage, hypothesis-testing technique that involves the generalized likelihood ratio test (GLRT) detector, spectrogram testing, and feature vector testing algorithms. The main contributions of this paper are the inclusion of noise kernels for signals likely to produce false alarms and a second stage classification algorithm which extracts parameters from candidate contact calls and constructs a scaled squared error statistic for parameters which lie outside the range of expected calls. Closed-form representations of the algorithms are derived and realizable detection schemes are developed. Test results show that the proposed technique is able to detect approximately 80% of the contact calls detected by the human operator with about 26 false alarms per 24 h of observation. Testing data set included 44 227 right whale contact calls detected by eight human operators who performed visual and aural inspection of the data spectrogram. Data were collected in different periods from March 2001 to February 2007, in Cape Cod Bay, Great South Channel, and in the coastal waters of Georgia. [ABSTRACT FROM AUTHOR]

The North Atlantic right whale inhabits the coastal waters off the east coasts of the United States and Canada, areas characterized by high levels of shipping and fishing activities. Acoustic communication plays an important role in the social behavior of these whales and increases in low-frequency noise may be leading to changes in their calling behavior. This study characterizes the ambient noise levels, including both natural and anthropogenic sources, and right whale upcall parameters in three right whale habitat areas. Continuous recordings were made seasonally using autonomous bottom-mounted recorders in the Bay of Fundy, Canada (2004, 2005), Cape Cod Bay, (2005, 2006), and off the coast of Georgia (2004-2005, 2006-2007). Consistent interannual trends in noise parameters were found for each habitat area, with both the band level and spectrum level measurements higher in the Bay of Fundy than in the other areas. Measured call parameters varied between habitats and between years within the same habitat area, indicating that habitat area and noise levels alone are not sufficient to predict variability in call parameters. These results suggest that right whales may be responding to the peak frequency of noise, rather than the absolute noise level in their environment. [ABSTRACT FROM AUTHOR]

This paper addresses the problem of passive acoustic detection of contact calls produced by the highly endangered North Atlantic right whale Eubalaena glacialis. The proposed solution is based on using a generalized likelihood ratio test detector of polynomial-phase signals with unknown amplitude and polynomial coefficients observed in the presence of locally stationary Gaussian noise. The closed form representation for a minimal sufficient statistic is derived and a realizable detection scheme is developed. The receiver operation characteristic curves are calculated using empirical data recordings containing known right whale calls. The curves demonstrate that the proposed detector provides superior detection performance as compared with other known detection techniques for northern right whale contact calls. [ABSTRACT FROM AUTHOR]

Humpback whale song lengths were measured from recordings made off the west coast of the island of Hawai'i in March 1998 in relation to acoustic broadcasts ("pings") from the U.S. Navy SURTASS Low Frequency Active sonar system. Generalized additive models were used to investigate the relationships between song length and time of year, time of day, and broadcast factors. There were significant seasonal and diurnal effects. The seasonal factor was associated with changes in the density of whales sighted near shore. The diurnal factor was associated with changes in surface social activity. Songs that ended within a few minutes of the most recent ping tended to be longer than songs sung during control periods. Many songs that were overlapped by pings, and songs that ended several minutes after the most recent ping, did not differ from songs sung in control periods. The longest songs were sung between 1 and 2 h after the last ping. Humpbacks responded to louder broadcasts with longer songs. The fraction of variation in song length that could be attributed to broadcast factors was low. Much of the variation in humpback song length remains unexplained. [ABSTRACT FROM AUTHOR]

Discusses the vocal activity of fin whales in the Ligurian Sea. Relative simplicity of fin whale sounds compared to most other baleen species; Most common fin whale sound referred to as 20-Hz pulse; Variability in the specific acoustic characteristics of pulses; Example spectogram showing portion of fin whale pulse sequence.

We recorded a series of 34 fin whale vocalizations using four calibrated hydrophones in a towed array. The whale's location was determined using arrival-time differences of each call at the hydrophones. The recordings showed evidence of interference between signals propagating along direct and surface-reflected paths (the "Lloyd Mirror"). We made preliminary estimates of source level (SL) using a spherical spreading model of transmission loss. We then applied a conservative correction for the effect of interference by subtracting the maximum possible signal enhancement from the preliminary SL estimate. These adjusted spherical spreading estimates had a median of 171. dB re 1 µPa at 1 m, with a range of 159-184 dB. These are the first SL estimates that explicitly attempt to correct for possible interference effects. We also propose a method that simultaneously estimates SL and source depth by fitting a Lloyd Mirror transmission loss curve to the measured received level, known receiver depth, and source-to-receiver range. Attempts to apply this method to the present data set yielded inconsistent results, probably because of the small number of hydrophones available. With more hydrophones in the interference field, this new method should produce reliable estimates of SL and depth of vocalizing whales. [ABSTRACT FROM AUTHOR]

An abstract of the study "Acoustic Communication in Mysticetes," by Susan E. Parks and Christopher W. Clark is presented.

Presents information on a study that concluded that only male fin whales produce low-frequency vocalizations. Techniques used; Purpose of the vocalizations; Intensities of the vocal sequences.