Multimedia from “Perceptual Soundscapes of Dolphins and Whales,” by Eduardo Mercado III. Acoustics Today 20(3), xx-xx.
Multimedia File 1. Examples of a vocal continuum. Recording (10 kHz sampling rate) of five units produced by singing humpback whales off the coast of Hawaii in 2015 (sounds in this file were selected from NOAA recordings; thousands of examples publicly available at https://patternradio.withgoogle.com/). These units were not produced in the sequence shown but are ordered to illustrate the continuum of membrane oscillations used by singing humpback whales. The first unit provides an example of a slow vocal pulse rate produced by a singer (analogous to vocal fry in human singers) and the last unit is an example of one of a vocalization with a higher pulse rate (analogous to notes in the whistle register of human singers).
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Multimedia File 2. Examples of unit morphing by a singing humpback whale. Recording of an unaltered segment of song (10 kHz sampling rate) produced by a singing humpback whale off the coast of Hawaii on 2/28/2015. (audio from NOAA; visualization available at https://patternradio.withgoogle.com/#1425107153z7). This sequence of units is typical for this singer and for others recorded during this period, though the specific acoustic properties of units vary within and across singers. In this instance, the initial unit pattern includes both shorter duration units and longer, higher-pitched units. As the singer progresses through the song, the pitches of units gradually decrease, their durations gradually extend, and their form gradually changes. The higher pitched unit becomes less variable in frequency modulation and the lower-pitched unit gradually acquires a more stable onset pitch. Three minutes into the song cycle, the durations, pitches, modulations and patterning of units all vary considerably from the initial units, though they are all clearly variants of the units immediately preceding them. Six minutes in, the singer begins to gradually shift the higher-pitched unit down in pitch again. Seven minutes in, the lower pitch unit which originally was rapidly modulated in pitch has been transformed into a unit that is almost constant in pitch. By minute nine, the lower-pitched unit has almost nothing acoustically in common with its progenitor at the beginning of the cycle. This type of slow morphing of units is most perceptually obvious to humans when songs are played back at higher speeds than the speed at which the song was recorded.
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Multimedia File 3 (Quicktime Demo Movie). Examples of similarities in humpback whale songs across singers within a population. Pattern Radio (see https://patternradio.withgoogle.com/) also provides recordings and spectrographic images of recordings, such as the ones shown here, of singers made by a single, bottom-mounted (i.e., fixed) hydrophone in a format that allows anyone to see and hear similarities in songs. Because singing humpback whales rarely remain in the same locale for more than one or two days, it is possible to compare songs produced by different singers by examining recordings from dates separated by two or three days. Clicking on “Start Exploring” brings the user to February 11, 2015, at 9:03 AM. One can zoom out (using the scroll wheel of a mouse to make the images shrink) to see a song cycle between 9:03 and 9:09 and can scroll out further to see six consecutive song cycles between 8:45 AM and 9:23 AM, all produced by a single singer. This reveals the similarity in song cycles produced by one humpback whale within a single session of singing. The visual signatures of these songs can then be compared to those of other whales by sliding the center line to other days (or by zooming all the way out and selecting a different day). For instance, there are song cycles present on February 5th, starting around noon, that follow essentially the same pattern evident on February 11th, such that the visual patterns appear similar on both days. Zooming in on individual sounds within songs and listening to segments of songs from different dates allows for more detailed comparisons across singers.
