Music of the Deep: An acoustic blueprint of sperm whale codas

Mudit Sinha; Sanika Chavan

cs.SDOct 25, 2026

Music of the Deep: An acoustic blueprint of sperm whale codas

Authors: Mudit Sinha, Sanika Chavan

Organizations: Independent Researcher, San Bruno, California 94066, United States

Abstract

Sperm-whale codas are usually described by the number and timing of their clicks. Earlier acoustic studies showed that individual clicks and longer coda sequences contain additional organization. We ask how that organization compares with music, whose smaller sounds also form larger units and ordered sequences. We compare codas with performed violin music, drum grooves, and sung melodies. Their sequences resemble music in some measures of predictability, yet codas show a different relationship between the smaller sounds within a unit and the order of units across a sequence. This combination was not observed in the musical references tested. Coda timing also varies coherently and carries information about individual callers. The recordings show another striking property: broad, reproducible variation along acoustic dimensions associated with human ratings of emotion, with a range comparable to human audio in most eligible tests. These findings motivate an acoustic blueprint that describes natural codas beyond their click timing. Its importance is apparent in synthetic audio: WhAM produces recognizable coda-like recordings, yet the tested clips remain distinguishable from natural codas in five of six acoustic comparisons after strict matching. The blueprint provides a fuller way to study natural codas and to evaluate how faithfully synthetic recordings represent them.

Figures & tables

Figure 1: Example codas and musical recordings used in the comparison, shown as waveforms and spectrograms. Each excerpt retains its original duration.

Question	What we measure	Main comparison or control
How do coda sequences compare with music?	Repetition, choices of next sounds, and prediction from earlier sounds	Unseen recording sources; matched event counts and frequencies; repetition-aware prediction
Do smaller sounds organize each unit similarly?	Contribution of constituent types and their original order to whole-unit acoustic form	Timing-only prediction; rearrangements retaining the same sounds and onset positions
What information is carried by click timing?	Coordinated changes in intervals and prediction of caller identity	Shuffled timing; unseen dates; recording-metadata and label controls
How much emotion-relevant variation occurs?	Reproducibility and range along human-rated valence and arousal directions	Validation on held-out human audio; resampling by recording source; measured-acoustic adjustment
Do selected properties respond to alteration?	Changes in sequence and waveform measurements following order or timing edits	Randomized changes and controls for edit severity
Do synthetic codas reproduce natural acoustics?	Natural–synthetic difference across six acoustic descriptions	Independent natural reference sets and strict matching of measured recording properties

Table 1: Main measurements and controls used in this study.

Figure 2: How constituent composition, original ordering, and earlier sequence context contribute in codas and the three structured musical references. Asterisks mark Holm-corrected ordering or prediction results; full estimates and controls appear in the Supplement.

Finding	Result	Reference or control
Adjacent click intervals change together	Correlation $0.13$	Shuffled reference near $-0.12$ ; adjusted $p=0.0015$
Phrase-final timing shift	$p=0.061$	Not supported after correction
Caller recognition from repertoire and rhythm	Balanced accuracy $0.43$	Shuffled labels $0.12$ ; $p=0.0012$
Caller information beyond recording context	Accuracy gain $+0.19$	95% interval $[0.05,0.31]$
Caller recognition from fine timing	Balanced accuracy $0.36$	$p=0.0008$
Human-validated reference directions	23 of 24 eligible	One excluded from confirmatory tests

Table 2: Main timing, caller, and emotion-reference results.

Figure 3: Strictly matched natural–WhAM acoustic comparison. Points show residual MMD 2 gaps relative to an independent natural–natural reference; bars show 95% intervals. Five of six intervals lie above zero. The comparison uses 17 generated codas within joint measured-nuisance support and two independent weighted natural donor panels.

Bioacoustics

Bioacoustics uses sound to study animal activity, communication, biodiversity, and ecological change.

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Rhythm of the Deep: Two-tier acoustic organization of sperm-whale codas from click waveforms to coda sequences
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Tufts University, Medford, MA, USA

Jun 15, 2026J/K move · Enter open · S save

Rhythm of the Deep: Two-tier acoustic organization of sperm-whale codas from click waveforms to coda sequences

Mudit Sinha, Sanika Chavan

Independent Researcher, San Bruno, California 94066, United States

Bioacoustics

Open paper AskPDF arXiv

Sperm-whale codas are usually described by the number and timing of their clicks. These measures have revealed patterns in whale communication, but leave open how click sound contributes beyond timing and whether the order of whole codas carries additional structure. We investigate these questions through two tiers of acoustic organization, first within codas and then across coda sequences. Frozen pretrained audio encoders provide a framework for measuring acoustic variation beyond timing. We use them to identify recurring forms independently for clicks and whole codas in 1,483 codas, then validate their differences through direct waveform measurements. Within codas, click sound provides information beyond timing alone, while timing remains informative when click composition is held fixed. At the level of complete codas, we also find recurring acoustic forms whose differences are not fully captured by conventional timing-based types. With these forms identified, we examine how ordering contributes at each tier. Within codas, click-form order adds little predictive information beyond composition. Across codas, knowing the last two codas improves prediction over knowing only the last one. Together, these findings support two tiers with different organizing rules: acoustic composition and rhythmic timing within codas, and predictive relationships among whole codas across recorded sequences.

Abstract

Bioacoustics

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Rhythm of the Deep: Two-tier acoustic organization of sperm-whale codas from click waveforms to coda sequences

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