Whales make sounds to communicate, find one another, navigate and locate food. Sound travels far more effectively through seawater than light, so acoustic signals remain useful in dark depths or across distances where vision fails. Different species produce clicks, whistles, pulses, moans and patterned songs.
NOAA’s overview of why whales make sounds separates two broad groups. Toothed whales use high-frequency clicks for echolocation as well as social calls. Baleen whales generally produce lower-frequency sounds that can travel great distances, though their calls also include shorter or higher components.
A sound’s purpose cannot always be inferred from the recording alone. Researchers combine acoustic data with observations, tags and environmental measurements. The same call may function differently according to season or social context.
Seawater carries sound beyond the range of sight
Sound consists of pressure waves moving through a medium. In seawater it travels roughly four times faster than in air, with exact speed influenced by temperature, salinity and pressure. Lower frequencies usually lose energy more slowly over distance.
Ocean layers can bend sound because speed changes with depth. Some low-frequency energy becomes trapped near a minimum-speed layer known as the SOFAR channel. Signals following that channel may cross an ocean basin under suitable conditions.
Whales evolved within this acoustic environment. Their ears and sound-producing anatomy differ from those of terrestrial mammals. Body tissues guide incoming vibrations, while specialized structures transmit them to the inner ear.
The NOAA SOFAR explanation describes the physical channel used by scientists and marine animals. A whale does not need to call from its exact axis for ocean structure to influence transmission.
Toothed whales build acoustic pictures with clicks
Dolphins, porpoises, sperm whales and other toothed whales produce rapid clicks. An outgoing click strikes an object and returns as an echo. Delay, intensity and spectral changes provide information about distance, direction and target properties.
Structures in the nasal passages generate the sound. A fatty organ in the forehead called the melon focuses the outgoing beam. Returning echoes are received largely through fat-filled channels in the lower jaw and conveyed toward the ears.
Echolocation allows hunting in darkness. Sperm whales search at great depth, while many dolphins use click trains near the seafloor or within schools of fish. Click rate often increases as an animal closes on prey, culminating in a rapid terminal buzz.
Toothed whales also whistle or pulse for social communication. Bottlenose dolphins develop individually distinctive signature whistles. Calls can help maintain contact when animals spread out beyond visual range.
Baleen whales communicate with calls and songs
Baleen whales do not have the toothed-whale echolocation system. They produce moans, pulses, knocks and other calls, often at frequencies suited to long-range transmission. Blue and fin whale calls can contain substantial energy below the range of comfortable human hearing.
Humpback males arrange sound units into repeated phrases and songs during the breeding season. Individuals within a population tend to sing a shared version that changes gradually. Researchers study how new patterns spread between populations.
A whale song is structured behavior, not simply a single long call. A full performance can repeat for hours, while the song itself follows a hierarchy of units, phrases and themes. Its exact reproductive functions remain under study.
The Smithsonian account of humpback songs explains how hydrophones revealed these changing cultural patterns. Passive listening lets researchers collect information without approaching every singer.
Calls hold social groups together
Resident killer whale communities use repertoires of discrete calls associated with family groups. Calves learn the sounds around them. Call similarities can therefore provide clues about social relationships and cultural transmission.
Contact calls help animals coordinate travel or reunite after separation. Mothers and calves exchange signals, although quiet behavior may sometimes reduce detection by predators. Feeding groups can also coordinate through sound.
Context changes interpretation. A repeated sound near prey may accompany foraging, while a similar acoustic feature during social activity can serve another role. Tags carrying microphones and movement sensors help connect a call with the caller’s behavior.
Human noise can mask whale communication
Ships, seismic surveys, construction and sonar add sound to marine habitats. Noise overlapping a whale’s call can reduce the distance over which another animal detects it. This interference is called masking.
Whales may respond by calling louder, changing frequency, altering timing or leaving an area. Responses depend on species, exposure level and activity. A change in behavior does not by itself reveal whether there is a population-level effect.
NOAA Fisheries uses passive acoustic monitoring to study ocean noise and marine life. Fixed recorders, drifting instruments and autonomous vehicles can document animals in poor weather or remote water. Analysts must still distinguish biological sounds from vessels and geophysical noise.
Quieting technologies include better-maintained propellers, slower vessel speeds in suitable areas and construction methods that reduce unnecessary sound. Measures work best when they address the frequencies, places and seasons important to vulnerable populations.
Scientists identify callers without seeing them
Acoustic archives become more valuable over time. A standardized recording can be reanalyzed with improved software or compared with future soundscapes. Good metadata about location, equipment and calibration lets later researchers judge what the instrument could detect.
Indigenous and coastal communities also hold generations of knowledge about whale occurrence and behavior. Ethical research partnerships can combine local observation with instruments while respecting governance, attribution and limits on culturally sensitive information.
Frequency and distance complicate interpretation
Frequency is measured in hertz, while amplitude describes pressure variation. Human hearing covers only part of the whale acoustic range. Researchers may visualize recordings as spectrograms, which display frequency through time and make repeated patterns easier to compare.
Distance complicates loudness. A faint recording may come from a quiet nearby caller or a powerful distant one. Transmission loss varies with depth, seabed, surface conditions and frequency, so estimating source level requires an environmental model.
Whales also hear sounds made by prey, predators and the physical ocean. Ice movement, rain and earthquakes contribute to the natural soundscape. The ecological question is not whether the sea was ever silent, but how added noise changes biologically useful cues.
Sound management requires context. Reducing noise near feeding or breeding habitat may bring more benefit than the same reduction elsewhere. Speed measures can lower ship noise and collision risk together when routes overlap whale concentrations.
Hydrophone arrays reveal seasonal patterns
Hydrophones extend human hearing underwater. One recorder documents timing and frequency, while an array estimates direction from arrival-time differences. Long deployments reveal seasonal presence in places difficult to survey by ship.
Species identification relies on call patterns, frequency and context. Some calls are distinctive, but overlapping repertoires demand caution. Automated classifiers accelerate analysis and still require validation against expert-labeled recordings.
Tags add missing behavior. Suction-cup instruments record sound, depth, acceleration and orientation from an individual. Researchers can test whether a call coincided with feeding, social contact or travel instead of inferring purpose from sound alone.
Limits and value of acoustic records
Acoustic population estimates require known call rates and detection probabilities. A quiet animal is not absent and distant sound may be masked. Environmental models estimate how far a particular call could travel.
Listening has limits. Recorders sample particular places, equipment can fail and analysts may disagree about ambiguous signals. Combining acoustics with photographs, genetics and visual surveys produces stronger conclusions.
Public libraries let people hear animals rarely seen at sea, but recordings are sometimes shifted or accelerated into human hearing. Captions should disclose processing so listeners do not mistake an interpretation for the original experience.
Long records reveal change. Comparable monitoring across years can show altered timing, distribution or noise exposure, provided equipment and analytical methods are documented clearly. Paired with visual surveys and movement tags, those recordings convert distant calls into evidence about how whales feed, travel and maintain contact in an ocean where sight quickly fails.
Related reading: marine snow and pelagic and benthic zones.
