Section 2. An ocean of sounds

The ocean is a rich and dynamic acoustic environment, teeming with sounds – from snapping shrimp and humming fish to singing whales, rumbling earthquakes, rain, and breaking waves.Even in the deepest parts of the sea where one might expect silence, sound is everywhere. 

Since the first measurement of the speed of sound underwater in 1829, scientists have come to understand how all these natural sounds contribute to a delicate acoustic ecosystem beneath the surface. For most of history, this soundscape was shaped primarily by natural sources. Today, however, human-generated noise from a range of human activities – including commercial shipping, industrial development, military exercises, fishing, and recreational boating – dominates many parts of the ocean, altering a world where life depends on sound, and posing a serious threat to marine life.

Why is sound important for marine life?

In the ocean, sound travels nearly 4.5 times faster than in air and much farther. It is the most reliable way to communicate and gather information underwater. As a result, marine animals, from fish larvae to blue whales, have evolved to use sound for nearly every major life function: 

Communication

• Finding mates through songs and calls
• Staying connected during migration
• Warning others of danger
• Defending territories 
• Parent-offspring communication

Finding food

• Using natural sonar (echolocation) to locate prey
• Listening for acoustic cues from prey
• Sharing information about feeding grounds
• In some species, stunning prey with powerful bursts of sound

Navigation

• Using consistent natural sounds (e.g., surf, reefs) as “acoustic landmarks”
• Listening to echoes from seafloor features 
• Following sound channels shaped by ocean currents and temperature

An increasing global threat

Since the industrial revolution, anthropogenic underwater noise from activities such as transportation, oil and gas exploration, construction, military exercises and recreational boating has become a major contributor to the ocean soundscape (Duarte et al., 2021).

Commercial shipping is the most pervasive source, with few areas in the ocean left unaffected (Jalkanen et al., 2022). Moreover, the problem is only expected to escalate in the coming years due to industrial expansion, increasing trade and tourism, and new Arctic shipping routes opening as sea ice melts. 

This global surge in underwater noise masks the important sounds that marine species depend on, disrupting communication, navigation, feeding, and reproduction.

The ocean soundscape

On land, a landscape refers to the visible features of an area, which may include both natural, geophysical features (e.g. mountains, coral reefs, and indigenous vegetation) and human-made structures (e.g. buildings and roads).

In the ocean, a ‘soundscape’ is the acoustic equivalent – it refers to the diverse array of sounds produced by animals, the environment, and human activities, varying across space, time, and frequency.

Studying soundscapes is a multidisciplinary field, linking: 

• Acoustics
• Physics
• Animal physiology
• Behaviour and ecology

Understanding ocean soundscapes is critical for conserving marine ecosystems and ensuring species can continue to listen, communicate, and thrive. 

Today’s ocean soundscape