Increased CO2 emissions caused by marine shipping have made the ocean less acoustically absorbent. As a result, animal sounds travel further, creating an underwater cacophony that may affect marine life.

The journal Nature Geoscience published a letter online yesterday suggesting these findings.

The researchers claim that oceanic pH levels have declined (i.e., become more acidic) due to a greater prevalence of CO2, especially in regions such as the North Atlantic that have lots of commercial ship traffic. As the water becomes increasingly acidic, a number of key sound-absorbing chemicals are broken down, and the marine atmosphere becomes far more resonant, particularly at low frequencies, near what human beings hear as bass.

For animals that communicate in this frequency range, the sonic environment may thus become cluttered and confusing. We can imagine an analogue of mass amplification on land: it is as if, gradually, the air began to carry people’s voices further and further, until conversations a block away were audible in our living room. We would feel stress, frustration, a compulsion to move to more remote places, and a need to reformulate our interactions in significant ways. Although the recent study does not include any behavioral research (though such research has been conducted elsewhere), the authors clearly imply that animals could act on similar impulses, with consequences for ecosystems.

For Sound Studies, these findings demonstrate the relevance of sonic material to any robust understanding of environments. The aural field is not absolutely divided from the chemical one. In fact, changes in either can affect the other directly. But because of a general prejudice about the distinction between senses (hearing and feeling, for example), the materiality of sound is not empirically obvious. As a result, sound is mainly interpreted as a source phenomenon, rather than as stuff that propagates and accumulates – that itself constitutes environments, and that thus should be a site of empathy. This connects to earlier discussions in the present space.

Finally, the situation underwater resonates with the actual situation above it, albeit owing to different causes. Technology – subwoofers, heavy traffic, air conditioners – is often the culprit when we complain about noise. More powerful devices mean that our everyday actions are broadcast further and further to a wide, if inadvertent, audience. Like seals and whales, we have to adapt our communications in response to the increased volume and density, inevitably faring better in some efforts than others.