Ecologist’s Diary with Richard Beason: If a tree falls in the forest and no one hears it… it does make a sound!

“If a tree falls in a forest and no one is around to hear it, does it make a sound?” was a philosophical question posed by George Berkeley to explore various concepts relating to perception; is a sound only a sound if someone hears it, how much can we truly know about the unobserved world and so forth. I’m not looking to start a metaphysics debate (honestly!) but, for me, the answer is decidedly ‘yes, it does’. At least that’s the case if you happen to have an acoustic recorder somewhere in the vicinity of said tree when it falls.

fallen tree
Did this tree make a sound when it fell?

If the hypothetical tree, or anything else for that matter, only made sounds when someone was around to hear them then my research would be very dull with many days spent analysing hours of absolute silence. Fortunately, this isn’t the case and the growing use of automated acoustic recording devices is providing us with an ever increasing insight into this previously ‘unobserved’ world of sound.

Until fairly recently, if you wanted to record the sounds of nature you’d have to take a microphone and tape-based recording device into the field and do it yourself. Thanks to rapid developments in micro-electronics and digital audio storage technology, there now exists a variety of cost-effective, automated acoustic recorders (e.g. SOLO and Audiomoth) designed for this very task. You attach them to trees (preferably none about to do any falling), switch them on and then leave, only returning a few days, weeks or even months later to swap batteries and data cards.

The development of such devices has enabled researchers to simultaneously record sounds in different locations over long, continuous periods, in all weathers, day and night. It’s actually an advantage if, similarly to the falling tree question, no one is around to hear these sounds when they’re been recorded. Previously, there was always the possibility that any species being recorded could have been disturbed or otherwise influenced by the presence of the person recording them. Indeed, it’s benefits such as these that have seen the widespread adoption of camera traps by the ecological community.

You still end up listening to quite a lot of silence in this job, but it’s never absolute and there’s usually some light breeze or background sound of some kind. Recent approaches to examining the sonic environment, such as soundscape ecology, are even interested in sounds like these and any others emanating from a landscape i.e. its soundscape; not just those made by animals, known as biophony, but also non-biological natural sounds like wind and rain (geophony) and human-generated sounds such as gunshots, traffic and airplane noise (anthrophony). In addition to offering a potential wealth of biological and environmental information, recording a soundscape also preserves it for posterity and future comparison or analysis. While we have fossils, photos and maps to inform us what the world used to look like, there are very few records of what it sounded like pre-1970s!

Though a very brief introduction, hopefully I’ve given you some idea of the benefits that make this field of research so exciting. Sadly, I don’t have a recording of a tree falling in the forest, the best I can do for now is a large branch plus some of the more interesting non-silences I’ve recorded, but you’ll be first to hear it if/when I do so be sure to stay tuned.

Sound links & titles:

  1. A large branch doesn’t have quite the same impact as a tree
  1. Yes, deer: Adult red deer & calves in Richmond Park, London
  1. Wild boar in Hainich National Park, Germany
  1. Tawny talk: Female tawny owl & juvenile in Richmond Park, London

Read more Ecologist’s Diary posts here and more posts from Rich here!

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