On a Falling Tree

Everyone knows this riddle: If a tree falls in a forest and nobody is there to hear it, does it make a sound? Here is the good news – I will answer the question. – However, the bigger question is will you agree?

The key is in the definition of two key words: sound and sound waves. The question is whether one considers these two terms as the same or different.

Sounds waves are sequence of a repeating pattern of high and low pressure waves passing through a solid, liquid, gas, or plasma. Waves can be of different frequencies, the number of repeated waves over a period of time (usually seconds). Think of different musical notes having different frequencies.

Sound is the interpretation of sound waves. From an organism’s point of view, in order for sound to occur, the organism needs a mechanism that converts sound waves into nerve impulses that are another mechanism translates them into a sound.

Does a dog whistle make sound waves? Unquestionably yes. Does it make sound? To a dog, yes – but to humans, no.

Does the symphony make sound waves? Yes. Does a totally deaf person in attendance hear the sound? No – not to them; but to one with healthy hearing, yes.

Therefore, the falling tree unquestionably produces sound waves – but if nothing is there that is capable of translating sound waves, there is no sound.

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50 thoughts on “On a Falling Tree

  1. Hi,
    I thought you explained sound very well.
    However if someone is deaf they do actually hear the music, just in a different sense, they feel the vibrations in a lot of cases, especially with an orchestra, these also are waves of a different kind. :)

    Very thought provoking video, but I love the song. :)

  2. Well first, I believe it is impossible to have a forest with “nobody” (an unspecific term with regard to animals or humans) in it, some body heard it. Agreed, sound waves etc.

    • Christine,
      And in the post, I used “organism” as my reference point. :) After all, a forest for no organisms capable of hearing doesn’t seem ecologically feasible. Thanks for stopping by.

  3. Very well explained. Now, if you go on to explain one hand clapping (something I have heard many times), you will totally disable the contemplation of the young, around the world (just kidding). Have a nice day.

  4. I have a Bruce Cockburn Christmas CD. Yes, I agree, this is like how years ago they didn’t think whales could talk to each other but now they know they have a really intricate language, it’s just we can’t hear it – and just because we can’t hear it, it doesn’t mean it doesn’t exist! xx

    • Spiced,
      I see we have another Bruce Cockburn fan (whom I did not know before this video). Ah ha … there are numerous ways to communicate! Thanks for visiting.

  5. I totally agree. it’s not about the noise making it’s about hearing. And if there’s no sense gate to perceive it , there’s no sound.

  6. This was interesting… I love these kind of questions and thinking… But I don’t think that if a tree falls and nobody hears… This seems to me impossible too…
    But but what they say, reminded me now… This is something in the philosophy like Schroedinger’s Cat… it will be going on to make busy our minds… :) Thank you dear Frank, with my love, nia

    Philosopher George Berkeley, in his work, A Treatise Concerning the Principles of Human Knowledge , proposes, “But, say you, surely there is nothing easier than for me to imagine trees, for instance, in a park and nobody by to perceive them. The objects of sense exist only when they are perceived; the trees therefore are in the garden no longer than while there is somebody by to perceive them.” Nevertheless, Berkeley never actually wrote about the question.

    Berkeley’s example is referred to by William Fossett twenty years later in a consideration of the emergence of meaning: “[T]ease apart the threads [of the natural world] and the pattern vanishes. The design is in how the cloth-maker arranges the threads: this way and that, as fashion dictates. To say something is meaningful is to say that that is how we arrange it so; how we comprehend it to be, and what is comprehended by you or I may not be by a cat, for example. If a tree falls in a park and there is no-one to hand, it is silent and invisible and nameless. And if we were to vanish, there would be no tree at all; any meaning would vanish along with us. Other than what the cats make of it all, of course.”

    Some years later, a similar question is posed. It is unknown whether the source of this question is Berkeley or not. In June 1883 in the magazine The Chautauquan, the question was put, “If a tree were to fall on an island where there were no human beings would there be any sound?” They then went on to answer the query with, “No. Sound is the sensation excited in the ear when the air or other medium is set in motion” This seems to imply that the question is posed not from a philosophical viewpoint, but from a purely scientific one. The magazine Scientific American corroborated the technical aspect of this question, while leaving out the philosophic side, a year later when they asked the question slightly reworded, “If a tree were to fall on an uninhabited island, would there be any sound?” And gave a more technical answer, “Sound is vibration, transmitted to our senses through the mechanism of the ear, and recognized as sound only at our nerve centers. The falling of the tree or any other disturbance will produce vibration of the air. If there be no ears to hear, there will be no sound.”

    The current phrasing appears to have originated in the 1910 book Physics by Charles Riborg Mann and George Ransom Twiss. The question “When a tree falls in a lonely forest, and no animal is near by to hear it, does it make a sound? Why?” is posed along with many other questions to quiz readers on the contents of the chapter, and as such, is posed from a purely physical point of view.

    • Nia,
      To me it’s not so philosophical, but one based on how one defines sound and hearing. Nonetheless, the philosophical view is interesting to ponder! Many thanks for visiting and sharing.

      • Dear Frank, yes I know, I just wanted to share these philosophical parts too :) I hope I didn’t make it so different from your subject… “Sound and hearing”
        This is really great subject in all ways… Sorry for this. You are welcome and Thank you, love, nia

  7. I have low end hearing loss below 3000hz, a genetic thing or another. Anyway, my ears do not hear that big thumping base from the cars with the big boom box speakers, but I can FEEL them. So I do not hear the sound so to speak, but can feel it due to the waves. Only folks with conjunctive hearing loss know what I mean. It also explains why I do not listen to much music any longer, it all sounds tinny or like the treble has been turned up big time.

    • Randel,
      Personal perspectives and examples are always good. Many thanks for sharing. Interestingly, you were here just before I visited your site. :) Thanks for stopping by.

  8. Dang, Randel got my answer – sort of. I worked with a deaf fellow, who could regain some hearing ability through bone transduction hearing aids. (Vibrates the head to get to the nerves, getting around damaged eardrums, which he lost to a childhood illness). Even without the aids, he could hear via the vibrations, especially in his car, which he had equipped with a massively powerful system.
    Although I guess you could add the old “What if the person hearing the sound wasn’t listening?” (Something we married guys are frequently accused of, right, Frank? :D )

  9. Excellent well thought out and written post, Frank.
    I think the more important question is “if a tree falls on a mime does he make a sound?”

  10. Ah, the difference between the science of sound and the perception of it. Though, assuming that we don’t live in a vacuum, it is highly likely that every sound vibration is perceived by something, whether the perceiver is human or not. We know that plants respond to music even if they don’t have hearing apparatus in the human sense. I tend to think of John Cage’s preoccupation with “silence” which of course was about the fact that there really is no silence in the physical world, merely selective attention. Great post, Frank.

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