If A Tree Falls In A Forest, Does It Produce A Sound If Nobody Is There To Hear It?
The first time I heard of this conundrum was in my first recording engineering class at Berklee College of Music.
The class was called “acoustics”, and it is the first class you take at the start of your M.P.& E. (music production and engineering) major.
This conundrum crossed my mind again in a guitar lesson yesterday, where I discussed “musical definitions” with a student.
I taught various definitions of abstract concepts like “rhythm” or “sound”.
When we got to the discussion of sound, I presented the student with the above conundrum before giving the definition of sound.
This lead to the student challenging the response to the conundrum.
Following are some thoughts I jotted down after the discussion I had in that lesson on the topic.
If you have a red object: is it really red… or do you merely just perceive it as red?
The answer is the latter.
It isn’t red if you don’t perceive it.
Its color is not an absolute quality.
In the absence of light, the red color isn’t there anymore.
The reason has to do with the definition of color.
the property possessed by an object of producing different sensations on the eye as a result of the way the object reflects or emits light.
It is a perception of a phenomenon or property, not of an absolute… the phenomenon being that we’re seeing the reflection of light leaving the object’s surface, reflected in such a way that predominantly more of the red part of the color spectrum is emitted to our eyes when reflecting from that object.
Looking at it another way: we’re perceiving a reflection of a part of the color spectrum (the red frequencies) where our brain interprets the perceived incoming signal as being red… as opposed to seeing the actual color of the box.
This is why in the absence of perception.. it isn’t red anymore.
How could there be an absence of that perception?
When it gets dark (absence of light).
The red color changes in our perception to a darker shade of red, till it disappears completely.
You could still see enough to see the (previously red) object, but it is going to look black now.
Is the color red still there?
No, it isn’t! We never saw the color of the object in the first place. We saw a reflection hitting our eyes.
THAT is why the definition of color (or any other visual stimuli) is perception and not true reality-based.
Someone who’s color blind is going to swear the red isn’t there and doesn’t exist.
He’s right: it isn’t because he can’t perceive it and because it is a property (a quality or characteristic) that gets perceived differently by different people for different reasons.
By the same token…
When you turn down the volume on a sound source, it quiets down.
The sound changes in property to the point where it disappears completely into silence.
Therefore: silence is the absence of sound.
Hence: there is no sound if nobody can hear it. It is a perception.
The same principle applies here as for color: when a tree falls and you are there to perceive it, you never hear a direct sound in the first place.
You perceive air molecules, moved by the motion of the tree, hitting your ear.
Sound is merely a perception of a transmission (air molecules traveling through the air and hitting your ear).
If the transmission isn’t there… it isn’t happening.
If a tree falls in the forest and there is one deaf person there right next to the falling tree: it didn’t produce a sound.
The deaf person couldn’t hear it.
If he can’t hear it, then that means that the silence never stopped.
Since “silence” means “absence of sound” you cannot have one and the other simultaneously. You either have silence or you’re hearing something (sound).
If you’re not hearing something, there is no sound.
The falling tree only produces a sound because we’re born with ears.
The concept of sound only exists because we have ears.
In other words: The existence of the concept of “sound” is dependent upon the existence of the means to perceive it
That is why the definition is centered on the fact that sound is a perception, not an absolute.
If it were absolute: then every tree falling in every forest at any distance from our ear would create exactly the same volume/loudness.
We all know that that isn’t the case.
Because we know that isn’t true, it’s not an absolute but a perception of a property.
To take this a bit further:
If that tree indeed falls in a forest and there is nobody there to perceive it, BUT there is a tape recorder there recording it: did it produce a sound?
It produced a motion of air molecules that hit the microphone connected to the recording device, and the recording device registered and recorded fluctuations of air pressure hitting its microphone.
Recording devices don’t record “sound”. Sound is an illusion.
Meaning: it is a perception of a phenomenon (vibration) which our senses INTERPRET as a sensation we call sound.
Recording devices pick up and record changes in air pressure which it records as voltages and frequency fluctuations (of electron motions in the electrical wires) inside the device.
When you later listen to the recording you made of that falling tree; even then you aren’t actually hearing a tree fall in that recording.
You are hearing a representation of registered air pressure changes, that were originally picked up by the mic and that are now played back in the form of voltage changes.
The recording device sends these voltage changes to a magnet in an attached speaker cone, which causes the cone to move back and forth.
That back and forth motion of the speaker cone during playback is a representation of the air pressure changes that hit the mic picking up the hits of pockets of air molecules.
And you are now perceiving all of this as something that sounds somewhat like a tree falling.
You aren’t really hearing that though.
You are instead “interpreting” the perception of a different phenomenon (speaker motion hitting air molecules to your ear) to be something you interpret as the sound of a tree falling.
Another good analogy: if you look at a movie of a tree falling down in a forest, but your volume is complete off on your TV set, did that tree produce a sound?
Well, could you hear anything?
If the answer is no, how can you have perceived a sound if you didn’t hear anything?
You’re really only assuming that the tree produced a sound based on past experiences with things falling.
It did probably produce motion of air molecules at the live event during the fall, but with nobody there to receive the transmission of that motion of air molecules, there was also no sensation happening to be interpreted into what we call “sound”.
That… is why the definition of sound cannot be based on anything else but merely being a perception of something.
Interesting stuff. 🙂
And THAT is one of the reasons why I love teaching so much.
I would never take the time to think about things so deeply or thoroughly if it weren’t for my students challenging and motivating me to do so.
I never would have thought about all the above, and these thoughts and ideas never would have come to me if it weren’t for the student who could not accept that the definition of sound is based on perception.
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