> Taking all factors into consideration, I'd have to side with Den-Kara's cousin. :-) I think I'm forced to go with the physicist's definition of the radio's Sound being "mechanical vibrations of energy as transmitted by pressure waves through the air." That's because even if you physically leave the house -- thereby removing your own "observer status" for subjectively experiencing the radio's sound with your own ears -- you can, nevertheless, assign non-human observers to witness the sound in your absence.

> Say, for example, you set up a microphone with a timed tape recorder that reports specific intervals during which the radio was on. When you get back to your house, you play back the tape recorder and objectively verify that the radio did indeed make noise during your absence. A direct human observer to the auditory event is not necessary. This methodology is called deductive inference. We use techniques like this, in our everyday lives, to learn many things about our immediate environment which we ourselves did not (or cannot) directly observe.

> Wolfspirit

As I've already mentioned, /both/ definitions of "sound" are correct -- there's not a "right" or "wrong" way to refer to that word in an abstract sense. However, you have a persuasive argument...I'm starting to think that the answer to the question "If a tree falls in the forest, or a radio is left on in a cottage, and nobody is around, does it make a sound?" /must/ be "yes". Here's why:

Let's accept, for a moment, Den-Kara's definition of sound as "the sensation perceived by the sense of hearing". In this case, it's obvious that if a radio is left on and nobody is around, then the radio doesn't make any sound -- it creates pressure waves, but nobody's aural and nervous system is around to translate those pressure waves into "sound". Den-Kara would argue (I imagine) that if you take a tape recorder and record the radio, then play it back, it's /not/ the radio that created the sound. The radio created pressure waves which were recorded, but it was the tape recorder and not the radio that produced the waves that were turned into sound.

The problem with this argument is what happens when you consider the following scenario: Let's say there's a cottage, and somebody in it, /and/ there's a radio that's on. Does the radio produce a sound? The answer must be, "No!" Sound is defined, in this case, as a sensation created by a sense of hearing. The radio does not have a sense of hearing. It is therefore /incapable/ of producing sound. All it can do is create pressure waves. Somebody else's sense of hearing /might/ interpret those pressure waves as sound, but in that case, it's the person's sense of hearing and /not/ the radio that actually produced the sound. So according to this definition of "sound", a radio can /never/ produce sound, regardless of whether or not somebody is around.

Clearly, this is absurd. The question "does a radio produce sound when nobody is around" seems to imply that if /somebody/ is around, then the radio /will/ produce sound. This can only be true if sound is defined as pressure waves, since pressure waves are the /only/ thing that the radio can produce. Thus, Wolfspirit's definition of sound is the only one that fits the question, and her answer must be correct.

Of course, the way we get around this is simply to rephrase the question: "If a radio is left on in a cottege and nobody is around, is a sound produced?" This version of the question does not assume that the sound must be produced by the radio -- so neither definition of "sound" is implied.

-SB