Post by thread:Totally [OT]

So I'm building this MP3 player, and I'm listening to the music through headphones. Then I take the headphones off and hold them away so that I can still faintly hear the music. And the strangest thing -- there's a very dramatic drop in apparent musical pitch. I put the headphones back on, and the pitch goes back up. I take them off again and the pitch goes down again. Now, I don't think the frequency is actually changing (unless perhaps the bulb in the refrigerator is also staying on.) But I'm wondering what's going on? Is this a known phenomenon, i.e. large changes in apparent amplitude and/or apparent bandwidth translated by some psycho-acoustic process into changes in apparent frequency? Or perhaps I AM the psycho in 'psycho-acoustic'? :) -- Rich

Rich, I do think that there is a psycho-acoustic relationship between pitch and amplitude, however I thought that it was that changing pitch made the amplitude seem to change. I don't know about the reverse. Another thing that might be happening (more likely, IMO) is that there is significantly less low-frequency coupling between your headphones and your ears/head when they are removed from your head. i.e., the path from headphones thru air to your ear acts like a high-pass filter, possibly making music sound tinny. I have noticed this with headphones plugged into my CD player, for example. I don't know how well this would work, considering all the stange non-linear encoding which MP3 does, but you could try making an MP3 of a pure sine wave and then trying this experiment again. If there is only a change in loudness, then the answer is that the headphones need to be on your head to effectively transmit low tones. If you still hear a change in pitch, something else may be going on. Sean At 10:15 PM 4/6/00 -0700, you wrote: {Quote hidden}>So I'm building this MP3 player, and I'm listening to the music through >headphones. > >Then I take the headphones off and hold them away so that I can still >faintly hear the music. And the strangest thing -- there's a very dramatic >drop in apparent musical pitch. I put the headphones back on, and the >pitch goes back up. I take them off again and the pitch goes down again. > >Now, I don't think the frequency is actually changing (unless perhaps the >bulb in the refrigerator is also staying on.) > >But I'm wondering what's going on? Is this a known phenomenon, i.e. large >changes in apparent amplitude and/or apparent bandwidth translated by some >psycho-acoustic process into changes in apparent frequency? > >Or perhaps I AM the psycho in 'psycho-acoustic'? :) > >-- Rich > | | Sean Breheny | Amateur Radio Callsign: KA3YXM | Electrical Engineering Student \--------------=---------------- Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 spam_OUTshb7TakeThisOuTcornell.edu ICQ #: 3329174