----- Original Message -----
From: Charles Henry czhenry@gmail.com To: Jonathan Wilkes jancsika@yahoo.com; pd-list@iem.at Cc: Sent: Thursday, August 25, 2011 12:22 PM Subject: Re: [PD] Headphones question on pd list
On Wed, Aug 24, 2011 at 5:40 PM, Jonathan Wilkes jancsika@yahoo.com wrote:
Without knowing anything in advance about the speakers being used, is there
a way to construct some kind of [aural-faxbomb~] that outputs in the -1 to 1 range which could be used generally to at least get in the ballpark of what you want the maximum level of perceived loudness to be when wearing headphones?
You should be able to pick a suitable frequency band. A reasonable expectation is that headphones can produce sounds between 200Hz and 20kHz. Loudness seems to fall off pretty quickly above 10kHZ, so there's no point in including much of the higher frequencies, if avoidable.
Maybe another way to ask: can you construct an example patch with output
that is louder than [noise~]--[*~ max_float_value]--[clip~ -1 1]--[dac~]?
The spectrum distributes energy to frequencies that will not be reproduced or perceived loudly (which should be the case for the above, having a very flat spectrum). If the sound gets focused into a smaller band, which is more relevant for speakers/hearing, the loudness will be greater.
I think one place to start looking is a non-bandlimited square wave function. It's known that this kind of function has odd-numbered partials that fall off according to 1/n, or in other words, the power spectral density falls off at -6dB/octave.
The only problem with this function is that again the sound could be more focused into a narrower band. One thing that comes to mind is multiplying square waves together (since this keeps the values at +1/-1), but that would only distribute more energy to higher frequencies. What about PWM?
I think we are designing the worst possible sound here. "Sound check. Play the horrible noise, so we know nothing that comes after that can sound as horrible."
That's what I meant by [aural-faxbomb~]. A fax bomb is a completely black page continuously sent to a fax machine, which uses up all the ink. I would imagine that this sound, continuously played, would wear out the speakers -- not to mention one's ears. But one could use it as a reference point to set levels. (I'm not sure an actual faxbomb has any use other than wreaking havoc.)
-Jonathan