[dalythu]

I would like to see a program that uses the iPhones mic to detect ambient noise and cancel them out so that i could use normal headsets and have the iPhone as a built in noise canceler. It could run in the background of the ipod. Would anyone else like to see this?

[RonanM]

Sorry, not possible. The speaker is too far from the mic. The mic needs to be less than 0.5cm from the speaker to cancel frequencies up to 30kHz. At about 30cm, or 12 inches, noise cancelling could only be acheived for frequencies up to about 500Hz. Without even considering the processing power, the harmonics that can be filtered are physically dependent on the distance of the speaker to the mic.

[gameviper]

agreed with ronanm

[smuth]

Originally Posted by RonanM

Sorry, not possible. The speaker is too far from the mic. The mic needs to be less than 0.5cm from the speaker to cancel frequencies up to 30kHz. At about 30cm, or 12 inches, noise cancelling could only be acheived for frequencies up to about 500Hz. Without even considering the processing power, the harmonics that can be filtered are physically dependent on the distance of the speaker to the mic.

i feel like Ronan has gone to college

[gQstatus05]

Ronan just owned this thread!

[RonanM]

Thanks guys, it was nuthin' really. I guess smart people "Mod their I-s"
I wrote my first sound digitizer and compression algorythm in 1985, so I'm a bit long in tooth as far as this stuff goes. I'm not a professional, just do audio for fun.

For cost effectiveness, I would suggest in-the-ear phones. Simply put, they are not bad at blocking outside noise, by just plugging up the gap! Add a decent micro speaker, and you're set.

I use something like this in airplanes, index
and they perform better than the bulky, expen$$$ive digital noise cancelling mics. Stands to reason, the same would hold for the iphone.

I havn't tried the iphone specific ones like V-moda Duo, or Ultimet Ears Super.fi 4vi (yet). V-moda has (on paper) a better frequency response, but audiophiles seem to like ultimate ears more (then again, they also like analog, vinyl and tube amps)

The best one is the one that sounds best to you, not the one that necessarily produces the most exact copy of the original sound.

Oh, and rip your music at 192k-256k. I find 128k is OK for a car stereo, just doesn't cut it with the "3D" effect, or "imaging" when you play back on headphones.

I'll spare you the neurophysiology of 3-dimensional sound perception (unless you want to know more).

[the_seraphim]

i would love to know about the neurophysiology of 3-dimensional sound perception.. and yes i did register, just to ask this... honestly i want to know! lol

[RonanM]

I typed up a long description, but the forum would not take it, so rather than type it out again, I'll refer you to "Neuroanatomy" by MJT Fitzgerald, 3rd edition pages 158-162, ISBN 0-7020-1994-1. Should be possible to get this or similar at any library.
In summary, some spacial processing is done at the brainstem level. It is thought that some phase and tone processing is done there, and the resulting information forwarded to the cortex for additional interpretation.
The olovary nuclei can probably use phase and volume to source a sound.
The same sound arining at both ears will in one ear be louder, and be out of phase to a certain degree, depending on the frequency and direction.
Front/rear processing relies more on the tone profile of recognized sounds changing according to position. The shape of the ear will amplify higher frequency sounds from the fropnt, but from the rear, these same sounds are dampened.
If these effects are applied to a good pair of earphones, the sound can be made to seem like it is coming from any direction.
So why have a whole bunch of speakers for surround sound, if it can be done with two? In a less well controlled environment, eg a room or movie theatre, it is not possible to make the phase and frequency shifts work well for all positions of the listening area. More speakers means that the sound can actially be sent from close to the desired direction, rather than relying on simulating the end users experience.
A really good pair of headphones with spacializing software should give just as good, if not better result, except for the low base, which is sensed by the body, and not in the ears.

[Simtech]

^^^
That's what I was going to say...

[taniban@hotmail.com]

Utimate Ears are quality head phones. I own a pair but the connection at the end was loose because of me being stupid and careless. But the sound quality is very good.