[time-nuts] Striking change in iPhone time accuracy with 8.2

Hal Murray hmurray at megapathdsl.net
Wed Apr 1 16:50:58 EDT 2015

albertson.chris at gmail.com said:
> Sound travels at about 1 foot per ms.  So you can effectively delay the click
> on one phone my placing it 8 feet farther away then the other  phone.
> Adjust the distance until  the clicks seem to occur at the same time.   That
> said, I doubt your ears are sensitive enough to work at the single digit ms
> level.

Your brain uses the difference in arrival times at your ears to determine 
direction.  That works better with high frequency clicks rather than low 
frequency rumbles.  You can work out how good it has to be to get reasonable 
results, but it's well below 1 ms.

The usual test case is to jingle some keys.  Sit on a stool with your eyes 
closed.  Have a friend jingle the keys in various locations.  Right-left 
works well.  Up-down doesn't work very well.

It would be fun to play with a pair of beeping iPhones and see what sort of 
direction they appear to be coming from.  I wonder how much the length of the 
beep influences things.

These are my opinions.  I hate spam.

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