[time-nuts] Striking change in iPhone time accuracy with 8.2
Chris Albertson
albertson.chris at gmail.com
Wed Apr 1 18:29:41 UTC 2015
On Wed, Apr 1, 2015 at 9:33 AM, Reid Oda <reid.oda at gmail.com> wrote:
... Once we got this lock, the
> clocks were then synchronized to within a few ms of each other. I estimate
> 8 ms, but our method (listening to ticks from a homemade app) was not ultra
> accurate.
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. Some musicians have learned to
keep in time and can hear a 20ms difference. Most people can hear a
50 ms delay. But as the clicks get close we hear them as one sound
If you have a computer with a microphone yo can record the clicks at
some high sample rate and then look at the spike on the audio
waveform. This WILL sub-ms clicks.
--
Chris Albertson
Redondo Beach, California
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