[time-nuts] Visual clock comparison

Charles Steinmetz csteinmetz at yandex.com
Sat Apr 18 03:52:32 EDT 2015

/tvb wrote:

>That would make a fun time experiment. One that you should do and 
>report back to us.
>I see two experiments: one using LED flashes and one using speaker ticks.

The research has been done with audio tics.  Under ideal conditions 
-- fast tics (risetime < 1uS, duration < 10uS) mixed electronically 
and delivered to one speaker (to avoid differential air path delays 
and binaural effects) -- people can steer an adjustable tic into 
coincidence with a reference tic with an error of a mS or less.  (The 
"speakers" used for these experiments are piezoelectric sounders with 
acoustic bandwidths in the MHz region, much faster than any moving 
coil tweeter.)

I strongly suspect the flashing light (LED, flashtube) experiment has 
also been done.

Note that conditions must be optimized -- the output device (LED, 
flashtube, speaker) needs to have rise and fall times much shorter 
than the expected human perception limit (note that LED optical 
switching speeds range from nS to mS), and they need to present to 
the subject essentially coincidently (tics mixed electronically and 
delivered to one speaker, fast LEDs of the same color immediately 
adjacent to each other).

Best regards,


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