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Author Topic: Does the sound of Big Ben reach radio listeners first?  (Read 2677 times)

Neil S. Briscoe

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Neil S. Briscoe  asked the Naked Scientists:
   
Hi

Years ago, it used to be the case that a man standing under the clock of Big Ben would hear the chimes later than a man listening on a (presumably short wave) radio.  This was because radio signals, travelling at almost the speed of light, can circumnavigate the globe seven times a second.  

The sound waves propagating down from the bell took longer to reach pavement level.

In this day of digital communications, which we know adds some delay, would the man in Singapore (listening via the Internet) pick up the sound before or after the man standing on the street below?

Regards
Neil, Bristol UK

What do you think?


 

lyner

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Does the sound of Big Ben reach radio listeners first?
« Reply #1 on: 15/04/2009 14:58:51 »
The main source of delay is in the coding of the analogue sound signal into digits, putting it into the 'multiplex' of the digital broadcast signal and back again. This takes about a half second (listen to DAB and FM at the same time).
So, if you were a couple of hundred metres from big ben, you might hear the two signals at the same time. (Traffic permitting)
The delay to Singapore for a digital sound signal would not be much different (only a few tens of milliseconds)
« Last Edit: 15/04/2009 15:00:57 by sophiecentaur »
 

Offline Karsten

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Does the sound of Big Ben reach radio listeners first?
« Reply #2 on: 17/04/2009 20:54:01 »
I once went to a drag race. The sound of the top fuel racer's engine (EXREMELY loud) reached us through the speakers before it reached us through the air. It was a bit weird but sure noticeable. But that sound was delayed directly without internet. When I talk to people via skype I hear myself sooner than I hear the sound arriving at my friends place. Assuming it has to be transmitted back to me, it probably arrives there still a bit later than mouth to ear. But then again, bell to ear is much further. Where are the microphones located for the Big Ben transmissions?
 

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Does the sound of Big Ben reach radio listeners first?
« Reply #2 on: 17/04/2009 20:54:01 »

 

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