Re: beats/sec VS Hz
- From: chuck <nospam@xxxxxxxxxx>
- Date: Thu, 27 Apr 2006 15:32:48 GMT
Jonathan ;o} wrote:
"Cy Shuster" <cy@xxxxxxxxxxx> wrote in message news:O8ednZ8EbYc4sM3ZnZ2dneKdnZydnZ2d@xxxxxxxxxxxxxx
"Herz" is the same thing as "beats per second". It's a unit of measure in physics, named to honor Heinrich Herz. You can use it for modem speeds as well as sound.
http://en.wikipedia.org/wiki/Heinrich_Rudolf_Hertz
Probably if you tune by ear, you might use "beats per second", and if you use an electronic device, Herz.
--Cy--
Hertz = cycles per second, as in note A above Middle C is a vibration of 440 Hz.
Beats per second = a "pulse" which occurs when two or more things (strings, reeds) of slightly different Hertz vibrate and consequently phase in and out in relation to one another.
Seems to me that if you have a reed vibrating at 440 cycles per second (Hertz), and another reed vibrating at 442 cycles per second, you can't measure the observed phasing of those notes (or "beats") in Hertz as well, hence the use of the other phrase.
A reed vibrating at 440Hz and another reed at 442Hz can phase in and out twice in one second, giving an observed "beat". As the pitch of one of the reeds is changed (or as a string is tuned) so do the beats. I don't know how closely the difference in Hz and the beats are related, and I also don't know if this is true for all frequencies. If so then a difference of 2Hz between two notes will always give 2 beats per second, which doesn't seem likely.
Anyone?
Jonathan ;o}
Keep it simple. Hertz and beats/second refer to exactly the same thing. The physics community, in keeping with their adopted practice of naming things after prominent physicists, stopped using "cycles per second" and began using Hertz some time ago.
Phase generally refers to the fraction of a complete cycle elapsed as measured from a specified reference point (http://www.thefreedictionary.com/phase). The notion of phase does not apply meaningfully to waves of different frequencies.
Technically, the 440 Hz and 442 Hz in the example produces a "beat" with a frequency of two Hz or beats/second. Any two sound waves will produce a beat equal in frequency to their frequency difference. This beat frequency is properly measured in beats per second or Hertz. But don't use the word phase here as the idea of phase is not involved. It would be better to think in terms of periodic reinforcement and cancellation of the sound waves as the mechanism producing the beats.
Chuck
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