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Bell ringing frequency

by UUallace
Tags: acoustics, resonance
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UUallace
#1
Dec2-08, 07:55 PM
P: 5
How do I calculate the frequency of an 8.5 cm diameter bell ?
The bell is cast brass for resonance, but I intend to activate it with a buzzer so sound will last for more than a few seconds. Does the weight affect anything other than volume ? I intend to use it inverted, supported near the "top".
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f95toli
#2
Dec3-08, 04:53 AM
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You don't.
For a real bell you would need to use numericial methods to solve the equations (unless you have a VERY simple bell, i.e. something very symmetric) but even then you are not very likely to get a useful answer, partly because real bells are note made of a "perfect" material; various imperfections etc (which in turn depends on how the bell was cast) can have quite a large influence on the resonance frequency.

Is there any reason why you simply can't measure the frequency? It should be easy, all you need is a microphone connected to the sound card of a computer+some suitable software.
DaleSpam
#3
Dec3-08, 07:19 AM
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P: 16,969
Here is a description of what you have to do to model the sound of a bell.

"dividing the surface of the bell into a grid made of 450 squares. 'There's an equation describing the vibration of each square, and the computer can solve all the equations simultaneously,' "

UUallace
#4
Dec3-08, 08:24 AM
P: 5
Bell ringing frequency

"a traditional English-bell profile "
What I need is the "dominant strike chord"

Any suggestions on "some suitable software" ?
f95toli
#5
Dec3-08, 09:32 AM
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Well, all you need is some software that can show you the frequency spectrum of the signal from the microphone. Sigview comes to mind and you can download a free trial version.

However, you could also try something VERY simple such as AP Tuner which is a program used to tune guitars, by default it will only show you what note you are playing (i.e. A, C# etc) but if you look n the "Recording Device and Calibration" it will also show you the last detected frequency.
Or, alternatively, you could just look up what frequency e.g. C# corresponds to (chances are that a bell will be reasonably well "tuned" to a note).
LURCH
#6
Dec4-08, 12:06 PM
Sci Advisor
P: 2,510
Alternatively, you could simply listen to the note the bill produces and try to find that same note on a keyboard. Then you can look up the frequency here:

http://www.phys.unsw.edu.au/jw/notes.html

or buy one of these:

http://www.pas-products.com/analive.html

And let it analyze the frequency for you.
UUallace
#7
Dec18-08, 12:28 PM
P: 5
I need piezo(?) alarms to ring my bell. I need a resonant frequencies of 392 hz and 1700 hz, 12 volts would be best. Also need a 30 minute timer.


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