Formula to Find Resonant Frequencies?

On Sun, 13 Mar 2011 13:33:24 -0700, Jerry Avins wrote:

> Tim's setup -- a microphone, amplifier, and speaker --  provides an easy
> to find the dominant resonance. Just turn the gain up until acoustic
> feedback makes the system howl. The frequency of the howl is the
> strongest resonance. A notch filter that blocks that frequency will show
> the next weaker resonance.

You're crediting me with more sense than I showed -- mine was the "guy 
with education and no experience" approach, i.e. do a measurement and 
then do some system ID.  (Although, if you use a swept sine wave for the 
measurement, then the resonances will pop out at you when you make a Bode 
plot).

-- 
http://www.wescottdesign.com

On Mar 14, 9:33&#4294967295;am, Jerry Avins <j...@ieee.org> wrote:
> Tim's setup -- a microphone, amplifier, and speaker -- &#4294967295;provides an easy to find the dominant resonance. Just turn the gain up until acoustic feedback makes the system howl. The frequency of the howl is the strongest resonance. A notch filter that blocks that frequency will show the next weaker resonance.
>
> Jerry
> --
> Engineering is the art of making what you want from things you can get.

Wonder if you can demolish a house that way if the dB level is strong
enough? (from the inside!)


Hardy

On Mar 13, 12:01&#4294967295;am, Raeldor <rael...@gmail.com> wrote:
> Hi All,
>
> Is there a formula or mathematical concept to find the resonant
> frequencies in a sound wave?

No.

Resonance moght be a property of the scenario in which the
sound propagates. I say 'might be' because resonance may
or may not exist (it usually doesn't).

Rune

I don't know about from the inside, but consider the walls of Jericho. :-)

Jerry
-- 
Engineering is the art of making what you want from things you can get.

Jerry Avins wrote:
> I don't know about from the inside, but consider the walls of Jericho. :-)
>
> Jerry

Or more recently the Tacoma Narrows bridge.
Youngsters see
http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)

Rune Allnor wrote:
> Resonance moght be a property of the scenario in which the
> sound propagates. I say 'might be' because resonance may
> or may not exist (it usually doesn't).
>
> Rune

I had such a case once in a 'Discothek';

At certain Frequencies the 50x40cm metal casing of
the aircondition canal, at a certain distance from the
speakers, was just _SCREAMING_ at you :-P

	-rasp

Well,

94 dB SPL (sound pressue level) is 1 Pa.

Athmospheric pressure is about 100.000 Pa.

Therefore, 194 dB SPL would result in cavitation, probably crashing a 
house...



On 14.03.2011 06:56, HardySpicer wrote:
> On Mar 14, 9:33 am, Jerry Avins<j...@ieee.org>  wrote:
>> Tim's setup -- a microphone, amplifier, and speaker --  provides an easy to find the dominant resonance.

Just turn the gain up until acoustic feedback makes the system howl.

The frequency of the howl is the strongest resonance.

A notch filter that blocks that frequency will show the next weaker 
resonance.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>
> Wonder if you can demolish a house that way if the dB level is strong
> enough? (from the inside!)
>
>
> Hardy