Q: Finding resonant frequency

P

Peter Lowrie

Guest
Hello me again...Darn it.

This question is about finding the resonant frequency of a piece of
stainless steel. Wondering if there were formulae for this purpose I did
some searches in Yahoo and Google but, alas turned up nothing.

The piece of stainless is a 14swg perforated disc measuring 80mm in
diameter.

I hung it up by wire and recorded the sound it makes by tapping with another
piece of solid stainless, looped the sound file and attempted to measure it
with fft anaylsis but with disappointing results.

Who has bright ideas on methodology to accomplish a result?

Thank you for your indulgence.

PEL.
 
"Peter Lowrie" wrote ...
This question is about finding the resonant frequency of a piece of
stainless steel. Wondering if there were formulae for this purpose I did
some searches in Yahoo and Google but, alas turned up nothing.

The piece of stainless is a 14swg perforated disc measuring 80mm in
diameter.

I hung it up by wire and recorded the sound it makes by tapping with
another
piece of solid stainless, looped the sound file and attempted to measure
it
with fft anaylsis but with disappointing results.

Who has bright ideas on methodology to accomplish a result?

Thank you for your indulgence.
Click to expand...
Why can't you just measure the distance between a couple of
good-looking waveforms and calculate the frequency?
Shouldn't need to use FFT for something that simple.

Is the frequency of the "tink" sound different when you "hang"
it through different holes (in the perforation)? It may have more
than one mode of resonance.
 
You have the right idea but I would feed to output of the microphone into a
spectrum analyser. Look for peaks.

Another way might be to mount a small directional speaker next to the plate
and feed it with a sine wave. Bounce the sound off the steel into a
microphone. Ramp the frequency and look for the power _absorbed_ by the
steel plate. This should be a max at resonance..



"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vt6gls7g0bei3f@corp.supernews.com...
"Peter Lowrie" wrote ...
This question is about finding the resonant frequency of a piece of
stainless steel. Wondering if there were formulae for this purpose I did
some searches in Yahoo and Google but, alas turned up nothing.

The piece of stainless is a 14swg perforated disc measuring 80mm in
diameter.

I hung it up by wire and recorded the sound it makes by tapping with
another
piece of solid stainless, looped the sound file and attempted to measure
it
with fft anaylsis but with disappointing results.

Who has bright ideas on methodology to accomplish a result?

Thank you for your indulgence.

Why can't you just measure the distance between a couple of
good-looking waveforms and calculate the frequency?
Shouldn't need to use FFT for something that simple.

Is the frequency of the "tink" sound different when you "hang"
it through different holes (in the perforation)? It may have more
than one mode of resonance.
Click to expand...
 
CWatters wrote:

You have the right idea but I would feed to output of the microphone into
a
spectrum analyser. Look for peaks.
Click to expand...
Yep, did that.

Another way might be to mount a small directional speaker next to the
plate
and feed it with a sine wave. Bounce the sound off the steel into a
microphone. Ramp the frequency and look for the power _absorbed_ by the
steel plate. This should be a max at resonance..
Click to expand...
Ooh, that's clever it like a grid dip meter in RF apps.

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vt6gls7g0bei3f@corp.supernews.com...

Why can't you just measure the distance between a couple of
good-looking waveforms and calculate the frequency?
Shouldn't need to use FFT for something that simple.

Is the frequency of the "tink" sound different when you "hang"
it through different holes (in the perforation)? It may have more
than one mode of resonance.
Click to expand...
Hmmm. Situation Solved, as follows:

Who says the frequency has to me measured, it does not. The thing only has
to resonate.

Did it like this: Large air wound coil slipped ofer terminal with disk
attached, amplifier, sweep function generator...Viola, humming stainless
steel disk.

:-0 Peter Lowrie

PS: Thanks to those that helped.
 
In article <2017616.LFM6z2qoi2@xbox.pelnet.net>,
peterlowrie@consultant.com mentioned...
CWatters wrote:

You have the right idea but I would feed to output of the microphone into
a
spectrum analyser. Look for peaks.

Yep, did that.

Another way might be to mount a small directional speaker next to the
plate
and feed it with a sine wave. Bounce the sound off the steel into a
microphone. Ramp the frequency and look for the power _absorbed_ by the
steel plate. This should be a max at resonance..

Ooh, that's clever it like a grid dip meter in RF apps.

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vt6gls7g0bei3f@corp.supernews.com...

Why can't you just measure the distance between a couple of
good-looking waveforms and calculate the frequency?
Shouldn't need to use FFT for something that simple.

Is the frequency of the "tink" sound different when you "hang"
it through different holes (in the perforation)? It may have more
than one mode of resonance.

Hmmm. Situation Solved, as follows:

Who says the frequency has to me measured, it does not. The thing only has
to resonate.

Did it like this: Large air wound coil slipped ofer terminal with disk
attached, amplifier, sweep function generator...Viola, humming stainless
Click to expand...
http://www.mit.edu/~jcb/jokes/viola.html

steel disk.

:-0 Peter Lowrie

PS: Thanks to those that helped.
Click to expand...
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
On Thu, 11 Dec 2003 3:29:34 -0800, Peter Lowrie wrote
(in message <2017616.LFM6z2qoi2@xbox.pelnet.net>):

Did it like this: Large air wound coil slipped ofer terminal with disk
attached, amplifier, sweep function generator...Viola, humming stainless
steel disk.
Click to expand...
Peter,
I can't picture this. A coil attached to amplifier driven by sweep gen.
What's the "terminal"? How is it attached to the disc? Is this like a speaker
voice coil? You just drove a magnet or piece of metal attached to the disc?

More details, please.

Dave
--
DaveC
me@privacy.net
This is an invalid return address
Please reply in the news group
 
"Peter Lowrie" wrote ...
This question is about finding the resonant frequency of a piece of
stainless steel. Wondering if there were formulae for this purpose I did
some searches in Yahoo and Google but, alas turned up nothing.

The piece of stainless is a 14swg perforated disc measuring 80mm in
diameter.

I hung it up by wire and recorded the sound it makes by tapping with
another
piece of solid stainless, looped the sound file and attempted to measure
it
with fft anaylsis but with disappointing results.

Who has bright ideas on methodology to accomplish a result?
Click to expand...
get a guitar, kick the disc with a stick & compare the sound, when you
find exact tone it matches to a guitar tone (or piano tone) - basic
tone, not harmonics! than go to my site to se a tone frequency chart
under electronics/fan stuff 3 second page ... :)

-- Regards, SPAJKY
& visit site - http://www.spajky.vze.com
Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
E-mail AntiSpam: remove ##
 
In article <0001HW.BBFEA75100207E38F0080600@news.individual.net>,
me@privacy.net mentioned...
On Thu, 11 Dec 2003 3:29:34 -0800, Peter Lowrie wrote
(in message <2017616.LFM6z2qoi2@xbox.pelnet.net>):

Did it like this: Large air wound coil slipped ofer terminal with disk
attached, amplifier, sweep function generator...Viola, humming stainless
steel disk.

Peter,
I can't picture this. A coil attached to amplifier driven by sweep gen.
What's the "terminal"? How is it attached to the disc? Is this like a speaker
voice coil? You just drove a magnet or piece of metal attached to the disc?

More details, please.
Click to expand...
If you drive an unmagnetized core coil with an AC current from an amp,
the lack of magnetization will cause it to put out a very non-linear
magnetic field. It would be better to superimpose the AC on a DC
current so that the DC current causes the coil to stay magnetized for
the full AC cycle.

I built one of these with the 'I' laminations removed from the core of
an audio output transformer. I turned the steel side of a washing
machine into a speaker.


Dave
Click to expand...
--
@@F@r@o@m@@O@r@a@n@g@e@@C@o@u@n@t@y@,@@C@a@l@,@@w@h@e@r@e@@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@t@h@e@@a@f@f@l@u@e@n@t@@m@e@e@t@@t@h@e@@E@f@f@l@u@e@n@t@@
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top