Sounds crazy but I want to find out how I should go about determining
the resonant frequency of a water-filled bath tub. I'd have to take
into account different fill heights and bath tub materials of
construction for sure, but what sorts of organisations (in Australia)
are set up to tackle such an unusual request? |
Request for Question Clarification by
sgtcory-ga
on
29 May 2003 06:59 PDT
Hello bathberg,
I have written an email request to an Australian acoustic/vibration
analysis laboratory to see what they can offer, even if it's a good
lead.
In the meantime, another researcher may find a suitable answer for
you. When I get the information back, should the question already be
answered, I will offer what information I was able to gather for you.
Thanks for the question!
SgtCory
|
Request for Question Clarification by
sgtcory-ga
on
30 May 2003 07:23 PDT
Hello bathberg,
I've gotten a response from the company that I emailed. In short, they
confirmed my suspicion that a 'standard' may exist for these types of
measurements, depending on what your end desire is.
What is the ultimate goal you are trying to achieve? Are you trying to
reduce the noise and vibration, or do you wish to actually test
designs that are not yet built?
Their reply was as follows :
"I suspect that the person asking the question in fact wants a
different
test to the one he or she has asked for. For example, if the problem
relates to vibration isolation of spa baths, then you dont need to
know the
behaviour of the bath because there are standard documented solutions
for
solving noise & vibration generated by spa baths.
Nevertheless, the answer is that the resonant frequency(s) or more
properly
the modal frequencies of any structure (including a bath tab) can be
determined by either measurement or prediction modelling. The problem
is
that the cost of doing this is many thousands of dollars per
test/prediction."
While I agree with most of this reply, it's not our place to assume
that you don't want to pay the thousands of dollars for such testing.
The reply also assumes that you wouldn't need to know the behaviour of
the bath, however this may be the data that you indeed are after.
Thanks for the clarification -
SgtCory
|
Request for Question Clarification by
hedgie-ga
on
31 May 2003 04:44 PDT
Hi Bathberg
Sarge is quite right. Commisionning an professional firm
is expensive - and would produce a thick report which you
may not care to read.
However, if you describe a bit of what you are after and what
your resources are, not just financial but also time, skills,
equipment .. - perhaps we can come up with a useful answer.
The question is not crazy, but is incomplete: Complex object has
many frequencies, each with different mode of vibration. One way
to determine dominant frequencies is to hit the edge with a small
hammer and to listen. Next step would be to use a microphone and a
spectrum analyser (which you can rent for few days) and so on...
So - how complete, accurate and how expensive method you want?
|
Clarification of Question by
bathberg-ga
on
01 Jun 2003 04:16 PDT
SgtCory and Hegie, my question is not because I have vibration that I
wish to isolate. It's not even about spa baths. MORE DETAILS...I want
to INDUCE the vibration into an otherwise stable structure. Indeed I
want to maximise the intensity of vibration with respect to the
intensity of the inducing force intensity...an efficiency issue. I am
keen to find out the range of frequecies that will cause resonance for
a range of bath materials of construction in combination with a small
range of different fill heights eg half full and full. Any indication
of what I might be looking at in terms of cost to commission such
research would also be helpful. I will need Government grants to
advance this if laboratory modelling is the only way forward and I
work full time and have a wife and 3 young kids so life is busy.
Whilst I have many relevant skills (strong problem solving,
electro-mechanical tradesman) I can't set up a laboratory to find out
what I want and I don't have a lot of money.
|
Request for Question Clarification by
hedgie-ga
on
01 Jun 2003 12:06 PDT
Thank you bathberg
Your clarification was useful
but still not quite enough.
To do some measurements - as indicated above, may cost few hundred
dollars
and take few weekends. It does not have to be a huge project.
For some $2- to $200 you may get suggestions and advice how to start
-
- GA is fairly unique here.
But perhaps you want some theoretical guidance. That is also
possible
in the same price range . The size of the structure, the materials,
all have an effect and there are some simple rules of thumb and
solutions for simple structures (cylinders, plates ..). You will not
get exact numbers ( you
did not specified any structure or materials) but even if you would,
it
is not that simple.
A professional acoustical lab service would cost significantly more.
To set up a mathematical model itself
- a numerical model using Finite Elements and use large computer-
would start at few thousand dollars (USD).
Most professional studies do both - a numerical model
and measurements on a structure. With few iterations you are talking
of
of a study starting at 10 grands. Structures like a frame of an
impact printer are analysed this way, for example.
So - at this point, you may want to choose - to get some info on
standing
waves, some rules of thumbs on vibration of simple structures or some
advice
on how to mesure these properties on a contraption you have.
That will show you what you may get for $20. If it makes sense, you
may then proceed to more complex question and higher awards.
By The Way - you know stories of Tesla's experiments and the wine
glass demonstrations ?
hedgie
|
