What's the most basic setup for tuning pipes?

This a more or less theoretical question:

Given some pipes freely hanging from a wire?,fishing line? or ...?, what could be the most elementary set up to measure their natural frequency when hit with a solid object?

I am talking about pipes open at both ends. I am basically aware that dimensions and resonant frequency ar closely related but I am not so familiar with common terms like "overtones" and the like.

My interest is focused on the setup to measure the resonant frequency or whatever is the name you give to that.

A small mike connected to an oscilloscope (not a DSO!) could help, I think, but since vibration is attenuated so quickly (for small pipes) how could I measure it reliably?

My bench is not fitted with sophisticated equipment, just a 10 MHz dual input scope.

Thanks for any reply.

Agustín Tomás

Resonance of a pipe open at both ends occur at whole multiples of half wavelengths of a sound wave. Thus the shortest pipe would be one-half wavelength of the sound. Knowing the velocity of sound waves you could calculate the wavelength at a certain frequency.

Wavelength in meter = v/f

where v = speed of sound in meter/sec
f = Sound frequency in Hz

Speed of sound in air is approx 332 m/s at 0 deg C and increase 0.6 m/s for every increase in deg C

if you have an oscilliscope that can display slow moving or non-repeating signals, you could store that sound wave and see it as if time were frozen.

You need at least a small speaker and some form of variable audio frequency generator. With the speaker placed near the opening of the pipe, by varying the frequency in the region as calculated you should be able to detect some amplification of the sound at resonance.

There are various tuning instruments available, the most common ones being for guitars - they aren't restricted completely to just the six strings, they usually cover bass guitar strings and 'drop tuning' as well. Obviously the more expensive ones are more versatile, but even those are still quite cheap.

As already suggested in an earlier post, together with your ideas, you have a pretty good system. You might use the speaker/audio generator as an exciter. It would seem that when the generator is at or near the resonant frequency of the tube, that the tube would ring, resonate or otherwise appear to amplify - and the output from a properly placed microphone would appear to increase, peak then decrease as you sweep past the resonant frequency.

I don't want to force your scope out of the picture but if you could accurate generate something loud enough to drive a small speaker (possibly sound card and your PC) then watch for the mic output to peak (then see what that frequency is) you'd have it. The output of a mic could be amplified slightly to drive an analog meter - all you need to know is the peak - the actual value isn't important. Got to wonder if you couldn't use a PIC to generate the audio - or even sweep thru the frequencies and make note of the peak.

Sounds like what you are looking for is the mechanical vibration of a tube and not the acoustic vibration of the air inside. What you have to calculate is the bending stiffness of the tube (spring) and the mass per unit length. The vibration mode is dependent upon the support type and location. Fixed on one end you have a quarter wave length, fixed on two ends you have half wave length. Fixed at quarter length you have one wave length (maximum displacement at both ends and middle, nodes at 1/4 and 3/4). Moving the support along the tube will effect the harmonic frequencies faster than the fundamental.
Hitting the tube at points other than the fundamental maximum displacement point will excite higher harmonics so if you are looking for the fundamental, strike it at midpoint for a tube suspended at quarter length. Same effect by plucking a guitar string at the 12th fret rather than by the bridge.
Depending upon how sensitive your scope is you should be able to set the horizontal sweep trigger to a level that will start the trace at the moment of strike from the microphone output. Otherwise, run it through your stereo amplifier to get a signal level you can work with.
The acoustic fundamental wave length is slightly longer than the physical length of the tube depending upon the end conditions. For a simple thin wall tube it can be modeled as a spherical end.