Are there generally accepted “sounds” or aural characteristics of the various materials used in making whistles? In other words, can it be said the aluminum is softer or more mellow than brass or nickle? Or that wood is more “airy” but quieter than plastic? (I just made those up as examples.) For example… Tony Dixon make two versions of his “Traditional” whistle, one in brass and one in nickle. Could we predict the tonal characteristics of each? Or does this depend more on its design and construction, than the actual materials used?
That’s a perennial debate. The short answer, I think, is that no one has been able to demonstrate a material-caused musical difference objectively (that is, scientifically) for either flutes or whistles, or really even to come up with a convincing model of how the science might work. Unlike a violin or guitar, in a flute or whistle no part of the instrument vibrates in producing the sound. It’s all air. There’s no analogue to the soundboard of a piano or the top and back of a guitar.
That said, lots of players and maybe some makers are pretty convinced that they can hear distinctive differences.
I’m with Simon on this one. I really can’t convince myself that the choice of the material makes a huge difference for exactly the reasons given. On many occasions I’ve made two or more whistles using wood cut from the very same piece and ended up with very different tones in the finished instruments. Very tiny variations in the dimensions of the blade, window, windway are inherent in handmade instruments, but these tiny variations can make a huge difference in a whistle’s sound. Sometimes a “tweak” of a whistle involves nothing more than a very light touch with an extra fine diamond needle file.
If wood doesn’t vibrate much, imagine how much less different metals vary especially if you look at a thick walled whistle such as a Copeland. I’ve heard people swear that brass sounds different than nickle, but I’ll bet that that difference is also due to variations in voicing.
Ok, my unconvincing model of how the science might work is that the vibrating air column sets up bending vibrations in the body of the whistle, which in turn either excite or damp additional vibrational modes in the air column. It seems that some whistles have bending frequencies in the acoustic range of the whistle. Different materials have different stiffnesses, so will behave in different ways. Of course, I haven’t tested this theory rigorously (yet). 
I could think of an experiment to test this. Set up a whistle with a precisely measured and regulated air source. Place a microphone at a precise distance, and attach a mechanical transducer (or multiple transducers) to the whistle body. Then record the acoustic spectrum of the whistle in air, and the vibrational spectrum of the whistle body.
Now air-drive the whistle again, but this time feed the vibrational spectrum back through the transducers at it’s original level but 180 degrees out of phase, while recording the acoustic (microphone) result. This should cancel any tube damping or resonance, simulating a perfectly rigid tube, and let you see the effect (if any) on the acoustic signature of the air column.
I opt with those who guess that material alone makes no discernible difference, though secondary characteristics of the material may, by affecting bore texture, fipple edge geometry, etc. But I’m willing to be convinced otherwise.
Yes - all I need is time and money
Time … sure. Money … I’d think you have most of the gear lying around the labs. A regulated air supply and tubing, microphone, piezo transducer. and a computer to record and run the spectrum analyzer. I guess you’d need an anechoic room, too.
But don’t listen to me. I’m the guy who once panicked the entire Physics department at Stony Brook when my experiment on audio modulation of plasma envelopes went wrong. My Faraday cage failed, and I ended up spewing RF energy all over the labs. The number of other people’s test equipment I screwed up corresponded roughly to the number of angry physicists who came running in to see me. 
I would think that any scientific study would have more than one sample and average the results. 10 would be a possible minimum of one type, 100 would be better. Considering that it only needs to play one note, and could be machined on CNC in large quantities, it would not be a real problem.
I like going to the hardward store and cupping and popping the palm of hand on the end of the different sizes of pvc piping. A sales clerk always stops by to see what’s going on.
I’ve got a different take on the materials used in a wind instrument. It’s been my experience that there are subtle differences in the tone depending on the density of the material used. For example the main wood I used to use for my low whistle heads was maple and I made a custom head out of Brazilian rosewood for a friend and the tone was definitely different. I think this mainly applies to the head as this is where the tone is generated. Granted, as Paul has pointed out, subtle differences in the voicing can shift the way the instrument plays but what I hear is a difference in timbre which I feel is due to the density of the material.
I believe that when the oscillations occur across the lip of a head they can’t help but set up a vibration in the surrounding material, subtle as it may be, it colors the tone of the instrument. The body of the instrument I believe is affected less than the head but it still picks up some of the vibrations inside it and to some degree affects the tone. I notice this affect mainly between brass and aluminum which have very different densities. These differences may be very difficult to hear for the average player, but for me, as I spend a large part of my day tuning whistles, are noticeable.
So perhaps it’s more about aesthetics for most people as to what materials are used and the whole discussion is a mute point.
Happy Thanksgiving
Ronaldo
What Ronaldo said.
No question in my mind that boxwood, rosewood, blackwood and cocus lend different sound
to flutes, ceteris paribus. His explanation is the most plausible one I can think of.
Most people can hear a difference between mute and moot, but I suspect it has a lot to do with one’s mood. 
Ah - the black art of whistle voicing.
I’ve found it to be true that the parameters of the windway, window, blade and bore have dramatic affects on the timbre.
But it seems a no-brainer that the materials will have some affect - If I were to make a whistle out of jello, I would expect a lot of the energy in the oscillation to be absorbed by the material. If one were to make a whistle put of something really really rigid (say diamond) then I would expect little or no energy loss.
Assuming some degree of energy dissipation by the material, It seems reasonable that different materials will have a different signature of what they remove from the energy spectrum. At the very least, I would expect some modulation to amplitude.
I aplaud the suggestion that empirical testing would yield results, however, there are some mittigating factors against that:
Firstly, The phenomenon that gives rise to sound from a whistle is fluid turbulence. The math is well known - it is a chaos system. As Paul has pointed-out, minute changes in the parameters produce large results. The results are non-linear and absolutely dependent on the starting conditions. This is one of the basic conundra of chaos systems - that it can be impossible to measure starting conditions in a chaos series. One can have absolute accuracy in the formula, but without the starting conditions, one cannot get an absolute answer. In this case, the starting conditions are at the molecular level and include the energy state of every molecule in the system - IF one had the technology to measure this, the very act of measuring would impose unpredictable changes and negate any empiracle result.
Secondly, The materials themselves have chaotic properties. Most materials have a fractal nature, once again, the distribution of structures in a material canot be predicted. This goes doubly for wood, which has a macro-fractal structure in addition to its micro-fractal structure. The macro-fractal signature is a different one from species to species. In the scale of a whistle, the density and resonant structure can vary significantly along teh length of teh whistle.
Thirdly, The behavior of tools changes as they are applied to different materials. - another multiplicative factor. Even more chaos.
Fourthly, the craftsman’s mood also affects the process of voicing. One can have a like or dislike of a material that will affect teh result. More chaos.
For myself, I don’t really care what causes the differences, I am accustomed to blackwood sounding like blackwood and gidgee sounding like gidgee.
But also consider, for someone who is a wet player - they will be playing a tube of water, no matter what the whistle is made of 
Geez Mitch that was well put!
Philo
I really should test it though - all I gotta do is work out how to make a jello whistle .. anyone got a 1-foot length of diamond they can spare?
(Actually, we whistle makers are all pulling your legs…the whole thing has to do with magic )
Don’t be modest. As long as you’re asking for diamond, make a low whistle!
Materials can make subtle differences.
http://www.youtube.com/watch?v=3Aa_0OnEwXM
SHHH! You’ll blow the gaff! I’ve got a little island picked out - it only costs the price of a 1-foot length! If I go too low, Europe will get suspicious!
Interseting posts and discussion - here’s some refelctions…
Just because the process is turbulent (and please note that turbulence and chaos are not necessarily the same thing. Trust me, I have a PhD in chaos theory and I’m a fluid dynamicist by day) doesn’t mean that it’s completely unpredictable. Actually the turbulence sets up a nice regular vibration in the air column which is extremely predictable.
Yes, materials have variable properties, particularly natural materials, but that doesn’t make their macroscopic behaviour unpredictable, or else I’d never set foot on a bridge or fly in a plane. Density variations along a wooden whistle might be significant, but somehow I doubt it. They certainly won’t be as significant as the change in structural stiffness/integrity caused by the hole placement.
Yup.
Ah, but I’m an engineer, so these questions keep me awake at night
Yup.