thin and thick walls

Whistle
1

I like to ask those of you who have experience with a variety of low whistles:
Are whistles with thin walls (with a body probably made out of brass tubing) easier to play than comparable thicker wall whistles (with bodies made probably out of aluminium tubing, or plastic, or other composite material)?

In some forum post I read that Howard low D whistles are easy to play because of the thin brass tubing of the body. I wonder if it is easier to close the holes if the wall is thin. or if some other reason makes thin walled whistles easier to play, if this is at all the case.

I guess any effect will not only show with low whistles, but in low whistles it will be more pronounced, because of the increased tube diameter, and increased hole sizes used.

What is your experience with thin vs. thicker walls?

~Hans

2

Hi Hans,

This is going to be a theoretical answer rather than an empirical one because I’ve not played very many different low whistles. But here goes…

For a given OD and hole diameter covering the hole will be the same no matter how thick the wall is. You finger interacts with the outer surface. For a given ID a thick wall instrument will have a larger OD of course, and covering a larger OD can be harder to do if you have small hands compared to the hole spacing.

Hole sizes and/or position will differ as wall thickness changes A tone hole vents the bore to the atmosphere. The hole is a chimney to the pressure waves in the bore and a longer chimney presents more resistance to the air moving through it if we can think of it that way. Thus to produce the same note with everything else being equal, it will require a larger hole in a thick wall. So while not strictly required, thick wall instruments would tend to have larger holes.

For example, in .113 in material the L1 hole is calculated to be 0.375 in in diameter and placed 11.702 from the bottom end of the whistle. Keeping everything else the same but making the wall thicker to .213 in, the same hole would need to be .418 in in diameter. I used flutomat to do this calculation, which is available here if you would like to explore it yourself.

http://www.cwo.com/~ph_kosel/flutomat.html

If the holes have very square or sharp corners they will act smaller than holes that are properly chamfered or undercut, so in practice there are things the maker can do to make this better.

In addition to reaching the holes there is the response of the instrument. Response meaning how quickly the note responds when you vent a hole. Thicker walls can take longer than thinner because the chimney is longer. But again other factors such as bore diameter and chamfering will affect this.

I personally feel that the material or rather it’s propensity to absorb sound of certain frequencies results in instruments of different materials delivering a different sound. And of course the design of the windway and fipple will be a big part of how the instrument plays. You might prefer the sound of a thick walled instrument to one with a thin wall.

These factors are just that - factors, to be managed by the designer into a pleasing package. It’s not possible to say this is good and that is bad, you have to consider the whole result. But I would say making a low whistle out of thin walled material allows the designer more freedom in selecting hole sizes and spacings. But they still have to get it right.

So have a look at the instrument you are considering before dismissing it for having a thick wall.

3

Hi Hans,

I find thicker walls create more of a solid sound which projects cleaner then a thinner walled low whistle. In violin or acoustic wood instrument construction it is important that the body resonates. This is not the case with whistle construction, the body should not resonate…the separation(tube wall) between atmospheric pressure and the pressure inside the tube is key to an efficient vibrating column of air that produces that beautiful pure sound.

Best Regards,
Greg

www.thelochlan.com

4

Hans

Greg and Carey have made some good points. I would like to add some “Acoustic Rules” to this subject.

Each tonehole is a cylinder. If that cylinder has any depth, it also contains a specific cubic volume of air. Under normal conditions, the first register has very low internal pressure and deep toneholes have little effect on the frequency. When a player “overblows” the upper registers, the increased pressure extends the “used” cubic volume of the aircolumn, up into the deep toneholes (and the bore end hole and voicing hole). This produces flat pitch that the player must compensate for by blowing harder (increased aircolumn velocity = higher frequency).

Simple conclusion: Whistles with a deep voicing but thin toneholes are more accurate in pitch across the registers as well as more “responsive” because the thin toneholes offer less resistance (the air flows freely into and out of thin toneholes). Deeper toneholes can improve acoustics if they are tapered on top and bottom, similar to the inside of a “doughnut”. The technical term is “Hyperboloid” like this…

The sharp edges of deep toneholes (shaped like a cylinder) create turbulence or “eddies” that disrupt and slow the response time. The main reasons Instrument Makers compromise and create Whistles and Recorders with deep toneholes is…

  1. To adjust the spacing between toneholes (Deeper toneholes can be placed closer together. The last tonehole on a Recorder is deeper so it can be placed closer and within reach of the pinky finger).

  2. Structural Integrity (Thin wood is prone to breakage and swelling from moisture)

3)Thin materials vibrate and rob the aircolumn of Acoustic Energy (dampen frequency amplitude). This energy should be transmitted to the soundwaves that travel through the air.

(I think I just put everybody to sleep.) :sleep:

5

I appreciate this question and discussion. Currently I’m playing around with 1/2" CPVC for a high D whistle and wonder if its wall thickness (0.075" - 1.9mm) is too great. Anyone care to comment on this?

Thanks.

RVC

6

It works just fine!

Carey

7

No, not at all! This is all very fascinating, also Greg’s and Carey’s answers. It would be nice to compare these theoretical considerations with practical experience of low whistle players.

Maybe this offers an explanation of buzzing, which I raised in another thread?
I could round the edges of all tone holes and see what will change…

One thing I like to add: if the wall is really thin, less than a millimetre, as it is with a brass tube, the fingers pressing on tone holes will actually protrude into the bore cylinder. they will not only eliminate tone hole air spaces, but act as constrictions in the bore, and make it virtually a bit slimmer. This should have an effect on the tuning as well.

I have not seen this geometrical effect being considered in a flute design spreadsheet or script.

~Hans

8

Hans

Yes, the fingertips that protrude into the bore on thin walled whistles actually help to correct pitch in the upper registers by reducing the internal cubic volume slightly. The player still must (subconciously) compensate a little for flat pitch, but less so in thin walled instruments.

9

RVC

You can sand “saddles”, like the “pits” on Recorder toneholes. This will reduce the thickness and is easy to do with a dremel tool sanding drum.
http://www.bradleyjacobs.com/carputer1/dremel-drum.JPG

10

even though in theory thicker wall instruments are slower to react, this theory has to consider how much slower and if the human ear can consciously recall this difference…the physics of what goes on happens a fair bit faster then the speed of your breath or fingers…to the human ear it is instant!!! but in theory there is a delay…this delay is not important because you cannot hear it…no man/woman on earth can move his/her fingers faster then what goes on inside and outside a tube to make sound…What is important is how clean and clear the note to note is,…so although a thinner walled whistle maybe a fraction of warp9 speed faster then the thicker walled whistle…the thicker walled instrument is clearer…and thats all you can really hear, which in effect sounds more responsive

Best wishes

Greg

www.thelochlan.com

11

Not taking sides on the specific wall-thickness thing … :wink:

… but I wouldn’t underestimate the speed of finger movements or acoustic perception either. For example, at a common reel tempo of 1/2 = 120, each eight note (quaver) takes 125 milliseconds. If you play a condensed roll on one of those notes, each of the 5 finger movements (note, cut, note, tap, note) takes around 25 milliseconds. And transients will occur even faster, and may be quite audible depending on your aural acuity. So it seems to me that a whistle’s physical response characteristics as short as 10 milliseconds or so may make a difference.

12

Greg -
you find a big difference trying to trill on a small hole or on a big hole. It shows what is generally perceived for flutes at least: that smaller holed flutes are faster than bigger holed flutes. But this needs to be balanced against power: bigger holes vent better and give more power. And we need to design for practically possible hole placements, so for big whistles and flutes hole sizes will be compromised because of position.

Take two low D whistles for example:
whistle A is made of aluminium tubing with 2.5mm wall thickness,
whistle B is made of brass tubing with 0.5mm wall thickness.
For equal bores and equally spaced finger holes you find that for whistle A you need to increase the hole diameters of hole 2 and 5 by 1.5mm over what you have for whistle B, because of the wall thickness. This is not insignificant. You could juggle hole sizes a bit by decreasing holes 3 and 6 a little, so holes 2 and 5 don’t need to be increased so much. You still will have 1mm bigger holes 2 and 5. This will have some effect on speed.
Edit: these calculations are wrong! See my next post!

But please don’t think I am advocating thin walled whistles, or think one is better than the other. I am merely curious about other’s experiences with whistles of different thicknesses. I am also taking your point that a whistle tube should not be so thin that it starts resonating, it needs to be stiff enough. my example may well be wrong in this: 0.5mm thick brass tubing might not be enough for a low D whistle. But I have no example at hand.

Cheers,
Hans

13

Mtguru…Wow!!! but sound still travels faster then your fingers…17cm per millisecond

Hans…I agree 100% …the trick seems to be balancing all of these factors.

Greg

14

Thick wall whistles are heavier than thin wall whistles.

15

Greg -
my example is flawed, in fact quite erroneous. While it is true that we would need on a thicker tube a bigger hole at the same location to achieve the same note, and thus would need bigger holes all along, if we wish to preserve the hole locations (as Carey pointed out above), we do not need to do so, if we just want to keep the same finger spread for left and for right hand, i.e. some hole locations fixed relative to each other.

My example should have shown that, but I mixed up the results: for whistle A we can actually reduce the hole sizes of the two biggest holes (2 and 5), relative to the thin walled whistle B. The difference is about 1mm; holes 2 and 5 are 1mm smaller for tube A (2.5mm walls) than for tube B (1mm wall)(1mm wall thickness is better for a low D brass whistle I reckon).

~Hans

16

More like 34 cm/ms, no? (I know, picky picky).

Just thinking out loud … 34 cm is about half the length of a low D whistle. Which means it takes around 4 milliseconds (OK, 3.4 ms) for the standing wave of a bell note D (294 Hz) to make a round trip in the tube. And that’s already approaching the time scale of auditory awareness and finger motion.

17

Thanks Carey and Thomas-Hastay for the pictures and info.

Carey, have you left the inside diameter of the CPVC stock or have you increased it slightly? The pictures make the wall thickness look thinner than what I have.

Thanks.

RVC

18

No worries lol…I knew what you were getting at Hans,…I do this all the time aswell, it might have something to do with breathing aluminium dust all day long…lol
As I said I agree there is a balance between the objective results of hole placement, bore size etc. etc…

Greg

19

Greg, I like thick walled whistles, including the super-thick walled Lochlan, but I have a “naive” question ? If thick walls are better for the sound of a whistle, why Howard and Burke whistles sound so good ?

20

Gerardo you said you were surprised that an aluminium whistle like the lochlan sounded so warm? I believe this was you i’m not sure…but my findings are because it is a thicker walled whistle…I gotta go, dogs howling, babies crying…arggghhh