A glance into the Whistlemaker's Notebook
last update: 29 february 2008

This document is by no means the last and final word on the topic of whistle-design.
If anything below is contradictory to other whistlemaker's experience and findings, I would be very grateful for comments.

Traditional massproduced whistles have some unfortunate characteristics that makes them, in some people's opinion, not even worth playing.
The term "not even worth playing" should be taken with a pinch of salt, after all wonderful music is constantly being played on these "unplayable" instruments.
Below is a list of characteristics that some people find to be intolerable, and allow me to add that not all of the mentioned characteristics need to apply to all whistles at the same time:

Lowest note requires very little pressure to sound in tune with rest of scale.

Second octave not very well in tune with first octave.

First octave notes blend in with second octave notes when second octave notes are played.
    (On a D-whistle this usually occurs easiest on the second octave E-note).

Gurgling tendency on second octave notes.

Rasping and coarse type of breathiness.

Difficult to play second octave D without opening topmost fingerhole.

Shrill sounding second octave notes.

Second octave notes need too much breathing pressure.

Pitch varies greatly with small amounts of breathing pressure changes.

If these illnesses are being dealt with, the typical cheap whistle could in fact become very good.
All of the above symptoms can be easily avoided if the designer sets out to optimize the different parameters of any given whistle.

The term parameter, could be defined as:

shaft diameter,

window area and shape,

windway size and shape,

windway-exit/lip distance,

  etc.

It is tempting to change the parameters in a design so that they are all very different from the Generation, Feadóg etc. style of whistles.
This may be tempting if one is not aware of the fact that not everything necessarily needs to be wrong with the above mentioned whistles.
Changing certain parameters too much or even at all, could very well produce a good instrument, but it wouldn't perhaps sound much like a traditional whistle. In other words, a sound philosophy would be to only change that which is responsible for the above mentioned illness symptoms, and leave the rest of the parameters alone.

Below is a list of some of the parameters that will affect the sound of a whistle:

Length to bore ratio

The length to bore ratio is an important parameter that usually lies between 20:1 and 24:1.
As an example the Feadog whistles has a ratio of 22:1, which means that the internal bore has a diameter 22 times smaller than the length measured from the center of the mouthpiece-window to the end of the shaft.
A diameter greater than this will produce a stronger low register and a weak high register, and the opposite is true for a diameter smaller than this.
If the length to bore-ratio becomes too high (narrow bore), the lower notes will suffer from it and become to weak.
If the length to bore-ratio becomes too low (wide bore), a lot of air needs to be set in motion by the mouthpiece, and the whistle becomes sluggish in its response.
A length to bore ratio of 22:1 could be regarded as a best compromise in order to achieve a good sound through both octaves. In my opinion it is best not to stray to far away from the beaten track in this respect in order to ensure a good sounding whistle.

Shaft wall thickness

The wall thickness of the shaft will affect octave tuning. A great wall thickness will make the second octave too low in pitch. It is possible to adjust for a low pitch by blowing harder when playing the second octave notes, but this makes the second octave notes sound unecessarily shrill. A good choice of wall thickness would lie between 0.2 and 0.3 millimeters. If a greater wall thickness cannot be avoided, undercutting of the fingerholes could be used as this will reduce the wall thickness in the area around the fingerholes.

The mouthpiece window

Whistles having a plastic mouthpiece usually have a window width of approx. 1.1 times the internal diameter of the shaft. The distance between the lip and the windway exit is approx. 88% of the internal diameter of the shaft. Whistles made from one piece of tubing, (shaft and mouthpiece in one piece), usually has a window width of 73 to 75% of the internal diameter of the tubing.
The width/length relationship of the window is often referred to as the cut-up, and a low cut-up favours the fundamentals, while a high cut-up favours upper harmonics.
A high cut-up can be seen at the right in the image below, and a low cut-up at the left.

A low cut-up reduces the breathing pressure required to produce a certain volume of sound, and also tends to make the sound less breathy.
But the downside is that a low cut-up also lacks "life" and the sound could be described as lifeless and dull. Another side-effect of a very low cut-up is that the whistle will jump up an octave very easily and unpredictably.
A very high cut-up sounds loud, but if made too high the first symptom you'll detect is a squeaky second octave D when this note is played without opening the topmost fingerhole.

The area of the mouthpiece window affect the following characteristics:
Large: - A lot of volume, less good octave tuning, favours the low register.
Small: -Less volume, improved octave tuning, favours the high register.

The lip's vertical position relative to the window exit is the most critical parameter when designing a whistle.
An otherwise excellent design could be ruined by an unfortunate choice of this position.
Feadóg, Waltons and Generation plus probably also the rest of the cheap whistles all have designs that lets the lip point toward a point in the windway exit which is quite high.
The lip points more towards the ceiling than to the floor of the exit in these designs.
The result is a strong tendency towards squeakiness and a rasping and unpleasant high register.
Also the low octave notes blend in when the high octave notes are played.
Experiments with the Feadóg D and C-whistles clearly indicates that vertical lip alignment is the cause of nearly all of the above mentioned illness-symptoms as far as the Feadóg whistles are concerned.

There has been some discussion in different whistle forums on where the lip should point, and all participants in the discussion seem to agree that the optimum alignment is just below the middle of the windway-exit.
This conclusion is only partly correct, and I have found that Feadog whistles sound their best when the lip is pointing towards a very low position relative to the windway-exit. Generation whistles prefer a higher location where the lip points to somewhere between the middle and the bottom of the windway-exit. Aligning the lip correctly in relation to the windway-exit fixes almost all the unwanted characteristics associated with some specimens of cheap whistles.

Some mouthpiece designs require a very low position of the lip, but as some designs will become easily clogged up by moisture, such a lip position could pose problems. Metal mouthpiece-blocks get easily clogged up, and if moisture is accumulated on the windway floor, the lip could suddenly end up "below the horizon" as viewed from the exit.
This as a result of the windway floor being elevated by moisture, and now the position of the lip will be below the newly created windway floor. This usually prevents the whistle from sounding at all.
Traditional whistles having plastic moutpieces do not seem to suffer from clogging up even when re-aligning the lip's position to a very low one.
An optimum position of the lip will make the high register very smooth and pleasant sounding, allowing a good tone even with quite modest amounts of breathing pressure.
Interestingly enough, whistle stores on the internet now sell tweaked whistles. The tweak is mostly based on locating the lip so that it points towards an optimum position relative to the windway.
I discovered this modification years before reading about whistle-tweaking on the internet, and the fact that more than one person lands on the same conclusion is a good sign.

If anyone wants to learn the secrets of whistle mouthpieces, purchase a bunch of cheap whistles and split the mouthpieces as shown in the drawing above.
I've learned more by doing this than from building whistles from scratch since now all changes will be made from a firm and steady design basis.
When making several mouthpieces from scratch with the intent of changing one parameter only, this can easily be thrown out the window by the fact that other parameters may also be slightly changed from one specimen to the other.

Windway height

The windway height is perhaps not so critical as the lip's vertical position,
but it sure comes next in line in this respect.
Once the lip's vertical position and the windway height are more or less correctly chosen, the distance between the windway exit and the lip can be increased slightly from what could be considered as the optimum distance without very much change in sound.
The lip's vertical position and windway height are the parameters that focuses and directs the airstream towards the lip in the most efficient way.
If these two parameters fail to do their job, which is focusing and directing the airstream, then the distance between the windway exit and the lip must be made quite small in order to obtain a focused airstream.
In reality you will never get a good sound in this way, since the wrong parameter is used to focus and direct the airstream. Surely, if the windway-exit is close enough to the edge of the lip, the air just has to hit the lip . . . won't it?
The only problem is that the sound will be lacking volume and a few other important characteristics also. In other words;-by letting the lip's vertical position and windway height focus and direct the airstream, the whistle will no longer be extremely dependent upon the distance between windway-exit and the lip.
The optimum value for the lip's vertical position is discussed above, but as far as windway height is concerned, there is no such thing as an optimum value. Well, a small as possible height would of course direct the airstream more efficiently towards the lip, but if it is made to be too small, then the amount of air allowed through the windway would also become too small to produce much sound at all.
An optimum height is therefore a matter of choosing between two evils;-a loud volume but less good focusing, or a low volume and a good focus of the airstream. That would be much like having to choose from playing cards with the devil or with the devil's mother-in-law . . . it's rather difficult to figure out whom to choose since none of them will let you win the game.
Seek a compromise between the two, so that both volume and focusing of the air-stream are within reasonable limits.

Tunability

What determines the lowest note of a whistle is the distance between the center of the mouthpiece window and the end of the shaft. Now, the fingerholes are located in accordance to this length so that the whistle plays the scale correctly.
If the total length is changed, (by pulling out or pushing in the mouthpiece) then the fingerholes would need to be re-located in order to play the scale correctly. Since re-locating the fingerholes once they're made is impossible, the whistle will no longer play the scale in tune now that the bottom note has changed its pitch.

It could be argued that one could tune a whistle so moderately that the ruining of the scale will be almost undetectable.
Well, that means that the change in pitch resulting from it is equally undetectable. This is a no loss/no gain situation, so what's the point?

There are several ways of realizing tunability which can be seen in the image below:

All of the above methods will introduce abrupt changes in the internal bore that will create turbulence in addition to messing up the scale.
And . . . does it look pretty?
In my opinion it does not. Method "C" is acceptable as long as the wall thickness of the mouthpiece is kept very small. All of the above methods (exept "C") intoduces a sudden change of the shape of the whistle that could easily mess up the look of the whistle.

Chamfered windway-exit

In the image above you can see a trick used when making recorder-flutes.
Gases and liquids will tend to cling to any smooth surface when flowing, and if the surface curves evenly, the gas/liquid will flow with it.
This is a well known property of gases and liquids which is exploited when making jet-engines. Whistles can probably do without this method, but in order to avoid the effect created by moisture build-up when the lip is aligned very low as mentioned before, the curved exit would cause the airstream to fan out and make the air hit the lip regardless of moisture build-up on the windway-floor. I haven't tried this myself, but at least in theory it could minimize the effect of moisture build-up inside the windway.
Another effect would be less turbulence when the air leaves the exit, since turbulence will be the result of any sharp edge. Turbulence will create less tone and more breathiness.
Depending on the design, this trick may increase the strength of the bottom-note.

Windway shape

When the windway area is greater at the inlet than at the exit, it makes the sound go loud.
The usual trick in order to make a loud whistle is to make the distance between the lip and the windway-exit very large, but this introduces many additional problems. Making the inlet larger than the exit is a possible alternative, since now the exit/lip-distance can be kept at a moderate value. I usually allow the inlet-height to be twice that of the exit-height,-or even more. I don't know why the sound gets louder, either it's some pressure effect or simply a better directionality of the air-stream . . . or both.
And the extra loudness isn't just marginal,-it's quite simply tremendous in some cases.
Don't leave home without it.

A rounded lip and a similarly rounded windway is probably the optimum solution.
This is perhaps the solution that best exploits the potential energy of the air stream, and the circular design also allows for moisture inside the windway to run easily out of harms way.
In the drawing below you will see four different ways of making the block
(the block is viewed from the blowing end):

  "A" shows the easiest way, where the block is simply made from some piece of rod
having a smaller diameter than that of the tubing.
The windway floor, ceiling and lip will all have different degrees of curvature,
and the height of the windway will be governed by the wall-thickness of whichever
kind of tubing you choose to use. The wall thickness will determine the windway
height, which is quite an important parameter.
Not a very clever design, as a lot of air will never hit the lip.
 
"B" shows an equally easy way of doing it.
Here the block fits snugly inside the tubing and the windway floor is made flat.
This is the exact same principle which is used with the Clarke original whistles.
It's perhaps an improvement compared with the example shown in "A", but this one
will also produce a lot of air that will never hit the lip. If a very breathy
whistle is what you're after, this may be the way to go.

Example "C" is not too bad a solution, although it will look a bit clumsy, it is a better solution than "A" in that it will direct the air-stream towards the lip more efficiently. This design is dependent on the tubing wall having the correct thickness.

Example "D" is starting to get somewhere, but still the windway ceiling is giving us some problems with respect to airstream focusing.

Example "E" is probably the solution that gives the most freedom of design.
The lip can now be made to have the same size and shape as that of the windway, and this produces an accurate focusing of the airstream throught the windway.

Examples "A" and "B" will cause some of the airstream to not hit the lip
very accurately. This produces extra breathiness, and if the sound is found to be too much breathy one has to move the windway closer to the lip in order to achieve a clearer sound.
In the same time the above mentioned cut-up could easily become too low.
A very low cut-up sounds dull and uninteresting, and it would be a good idea to
make a design that is energy-efficient from the very start so that this could be
avoided. It is not a good idea to be in a situation where one of the parameters is
optimized, but throws all the rest out the window.

Conical (tapered) bores

What exactly does a conical bore do, and what are the rules that apply for such bores?
I have come up with some theories based on observation, experience and some testing, but I fear that whistle-physics is a bit more complex than what it seems to be.
From what I can hear when playing different whistles, a straight bore has some problems with the second octave being too low in pitch.
A conical bore on the other hand, has a problem with the second octave having too high a pitch.
My only experience with tapered bores are the Clarke original and the Clarke Sweetone. The Clarke original in particular have a second octave which is very high pitched. Problematically high in fact. To get the second octave in tune you need to blow with very little strength, which makes you loose a decent tone quality completely.
By looking at the Clarke whistles, it is noted that the diameter at the mouthpiece-end is quite large, while at the bell-end it is quite small. -A quite extreme taper so it seems.
One could express the taper in terms of length to bore ratios.
One L/B-ratio at the mouthpiece-end, and another L/B-ratio at the bell-end.
The L/B ratios for the Clarke original are: 1:16 to 1:30.
To me it seems that the more extreme taper, the higher the second octave will be in pitch.
Is there some rule of thumb for an optimum degree of taper?
I've been studying the measurment-ratios using a photo of the Copeland low-D whistles.
It turnes out that the bell-end of these whistles has a diameter which is 70% of the diameter found at the mouthpiece-end.
This might be a crude rule of thumb, and since the Copeland whistles sound very good, I guess this would be a rule of thumb as good as any as far as taper degree is concerned.

As mentioned before, straight bored whistles suffer from a second octave being slightly low pitched. This, however has never been experienced as a problem, at least not for me.
The problem arises when the Clarke manufacturer and others try to solve the second octave problem by making, in my opinion, an extreme degree of taper, since now the pitch of the second octave becomes way to high. It would be like drowning someone who's hair is on fire. That's equal to solving a small problem by introducing a more serious one.

I wish I knew more about physics, since then it would be easier to understand the "mechanics" of these things.
However, I do have an idea about what's going on inside the mysteries of tapered bores and octave tuning etc.
1) The clarinet for instance, has a straight bore and a reed inserted at one end.
When a reed is inserted like this, it is said that the clarinet is a closed resonance tube.
2) The whistle and the flute has no reeds, but a sound-hole, and is said to be
open resonance tubes.
3) For a straight bore, the closed resonance arrangement (a reed instead of a sound-hole) causes the second octave notes to jump up one and a half octave (clarinet).
The open resonance arrangement (whistles/flutes) causes the octave to jump one octave only.
4) We know that a small sound-hole or a small mouthpiece window causes the second octave to go sharp, while a large sound-hole or a large mouthpiece window causes the second octave to go flat.

I can't see any other reason for this that as the soundhole/mouthpiece window is made smaller, it gets more and more equal to a closed resonance system, consequently causing the raise in second octave pitch. The chanter of the Uilleann-Pipes has an octave relationship like that of flute and whistles, despite the fact that the Uilleann-Pipe chanter is a closed resonance system.
-Why???
-Because it has a taper that widens towards the bell-end, a shape that evidently lowers the pitch of the second octave notes. Is this why flutes and whistles that have an opposite taper (smaller as you approach the bell-end) tends to go higher in pitch on the second octave notes?

The practical consequence of this would be that a bore-diameter that gets smaller as you approach the bell-end will raise second octave pitch, and more so if the degree of this taper is extreme. (Is this the explanation why the Clarke Original has a lower pitched second octave compared to the Clarke Sweetone? The Clarke Original does have a much larger mouthpiece window). In opposition, as the taper gets wider towards the bell-end, it tends to lower second octave pitch. It is then also true that large sound-holes/mouthpiece windows need a more extreme taper of the bore to stay in tune between the octaves. Another practical consequence of a conical bore would be that fingerholes could be made larger without risking a low pitched second octave. Very convenient, as this would produce a louder whistle.

This all adds up to the fact that all the parameters of a whistle work together and are inter-dependent, at least to some degree. Change one thing, and all the other parameters will become affected. The perfect whistle would then be a whistle where all the parameters are at their optimum values, which will never happen in real life.
What is possible, on the other hand, is to make a whistle where all the parameters are within reasonable values.

Let me give an example of a whistle design that would be less than well optimized:
Large wall-thickness, large fingerholes and a mouthpiece window having a large area would produce a whistle with poor octave tuning.
Now three different parameters are pulling together in the same direction, namely lowering second octave pitch.

If whistle designers reckognizes these practical consequences as something they have experienced themselves, it then shows that the above theories holds water. If they wouldn't, then welcome to the world of lunacy.

Making a cavity underneath the windway has the effect of lowering the pitch of the second octave notes, and particurarly that of the second octave D. This could be useful when second octave pitch is found to be too high when making whistles having a tapered bore. The rule of thumb is that the amount of cavity volume creates a correspondingly low second octave pitch. I have found that tapered bores notoriously show up with a second octave pitch so sharp that it makes them unplayable. A large cavity seems to cure this tendency.
See the image below:

As mentioned before, the wall-thickness of the shaft influences the second octave pitch, in such a way that a great wall-thickness tends to lower the pitch of the second octave. It is therefore wise to take this fact into account when making conical shafts that causes the second octave go sharp. Such a shaft may require a cavity volume which is less compared with shafts having a smaller wall-thickness.

So why does cavity volume affect pitch in this way? I believe that the answer lies in the above discussion on open versus closed resonance systems. A closed resonance system raises second octave pitch while an open system lowers it. By making the cavity larger, the degree of "openess" increases or adds to the mouthpiece window if you will, thereby counteracting the tendency towards the second octave going sharp in tapered bores. This implies that the mouthpiece window/soundholes and fingerholes in whistles and flutes also affect second octave pitch. Small equals higher pitch, and large equals lower pitch.

To sum it all up, a straight bore shouldn't have a cavity at all, (unless the mouthpiece window is larger than normal), and in some instances the block should extend into the mouthpiece-window area, whilst a tapered bore must have a cavity,- and the size of the cavity in such a case must be increased in accordance with the degree of taper. Furthermore, a small mouthpiece window needs a larger cavity than a large window does.
Also a steeply tapered shaft needs a larger cavity than a less steep taper. This knowledge, if correct, is actually very useful, since now you could make a bore that has quite an extreme taper and fix the octave tuning problems by manipulating the volume of the cavity. I see a connection between a steep taper and a reedy sound in whistles. If such an observation is correct, one could safely just "taper away" till the sound gets that nice reediness, without worrying about octave tuning.

The above theories are based on a minimum of testing and a whole lot of reasoning. Although I think this theory should be taken with a pinch of salt, I still can't help to notice that the different statements sum up with each other, which at least is a good sign.

Different materials

PVC, resins and any other synthetic material I have encountered so far sounds a bit dull and lacks that bright sound that I think is so important. Even brass sounds dull compared to nickel plated steel, so obviously the material used has an effect on the sound. This is of course a matter of taste, and mine is definitely with metals.

Every choice of production method and choice of materials has advantages and disadvantages. The tricky thing is to make everything fall into place. One method may require a lathe, and if a lathe is out of the question, it prohibits the use of that particular method. By ruling out one thing, other things are also ruled out, like a certain appearance, sound characteristics etc. To me it is important to comply with the demands that a certain sound, appearance etc. will require. This pretty much determines the materials that need to be used, the production methods and the tools which are necessary. So far I have tried to fulfill all these conditions by trying out different shortcuts, with little or no success.
In short, if you need a lathe, you need one . . . period.

With the method I used when making whistles from PVC-tubing, the fixed wall-thickness also resulted in a fixed height between the windway "floor" and "ceiling".
This is not a good situation as it limits freedom of design. The conduit tubing method worked well for the low-G and low-D whistles, but the sound of the high D and C whistles suffered greatly by it. The latter whistles never really sounded good because of this. For a good result, it is important that all the parameters are within the control of the whistle-maker.

If one is willing to experiment, it is well within the reach of almost any person to make excellent whistles. Is it rocket science . . . or black magic? -No, it isn't.
It's all about choice of materials and design, and of finding a proper production method that ensures quality consistency. And first of all, it's about being confident with the basics of whistle design.

Purpose or circumstance

There are basically two different approaches towards making a whistle or anything else for that matter:
1) Grabbing anything that is at hand and let circumstance design the whistle, and live happily with the result ever after, or . . .
2) . . . leave no stone unturned and experiment until you find the design and production methods that gives the result you are really content with.