Whistle mute (and an unexpected improvement)

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Moof
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Whistle mute (and an unexpected improvement)

Post by Moof »

I was trying to create a muted whistle today for late evening practice. I was concerned about damaging the blades on my metal whistles by covering them with Blu Tack or whatever (moisture inevitably gets underneath it), so I picked up one of my vintage Feadogs.

One of them has nasty buzzy overtones, so ideal for experimenting on. I found the most reliable to apply a temporary mute seems to be layers of 2" long pieces of PTFE tape smoothed over the blade and down into the head, then built up until the required degree of muting is reached.

What I didn't expect was to find that putting the first two layers on, which produced very little muting, completely eliminated the overtones. It transformed a rough whistle that would have gone in the bin years ago had it not been a present from a relative, into a lovely sweet player. I'm not sure what's wrong with the blade – it looks level, sharp, and in much better nick than my favourite old Feadog – but whatever it is has been resolved.

Home-made mutes tend to cause a bit more clogging than usual, but it seems to be minimal with PTFE tape. It might get worse if it starts to curl up inside the head, but applying it only took two or three minutes, so it wouldn't be the end of the world if it needs replacing every now and again.
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Terry McGee
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Re: Whistle mute (and an unexpected improvement)

Post by Terry McGee »

Ha ha, well done, Moof. Once more you have empirically demonstrated how the old time-honoured theory on how whistles worked was completely wrong.

The theory I'm referencing is the old "split the windstream" theory. It goes back to recorders and before that organ pipes. This theory proposes that the windway forms a windstream, that windstream crosses the window and is "split" by the "blade", the sharp edge at the start of the ramp. The theory then goes on to suggest that a short period of chaos ensues, "the chiff", but then order is brought to the chaos by some random agreement between the forces involved. I wondered if the United Nations might be implicated?

Inspired by all the talk of "whistle tweaking" and having a cupboard groaning under the weight of 60 years of old Feadogs, Generations etc, I looked into this myself, and confirmed that the "split the airstream" theory is a dud. I found that, for good results, you need the airstream to deliver its beam of air a little up from the tip of the ramp, rather than split by the tip of the ramp.

Having the airstream hit up the ramp a bit forces some discipline on what follows. You blow into the whistle. The airstream hits a little way up the ramp and is deflected outwards, up through the window. This creates a negative pressure below the ramp, which propagates as a negative pressure wave down the whistle to the first open hole and then back to the window, where it "sucks" the airstream down below the ramp. Now a positive wave propagates down the tube, reflects back, and deflects the airstream back up the ramp. Rinse and repeat. Hey, we have a system!

So, my guess, Moof, is that it's the end bits of PTFE tape under the ramp that have led to this dramatic improvement in free speech. You could test my theory by carefully stopping the PTFE at the tip of the ramp, rather than wrapping it under.

I've been achieving the same improvement by supergluing scraps of credit card under the ramp. The Feadogs love it! (Give us Credit, they plead!)

This approach, of having the airstream or "jet" hitting one side or other of the "edge" is familiar to Irish flute players, teachers and makers. We've long given up telling players to aim "at the edge". We now tell them to aim "at the bottom of the embouchure hole". This creates an offset from "the edge" which sets up the same sort of offset that having the airstream stike a bit up the ramp does in a well set-up whistle. Interestingly, it would seem to be in the opposite direction, but hey, who cares? Because the airstream is offset from the edge, and that there is a mechanism to go to the other extreme, chaos is avoided. Chaos is what caused the objectionable overtones on your untreated Feadog. And on mine. So many of mine. All of mine?

Seasonal update. A year or two back I tweaked an old Feadog using the "superglue credit card under the ramp" approach. It's now spent the intervening years in the side pocket of my car, which gets to park out in the open. Despite several Australian summers, it still works fine.

Like Moof's Feadog, it was on the "recycle" list. It's now a great whistle. I look forward to being held up by roadworks so I can play the whistle!
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