Nasal Sounding 'inboard' Reeds

[ttonon]

 

I never knew that! So, it's not like resting a tuning fork on a guitar body to get it to resonate more loudly? Have you ever noticed a reed increasing in volume when you set it down on a piece of wood while it's vibrating?

You might be able to observe that effect if you actuate a reed by plucking it, but that's not how a reed operates when it's being played.

 

You may be able to convince yourself of this by biting down on the corner of a harmonica as you blow through the first hole-- the sound doesn't get particularly louder or softer, and the harmonica doesn't vibrate your teeth like a tuning fork would.

 

 

 

Ransome, I think there’s a complication here worth mentioning. A free reed mounted properly in its wood slot will sound much differently than the same reed sounding while not being mounted, or mounted very loosely. When the reed is not mounted securely, the frame of the reed vibrates with much more amplitude than it does when it is mounted securely, and this vibration affects sound. Poorly mounted reeds will even sometimes buzz against their mounting.

 

The reason for the different sound is that the relative motion between the vibrating tongue and the frame slot can be significantly different between the two cases, and this difference shows up particularly as a difference in relative velocity. If the motion of the frame in the unsupported case is dominated by the fundamental mode, as I’d guess, there can also be a possible difference in phase between the fundamental of the emanating sound and the rest of its partials, though I’m speculating here. But most importantly, the relative velocity amplitude will definitely affect the volume of the tone, with some probable effect on timbre, depending on how poorly the reed is mounted. Buzzing (and air leaks) will of course add considerable complication to the resulting sound.

 

Although the free reed does not rely on the motion of a soundboard, as with string instruments, there’s still a relationship between the sound produced, the mounting, and the woodwork. The crux is how much the frame of the reed does actually move, even when the reed is securely mounted. Depending on the mass of the vibrating tongue, which depends on the pitch of the reed, and the geometry, density, and rigidity of the supporting woodwork, there may be significant frame vibration, which can be theoretically transmitted through the supporting wood structures, and consequently radiated by sound to the air, if the associated geometries, masses, and rigidity are suitable. I’m talking about very small effects here, though I wouldn’t go so far as to say that there is absolutely no contribution to sound by the woodwork for all reeds at all playing volumes, without doing the proper experiments, which I haven’t.

Regards,

Tom

[Ransom]

Of course you're correct, Tom.

 

I tried to choose my words carefully to make my point clearly without getting down into the weeds. That being said, I do seem to remember reading one of these reed-physics conversations where Wim Wakker came out and said that he had done tests and was able to state with confidence that air driven by the resonance of the reed had a negligible effect on tone characteristics at playing volume. But good luck trying to find the reference on that... for present purposes, I'm content to allege that he might have said something like that, without tracking down what it was.

 

Anyone fascinated by this stuff might do well to take a hard look at the jaw harp... it rather awkwardly straddles the boundary of free reeds and idiophones.