Is there any connection between soundholes and 2 stroke silencer technology?

[John Cadd]

When guitar designers talk about soundholes they mention pumping of air in and out and this reminds me of the strange way that pressure waves behave in two stroke exhaust pipes.
Designers used to wonder why the gases seemed to turn back as they reached the end of the exhaust pipe.Japanese bike designers relied on the expertise of technicians in Ireland.
Both subjects are cloaked in mystery but you can`t argue with Physics.Reading about the Turnavoz mentioned in the Jose Romanillos book about Antonio de Torres reminded me how these topics seem quite closely related.

[Ron Frazier]

On a similar topic I was building speaker cabinets for the kids to put in their cars and
I read that the hole that the sound comes out have to be rounded over so the sound can find
a smoth surface to travel and not a square edge so the sound will have that back that the mufflers have.

I don't know but I have no sharp edged on the sound hole of my guitars.

I think that the better builders do a lot of things that they dont even know and that
is why they build better insterments.

Just ramblin

Ron

[John Cadd]

That`s true Ron ,there`s things like the air intake on a grand prix car.The edge is very thick and round and most people left to make their own would make it as sharp as possible.Nature (or physics)has lots of little mysteries to trip us up.

[Rob Mercure]

John,

Are you aware of the work that Maccaferi and others did using various resonators within the guitar bodies. While many of these were to prevent damping of the back by contact with the musician some others where specifically designed to keep as much of the output air in phase as possible. In some ways though I think this is almost the opposite of the two stroke technology cuz, as best I understand it, part of it is to also provide a muffling function as well as to move the charge in a more orderly manner (haven't read up on this for a while but I've got an old Yamaha 250 two stroke that I'm going to finish refurbishing some day and I did some extensive research on this a few years ago - but my memory is very poor).

Rob

[John Cadd]

No Rob I haven`t read about that.Fancy you having a 250 Yamaha .I used to ride a YDS2 which was the first proper Yamaha brought to England.It had a wonderful sound like a yowl.I even went to Brands Hatch on it to see Mike Hailwood.Oh yes and Giacomo Agostini on his MV Agusta.We worked out exactly where to stand to hear him change gear.I was a noise freak then.Hailwood was riding the immortal earsplitting Honda six.
About the output air in phase--This is getting closer to the other thread where I have been fine tuning the size of the soundhole to quell a troublesome resonance.I did the check again and found the 89mm diam hole works better at 76mms.Well it is a thin body and a slightly smaller model.I was double checking against a Spanish guitar.When I tried the same process on the the Spanish one It brought the instrument to life.It was quite cheap brand new but always seemed a bit woolly low down.Now it seems to have lots of nice tone not heard before.The process of making a guitar relies on a feel for stiffness.But this may not result in a perfect match with the air resonance,which is maybe easier to predict but leaves a mismatch depending on the top and back tap tones.Why would a pre-cut hole made in the early stages be the exact right size?Then think of all those factory made guitars hiding their lights under a bushel[whatever that is].

[Rob Mercure]

John, I have never really been a "noise freak" but during me teen years I used to make explosives and fireworks so I guess I've been a "bang freak" - now I'm much of a "silence freak" and have come to truly detest Harly riders (when I was a kid a common trick was to fasten a playing card with a clothes pin to a bicycle so that the bike's spokes hit the card and made some noise - I now equate the "Harley Charlies" with these still ungrown children). Anyhoo you should check out Macaferi and others - including both Gibson and Martin - experiments with internal baffles and sound boxes. As best I know almost all this work occured during the 1920s and 30s. Hmmm, slang and description vary between cultures - when you descibe frequency response as "wooly" what does that mean?

Rob

[John Cadd]

Woolly is dull ,weak ,unfocussed .the opposite of the Spanish word Growl.

[Rob Mercure]

Hmmm, guess I still don't understand what the song "Wooly Bully" is about then - was hoping for a clue !

R