Tech/maintenance Saxophone Pad Acoustics Study

[jbtsax]

I think the lower pressure at the flow points is less than atmospheric and would count as suction.

btw, why do you refer to antinodes twice in different contexts?

I have found nothing in acoustics literature to suggest that the pressure inside a sounding instrument drops to below atmospheric pressure.

"Node" means none or nothing, therefore at a pressure node there is zero pressure. At a velocity (or displacement) node there is no air flow. Conversely at a pressure antinode there is the maximum pressure, and at a velocity antinode there is the maximum air flow. This simulation should help to clarify these terms: Nodes and Antinodes

 

[Jeanette]

Wrong: many players I know really suck.

Did you have to ruin a perfectly on topic thread

Jx

 

[kevgermany]

Did you have to ruin a perfectly on topic thread

Jx

You tell him!

 

[kevgermany]

Thanks John. Wasn't thinking straight.

 

[jbtsax]

Wrong: many players I know really suck.

Why bring up harmonica players in a thread about saxophone pads. Sheesh. 😀

 

[abadcliche]

No pressure lower than atmospheric? Hmm, how to empirically test that without basically becoming a leak or octave pip...

Speaking of empirical tests, here is a quick one on a kangaroo skin pad with a magnahelic that someone I know did a few years ago. At the time, it was not yet accepted that some pad skins were porous. Now that's a little more accepted, but the jury is still out (for some) whether it matters or not.

One side of this pad was treated to make it airtight, the other side (the leaky side) is the as-purchased condition. The interface is just a piece of brass tubing that has been leveled and smoothed to act like a tonehole. This would be a completely unacceptable result if it was the result of a leak due to improper pad seating.

 

[jbtsax]

No pressure lower than atmospheric? Hmm, how to empirically test that without basically becoming a leak or octave pip...

In over 15 years of studying woodwind acoustic literature I have found no reference to a negative pressure inside a sounding instrument.

 

[jbtsax]

What types of pads are you going to test? As science is all about statistical significance, how many replicates per type are planned? As this will probably be published at some time as kind of a follow up investigation of the paper you linked to, numbers should't be to low. From your original post it seems that all pads are different at least colourwise. Since leather is a natural product, the results within one pad might differ depending on which portion is positioned on the chambers. Don't get me wrong. I think it is a great idea to test this, I am just wondering what sample size is used in accoutical sciences.

These are the pads that have been tested for porosity. There was only one of each type tested. All but the Pisoni WS 102 Waterproof pad which is the only one with a hole will undergo testing for their "absorption coefficient". I don't want to reveal the porosity results until the second part of the testing is complete. I will say however that there is a broad range of readings for the assortment of pads chosen.

Chocolate Roo Extreme
Saxgourmet Black Roo
White Roo
Chocolate Roo
Jim Schmidt Gold
Neoprene Control Pad
Music Medic Tan
Music Medic Tan Soft
Pisoni Pro 100 J
Pisoni DS 100 Premium Deluxe
Pisoni Pro 100
Pisoni Pro 100 J Black
Pisoni WS 102 Waterproof

 

[abadcliche]

Very cool. I look forward to the results.

Will you maybe add a layer of testing with an applied pad treatment? Like perhaps a super light coat of lacquer (an old timer's trick I have personally grown fond of for its anti-stick and light water resistance properties), or the "deck paint" type treatment sometimes seen.

 

[DavidUK]

Very cool. I look forward to the results.

Will you maybe add a layer of testing with an applied pad treatment? Like perhaps a super light coat of lacquer (an old timer's trick I have personally grown fond of for its anti-stick and light water resistance properties), or the "deck paint" type treatment sometimes seen.

Is this Matt Stohrer?
If so, you're very welcome and we are honoured to have you here!
If not, you're very welcome anyway!

 

[Jeanette]

If not, you're very welcome anyway!

and we would still be honoured to have you here 🙂

@abadcliche do introduce yourself in the doorbell section our members are very welcoming

Jx

 

[abadcliche]

That's me! Thanks for the warm welcome 🙂

Someone pointed me here the other day and the top post was this one, a topic I am very interested in. Looking forward to seeing what is found out.

 

[DavidUK]

See Matt Stohrer's fabulous YouTube videos and his website blogs and be educated. Always keen to help personally too, I've found. A great tech to add to the others who grace us with their presence.

 

[DavidUK]

@jbtsax - did you answer my question on how wet the pads will be when tested? Dry is easier to repeat, but who plays with dry pads?

 

[Dave McLaughlin]

I have found nothing in acoustics literature to suggest that the pressure inside a sounding instrument drops to below atmospheric pressure.

"Node" means none or nothing, therefore at a pressure node there is zero pressure.

Not quite. Zero pressure would be a vacuum. At a pressure node, there is zero fluctuating pressure.

At a velocity (or displacement) node there is no air flow. Conversely at a pressure antinode there is the maximum pressure, and at a velocity antinode there is the maximum air flow. This simulation should help to clarify these terms: Nodes and Antinodes

At a pressure antinode, there is the maximum pressure fluctuation. But it fluctuates, plus and minus, about atmospheric pressure.

 

[abadcliche]

So there are areas inside the saxophone that have, at least for a short amount of time, lower pressure than atmospheric?

At the risk of taking this out of graduate thesis pdfs and into the physical world, how much like what goes on inside the saxophone is the video below of standing waves in a wave tank? AFAIK: In a saxophone, you've got waves of high and low pressure coming from the mouthpiece that bounce off the atmosphere at the first open tonehole (or bell) and travel back up. By figuring out how much volume and length to have inside the tube, you can set up standing waves- which is where the outward and inward waves repeatedly intersect at the same spot, roughly doubling their amplitude in certain static spots. Which looks like what I see here, but I don't know how much of this to take and use for my mental picture.

 

[saxyjt]

A long time ago. I sailed and wanted to be a sailboat designer so I'm well aware of the waves and its relationship with the boat's length to atain maximum boat speed. At least for monohulls. Things have changed a bit with multihulls and even more recently with the America's Cup cats flying on foils. But I'm still struggling to figure what's going on in this tube we love...

I would also like to get a clearer mental view of this.

By the way. That's not mental. But is there anything like a micro USB camera to spy into the tube?

Just curious...

 

[abadcliche]

I have two super awesome (at least I think so) ideas that anyone is free to steal if they can do it before I can-provided you get me a video.

One is to install a tiny tube in a mouthpiece connected to a smoke generator, put a variable speed strobe light and high speed camera inside the body tube. This might work particularly well with one of those clear plastic saxophones from Vibrato.

Another is to hook a saxophone up to a rubens tube to illustrate overtones. I might do this one soon, so dibs until the end of this year at least.

Although I just found that someone has already played a sax into a rubens tube! Though I think I might make mine bigger and more dangerous, what with being American and all.

 

[saxyjt]

American or not, I'm not sure tidal wave style is a good idea! Although it may prove your point...

 

[ProfJames]

Tidal wave! How much saliver are you producing?