main slide position and temperature changes

[bloke]

Because I'm cheap, I tend to practice at temperatures between the lower-mid 60's and 80 degrees...and Mrs. bloke (who's also cheap) sometimes complains if I spend money to cool the room down to the low 70's or raise it up to the low 70's.

Even when the temperature in the room is NOT at these identified extremes, I'm finding that (with really LARGE widely-expanding bugle (much more surface area) tubas, I'm having to pull the main slide out MORE (compared to smaller tubas of the same length) when it's warmer in the room, and push the main slide in MORE (compared to smaller tubas of the same length) with it's cooler in the room.

Are these observations valid?

Is there a physics-related reason?

It it related to surface area/heat radiation/loss/collection?

For those who might actually be able to offer informed responses, please read these parts carefully before responding, particularly to the words in bold.

[matt g]

Regarding “tubas of the same length”, I remember there being a thread out there in the ether about 6/4 tubas being shorter than same key 3/4 tubas. I believe @UncleBeer has the textbook reference.

Thinking out loud, so to speak, you might be on to something with the notion that a larger tuba warms or cools more quickly since the bugle is more “accessible” to a temperature gradient from a larger surface area and wider air column. Maybe?

There may be something that’s more related directly to acoustics, but nothing is clicking yet.

[bloke]

...so I'm thinking (??) that I have to correct a FATTER same-length tuba MORE with the SAME amount of temperature change.

(to restate it with different words)

[UncleBeer]

Scientific explanation: the speed of sound increases in warmer air, raising the pitch.

For tubas, each degree change centigrade will change the instrument's pitch by 3 to 3.5 cents. Lots of variables here though: length of the instrument (BBb, CC, Eb, F) as the player's breath quickly cools and so the effect of the player's warm air on intonation quickly diminishes along the length of the horn. Also wall thickness to a much lesser extent.

[the elephant]

Yes. Bigger tubas take more correction. If I have to play my 186 and my Holton at the same outdoor concert (which has actually happened a few times, unfortunately) I will have to pull out on the 186 about a half of an inch but more than twice that to correct the Holton.

Conversely, my thin, light, compact 186 warms up to pitch in a cold room very quickly. The Holton, in the same situation, has to be tuned ice cold and then will require little to no adjustment unless we are really blowing on something for an extended time.

[bloke]

Thanks, you guys.

OK...
I'm having to pull about an inch - now that summer is sort of here and the temperature in here is more like 79, rather than 69. I guess that's not a ton, even though 1 in. is 2 in., actually.

Its just that I haven't had this horn forever, and pulling the slide out this far as a little bit adventuresome/new-territoryish.

I don't claim to have so-called perfect pitch, and I'm not sure that it isn't either trainable or a myth, but for some reason I'm able to tell when everything starts sounding slightly goofy.

Right off the bat, it was sounding a little bit goofy, and - as I added my own warm breath to raise the temperature even more - it was sounding goofier and goofiest.

(Those who check into the nerd forum may have noticed that I had to cut the main slide ferrules down considerably in order to get the instrument up to pitch, when blokeplace and performance venues were cooler )

I will add this:
Making the instrument 2 inches longer - in order to play at the same pitch level - does make it sound ungoofy, but it doesn't keep it from feeling goofy, compared to how I'm accustomed to it feeling. I'm still ~feeling~ the extra 2 inches of tubing, in other words..and this big-ass Miraphone is crazy thin, so it's changing fast and changing a lot.

Having just reread what I just wrote, I hope no one thinks I'm stupid enough to believe that I'm particularly gifted nor sensitive nor anything. I'm just a fat old tuba player who plays donuts in the back of the band.

bloke " ' no sidebar 'perfect pitch lectures, please. I can hear what I can hear, and I don't need other people telling me why I can or why I can't."

[Mary Ann]

Outdoor concerts in 100+ degree heat are the only time I have to pull my tuning slide. Most of the time it's all the way in and I have to lip up. I have no idea of the physics except for where the spit collects in a horn, which is where the horn's temperature is at or below the dew point of the air moving through it.

[peterbas]

.

[the elephant]

This is what happens when you guys use air-cooled tubas instead of liquid-cooled ones. In the South, you need your pistons to be liquid-cooled.

[bloke]

This is what happens when you guys use air-cooled tubas instead of liquid-cooled ones. In the South, you need your pistons to be liquid-cooled.

Well I use an awful lot of valve oil, and I'm not using a lot of pistons...