stupid question from a non music major

[stufarris]

I'm in a brass quintet that was playing outside in 100+ weather (heat index around 110-115) the other day and when we tuned, the music major amongst us told us we were going to need to pull way out to get in tune. I thought that can't be right, but sure enough, I had to pull out that bad boy about 3 inches. But doesn't heat make the metal "tube" expand and become longer? So why would we not push in to compensate for the weather? Thanks for tolerating stupid questions.

stu

[Michael Bush]

There was an extensive discussion of this on here once. A search would no doubt turn it up.

The lore masters said that the issue is the speed of sound in air of different temperatures. Since the air column is hot, the sound moves faster and sounds sharp. The opposite happens with with cold air.

I know nothing about it, just repeating what I read here before.

At an outdoor concert earlier this month, it was 108. We just tuned to a sharp pitch rather than trying to force the pitch down in that impossible situation.

[stufarris]

thanks for the reply. That makes some sense. I looked online about this and got side-tracked into a discussion of velocity varying proportionally with the square root of the absolute temperature over the molar mass, and how density and tension forces of mass apply. Yeah.

stu

[MartyNeilan]

. I

thought that can't be right, but sure enough, I had to pull out that bad boy about 3 inches.

stu

If you are pulling the main slide that much, you will have to adjust all the valve slides accordingly, especially the fourth. I am with Bloke, adjust the tuning of the group to where you are all within normal tuning slide range.

[Heavy_Metal]

Stu, there's no such thing as a stupid question- unless it's a question you didn't ask.

[ursatz]

Not too bad to perform in weather with other wind players.

Years back I did a gig with electronic keyboards in near freezing weather (outdoor Easter sunrise at Red Rocks). Tuning was.... challenging.

No clue about the physics. Now I'm curious.

[Art Hovey]

It's not a stupid question.
Since you asked, here's my nerdy answer.
(I am also a non-music major.)

http://www.galvanizedjazz.com/tuba/temperature.html

[iiipopes]

Having played quite a few outdoor funerals in the dead of winter with "professional" musicians, there has never been any nerd who has whipped out their electronic tuner and insisted that everyone "push in" three inches shorter than all-the-way-in.

I resemble that remark. For this purpose, I am your nerd. We played a concert band gig last Friday evening, and it was so hot (100F @ 5:00, not much cooler by tuneup @ 6:30 for concert at 7:00) I went ahead and reset my electronic tuner to A=445 for the concert and passed it up to the band administrator to tune the band.

[iiipopes]

Yeah, but that's how he wants to do things, so I oblige.

[musicman26]

Let me confuse the matter even more. While the air may go faster thus causing the instrument to be too short in hot weather, I was always taught that it was the length of the air column that got longer in hot weather, and that made the instrument too short. The reverse applies in cold weather. The air column shrinks therefore the instrument becomes flat. Either way, the instrument contracting or expanding is so minimal, compared to the air, that it does not figure into practical use. Wilbert in SC

[Rick Denney]

It's all about air density. The hotter the air, the less dense it is. As density decreases, the speed of sound increases. As the speed of sound increases, the more quickly the pulse of air reaches the end of the tube. When it bounces back, the return pulse arrives sooner, reinforcing the next pulse more quickly. That results in pulses happening more often and therefore a higher pitch. Pulling the slide increases the length to counter the effects of the faster pulse.

Rick "whose slide isn't long enough to account for hot temps, necessitating hiding the oboist's tuner" Denney

[iiipopes]

It's all about air density. The hotter the air, the less dense it is. As density decreases, the speed of sound increases. As the speed of sound increases, the more quickly the pulse of air reaches the end of the tube. When it bounces back, the return pulse arrives sooner, reinforcing the next pulse more quickly. That results in pulses happening more often and therefore a higher pitch. Pulling the slide increases the length to counter the effects of the faster pulse.

Rick "whose slide isn't long enough to account for hot temps, necessitating hiding the oboist's tuner" Denney

Air, as a fluid, is more reactive to temperature changes than the brass, as a solid. What Rick said. Word.

[stufarris]

Thank you everyone for your response! Very educational.

Stu