Intonation 2 degrees and horn very flat

[nigeld]

So, and bear in mind I'm asking this question from a complete thicko perspective, is this why I blow (silently, just to warm it up) down the sax before I play? I've always done it when I can (gig dependent), would it have an effect on pitch (would rather have an answer here than try it at a gig 🙂 )

A cold sax is flatter than one which is warmed up, so warming it up to playing temperature is a good idea.

 

[Colin the Bear]

I find the crook is the most important part to warm.

 

[rhysonsax]

So, and bear in mind I'm asking this question from a complete thicko perspective, is this why I blow (silently, just to warm it up) down the sax before I play? I've always done it when I can (gig dependent), would it have an effect on pitch (would rather have an answer here than try it at a gig 🙂 )

Yes, it's about getting the saxophone and the air it contains up towards the target temperature - probably something around 20 - 25 deg C.

Blowing warm air down the instrument would be a waste of time on a hot day and wouldn't be fully effective on a really chilly day out of doors.

Rhys

 

[nigeld]

Just to labour the point - there are two factors which affect the pitch of a note for a wind instrument:
1. The length of the tube
2. The speed of sound inside the tube

If a metal instrument warms up then it expands, and thus gets a little bit longer, which lowers the pitch, but only very slightly.

However if the air inside the instrument gets warmer then the speed of sound inside the body gets faster, which raises the pitch.

(The humidity of the air also affects the speed of sound, and thus the pitch.)

The effect of warming up the air is much bigger than the effect of expansion of the body, so a warm sax plays sharper than a cold one.

If we think of, for example, a bari sax, then on a cold day the player’s breath will not warm up the whole body or all of the air inside the sax - there will be a temperature gradient for the air inside the body. Unless one knows exactly what this gradient is, then exact calculations of pitch will not be possible. I presume that warming up the sax will affect the notes close to the mouthpiece more than the bell notes because the air near the mouthpiece is warmer.

 

[mizmar]

My hunch is that, in addition, if the air between the instrument and the listener is significantly cold, it'll sound flat even if you warm up the horn. Maybe someone with better ears then me would like to comment if they'd noticed - or not - such a thing with instruments like stage ePianos or wind controllers playing outside in the cold?

 

[Jeanette]

So, and bear in mind I'm asking this question from a complete thicko perspective, is this why I blow (silently, just to warm it up) down the sax before I play? I've always done it when I can (gig dependent), would it have an effect on pitch (would rather have an answer here than try it at a gig 🙂 )

Yes 🙂

 

[Colin the Bear]

Length of tube and diameter of bore.
A fat short one is similar to a long thin one.
Oh er missus. Slapped the wife for knowing the difference.

 

[nigeld]

My hunch is that, in addition, if the air between the instrument and the listener is significantly cold, it'll sound flat even if you warm up the horn. Maybe someone with better ears then me would like to comment if they'd noticed - or not - such a thing with instruments like stage ePianos or wind controllers playing outside in the cold?

I don’t think that is right. The air temperature affects the resonant frequency of the instrument, but once the sound is generated I don’t think the air temperature outside the instrument will affect it.

However if the sax player is in a vehicle that is travelling fast away from the listener then the pitch will seem lower to the listener. (Like when a fire engine or a train goes past.)

 

[jbtsax]

Something I learned as a band director is that large instruments take a lot longer to warm up than the shorter instruments so at the beginning of the rehearsal they may need to move the tuning device in at first and pull out as the instrument warms up gradually. Also, as a group performs on a warm stage and the pitch center rises from A=440 to a higher pitch, it is never a good idea to retune the group and have everyone pull out.


The reason the temperature of the air effects the pitch inside a "wind instrument" is because the wavelength remains constant. On woodwinds it is determined by the distance to the tonehole plus a small amount added called the "end correction. When soundwaves travel outside the interior of an instrument, the temperature of the air has no significant effect upon the pitch since the wavelengths are not "fixed".

On cylindrical instruments like the clarinet that are closed on one end, the soundwave travels down and back two times making the wavelength equal to 4X the physical length of the instrument. On conical instruments the soundwave travels down and back just one time making the wavelength 2X the physical length of the instrument. This is why the clarinet can play much lower than a soprano sax even though they are approximately the same length. On cylindrical instruments that are open on both ends like the flute, the soundwave travels down and back just one time the same as for conical instruments. Trumpets and trombones are mostly cylindrical but behave acoustically like conical instruments due to the effects of the mouthpiece and large bell which I totally don't understand.

The effect on intonation of the expansion or contraction of the body of the instrument is totally insignificant. This website: Linear Thermal Expansion provides a calculator. The thermal expansion coefficient of brass used in musical instruments is approximately .000011 so a tenor sax measuring approx 36" would increase in length to 36.0048" with a temperature rise from 60° to 72°. @Dr G is an expert in this field who can give more information on this topic.

 

[mizmar]

UNSW says 1/4 wavelength for both straight and canonical tubes,
Closed = high pressure node, open = low pressure node.
No?

Pipes and harmonics: cylindrical and conical bores

What are the harmonics of different bores? Why do closed conical bores have the same set of resonances as open cylindrical bores of the same length, whereas closed cylindrical bores of the same length have only odd harmonics starting one octave lower?

www.phys.unsw.edu.au

But sure. My only point was that the effect due to expansion is small compared with air temperature.

And the speed of sound changes changes inside or outside the tube. And v = fλ; if v changes, λ or f must. No?
Since you are much more knowledgeable in this area, maybe you can explain what does happens?

Edit: wracking my old brain:
f remains constant, you hear the same note. But the wack wavelength of a given note changes with v. So jbtsax is right for the wrong reason. Here endeth the GCSE revision

 

[jbtsax]

A "standing wave", also called stationary wave is defined as a combination of two waves moving in opposite directions, each having the same amplitude and frequency.

UNSW says 1/4 wavelength for both straight and canonical tubes,
Closed = high pressure node, open = low pressure node.
No?

Pipes and harmonics: cylindrical and conical bores

What are the harmonics of different bores? Why do closed conical bores have the same set of resonances as open cylindrical bores of the same length, whereas closed cylindrical bores of the same length have only odd harmonics starting one octave lower?

www.phys.unsw.edu.au

Here are some quotes from the linked page:
"So for the flute we want a zero in pressure at both ends, and that is met by sine waves with wavelength 2L/n where L is the length of the instrument and n is an integer. . ." This means that the "standing wave" travels down and back to produce one wavelength. The integer "n" means that the wavelength can be divided by whole numbers 1, 2, 3, 4, etc to produce harmonics frequencies 2, 3, 4 times the frequency of the fundamental.

"For the clarinet, we want a zero at the open (bell) end, and a maximum at the reed. This is met by cosine waves with wavelength 4L/m where L is the length of the instrument and m is an ODD integer." This means the wave travels down and back twice for a total of 4 trips and the odd integer "m" means that the harmonics are 1, 3, 5, etc times the frequency of the fundamental. This is why the cylindrical clarinet overblows a 12th rather than and octave like the saxophone and flute.

For the conical tubes (oboe et al) we also want a zero at the bell and a maximum at the reed. . . " So like the flute there is a sine wave with a wavelength which is 2L/n, where L is the length of the instrument and n is an integer. This means the "standing wave" travels down and back to produce one wavelength and there are harmonics that are 1, 2, 3, 4, etc times the frequency of the fundamental.

And the speed of sound changes changes inside or outside the tube. And v = fλ; if v changes, λ or f must. No?

This is true of standing waves inside an instrument. For woodwinds the wavelength is determined by the number of closed toneholes and is a constant for each note. This means when the speed of sound increases due to a rise in temperature, the frequency or pitch goes up as well. Soundwaves in the outside air are longitudinal waves and behave differently. The speed that the soundwaves travel changes with changes in the temperature of the air, but the frequencies remain unchanged. I hope this explanation is clear. I am certainly not an expert in this subject, but it has been an interest of mine since high school.

 

[lydian]

A drop in temperature from 20 deg C to 0 would result in less than 1 mm change in the total length of a tenor, even less in smaller horns. So that has essentially zero effect on intonation. What does have an effect is the change in density of the air inside the instrument.

Here's a site where you can do your own calculations:

Linear Thermal Expansion: Formula, Coefficients & Calculator

Online linear temperature expansion calculator.

www.engineeringtoolbox.com

 

[mizmar]

Here are some quotes from the linked page

Where you didn't quote the bit that says the L/2 of a cone is due to the spherical harmonics. Fair enough, spherical waves are difficult. Certainly not due to a sound wave deciding "oh, I'm in a saxophone, I'm only going to travel down and back once. Wish I was in a clarinet".

This is true of standing waves inside an instrument

I'm pretty sure v = fλ applies always. But I agreed with your point that, within the instrument, λ and v are constrained, so f changes. Outside, crossing a temperature gradient, λ changes.