Yes, and now you have the result for one bar in one marimba.
Hmmm, tuning a marimba seems a bit complicated:
http://www.lafavre.us/tuning-marimba.htm
Do analog Peterson strobe tuners compensate for temp?
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Yes, and now you have the result for one bar in one marimba.
Hmmm, tuning a marimba seems a bit complicated:
http://www.lafavre.us/tuning-marimba.htm
SSLtech
Well-known member
Been away for a while. but regarding the question as to why you don't need to compensate for a changing wavelength:
A strobe tuner doesn't measure wavelength. -It doesn't CARE about wavelength. It doesn't know whether the wave came through cold air, hot air, or sea water.
It measures FREQUENCY, not wavelength.
A 1kHz frequency passed through cold air may pass at a significantly different speed, therefore have a significantly different wavelength, but -and here's the crucial point- the RECEIVING point (be that a listener's ear or a tuner's microphone) still receives one thousand pulses every second.
It's like a pining distant lover who mails out a letter every day to a loved one, a fixed distance far away. -So long as the mail moves at a constant speed, it doesn't matter even slightly HOW LONG it takes each letter to arrive, the recipient wills till receive the letters once every 24 hours. -If the mail were to move at half the speed, the letters IN TRANSIT would have twice the distance between each one, but the recipient isn't ever aware of this, nor do they consider it... only that they get the letters once every day. -If the frequency of the letters slows down, something may be wrong (another suitor on the horizon, perhaps?).
In a WIND instrument, the speed through air is crucially important to determining the pitch, because the resonance of air in a cavity is highly dependent on how quickly the air travels and reflects... but this is NOTHING to do with how quickly the air transports the sound -once produced- to the listening position; -I think that's where you made your wrong assumption.
As I said at the start, common sense should ring an alarm bell... if a Marimba were able to drift by a full semitone over 30 degrees centigrade (according to the math taken as the basis of your calculation) then even a few degrees of temperature shift would put the Marimba unusably out of tune with everybody else.
As a wind instrument player, I know that they are subject to pitch/temperature fluctuations, but that's why a brass instrument would be completely UNUSABLE in any ensemble without a tuning slide... Marimbas, glockenspiel and xylophones however, don't need tuning from hour to hour, and still remain perfectly usable for orchestral gatherings.
Keith
A strobe tuner doesn't measure wavelength. -It doesn't CARE about wavelength. It doesn't know whether the wave came through cold air, hot air, or sea water.
It measures FREQUENCY, not wavelength.
A 1kHz frequency passed through cold air may pass at a significantly different speed, therefore have a significantly different wavelength, but -and here's the crucial point- the RECEIVING point (be that a listener's ear or a tuner's microphone) still receives one thousand pulses every second.
It's like a pining distant lover who mails out a letter every day to a loved one, a fixed distance far away. -So long as the mail moves at a constant speed, it doesn't matter even slightly HOW LONG it takes each letter to arrive, the recipient wills till receive the letters once every 24 hours. -If the mail were to move at half the speed, the letters IN TRANSIT would have twice the distance between each one, but the recipient isn't ever aware of this, nor do they consider it... only that they get the letters once every day. -If the frequency of the letters slows down, something may be wrong (another suitor on the horizon, perhaps?).
In a WIND instrument, the speed through air is crucially important to determining the pitch, because the resonance of air in a cavity is highly dependent on how quickly the air travels and reflects... but this is NOTHING to do with how quickly the air transports the sound -once produced- to the listening position; -I think that's where you made your wrong assumption.
As I said at the start, common sense should ring an alarm bell... if a Marimba were able to drift by a full semitone over 30 degrees centigrade (according to the math taken as the basis of your calculation) then even a few degrees of temperature shift would put the Marimba unusably out of tune with everybody else.
As a wind instrument player, I know that they are subject to pitch/temperature fluctuations, but that's why a brass instrument would be completely UNUSABLE in any ensemble without a tuning slide... Marimbas, glockenspiel and xylophones however, don't need tuning from hour to hour, and still remain perfectly usable for orchestral gatherings.
Keith
First I need to apologize for my earlier dismissive response. I believe one source of confusion is the true nature of the marimba and how the tuning is performed. While the wooden tone bars are the primary determinant of vibrating pitch, and will have one temperature coefficient related to the wood. The hollow resonator tubes, will be responsive to the speed of sound in (cold) air and have the much greater temperature coefficient.
While I have never looked at a marimba closely or ever tried to tune one, I will speculate that the fine pitch may be varied by tweaking the length of the resonator pipes (with slides?). While the pitch is generated in the wooden tone bars, the resonator tubes can pull that note slightly sharp or flat based on their length (and speed of sound in air).
So you were on a reasonable track to try to compensate for air temp in the resonators.
What I sure don't know is how reliable that approach would be dealing with dual vibrating sub-systems (wood and air).
I would sure be tempted to stick with tuning in the temperature it will be used in, or do some trial and error experiments.
The answer to the original question stands, the tuning equipment will be measuring frequency so doesn't care about temperature, other than any internal attempts to retain pitch accuracy. The instrument OTOH will vary with both the speed of sound in wood and air as that varies with temperature different amounts.
Good Luck.
JR
While I have never looked at a marimba closely or ever tried to tune one, I will speculate that the fine pitch may be varied by tweaking the length of the resonator pipes (with slides?). While the pitch is generated in the wooden tone bars, the resonator tubes can pull that note slightly sharp or flat based on their length (and speed of sound in air).
So you were on a reasonable track to try to compensate for air temp in the resonators.
What I sure don't know is how reliable that approach would be dealing with dual vibrating sub-systems (wood and air).
I would sure be tempted to stick with tuning in the temperature it will be used in, or do some trial and error experiments.
The answer to the original question stands, the tuning equipment will be measuring frequency so doesn't care about temperature, other than any internal attempts to retain pitch accuracy. The instrument OTOH will vary with both the speed of sound in wood and air as that varies with temperature different amounts.
Good Luck.
JR
> marimba bar tuning
Yes, marimba bars have a very different mess of resonances than strings or pipes. I'm not sure which way the end-effect goes, but is clearly different than stiff piano-wire at a bridge (overtones increasingly sharp). Marimba bars also have significant width and a strong transverse resonance.... hit the end you get one tone, hit the EDGE and you get a very different higher side-to-side tone, and the two better play well together.
Not sure how a Peterson resolves that but maybe that's why nobody wants me carving on their marimba.
> 440Hz @ 72 degrees and then move it to a 50 degrees temp...
On simpler resonators, that would work.
Since he is checking several resonances, and has several grinding-angles to work with, it may not be practical on marimba.
Wood is inconsistent. The ratio of cell-walls to empty space varies: it is a composite matrix of cellulose and damp pith and air. Even pieces from the same log will not be similar-enough for musical pitch accuracy. Obviously the difference is small for small changes, or you could only play marimba _AT_ 72.0 deg F. (I have known pianofortes where the owner/tuner/player cried over 2 deg changes.) BIG temp change makes difference a tin-ear can hear: come out and sling wood in my firewood pile, summer and winter. thud. tink. Of course that means from very-damp to frozen-solid, but I can hear month to month changes in firewood sounds.
All of which goes back to: two 4x8 sheets cellotex or styroboard to make a 2x2 closet, shelves, couple 100 Watt lamps and a line thermostat. Warm for an hour, test, note. Take bars one at a time out into the cold shaving/grinding shed and take a 90% cut, put back in warmer. By the time you cut the 38th bar the 1st bar is warm enough to re-check, note and take 90% of the error off.
> the difference between air temp being a factor is instruments using air volume, and instruments not using air volume
Take the gizmo into outer space.
A tuning-fork, electric guitar, or piano will still vibrate and have a pitch. Hold the tuning-fork stem to your space-helmet, you can even hear the pitch.
A tuba or jug, organ-pipe or marimba-tube will not resonate at all. (Actually, the metal/glass will clang, but this is not the resonance mode used on musical stage.)
A light nylon-string guitar will resonate in vacuum but MAY be off-pitch. The string drags air with it, increased mass.... no air, it may be sharp.
As an intermediate case: cold dense air has a smaller effect in the opposite direction. The tuning fork won't care. The marimba bar may care only slightly abotu the air around it.
So does the resonant pitch NEED air, is not primarily air but air has a weak effect, or air has "no" effect at all?
Other question: what does pure temperature change do?
In air, mass (density per quart) changes, and I think stiffness changes too. So resonators tuned by air-length (tube) or volume/hole ratios (jug) will change pitch with temperature.
Imagine a pure string instrument with invariant frame and bridge (let God hold it), and a steel string. Make it cold. The string mass does not change (same number of iron-atoms). The cold iron shrinks. Tension rises. Same mass higher tension, pitch rises. (In a piano, there is first-order compensation because iron frame shrinks about as fast as strings shrink. Wood frames less simple.)
So cold wood has essentially the same mass but the wood stiffness changes like firewood in November. For most wood-users, the change of stiffness with temperature is lost in changes of stiffness from board to board, species to species, from green to seasoned to aged. Someone's probably done a study. I don't see why wood-stiffness would change the same way as air.
Yes, marimba bars have a very different mess of resonances than strings or pipes. I'm not sure which way the end-effect goes, but is clearly different than stiff piano-wire at a bridge (overtones increasingly sharp). Marimba bars also have significant width and a strong transverse resonance.... hit the end you get one tone, hit the EDGE and you get a very different higher side-to-side tone, and the two better play well together.
Not sure how a Peterson resolves that but maybe that's why nobody wants me carving on their marimba.
> 440Hz @ 72 degrees and then move it to a 50 degrees temp...
On simpler resonators, that would work.
Since he is checking several resonances, and has several grinding-angles to work with, it may not be practical on marimba.
Wood is inconsistent. The ratio of cell-walls to empty space varies: it is a composite matrix of cellulose and damp pith and air. Even pieces from the same log will not be similar-enough for musical pitch accuracy. Obviously the difference is small for small changes, or you could only play marimba _AT_ 72.0 deg F. (I have known pianofortes where the owner/tuner/player cried over 2 deg changes.) BIG temp change makes difference a tin-ear can hear: come out and sling wood in my firewood pile, summer and winter. thud. tink. Of course that means from very-damp to frozen-solid, but I can hear month to month changes in firewood sounds.
All of which goes back to: two 4x8 sheets cellotex or styroboard to make a 2x2 closet, shelves, couple 100 Watt lamps and a line thermostat. Warm for an hour, test, note. Take bars one at a time out into the cold shaving/grinding shed and take a 90% cut, put back in warmer. By the time you cut the 38th bar the 1st bar is warm enough to re-check, note and take 90% of the error off.
> the difference between air temp being a factor is instruments using air volume, and instruments not using air volume
Take the gizmo into outer space.
A tuning-fork, electric guitar, or piano will still vibrate and have a pitch. Hold the tuning-fork stem to your space-helmet, you can even hear the pitch.
A tuba or jug, organ-pipe or marimba-tube will not resonate at all. (Actually, the metal/glass will clang, but this is not the resonance mode used on musical stage.)
A light nylon-string guitar will resonate in vacuum but MAY be off-pitch. The string drags air with it, increased mass.... no air, it may be sharp.
As an intermediate case: cold dense air has a smaller effect in the opposite direction. The tuning fork won't care. The marimba bar may care only slightly abotu the air around it.
So does the resonant pitch NEED air, is not primarily air but air has a weak effect, or air has "no" effect at all?
Other question: what does pure temperature change do?
In air, mass (density per quart) changes, and I think stiffness changes too. So resonators tuned by air-length (tube) or volume/hole ratios (jug) will change pitch with temperature.
Imagine a pure string instrument with invariant frame and bridge (let God hold it), and a steel string. Make it cold. The string mass does not change (same number of iron-atoms). The cold iron shrinks. Tension rises. Same mass higher tension, pitch rises. (In a piano, there is first-order compensation because iron frame shrinks about as fast as strings shrink. Wood frames less simple.)
So cold wood has essentially the same mass but the wood stiffness changes like firewood in November. For most wood-users, the change of stiffness with temperature is lost in changes of stiffness from board to board, species to species, from green to seasoned to aged. Someone's probably done a study. I don't see why wood-stiffness would change the same way as air.
Mbira
Well-known member
On my phone, so I won't type a lot now, but thanks very much for all the teaching. Keith hit the nail on the head that I was confusing wavelength with frequency. Indeed, I can see that we'd live in a very different world if my thoughts were correct (jump underwater, and all the sudden the pitch of everything would modulate up multiple octaves... :-D)
To add some specific data to this conversation, I currently am building 8 marimbas that are here in my shop now. I tuned the keys at between 72-75 degrees. Currently it's about 50 in the shop. The padauk keys are a very good quarter sawn quality and have a consistent grain from key to key. Checking middle c and then c two octaves higher the keys are +11 cents across every key plus or minus one cent. So they are maintaining pitch shift consistently. The overtones are also remaining constant.
The baritone keys are cherry and are thicker. They have had a +20 cent increase with the temp change.
To add some specific data to this conversation, I currently am building 8 marimbas that are here in my shop now. I tuned the keys at between 72-75 degrees. Currently it's about 50 in the shop. The padauk keys are a very good quarter sawn quality and have a consistent grain from key to key. Checking middle c and then c two octaves higher the keys are +11 cents across every key plus or minus one cent. So they are maintaining pitch shift consistently. The overtones are also remaining constant.
The baritone keys are cherry and are thicker. They have had a +20 cent increase with the temp change.
I though tuning drums were difficult, but after reading the Lafavre link I've had to adjust my thinking.
At least you have a damn good excuse to heat the workshop to a more comfortable temperature.
JR
At least you have a damn good excuse to heat the workshop to a more comfortable temperature.
JR
SSLtech
Well-known member
It's an easy mistake...Mbira said:
Problem is, given that nothing changes, wavelength and frequency ARE directly linked... (inversely), but when anything changes, the direct link can no longer be assumed...
Incidentally, in my mail analogy, I mistyped the distance between frequency and distance between letters... but no matter... my mind was probably elsewhere.
This however, is an opportunity to make some measurements and observations, and possibly write some more definitive text on the matter... -You're the man to do it!
Keith
> confusing wavelength with frequency
And maybe the resonator with the transmission path?
Your unhappy customer calls, and holds the phone to the marimba. By experience, we know the pitch will be "right". But what is the speed of sound on a phone wire? Dang near the speed of light, thousands of times faster than speed of sound in air. What is the wavelength? Typically miles. However if speed of sound in the transmission line (and its length) are constant, the pitch is unaffected.
(Ah, and then there's cellphones, which use a store-and-forward network, bursting at speed of light then being held for random times at every node. However pitch-shift is undesirable so the system preserves pitch, even dropping bits when they do not arrive in good time.)
What is the speed of sound in your resonator? The speed of sound in WOOD. Which is several times faster than in air. Find a long wood beam, bridge, building, over 40 feet long. Have a friend hammer one end while you put an ear on the other end. You will see the hit, then hear it in the wood, then hear it through air. (It may be awful hard to find a wood structure big enough and tight enough to carry sound far enough to hear the difference in speed.)
Or what is the size of your air-pipe acoustic resonator compared to the size of your wood-chunk primary resonator? Even ignoring open/closed-end corrections, the pipe is a lot longer than the wood.
The wood is the prime resonator. Certainly you can play wood chunks without air resonators. And if the air resonator is mis-adjusted, the loudness is hurt far more than the pitch.
So first-glance, this is not relevant:
http://www.fonema.se/soundspeed/soundspeed.html
However at the end it addresses "Reed pipes". The reed is tuned and is the prime pitch. A naked reed is a harmonica, organ builders dress it up with a pipe. The graph shows a 3 semitone-off pipe shift the reed 1 semitone. Certainly a close-coupled pipe will bend the prime resonator. However the reed is very light and tightly sealed to the tube. A marimba bar is much heavier than a reed, much heavier than the air in the pipe, and there's a large gap between bar and pipe. Much looser coupling. Probably few-cents, not semi-tone errors.
I don't see free info on wood stiffness versus temp. "Generally" wood strength and stiffness go together.... it's all about the lignin. I'm not sure this can be generalized to temperature, but WTH.
Encyclopedia of Materials: Science and Technology ISBN:0-08-0431526 pp. 9732-9736
30 deg C change of temp gives 20% change of strength.
Understanding wood:..., Hoadley, Taunton Press, 2000, pg 95:
"...air-dry wood changes in strength by an average of 2% to 5% for every 10 deg F change of temperature." In deg C this is 2%-5% per 5.5 deg C. IOW 30 deg C gives 10.8%-27% change of strength.
There is also change of length with temperature. My gut says this is too small to worry about at bedtime.
Mass unchanged, stiffness increases (say) 20% in 30 deg C, or 1.2 times stiffer. Square-root stiffness times mass. Frequency should change to 1.095, or about 160 (87-216) cents, in 30 deg C. Being sloppy, 3 to 7 cents per degree C, 2 to 4 cents per deg F, pitch up when temp is down.
> tuned ...72-75 degrees
> about 50
> padauk +11 cents
> cherry +20 cent
23 deg F colder gives 11 or 20 cent sharp. That's 0.47 to 0.85 cents per degree F. Much less than over-extrapolated from strength trends. Not length-change: the bars are shorter when cold, which makes them more-sharp not less-sharp. God only knows (we could speculate) why tree-stuff stiffness does not rise in cold as fast as strength.
And maybe the resonator with the transmission path?
Your unhappy customer calls, and holds the phone to the marimba. By experience, we know the pitch will be "right". But what is the speed of sound on a phone wire? Dang near the speed of light, thousands of times faster than speed of sound in air. What is the wavelength? Typically miles. However if speed of sound in the transmission line (and its length) are constant, the pitch is unaffected.
(Ah, and then there's cellphones, which use a store-and-forward network, bursting at speed of light then being held for random times at every node. However pitch-shift is undesirable so the system preserves pitch, even dropping bits when they do not arrive in good time.)
What is the speed of sound in your resonator? The speed of sound in WOOD. Which is several times faster than in air. Find a long wood beam, bridge, building, over 40 feet long. Have a friend hammer one end while you put an ear on the other end. You will see the hit, then hear it in the wood, then hear it through air. (It may be awful hard to find a wood structure big enough and tight enough to carry sound far enough to hear the difference in speed.)
Or what is the size of your air-pipe acoustic resonator compared to the size of your wood-chunk primary resonator? Even ignoring open/closed-end corrections, the pipe is a lot longer than the wood.
The wood is the prime resonator. Certainly you can play wood chunks without air resonators. And if the air resonator is mis-adjusted, the loudness is hurt far more than the pitch.
So first-glance, this is not relevant:
http://www.fonema.se/soundspeed/soundspeed.html
However at the end it addresses "Reed pipes". The reed is tuned and is the prime pitch. A naked reed is a harmonica, organ builders dress it up with a pipe. The graph shows a 3 semitone-off pipe shift the reed 1 semitone. Certainly a close-coupled pipe will bend the prime resonator. However the reed is very light and tightly sealed to the tube. A marimba bar is much heavier than a reed, much heavier than the air in the pipe, and there's a large gap between bar and pipe. Much looser coupling. Probably few-cents, not semi-tone errors.
I don't see free info on wood stiffness versus temp. "Generally" wood strength and stiffness go together.... it's all about the lignin. I'm not sure this can be generalized to temperature, but WTH.
Encyclopedia of Materials: Science and Technology ISBN:0-08-0431526 pp. 9732-9736
30 deg C change of temp gives 20% change of strength.
Understanding wood:..., Hoadley, Taunton Press, 2000, pg 95:
"...air-dry wood changes in strength by an average of 2% to 5% for every 10 deg F change of temperature." In deg C this is 2%-5% per 5.5 deg C. IOW 30 deg C gives 10.8%-27% change of strength.
There is also change of length with temperature. My gut says this is too small to worry about at bedtime.
Mass unchanged, stiffness increases (say) 20% in 30 deg C, or 1.2 times stiffer. Square-root stiffness times mass. Frequency should change to 1.095, or about 160 (87-216) cents, in 30 deg C. Being sloppy, 3 to 7 cents per degree C, 2 to 4 cents per deg F, pitch up when temp is down.
> tuned ...72-75 degrees
> about 50
> padauk +11 cents
> cherry +20 cent
23 deg F colder gives 11 or 20 cent sharp. That's 0.47 to 0.85 cents per degree F. Much less than over-extrapolated from strength trends. Not length-change: the bars are shorter when cold, which makes them more-sharp not less-sharp. God only knows (we could speculate) why tree-stuff stiffness does not rise in cold as fast as strength.
