Do strings vibrate at the same pitch underwater?

[EssentialTension]

I found this TB thread totally fascinating:

[url="http://www.talkbass.com/forum/f16/do-strings-vibrate-same-pitch-underwater-960889/"]http://www.talkbass.com/forum/f16/do-strings-vibrate-same-pitch-underwater-960889/[/url]

[Delberthot]

Clearly someone, actually some people, with too much time on their hands.

Although it might come in handy the next time I gig in Atlantis

[mart]

[quote name='Delberthot' timestamp='1361616568' post='1988258']....
Although it might come in handy the next time I gig in Atlantis
[/quote]
Or play a gig on the Titanic?

[Mr. Foxen]

Too many people thinking string pitch is same as sound travelling in air, but the string is mechanical, so the medium the sound travels in later isn't relevant. If its in tune out of water, and in tune in water, they'll be the same. Dunking your bass is likely to make it out of tune though.

[EssentialTension]

What a fascinating thread this is turning out to be.

[ahpook]

the string will vibrate at the frequency if you ignore any effects of the damping of the water.

the note you hear will be higher as the speed of sound is different in water as compared to air, like saturation divers in a helium-rich atmosphere

i'd pass on trying a real-world answer talking into account the damping...the motion of the string is likely to be incredibly complex...i see reynolds numbers, non-linear flow and 3D vector calculus heaving into view.

Edited February 24, 2013 by ahpook

[KiOgon]

Surely pitch is down to the frequency/speed the string vibrates & the string under water, damped by it's surrounding 'heavier than air' will be slower - lower frequency therefore a lower pitch.

Edit: If anybody wants to come & play [b][u][i]their[/i][/u][/b] bass in my Koi pond they're welcome to. It's about 4 degrees C around now.

Edited February 24, 2013 by KiOgon

[ahpook]

[quote name='KiOgon' timestamp='1361731895' post='1990049']
Surely pitch is down to the frequency/speed the string vibrates & the string under water, damped by it's surrounding 'heavier than air' will be slower - lower frequency therefore a lower pitch.
[/quote]

i've done a bit of research and the increased damping does change lower frequency of the string in a predictable way (Sir George Stokes did the legwork for us), but it's a very small contribution - the shift in frequency between a string in a vacuum and in air is of the order of 10e-11 Hz.

from the equations*, very, very hand-wavingly it looks like the damping due to the greater density/viscosity of the water would be of the order of 10e9 larger than in air, so a drop of 10e-4 Hz [i]might just[/i] be an answer. an order of magnitude estimate, shall we say

i may be totally wrong though - i just fancied playing with some equations for a bit

[url="http://courses.physics.illinois.edu/phys406/Lecture_Notes/Waves/PDF_FIles/Waves_2.pdf"]*page 21[/url]

Edited February 24, 2013 by ahpook

[3below]

As a physicist I would resort to the time honoured method... suck it and see. With experimental evidence of the real situation we can see which effects dominate. .

Ahpook - how [color=#282828][font=helvetica, arial, sans-serif][size=4]very, very hand-wavingly were you? A drop of 0.0001 Hz seems low from intuition - which can be very wrong. You are bang on about the potential complexity with possible transition from laminar to turbulent flow, We could also see cavitation as well. [/size][/font][/color][size=4]An interesting problem, good for final year degree project or a more qualitative A level investigation I guess.[/size]

Edited February 24, 2013 by 3below

[Dad3353]

So no-one has an acoustic, perspex, alu-neck bass for trying this out..? Any takers for at least nailing an old string to a plank and listening in the bath..? If I only had a bath-tub (or Koi pond...) I'd try it...

[ahpook]

[quote name='3below' timestamp='1361745136' post='1990304']
As a physicist I would resort to the time honoured method... suck it and see. With experimental evidence of the real situation we can see which effects dominate. .

Ahpook - how [color=#282828][font=helvetica, arial, sans-serif][size=4]very, very hand-wavingly were you? A drop of 0.0001 Hz seems low from intuition - which can be very wrong. You are bang on about the potential complexity with possible transition from laminar to turbulent flow, We could also see cavitation as well. [/size][/font][/color][size=4]An interesting problem, good for final year degree project or a more qualitative A level investigation I guess.[/size]
[/quote]

well, i tried to follow the changes to the equations i posted if i plugged the changes in properties of the water ~1000 times denser and ~1000 times more viscous.

it struck me as very small - water isn't air ! but then most of the sources i saw said the contribution to the forces on the string from the viscous damping were low.

you're right - if the flow was to get very messy i'd imagine it would get very complex.

Edited February 25, 2013 by ahpook

[Dr M]

[quote name='ahpook' timestamp='1361743268' post='1990249']
i've done a bit of research and the increased damping does change lower frequency of the string in a predictable way (Sir George Stokes did the legwork for us), but it's a very small contribution - the shift in frequency between a string in a vacuum and in air is of the order of 10e-11 Hz.

from the equations*, very, very hand-wavingly it looks like the damping due to the greater density/viscosity of the water would be of the order of 10e9 larger than in air, so a drop of 10e-4 Hz [i]might just[/i] be an answer. an order of magnitude estimate, shall we say

i may be totally wrong though - i just fancied playing with some equations for a bit

[url="http://courses.physics.illinois.edu/phys406/Lecture_Notes/Waves/PDF_FIles/Waves_2.pdf"]*page 21[/url]
[/quote]

I'd agree that you're probably in the right ball-park. Purely qualitatively, If going from vacuum (no damping at all) to damping at atmospheric pressure only produces a change of 10e-11Hz, then the damping in a medium even ~1000 times denser is still not likely to produce that great a change.

In fact, in terms of the relative magnitudes of the changes, in comparison, the 10e-4Hz change in water is massive compared to the 10e-11Hz change in air.

Speaking as an engineer, I think the thing to bear in mind is that we're discussing the effect of a medium with a density of 1000 kg/m^3 on a vibrating body with a denisty of ~8000 kg/m^3.

[3below]

Speaking as an engineer and physicist I think I will have to get some students (lab rats) building the test rig. The problem is complex and of interest. Plywood, old strings, machine head and bath to be pressed into service. Watch this space.

Edited March 3, 2013 by 3below

[flyfisher]

I'm sure we're all familiar with the pitch change of the human voice after taking a lungful of helium. Helium is lower density than air so the vocal chords are able to vibrate more freely and thus faster, giving a higher pitch to the voice.

Wouldn't the same principle apply to a bass string underwater? Except that the density change is vastly more than the change from air to helium so the effect would be to slow the vibration so much that the frequency would become subsonic and thus inaudible.

[ahpook]

[quote name='3below' timestamp='1362346159' post='1998803']
Speaking as an engineer and physicist I think I will have to get some students (lab rats) building the test rig. The problem is complex and of interest. Plywood, old strings, machine head and bath to be pressed into service. Watch this space.
[/quote]

you complete star !

really looking forward to the results...and i'm sure some popular science publications might be too...




top thread btw - it's been nice to try to press some of the dustier parts of my brain into action again

Edited March 3, 2013 by ahpook

[Beer of the Bass]

[quote name='flyfisher' timestamp='1362346898' post='1998816']
I'm sure we're all familiar with the pitch change of the human voice after taking a lungful of helium. Helium is lower density than air so the vocal chords are able to vibrate more freely and thus faster, giving a higher pitch to the voice.

Wouldn't the same principle apply to a bass string underwater? Except that the density change is vastly more than the change from air to helium so the effect would be to slow the vibration so much that the frequency would become subsonic and thus inaudible.
[/quote]

I've heard it said by a few people that helium changes the timbre of your voice rather than the actual pitch. So all of those higher harmonics which would usually be damped are suddenly audible, making the voice sound much different although the pitch hasn't changed. A quick google would seem to support that - the clearest explanation I could find was here;
[url="http://www.phys.unsw.edu.au/jw/speechmodel.html"]http://www.phys.unsw.edu.au/jw/speechmodel.html[/url]

[3below]

[url="http://basschat.co.uk/user/1234-ahpook/"]ahpook[/url] [color=#222222]It Is a long time since I have been called a star [/color] [color=#222222] It is a phrase I use on my students, showing my age.[/color]


[size=4]The initial question is a really good one, and not readily soluble to mere mortals ( ie sub Einstein abilty) or me without experimental data. It is the sort of practical real world Physics I enjoy. Let's build a test rig and find out... Will there be a significant difference between E and G string due to mass/unit length and diameter? etc, etc[/size]

[size=4]Lastly I also have a beard ! They are essential for all sorts of reasons [/size]

Edited March 3, 2013 by 3below

[ahpook]

[quote name='3below' timestamp='1362349583' post='1998868']
[b] [url="http://basschat.co.uk/user/1234-ahpook/"]ahpook[/url] [color=#222222]It Is a long time since I have been called a star [/color] [color=#222222] It is a phrase I use on my students, showing my age.[/color][/b]


[size=4]The initial question is a really good one, and not readily soluble to mere mortals ( ie sub Einstein abilty) or me without practical data. It is the sort of practical real world Physics I enjoy. Lets build a test rig and find out...[/size]

[size=4]Lastly I also have a beard ! They are essential for all sorts of reasons [/size]
[/quote]



essential indeed...how do people without beards ponder ?

[Beer of the Bass]

It'd be very cool if your experiment was documented with audio files. You could perhaps coat a cheap piezo disc in epoxy to stop it from shorting and attach it to your plank...

[3below]

[quote name='Beer of the Bass' timestamp='1362349870' post='1998876']
It'd be very cool if your experiment was documented with audio files. You could perhaps coat a cheap piezo disc in epoxy to stop it from shorting and attach it to your plank...
[/quote]

Piezo is where I was going, but am also interested in magnetic pu, ie how does the (potential viscous) drag affect the magnetic response? showing a total lack of knowledge I also wonder about what frequency is propagated in the medium (water). Will it be the same as the string vibration? This is not my branch of Physics so I may be asking very simplistic uniformed questions about well understood effects. Time for a lit survey I think. I had not thought of audio files, however that would be straightforward since the data would be voltage - time to obtain frequencies.

The fun bit is it is a simple experiment to execute and provides good data to answer the question. Before anyone asks, I can access a swimming pool so boundary reflections can be negated lol.

[EssentialTension]

Well, I was slightly taking the p*** when I started this thread but I bow to those who have taken up the baton.

[ahpook]

[quote name='3below' timestamp='1362350789' post='1998895']
Time for a lit survey I think.
[/quote]

if there's any articles you can't get hold of, and would like to see, do let me know.

about time i annoyed them at the British Library again

[3below]

[quote name='ahpook' timestamp='1362351142' post='1998907']
if there's any articles you can't get hold of, and would like to see, do let me know.

about time i annoyed them at the British Library again
[/quote]

Thanks, offer well received since my current employment provides lab rats but no access to journals etc

Essential Tension.... be careful what you start

[flyfisher]

[quote name='Beer of the Bass' timestamp='1362349263' post='1998864']
I've heard it said by a few people that helium changes the timbre of your voice rather than the actual pitch. So all of those higher harmonics which would usually be damped are suddenly audible, making the voice sound much different although the pitch hasn't changed. A quick google would seem to support that - the clearest explanation I could find was here;
[url="http://www.phys.unsw.edu.au/jw/speechmodel.html"]http://www.phys.unsw...peechmodel.html[/url]
[/quote]

Interesting article - thanks for that link. The audio file examples were particularly enlightening and quite clearly show that actual pitch doesn't, in fact, change when breathing helium.

I reckon my previous post can now be safely ignored.