Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Kryptid on 03/09/2023 20:29:07
-
We are all familiar with the fact that inhaling helium makes your voice higher pitched. Does it do the same for all sounds travelling through it? If I was in a room filled with helium (while wearing an oxygen mask to avoid asphyxiation, of course), would things like footsteps, creaking doors, shattering glass, etc. sound higher pitched to me?
-
No it won't change sounds already made. What happens with inhalation is the resonant characteristics of the larynx are altered by a less dense gas. One can go the other way with a denser gas such as sulphur hexafluoride which will deepens one's voice.
-
No it won't change sounds already made. What happens with inhalation is the resonant characteristics of the larynx are altered by a less dense gas. One can go the other way with a denser gas such as sulphur hexafluoride which will deepens one's voice.
Would the same not be true of other objects set to vibrate in a helium atmosphere? Would shattering pieces of glass not have their resonant frequency changed?
-
I don't think so, Kryptid. The resonant frequency of the glass is determined by the physical properties and physical form of the glass. The larynx relies on gas properties, a bit like an organ pipe. Have look at organ pipes and how they work, with open and closed pipes influencing the frequency. There might be some slight effect with different gases.
-
SF6 has the opposite effect, turning a normal voice into a sub-bass.
-
Breathing helium does not alter the pitch of your voice.
It alters the timbre.
The pitch is dependent essentially on the tension and mass of the vocal cords (Men typically have bigger heavier voiceboxes and so they usually have lower pitched voices).
Helium affects the resonances of the cavities in the mouth throat nose etc and that's why your voice sounds weird. You get a different set of harmonics.
If you learn to control those harmonics to tally with the fundamental of teh note you are singing, this happens.
Or this
So, helium won't affect the note of a tuning fork, but it will for a flute.
-
A debatable point! The human voice is certainly more akin to a flute than a tuning fork, but there's more to it.
Wind instruments select a principal resonant frequency from an "edge tone" - essentially a square wave that determines the lowest frequency that can be selected. The fundamental will be suppressed if it is off-resonance with the air column, so the resultant is dominated by the selected pitch which is recognised as the pitch of the note, with any remaining harmonics or subharmonics determining the timbre.
In the case of a flute, the resultant is almost a pure sine wave. Reed instruments have a lot of upper harmonics, and brass instruments are colored by subharmonics down to the fundamental.
The term "formant" rather than timbre is more commonly applied to voice sounds . The vocal cords are similar to the pursed lips of a brass player but the output spectrum is dominated by the higher resonances of the larynx for vowels and the mouth for consonants, and the formant, the dominant part of that spectrum, is a function of gas density.
-
A debatable point!
The shape of the earth is "debatable", but the flat earthers are wrong.
The human voice is certainly more akin to a flute than a tuning fork
In the sense that, in order to sing low notes, one stretches one's neck to accommodate the longer wavelength.
Rather than holding a debate, we can look at an experiment.
https://newt.phys.unsw.edu.au/jw/speechmodel.html
-
A tone played through a loudspeaker will have the same pitch in air or helium.
If it is a bass reflex loudspeaker, the higher speed of sound in helium will make the bass response tail off at a higher frequency than in air. So the frequency of the tone will be unchanged, but lower frequencies will be less loud.
https://en.wikipedia.org/wiki/Bass_reflex
-
https://newt.phys.unsw.edu.au/jw/speechmodel.html
which clearly shows that the formant peaks are not, even in this crude model, at the fundamental.
In speech, you may have the illusion that the pitch has changed because one doesn't think much about pitch when listening to speech.
You can also convolve the format spectrum with the sensitivity of the human ear, so whilst it is true that the absolute frequency range isn't affected by the air density, the perceived pitch is.
-
from: alancalverd on Today at 08:34:21
The human voice is certainly more akin to a flute than a tuning fork
In the sense that, in order to sing low notes, one stretches one's neck to accommodate the longer wavelength.
I think you may be confusing a flute with a trombone. A Conversational Russian coursebook that was in wide use in the Sixties included the vital everyday phrase "That is not a tractor but a trombone", which suggests a particular Russian idiosyncrasy. Are you spying for Putin? You won't find much intelligence here!
-
I think you may be confusing a flute with a trombone.
In one case it's the length of an air column that determines the pitch, but in the other case, it's the length of the air column that determines the pitch.
Your job is to work out which is which.
-
You won't find much intelligence here!
Depends which posts I read.
-
In one case it's the length of an air column that determines the pitch, but in the other case, it's the length of the air column that determines the pitch.
Your job is to work out which is which.
Apart from the short tuning slide, the air column in my flute is exactly the same length at all times. I can however change the position of the principal resonant nodes by waggling the keys up and down. In principle, the air column length of a trombone is variable but right now, my slide has jammed, so I just have a very large bugle.
-
can however change the position of the principal resonant nodes by waggling the keys up and down.
It's almost as if you are changing the length of the resonating air column.
-
We also play "It's Almost Like Being In Love" (Lerner and Loewe) but it doesn't sound like "Being in Love" (Wet Leg). Nor does a flute sound like a trombone - at least it shouldn't!
The resonant column length changes in brass instruments, from a foot or so (piccolo trumpet) to 18 ft (Bb tuba) with roughly 12 equal fully resonant steps available to the valve combinations, but stays almost constant with woodwind - you just get a different distribution of nodes along the same tube length when you open and close the holes. Just to make it more interesting, there's a difference between conical bore (horns and saxophones) and constant bore (trombones and flutes) sounds: conical bores favor even harmonics and switch whole octaves whilst constant bores favor odd harmonics and switch a twelfth if you alter the edge tone.
-
When you play the flute, is the wood resonating, or is it the air?
-
Principally the air, but the length of the air column and the timbre of the harmonics are determined by the wood (or metal in most cases nowadays) .
But apropos the original question, Paul made an important point a while back: if you filled your trombone or bagpipe with helium, would that alter its pitch? It's not a completely daft question because contrary to what the Health Security Agency (or whatever it is called today) thinks, you don't actually blow much gas out of a wind instrument. Indeed in the case of a flute, you don't even blow into it. So you could in principle fill the column with any gas you like.
-
length of the air column and the timbre of the harmonics are determined by the wood (or metal in most cases nowadays) .
So, a brass flute would sound more like a tin whistle than like a wooden flute.
And a wooden flute would, I guess, sound like a recorder, rather a metal flute.
Or... not.
I suspect that the reason why plastic musical instruments exist is that, to a first approximation, the timbre depends on the shape of the instrument.
It would certainly be interesting to fill a flute with helium (or hydrogen, if you are concerned that He isn't a renewable resource) and close it with cling-film so you don't blow any air through it.
I suspect the tone would not be improved by a bit of thin plastic, but it would illustrate a point.
: if you filled your trombone or bagpipe with helium, would that alter its pitch?
One way to find out; check on YT and see if it's been done.
Apparently, if you put helium into a bagpipe it turns into laughing gas.
-
Not really a proper controlled experiment. Bagpipes always make people laugh. Or cry.
There is a significant difference in timbre between wood and metal flutes. A professional flautist friend selects from her considerable collection according to the mood of the piece she is recording or performing. I wouldn't dare to ask her opinion of a plastic flute, but
Fiberglass sousaphones can be found commonly in younger marching bands, such as middle schools, due to their lightened weight load. Depending on the model, the fiberglass version does not have as dark and rich a tone as the brass (King fiberglass sousaphones tended to have smooth fiberglass and a tone somewhat more like a brass sousaphone; Conn fiberglass sousaphones often had rough fiberglass exteriors and a thinner sound; the Conn is also lighter)
so the material and surface finish are important. Aficionados claim to be able to tell the difference between a brass and a silver band, but I don't aspire to play at such a level.
-
. A professional flautist friend selects from her considerable collection according to the mood of the piece she is recording or performing.
Not really a proper controlled experiment.
-
The control is exercised by her customers, who know what sound they want. Having heard her perform with various flutes in a single concert, I can vouch for the difference.
-
Is your computer hooked up with silver wires and gold-plated plugs and sockets?
Their customers swear that they know what sound they want.
So...
Not really a proper controlled experiment.
-
I can only suggest that you talk to, or preferably listen to, a professional flautist. Two good choices are both American, both work in London, and are both called Nancy: Nancy Hadden and Nancy Ruffer.
-
I can only suggest that you talk to, or preferably listen to, a professional flautist.
I have.
But there's no point if my "tin ear" can't distinguish their silver flute.
I'm not interested in someone's subjectivity and bias; not even if it's my own.
Has anyone actually done a double blind trial?
This sort of thing always reminds me of audiofools and the cobblers talked by wine experts.
-
BC, while I agree wholeheartedly with your dismissal of audiophools and wine "experts" I feel Alan has a valid point. Two popular electric guitars are the fender Stratocaster and the Gibson les paul and I, with my tone deaf ears, can distinguish them, unless the sound is heavily processed. The technical difference is in the pickup coils: the fender is a single coil job and the Gibson is a twin coil antiphase arrangement( as a hum cancellation effort ).
-
The technical difference is in the pickup coils: the fender is a single coil job and the Gibson is a twin coil antiphase arrangement( as a hum cancellation effort ).
It's clear that a humbucker coil would make a difference.
What's less clear is that a few microns of silver plating on a tuba would make a difference.
Somewhere there''s a cut off of audibility.
Does a plastic saxophone sound different because it's made of plastic, or because it has thicker walled pipes or because it looks tacky?
My point remains; until someone actually does a properly controlled experiment, we have not ruled out hype for silver flutes any more than we have ruled it out for gold plated fuses costing more than a car.
-
Having heard her perform with various flutes in a single concert, I can vouch for the difference.
Are the instruments meaningfully different, or does she play them differently because they are different?
(Or even because she's playing a different piece of music?)
Good luck with the experimental design.
https://en.wikipedia.org/wiki/Stradivarius#:~:text=The%20many%20blind%20experiments%20from,in%20numerous%20works%20of%20fiction.
-
a plastic saxophone
Some researchers are 3D-printing plastic violins. They model the structure on computers, so the sound is very much like a professional wood violin.
Unfortunately, you can't use a 3D-printer to turn yourself into a professional violin player!
https://www.sciencefriday.com/segments/3d-printed-violin-song/
-
A couple of years ago I heard a radio presentation on the subject of violin materials, mostly based on work at the University of Surrey. The timbre of a carbon fiber instrument was clearly different from a "reasonably priced" wooden one with the same strings and bow.
BC's source states The many blind experiments from 1817 to as recently as 2014 have found no difference in sound between Stradivari's violins and high-quality violins in comparable style of other makers and periods, nor has acoustic analysis.
(my emphasis) Which makes sense. The wood, brass or whatever doesn't know the name of the craftsman who made it.
"Comparable style" is a bit vague, however. You'd expect every violin made exactly to a Strad pattern with similar materials would sound pretty much the same but if you altered the shape of the f-slits alone, you'd change the resonances (you can see this with Chladni patterns or interferometry) and thus the resultant spectrum, which casts some doubt on the finesse of said "acoustic analysis". The distinguishing feature of Stradivarius, Guarneri and other famous instruments seems to be their longevity: "student" violins rarely survive a couple of generations before warping or splitting, whereas the historic instruments still sound bright and precise after 300 years, and this seems to be the result of very specific sourcing and treatment of the wood.
-
"Comparable style" is a bit vague
historic instruments still sound bright and precise
What are the units of brightness and precision in this context?
-
"Sound" in this context is very subjective. Anyone who has heard both Abba and Jacques Brel, or has played both fretted and fretless stringed instruments would know the difference. Or in the specific case of the violin family, the difference between my old (1960s) slightly warped Czech 3/4 double bass and an 1800s German concert bass in good condition. It would be nice to think that the owner of a million-pound Stradivarius would take care not to fall down the stairs of a pub whilst carrying the tools of his trade, but it can happen and at least you can repair a cheap bass with Araldite and a few screws without the next audience complaining.
-
"Sound" in this context is very subjective.
That's why we invented
"acoustic analysis"
-
You still have the problem of comparing an objective spectral measurement with a subjective appraisal of "niceness" or whatever it is that makes a solo violin acceptable to the human ear, when they are both subject to the huge variance in technique even with a single note repeated by an expert (which is what makes live music more interesting than a recording*).
Given the variance in technique, it would indeed be surprising if there was any consistent distinction between a Strad and a Guar under semilaboratory conditions (e.g. blind playing by human experts), but equally surprising if you couldn't distinguish between an "established" wooden and a new plastic instrument of any type played under laboratory conditions - i.e. mechanical bowing and stopping. If interferometry shows that different instruments deflect differently, physical acoustics suggests that they must have different radiated spectra.
That said, I would be delighted to meet anyone who buys goldplated fuses to listen to a Sarasate recording: I have a sack of magic beans for sale.
*Footnote (to be played on a shoehorn?): A jazz musician is defined as a guy who never plays the same thing once.
-
When it comes down to it, a piano played in helium will sound pretty much the same as in air.
But bagpipes are significantly funnier in helium.
There's a story about two guys who are arguing about the quality of a stereo system
The owner says it's good. The neighbour says it sounds artificial and he should change the cables.
They agree to do a blind testing on the cables using a recording of a flute solo. The neighbour will listen from the other room to see if he can tell the difference.
So the guy changes the cables, and the neighbour says it's still not right, and suggests a different tone arm.
So the guy changes it.
And again, listening from the other room, the neighbour still says it doesn't sound right.
At this point the guy is getting irritated.
So the next time, when the neighbour says he should change the speakers, he says he will and agrees to another test.
And when the neighbour says "it still doesn't sound right", the guy asks the flute player, still playing, to walk in from the next room.
All the neighbour needed to do was flood the next room with helium.
It would make little difference to the pitch of a recording played through a loudspeaker; but it would wreck the live performance.