There is an old paper where a musician claims to have used an oscilloscope to measure a particular trumpet tone and proved it was a pure sine wave. T here is no date available but probably late 50s, the company was started in 1956. So we're talking whatever scope technology would have been availabl e then.
I've always been a bit skeptical about the claims because there are some ot her aspects that don't make sense to me.
However, my question is about how you would use a 1950s era scope to determ ine a sine wave or the degree of harmonics present. Most musical tones hav e a series of harmonics above the fundamental that add the characteristic t one.
e to measure a particular trumpet tone and proved it was a pure sine wave. There is no date available but probably late 50s, the company was started in 1956. So we're talking whatever scope technology would have been availa ble then.
other aspects that don't make sense to me.
rmine a sine wave or the degree of harmonics present. Most musical tones h ave a series of harmonics above the fundamental that add the characteristic tone.
Seems doubtful, I mean I can play a pure sinewave into a speaker and I know what that sounds like. A trumpet sounds different.
An easy way would be to use a high pass filter or a notch filter to filter out the frequency of the note and then look to see if anything is left.
Look for a SINAD or distortion meter.
When you filter out the origioinal wave (first harmonic) anything that is left is from a frequency that is not the sine wave. It could be distortion or a harmonic. The scope could be used to determin what frequency or which harmonic is left over.
Well, given that the trumpet is driven by a relaxation oscillation of the player's lips, it would be quite strange if there weren't a lot of harmonics. Odd harmonics would be nearly resonant, I think, though the shape of the bell means that the resonance isn't really an organ-pipe mode.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
The eyeball is a really lousy detector of harmonics, though, especially odd harmonics.
Plus he had to use a 1950s-era microphone, so the scope bandwidth is irrelevant.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
I've used an RTA, but those hadn't been invented yet. Before my time, but wasn't there something called octave filters?
The experimenter wasn't real detailed but supposedly he could tell from loo king at the scope that it was a pure sine without harmonics. I was very sk eptical that 1950s technology allowed that. He is a believer that the mate rial a trumpet is made from determines the sound, whereas many of us believ e it is the shape of the air column.
I will quote the article:
****** At one time we ran an experiment in which we used steel, aluminum, various plastics, glass, silver, various combinations of brass and the last one we used was lead. To demonstrate results as quickly as possible, I will choose the two extremes. The steel bell, which we tempered so it was extremely ha rd, gave possibly one of the most interesting results. Many people test a b ell by tapping it with their finger or knuckle and in tapping the steel bel l, it would emit a very ringing sound, truly like a bell. However, when we played this instrument, the quality of sound was extremely dead. On searchi ng for the reason for this, we looked at the oscilloscope when the performe r played on the instrument and found the sine pattern very faint but the di stortion pattern, coming from the vibration of the bell itself, going throu gh at a very jagged and rapid rate, killing the brilliance of sound of the true tone. At the other extreme was the lead bell. This bell, if rapped wit h your knuckle, emitted an extremely dead sound like rapping on a piece of wood. However the sound that emanated when it was blown was extremely brill iant, brilliant to the point of being mechanical. This showed up on the osc illoscope as a perfectly true sine pattern, there being no distortions in t he harmonics either above or below, and, as a result, the sound was absolut ely pure but not usable musically, except for a general effect such as a pe rcussion instrument would give. The voice, you know, registering on an osci lloscope, gives harmonics both above and below the note. These distortions, if we may call them such, give warmth to the tone. We have to have that "d istortion" in order to have the sound acceptable to our ears as a musical s ound.
Well, he was wrong about that. Even 10% third harmonic isn't easy to spot unless you have a comparison sine wave on the screen at the same time. (I'm thinking about zero degrees relative phase, so the peaks are symmetrical. It's a bit easier to see at other phases.)
Unless he had a really expensive ribbon mic, his 1950s microphone had a heavy diaphragm and rolled off really badly above about 5 kHz. (One of the audio guys will correct this, but it's roughly right.) None of the nice 40-kHz piezo film mics you can get nowadays. (I have a matched set of Earthworks omni mics from about 15 years ago--their impulse response is about 15 microseconds wide.)
It's both.
Changing the material also moves all the mechanical resonances, which will have a huge effect.
Cheers
Phil "Not an audio guy" Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
I agree the material will have a huge effect on the mechanical resonances. It is not so clear that the mechanical resonances have any appreciable eff ect on the contained wind column resonances. There is no obvious theory wh y they should, and a couple of centuries of experiments have really failed to show much in the way of effect, whether done with listening tests or lab measurements.
Not always; I have no trouble looking at a filtered triangle-wave type "sine" and seeing the distortion, which is presumably under 1%. "Pure" to the ear doesn't require a spectrum analyzer with parts-per-million resolution and logarithmic display. I think the researchers were applying a loose definition.
Carbon microphone, maybe, but dynamic microphones were very well developed by then. A lot of early recordings were transcribed onto DVD, and the sound quality improved because the SINAD of microphone and tape were better than the rest of the phonograph process.
You're looking at the residual cusp, though, not the smooth details of the peak, right?
Sure, but they have big heavy diaphragms and coils, so their high frequency response stinks. (Velocity sensitivity helps, but low resonant frequency wins.)
A lot of early recordings were transcribed onto DVD,
I don't doubt that one bit. Record cutters especially.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
ted an extremely dead sound like rapping on a piece of wood. However the sound that emanated when it was blown was extremely brilliant, brilliant to the point of being mechanical. This showed up on the oscilloscope as a perfectly true sine pattern, there being no distortions in the harmonics either above or below, and, as a result, the sound was absolutely pure but not usable musically, except for a general effect such as a percussion instrument would give. The voice, you know, registering on an oscilloscope, gives harmonics both above and below the note. These distortions, if we may call them such, give warmth to the tone. We have to have that "distortion" in order to have the sound acceptable to our ears as a musical sound.
Could you give a citation, reference (or even a URL) to the article. I'd love to read it. Thanks
e to measure a particular trumpet tone and proved it was a pure sine wave. There is no date available but probably late 50s, the company was started in 1956. So we're talking whatever scope technology would have been availa ble then.
other aspects that don't make sense to me.
rmine a sine wave or the degree of harmonics present.
** The same way you might use a modern scope.
A sine wave has a distinct shape and the addition of harmonics visibly alt ers that shape. Instruments like the clarinet produce near square waves whe n playing most notes. Guitar strings vibrate with a series of harmonic freq uencies, depending how the string is struck. You can clearly see them on a scope screen if you plug an electric model into the vertical input.
Condenser mics were not common at that time, but certainly were not rare, either. The Altec 21B went to 15 kHz, which would handle the overtones of any real-world musical instrument easily.
Interesting foot note. A condenser microphone has a small plastic disk insi de that is always + on one side and - on the other. It is a charged condens er that can never be discharged no matter how you try to short it out. The molecules inside the plastic disk are frozen that way somewhat like a perma nent magnet.
Anyways to the subject at hand. If a guitar string is plucked in the middle of the guitar it makes a sound. If the string is plucked close to the brid ge it makes a different sound rich in higher harmonics. The difference betw een middle and bridge is the difference between sine wave and sine wave plu s higher harmonics. In short your ear can detect a sine wave without the ne ed of a oscilloscope. The same is true when repairing a graphic equalizer. The first time we bring out the guns with oscilloscopes , spectrum analyzer s and sweep generators. By about the tenth time doing this you just use a B eatles song and let your ear tell you if the graphic EQ is okay or needs sl iders cleaned or what not.
And that's if you know what you're looking for. Personally, I think I could detect lower, but I am not the norm. Second order harmonics should be easi er to detect with the aid of the "invert" button.
I have come to the conclusion that an invert on at least one channel is ess ential.
Anyway, I think the trumpet might be near sine wave at its upper ranges. Ju st from my ears a can guarantee it is not at the lower ones. Listen to, shi t, wait a minit...
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Most of the aggregation (is that the right word ?) of the sound is the atta ck and decay of course, but there is a wah wha part of it. Later, he gets u p to the higher notes, and then some of those could be sine waves. That hor n is a certain size and all that and the response does roll off at a certai n frequency just like a speaker.
At that whole system's highest possible resonant frequencies, the output mu st approach a sine wave.
I would go get you Pink Floyd - Dogs Of War for the super high notes on the saxophone. Unfortunately I can't find the right version in good enough ti me, it is late. But I suspect alot of wind instruments approach a sine wave at the upper end of their range.
Sure. At the risk of veering off topic, so with apologies.
Background: For centuries musicians have ascribed tone properties to the ma terials instruments are made of, while physicists shake their heads because the math seems to say that given sufficient wall thickness the material sh ould make no difference. Physicists who play an instrument are of course c aught in the middle.
When the argument gets rehashed, which happens frequently, the skeptics poi nt to the Smith review:
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There are of course many more papers than that that didn't find a differenc e but that's the easiest to find and understand. It reviews 13 of the bett er studies. It isn't that easy to make two identical instruments of differ ent materials, or in fact two identical ones of the same material.
There are only two "studies" that get quoted by the true believers: the Sc hilke study, quoted here:
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which is the one under discussion currently. You can see there is no date, no description, no publication, it's just a handout from a sales conventio n. The other one is the famous Conn study which suffers from the same absence of the actual original report so it gets quoted by both sides.
Thanks for the references. (I found the 'effect of lacquer' portion of Schilke's article really interesting and perhaps even convincing as my girl friend is considering de-lacquering her french horn) I play clarinet and the same sort of controversy exists for woodwinds - grenadilla vs. rosewood vs. delrin vs. ebonite vs. rubber, etc. In clarinets, it is clear that the performers are much more important than the composition of the instrument on which they're playing. But it's almost next to impossible to compare apples to apples since, as with brass instruments, the clarinets made of different materials also have different bore dimensions, undercutting, and other dimensional variations. And of course even with 2 instruments made of identical materials, one may cost $300, the other ten times as much. And 2 'identical' instruments, same make/model/vintage, may have subtle differences, particularly in intonation.
You are describing an Electret Microphone. It is a subset of Condenser Microphones. The others require a very well filtered high voltage source to keep the condenser charged.
By intonation do you mean the same thing as when you set up the neck of a g uitar ? On a guitar you basically set the twelfth fret to be exactly one oc tave up. I do not know about other instruments much. Fretless stringed inst ruments I guess you can set however you want, but that is not going to be t rue of brass, wood or wind.
Or are you talking about the harmonics ? The word intonation could be taken as that, and rightly by certain people who are talking about the tonal qua lity rather than the tone itself. Which is it ?
What's more, is there a way to set intonation, like on a guitar, on saxes, clarinets, and all that ?
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