Re: RE: OT HARMONIC SERIES - Acoustics
2001-11-21 by Murray McDowall
Hendrik Jan Veenstra wrote: >>>On a valve-less instrument a skilled player is able to play each of >>>those harmonics "seperately", which is achieved through a combination >>>of lip pressure, air pressure, tongue position, etc. >> I replied: >>There was an article on the physics of the trumpet published in Scientific >>American in the 70's I think -- the guy set up an physical oscillator to >>drive a membrane over a mouthpiece of the trumpet and studied the response >>of the trumpet to a range of vibration frequencies on the input. > > >Uhm... am I supposed to now go read that article? Don't suppose they >have a 30 year old article online, do they? :-) Hi Hendrik, Probably not ;-) I find Scientific American in most decent libraries but I am in Australia. I have played trumpet myself and I thought it was an interesting article. Actually, there was a series of such articles in Sci.American over a decade including articles on the physics of the piano, bells and the violin. I found them better than what is on a lot of books on the physics of instruments. >>He termed each of the "notes" played by a trumpeter a "regime of >>oscillation" as most of them included more than one harmonic from the >>series. We perceive the pitch of the note played to be that of the lowest >>harmonic sounding. > >Sure, what you hear can never be one single harmonic -- as that would >imply the sounding note to be a pure sine, which in nature simply >doesn't happen. However, I don't see how this contradicts my posting >(if your posting was meant to do so :). AFAIK it's still true that >valveless instruments are limited to playing harmonics -- with >whatever overtones may be added to _that_. Yeah that is pretty true. I was merely adding a clarification -- just pointing out that the notes are not pure harmonics as is often assumed. The set of harmonics sounding is peculiar to each note on the series and the ratio of their amplitudes would obviously have a lot to do with the tone of the player/instrument. From memory, the article explains that the bell reflects sound waves back toward the mouthpiece and thus it supports the establishment of standing waves inside the instrument. The sound that leaks out the bell to the audience is a treble-boosted version of what is sounding inside. It also points out that the valveless clarino trumpet of baroque music had harmonics which could be bent around quite a bit -- they weren't nearly so centred on a pitch as those of modern horns and this property made it possible to play notes with them which -- strictly speaking -- aren't in the harmonic series. It was also twice as long as a modern trumpet -- more like a trombone in length -- so that a lot of the parts written for it were full of notes in the octave between the 8th and 16th harmonics. Regards, Murray