 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Natural Science Forum / Physics / Acoustics / September 2005Why do conical resonators support even harmonics?
Aside from the clarinet and oboe having single and double reed respectively, the main difference in construction is that the clarinet has a uniform bore while the oboe has a conical bore. Supposedly, the clarinet will not generate strong even harmonics. The clarinet forms an closed boundary condition at the mouthpiece and an open boundary condition at the open end. On the other hand, the oboe with similar boundary conditions, along with the saxophone and other conical bore instruments, will readily support even harmonics. Is there a simple way, short of solving partial differential equations, to understand why this is so? Is there some way to determine how easy it is to excite such harmonics? Would that involve acoustic impedance seen at the mouthpiece? How does the cone angle affect excitation of the various harmonics? Bill I don't know of any way to show this other than by solving the partial diffential equation, which I can do. For many years I taught a course in the physics of music, and yearned to find a "hand-waving" way to show the resonances on a conical pipe, but never found one. Consider the acoustic pressure in an open-open pipe narrower at one end than the other. The pressure will be higher near the narrow end. (Of course it is close to zero right at an open end.) And the resonances will be as for an open-open pipe. Now imagine squeezing the narrow end down to where it is actually closed; then the pressure will be quite high at the point. But this is not the same as having a closed-open pipe, and the resonances will still be as for an open-open pipe. I don't regard the above as a good argument, though. For if one started with a closed-open pipe and narrowed one end, one would come to a different conclusion about the resonances! : Aside from the clarinet and oboe having single and double reed respectively, : the main difference in construction is that the clarinet has a uniform bore [quoted text clipped - 4 lines] : saxophone and other conical bore instruments, will readily support even : harmonics. : Is there a simple way, short of solving partial differential equations, to : understand why this is so? Is there some way to determine how easy it is to : excite such harmonics? Would that involve acoustic impedance seen at the : mouthpiece? How does the cone angle affect excitation of the various : harmonics? Try here: http://www.phys.unsw.edu.au/~jw/pipes.html On 9/1/05 10:20 PM, in article 1125638445.056791.201940@o13g2000cwo.googlegroups.com, "Apollo" <ddavis@pb.com.au> wrote: > Try here: > > http://www.phys.unsw.edu.au/~jw/pipes.html When I looked at this site, comparisons were made among flute, clarinet, and oboe of lengths that gave the same fundamental frequency. The flute and oboe were of the same length while the clarinet was half the length. I understand why the clarinet is half as long as the flute. But, that changes my question. Why does the oboe not support a closed-open resonance of a quarter wavelength the way a clarinet does? As the taper of the bore changes, when does that transition take place? Is it indeed true that an oboe and clarinet of the same length will not have the same fundamental frequency? Bill |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2009 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.