Thank you, David. I think we all like to hear "bravo" from time to time.
Certainly horn sound is the result of extremely complicated interactions with our surroundings and with ourselves. Some of the interactions are non-linear, such as your lip's response to the oscillations taking place within your horn. The point of my post was to suggest that we not worry about all of those technical details because we'll never completely figure them out. As a seismologist, I can say that the response of a building to an earthquake is also a very complicated problem. We will never be able to explain all of the details of how the fault ruptured at depth, how all of the seismic waves (some of which are sound waves) interact with all of the heterogeneous geologic materials along the path, or how each individual structure will respond to the shaking at its base. However we do understand a lot about how these things work. We can place seismometers (basically microphones) at the base and the roof of a building and, after a bit of processing, determine the building's transfer function for a particular set of incident waves. This is an empirical transfer function, not a theoretical or ideal one. Other sets of incoming waves will generate slightly different transfer functions. However, after measuring a few of these, we can see clear similarities. We can determine an average response for the building that allows us to predict how the roof will move when the base is shaken by some future earthquake. To use such an empirical transfer function for the horn, you would take the sound recorded at the bell, transform into the frequency domain and multiply by the transfer function in order to approximate the sound that would have been recorded if a microphone had been placed out in front. That transformation into the frequency domain suggests that this processing would have to be done later on a computer. Therefore it would be more useful for recordings than for live mixing and playback. Robert, I appreciate that some recording engineers can obtain beautiful horn sound from a mic placed in or near the bell. I have little to no experience, good or bad, but have read others complain about recordings made too close to the bell. It makes sense to me. For those of you still in the "huh" camp, just about every system involved in creating sound can be considered a linear filter. Most of these filters limit the amplitude of sound produced at some frequencies. For example, a good microphone or a good speaker will be "flat" to signals within some frequency band, but will fall off at higher and lower frequencies. The concert hall or your carpeted living room also act as filters, passing some frequencies and absorbing others. Linear filter theory says that the sound you perceive is the result of a whole bunch of filters, applied in sequence, to the sound generated at its source. By the way the source, your horn, is also a linear filter, an oscillator whose resonances are more complicated than simple physics can explain perfectly. Jeff Barker (Simple seismologist and even simpler horn player) Assoc. Prof. of Geophysics, Binghamton University, Binghamton, NY -----Original Messages----- Date: Thu, 18 Feb 2010 00:02:57 GMT From: "[email protected]" <[email protected]> Subject: [Hornlist] Empirical horn transfer function To: [email protected] Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1 Professor Baker - this is an interesting idea and I say bravo for thinking along such lines in response to a common, practical problem. I think such mucking around in the frequency domain is commonly done in generating/editing audio for certain effects, and in many recording and production circumstances. The problem is with this idea applied to recording is that the acoustic environment around a horn (the room) and its interaction with the horn and the microphones is fundamentally NOT a linear system. There are all kinds of nonlinear coupling and effects in such a complex acoustic system. Probably to a weak first-order approximation this transfer-function could be made, but I believe your suggestion relies on clean, linear-superposition of the behind and front acoustic signals, which would not be very accurate in a real situation. Check out the literature on acoustic source-separation and you'll find this problem ubiquitous in similar tasks. just my .02 cents. this would not be hard to mock-up in MATLAB sometime and try it out. any other thoughts anyone? david - physics and horn performance student ____________________________________________________________ Nutrition Improve your career health. Click now to study nutrition! http://thirdpartyoffers.juno.com/TGL2131/c?cp=7J1fl7BlM62h3OKqnQEtXwAAJz2tEPjwKKiSDPsz4fU1aV0DAAYAAAAAAAAAAAAAAAAAAADNAAAAAAAAAAAAAAAAAAASQwAAAAA= ------------------------------ Date: Wed, 17 Feb 2010 22:29:30 -0800 From: "Robert Dickow" <[email protected]> Subject: Re: [Hornlist] Empirical horn transfer function To: "'The Horn List'" <[email protected]> Message-ID: <001901cab063$bb87a3c0$3296eb...@edu> Content-Type: text/plain; charset="us-ascii" I've done studio recording gigs each with different mike placements. I did a Wells Fargo Bank commercial where the engineer put a mike directly in my bell, though I could still use my right hand in there. On the playbacks I fancied that the balance needed more horn, because it was kind of a nice line, so I played a little fuller on the next take. They just turned my levels down further! I don't know what kind of mike it was, but it sounded really nice. They put mikes very close to all the instruments, and I was impressed that they could isolate each component of the drum kit instruments amazingly well, given that they were right next to each other. Bob Dickow Lionel Hampton School of Music -------------- It is widely agreed that the best microphone placement for recording horns is in front of the player(s). This is because our concept of horn sound includes the effect of the hand in the bell...<snip> ------------------------------ Date: Thu, 18 Feb 2010 09:16:22 -0800 (PST) From: Herbert Foster <[email protected]> Subject: Re: [Hornlist] Empirical horn transfer function To: The Horn List <[email protected]> Message-ID: <[email protected]> Content-Type: text/plain; charset=us-ascii OK, this is getting technical, but where do the nonlinear effects come from? As I understand it, nonlinearity happens when the response is amplitude dependent. Reflections from hard surfaces, even complicated reflections, will be linear. Reflections from softer surfaces, say human bodies, may be nonlinear. Do the nonlinearities come from the bodies of the players? Beats, the wah-wah from different frequency sources come from the nonlinearity of the human ear. Multiphonics come from the nonlinearities of the player. Herb Foster
_______________________________________________ post: [email protected] unsubscribe or set options at https://pegasus.memphis.edu/cgi-bin/mailman/options/horn/archive%40jab.org
