Posted by Rick Denney on February 13, 2004 at 14:18:12:
In Reply to: Re: Re: Re: Re: Re: Low register dynamics posted by Alex D on February 13, 2004 at 13:08:53:
That study compared brass musicians on different instruments playing the same absolute pitch. But the subjects included Chicago Symphony musicians, and therefore only included top-flight players who all produce sound using efficient methods. Had the study included beginners, the results might have been different. None of these guys would be taking shortcuts by using pressure tricks to avoid the proper flow of air.
I can say from observing myself that many players use pressure to augment the impedance of their embouchure, with the result that they make the pitch but with a thin and poor sound. There are notes I can hit with my teeth clenched that I can't get any other way, and going on results alone might lead me down that path. But more interesting to me is why clenching the teeth actually works at all. The reason is that it increases pressure and force on the small area of the lips exposed to the air, as a means of making too little air still cause vibration at the correct rate. That the real reason they can't move enough air because their chest muscles are all bunched up may be true, but relaxing their breathing muscles won't make the clenched teeth go away. These effects were not likely to be part of the measurements you cite.
But remember that force and pressure are also not the same thing at all. A very low pressure applied to a large surface area might create a lot of force, while requiring very little muscular input to create that low pressure. But to apply that low pressure over a large area requires a lot of air. (For example, airplanes are big and contain lots of air, and a pressurized cabin puts about 500 pounds of force on a passenger window, making explosive decompression possible if the window blows out. But the pressure is only about 8 psi, and would put much less than a pound of force on an area, say, the size of a bullet hole, making explosive decompression from a bullet hole nearly impossible.)
The number you report of 7 or 8 ounces is a force, not a pressure. Without knowing what area that force is applied to, it says little about the pressure. It was probably a reading on their apparatus, and that reading probably can be applied to the opening of the tube going into the mouth. That tube would have had to be pretty small not to interfere with the player's embouchure, which suggests to me that the pressure might have been fairly high to make that middle C. I think the maximum pressure one can hold back in their respiratory system is in the range of 4-6 psi, but getting a reading of 8 ounces with a pressure tube 1/8" in inner diameter would require 40 psi of pressure, which doesn't make sense. Do you know how they obtained those readings?
I also remember from that study (as quoted by either Jacobs or Fredericksen in Song and Wind) that the flow required to produce a fff low F was something like 140 liters/minute. With a vital capacity of perhaps 4 liters, I'd run out of air in 1.7 seconds. That makes your point better than any other number. People like me try to extend that time by using pressure tricks (clenched teeth, etc.) to reduce the flow of air, and I think that limits the effectiveness of the low range more than anything for beginning and intermediate players. But it is a method that focuses on results without understanding the underlying mechanisms.
Rick "who breathes a lot more often than he used to" Denney