Here's why brass


[ Follow Ups ] [ Post Followup ] [ TubeNet BBS ] [ FAQ ]

Posted by Dan Schultz on January 15, 2002 at 23:46:30:

A week or so ago there was a discussion as to why brass in the material of choice for the manufacture of modern brasswind instruments. I received the following opinion from a friend of mine who has been working with acoustics for many, many years. It's about the most understandable explaination I have come across. He says:

There is a good reason to make horns out of brass. The "Q" of the resonant cavity of the horn body is what gives you the output. The higher the Q the more times the sound will oscillate in the cavity with each excitement from the mouthpiece. One of the elements in the formula for this mechanical Q is the modulus of elasticity of the material the cavity is made of. The great thing about brass is the Modulus of elasticity is the basically the same for all conditions, work hardened or annealed. Brass, aluminum bronze, nickel silver, and phosphor bronze are about the same. Some of the regular steels, stainless steel, pure nickel, and monel are higher and there are probably others.
There are other things to consider in making an horn. High Q gives you more output and a pure tone with less harmonics. To change the sound quality you have to increase the harmonics. You do this with mutes and other add on items and in the case of the french horn putting your hand in the cavity.
High Q horns can not be played rapidly without doing something to stop the oscillation. After you stop exciting the cavity it has several oscillating cycles, called Q cycles before it dies out, unless you do something to stop it. This is quite a problem in the piano where you have felt pads you touch the strings to stop the vibrations.
There are more things I could say about horns some time I will write a short
paper.

Mel Baxter
Scientist, inventor, and otherwise all-around nice guy



Follow Ups: