Saxophone Acoustics

[jbtsax]

In trying to mathematically recreate the node positions in an alto saxophone neck as shown by Ernest Ferron in his book "The Saxophone is my Voice" I discovered that Ferron made a mistake by dividing the distance between nodes by 3 to determine their relative positions.

If anyone is interested, the results of my study can be found at this link:

http://jbtsaxmusic.homestead.com/Acoustics.html

Since there are those in the music industry who have copied the illustrations of the neck node positions from Ferron's book and distributed them in the saxophone community as though they were accurate scientific information, I feel it is important to make the correct information available.

John

 

[acglass]

What a cool resource. What instrumentation did you use to produce these findings?

 

[jbtsax]

The illustrations were done with Corel Draw and the graph (spreadsheet) was done using Excel. There are just a few easy math equations involved in creating the data.

The wavelength (l) is the speed of sound (c) divided by the frequency (f).

The speed of sound in a warm moist instrument is usually represented by 347 m/s or 347,000 mm/s. Therefore the wavelength of A = 440 is: l = 347/440 = .7886 m or 788.6 mm.

A sound wave travels to the first open tonehole (or bell) and back to make a complete wave so the length of the instrument that sounds that note is always 1/2 the wavelength. Another way to say it is that the soundwave is 2L and the length of the saxophone is L.

For the note A Concert (F# on the alto sax) the length of the sound wave is 788.6 mm and the "sounding length" of the saxophone from the apex of the missing cone is 394.3 mm.

A great resource to learn more about saxophone acoustics is here: http://www.phys.unsw.edu.au/~jw/saxacoustics.html

John