Re: [Harp-L] RE: Fatigue and Reed Life: An Objective Test?

["Vern Smith" <jevern@xxxxxxx>]

> ----- Original Message ----- 
From: "Robert Coble" <robertpcoble@xxxxxxxxxxx>
To: <harp-l@xxxxxxxxxx>
Sent: Saturday, April 19, 2008 10:18 AM
Subject: [Harp-L] RE: Fatigue and Reed Life: An Objective Test?


We are certainly in complete agreement about the test design for evaluating
the fatigue properties of reed materials.

I am unable to resist a comment on the following:

> ..................... Take a good look at the Web site that Dave posted:
> http://www.seydel1847.de/epages/Seydel.sf/en_GB/?ObjectID=211764
> If that doesn't "prove" the existence of very sophisticated engineering
> test facilities, then I don't know what would. Those types of tests are 
> NOT
> performed by Joe Sixpack in his garage, ...........

In the past, that statement would have been true.  However, today Joe needs 
only a PC, and a  $50 downloadable software package such as "Spectrogram". 
Joe just plays a constant pitch and level into his PC for several seconds 
and the fourier-analysis software produces a spectrogram.

In '97, I made PC-computed spectrograms of machine-played diatonics having 
various comb materials.  I found that the reed-to-reed spectrogram 
variations in nominally identical harps were as different as the 
spectrograms of harps having different comb materials. It made me very 
cautious about drawing conclusions from differences in sample-of-one 
spectrograms.

I am inclined to believe that SS would be more resistant to fatigue because 
there are data on metal properties that support the claim.  That said, there 
are many alloys that are called SS and they have a large range of property 
values.

I am much more skeptical of claims to superior SS tone.   The characteristic 
sound of a harmonica does not emanate from the reed as from a bell.  It is 
generated by the modulation of the airflow as the moving reed opens and 
closes the slot and changes the flow area.  This is a function of reed 
shape, slot shape, frequency & amplitude of vibration.  Assuming that these 
variables are the same, no one has elucidated a mechanism that would account 
for a difference in tone arising from reed material.

What are the differences in repeated spectrograms of the same reed?
What are the differences in spectrograms of different but "identical" reeds?
What are the differences in averaged data of multiple reeds of each type?
Can human hearing perceive the differences seen on the sprctrograms?

Thus far, I haven't seen convincing test data or a theory that supports 
different SS tone. I have a 270 chromatic in which there is just one SS 
reed.  So far, no one has been able to identify it by playing or listening 
to the harp.  Since human perception is involved, a "blind" comparison is 
required.

Vern
Visit my harmonica website www.Hands-Free-Chromatic.7p.com