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

["Vern Smith" <jevern@xxxxxxx>]

----- Original Message ----- 
From: "Rick Dempster" <rick.dempster@xxxxxxxxxxx>
To: "Joe and Cass Leone" <leone@xxxxxxxx>; "Vern Smith" <jevern@xxxxxxx>
Cc: <harp-l@xxxxxxxxxx>
Sent: Sunday, April 20, 2008 5:17 PM
Subject: Re: [Harp-L] RE: Fatigue and Reed Life: An Objective Test?


> The two reeds, or the double-width reed, would be twice as loud, would it 
> not? providing the player was pushing enough air through.

Hearing is logarithmic, i.e. it takes a very large change in sound energy to 
make a perceptible change of loudness.   This is a great advantage. It 
enables us to hear the breeze sighing through the pines and the scream of a 
jet engine with the same ears.  The loudness of one sound relative to 
another is measured in decibels (db).  The difference in  loudness of two 
sounds in db is ten times the logarithm of the ratio of their sound 
energies.

You can demonstrate this easily with a chromatic harp.  Blow the C in hole 
4.  Now blow the C in hole 4 AND the C in hole 5. (The two reeds must be 
close enough to the same pitch that they do not beat.)  You won't notice 
much (if any) change in loudness.  You have doubled the energy output of the 
harp but have increased the loudness by only +3 db.

> Musing further on this, would it take twice the amount of breath to 
vibrate the two/double reeds - or is  my imagination on the right path when 
it suggests to me that, like a vehicle on wheels, there is an advantage from 
momentum once inertia is overcome?

The amount of air that flows past the tip of the reed would double.  The 
amount of air that flows past the sides of the reed would remain the same. 
The sum would amount to less than the doubling of the airflow.

> Lastly, while I'm thinking of it, why are XB40s so loud; they certainly 
> don't seem to need any more breath than a standard diatonic.

I have never seen a disassembled XB40.  I don't know.  Do you think that the 
XB40 is louder than the CX12 blown with the same breath pressure?

Vern
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