Re: [Harp-L] Re: Covers

[Vern <jevern@xxxxxxx>]

Yes, for the reasons stated in my previous post. Harp manufacturers, in a struggle to differentiate their products, dish out a lot of baloney and harp players seem eager to accept it.  

Vern

On Jul 15, 2010, at 4:21 PM, Frank Mangiapane wrote:

> Vern, if what you are saying about cover plates is true , then could the rhetoric about the design of the cover plates on the Manji M-20 ,in essence the opened back and side holes, be more hype than help ?

> On Thu, Jul 15, 2010 at 4:57 PM, Vern <jevern@xxxxxxx> wrote:
> 
> On Jul 13, 2010, at 9:57 PM, JohnnieHarp wrote:
> 
> > Coverplate design and mods is one that comes to mind given current
> > claims made by customizers and manufactures as to volume increases,
> > etc, resulting from different coverplate forms (Suzuki Manji for
> > instance) ... personally, I have my doubts in the validity of these
> > claims based on my experiences ...
> 
> There are acoustic principles to support your skepticism and experience.
> 
> Diffraction:
> Through openings of less than a wavelength, sound spreads equally in all directions along circular wave-fronts.  Think of a pebble tossed in a pond. Because it is much shorter than a wavelength, the shape of a harmonica cover will not affect the direction of the sound.
> 
> Logarithmic human hearing:
> The human ear has a logarithmic response...and a good thing that is!  The same ear that can hear the buzzing of a mosquito or the wind whispering through the pines is not destroyed by a clap of thunder or the output of a loud harmonica amp.  However, it means that a few holes or a slight change in shape of a cover that affect the emanated sound energy by a small amount will be imperceptible.  Besides that, the covers are usually touched, enclosed,  and their possible effect negated by a hand-cup.
> 
> Cover design might/could have very minor effects on harmonica sound level,  but in real-world situations, the differences will be imperceptible.  The function of covers is to keep your hands off of the reeds.
> 
> The cover materials have no effect at all.  Siegfried Nahrun made brass CX12 covers that sounded no different from black plastic ones.  The notion that a shiny gold coating on CX12 covers will affect the sound is laughable.
> 
> I have blocked off half of the cover opening of a diatonic with a slab of metal thicker than the cover without changing the reading on my sound-level meter.  This means that bending the cover to increase the opening is futile.
> 
> Vern
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> -- 
> Franko