Re: [Harp-L] Embossing and Compression (was Rick Epping, father of embossing)



On Dec 29, 2012, at 10:11 PM, David Payne wrote:

> 15 inches of water pressure? Vern, have you ever graphed that choking pressure for different gap sizes?

No. 15 inches of water pressure is approximately the choking pressure for a gap that allows the reed to speak at about 0.5 inches of pressure.  within limits, the choking pressure would probably go up slightly with a higher gap. However, so would the pressure to make the reed start.

> How does that go with the pressure and volume?

I think that the logarithmic response of the human ear is responsible for the flattening of the pressure vs loudness curve.

> Is that relationship the same as with added sound... say when two reeds play at the same time, the sound is not twice as loud?

I think that it is caused partly by the logarithmic response of the ear.  It may be also partly caused by canceling of the highs and lows of the two sounds.  If two sounds of exactly the same amplitude and frequency but 180 deg out of phase arrived at your ear, you would hear nothing.  Noise-canceling headphones use this principle.  There are microphones in each earphone that pick up the noise, invert it's phase, and add it to the signal going to the earphone speakers.  Because the wavelengths are longer, this works better at low frequencies.   

>  
> Does the amplitude of the reed travel have a linear relationship with the amplitude of sound? 
>  
> David Payne
> www.elkriverharmonicas.com
> www.hetrickharmonica.com
> 






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