[ntp:questions] Confused about pool rotation

Robert Scott no-one at notreal.invalid
Thu Feb 7 15:43:09 UTC 2013


On Thu, 07 Feb 2013 08:10:44 +0000, David Woolley
<david at ex.djwhome.demon.invalid> wrote:

> If it is measuring the 
>frequency, the first problem is going to be defining what you mean by 
>frequency.  In Fourier terms, the spectral width of a piano note is 
>going to be more than 12ppm and depend on the exact interval over which 
>you measure it.  I would also suspect that the zero crossing interval 
>changes significantly during the note, particularly at the start.

You are right.  Piano tones do not have a pitch that is measurable to
within 12ppm.  To some extent it is specsmanship.  The professionals
who use these products like the idea that the device is 10 times more
accurate than it has to be.  So to be competitive I have to offer that
level of accuracy.

And by the way we don't use zero-crossings.  We use quadrature phase
detection to get the most information out of the brief tone that the
piano makes.


>>> I don't see how $300 can be considered low cost.
>> 
>> It is quite simple.  There are no comparable apps to mine that cost
>> less.  There are two comparable apps to mine that cost quite a bit
>> more.
>
>This sounds like pricing is based on hardware designs that haven't 
>changed significantly in 30 years.

It is based on iPhone hardware.  My main competitors are also on the
iPhone.



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