Re: noise_table question

Paul -
I think you're correct that this ought to be clarified, that
the frequencies should be strictly greater than the previous.

I could imagine that someone might think to create a 
discontinuous interpolation by specifying
{ 1,5, 10,5, 10,1, 1e3,1 }
such that one gets 5 on the interval [1,10) and
1 on the interval [10,1e3].  However, 
a) the value at 10 is ambiguous
b) noise probably shouldn't be discontinuous like this
c) one can still get arbitrarily close to this by
specifying { 1,5, 10,5, 10.0000001,1, 1e3,1 }
and satisfy the new requirement.

-Geoffrey


Paul Floyd wrote:
> 
> In the 2.2 LRM, Section 4.5.4.3 it says
> 
> /"The noise_table() function interpolates a vector to model a process
> where the spectral
> density of the noise varies as a piecewise linear function of frequency.
> The general form
> is
> noise_table( vector [ , name ] )
> where vector contains pairs of real numbers: the first number in each
> pair is the
> frequency in Hertz and the second is the power. Noise pairs are
> specified in the order of
> ascending frequencies. noise_table() performs piecewise linear
> interpolation to compute
> the power spectral density generated by the function at each frequency."/
> 
> It's not entirely clear to me that each frequency must be greater than
> the previous one (as opposed to greater than or equal). If "greater than
> or equal" were permitted, then it would introduce the posibility of two
> frequencies having different power levels, which would make the
> interpolation ambiguous. Clearly this is not the intent.
> 
> Do you think that it is worth changing the wording to make it explicit
> that no duplicate frequencies are allowed?
> 
> Regards
> Paul

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