MathGroup Archive 2007

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Graph Fourier Transform

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78927] Re: [mg78901] Graph Fourier Transform
  • From: Sseziwa Mukasa <mukasa at jeol.com>
  • Date: Fri, 13 Jul 2007 05:58:04 -0400 (EDT)
  • References: <200707120921.FAA08359@smc.vnet.net>

On Jul 12, 2007, at 5:21 AM, efifer at fas.harvard.edu wrote:

> Hi,
>
> I'd really appreciate some help on how I should graph a Fourier  
> Transform of a
> sin function. I am trying to create a frequency spectra of a sound  
> and have the
> input:
>
> FourierTransform[Sum[ampout[i]*Sin[(2.*3.14159*freq[i])t], {i, 1,  
> 18}], t, ?]
>
> As I am trying to get the continuous Fourier Transform. However the  
> answer this
> gives me is full of dirac deltas, which will plot to zero on a graph:
>
> Plot[FourierTransform[Sum[ampout[i]*Sin[(2.*3.14159*
>       freq[i])t], {i, 1, 18}], t, 300], {t, 0, 40}, Axes -> True]
>
>
> Does anyone know how I can manipulate the data to get the major  
> frequencies in
> the sound to show up as peaks on the graph?

Are you sure you want the continuous Fourier Transform?  A Sin  
function has infinite energy since it is interminable, hence the  
Dirac Deltas.  Typically one is interested in a sampled signal and  
its Discrete Fourier Transform, especially when they wna to graph the  
spectrum.

Regards,

Ssezi


  • Prev by Date: Re: Log Error ( ? )
  • Next by Date: Re: Graph Fourier Transform
  • Previous by thread: Graph Fourier Transform
  • Next by thread: Re: Graph Fourier Transform