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
- References:
- Graph Fourier Transform
- From: efifer@fas.harvard.edu
- Graph Fourier Transform