Re: Discrete Fourier Transform Question


Erik wrote:
I have a question for people knowledgeable about the DFT. In the digital
audio workstation program "Cubase SX", there is a tool which performs a
DFT on a given audio recording. I'm a bit puzzled by one of its
features.

Before it performs the DFT, it asks the user to input the size, in
samples, of the analysis blocks that it will divide the audio into for
processing. This makes sense to me. As the size of the analysis blocks
increase, so does the frequency resolution increase, obeying the
relationship frequencyresolution = 1/T, where T is the length in seconds
of the analysis block.

However, the puzzling part is that if I set the size in samples of the
analysis blocks to a value greater than the length of the audio recording
being analyzed (in samples), resolution continues to increase. Is the
additional information provided by increases in resolution produced by
using analysis block sizes greater than the length of the audio recording
meaningless/garbage?

I've tried contacting Cubase's tech support department, but they're
clueless. Any help would be much appreciated, thanks very much =)

They are probably zero padding from the end of the audio data until the
FFT size. This produces an apparent increase in resolution, but it is
really just an interpolation and provides no additional information.

John

.

Relevant Pages

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