Might "spectral leakage" be irrelevant?

In another thread Rick Lyons said:
"Windowing is generally used to reduce the spectral leakage
that causes a strong (high amplitude) signal's spectral magnitude
to cover over (swamp out) the spectral components of nearby weak
signals.  If a weak signal (in which you're interested) is
3-4 FFT frequency bins away from a strong signal's center
frequency, use the Hamming window.

If the weak signal (in which you're interested) is more than,
say, 6 FFT frequency bins away from a strong signal's center
frequency, use the Hanning window."

I'm investigating speech.
I am externally constrained to use a sample rate of 44 khz.
My experimental procedure specifies looking at
      10 mSec, .1 Sec, and 1 Sec samples.

My thesis statement is that "speech may be suitably characterized by 
total power in bands no narrower than 1/x octaves". [ My current 
opinion is that .3 < x < .5 ].

Since any analysis I do will be based on a sample at least 40 bins 
wide, can i legitimately ignore leakage?

[ Aside to voice recognition lurkers, I'm asking ONLY if my approach 
is valid in DSP terms. ;]

On Fri, 02 Apr 2004 16:53:12 -0600, Richard Owlett
<rowlett@atlascomm.net> wrote:

>In another thread Rick Lyons said:
>"Windowing is generally used to reduce the spectral leakage
>that causes a strong (high amplitude) signal's spectral magnitude
>to cover over (swamp out) the spectral components of nearby weak
>signals.  If a weak signal (in which you're interested) is
>3-4 FFT frequency bins away from a strong signal's center
>frequency, use the Hamming window.
>
>If the weak signal (in which you're interested) is more than,
>say, 6 FFT frequency bins away from a strong signal's center
>frequency, use the Hanning window."
>
>I'm investigating speech.
>I am externally constrained to use a sample rate of 44 khz.
>My experimental procedure specifies looking at
>      10 mSec, .1 Sec, and 1 Sec samples.
>
>My thesis statement is that "speech may be suitably characterized by 
>total power in bands no narrower than 1/x octaves". [ My current 
>opinion is that .3 < x < .5 ].

Hi,

It sounds like you're building some sort 
of fancy spectrum analyzer.

>Since any analysis I do will be based on a sample at least 40 bins 
>wide, can i legitimately ignore leakage?

40 bins huh.  I'll stick my neck out and 
say that I don't think windowing will 
make much of a difference.

>[ Aside to voice recognition lurkers, I'm asking ONLY if my approach 
>is valid in DSP terms. ;]

The good news is, Rich, once you get your 
entire process working properly, 
you can test to see what effect 
windowing the time samples has.

Good Luck,
[-Rick-]

Rick Lyons wrote:
> On Fri, 02 Apr 2004 16:53:12 -0600, Richard Owlett
> <rowlett@atlascomm.net> wrote:
> 
> 
>>In another thread Rick Lyons said:
>>"Windowing is generally used to reduce the spectral leakage
>>that causes a strong (high amplitude) signal's spectral magnitude
>>to cover over (swamp out) the spectral components of nearby weak
>>signals.  If a weak signal (in which you're interested) is
>>3-4 FFT frequency bins away from a strong signal's center
>>frequency, use the Hamming window.
>>
>>If the weak signal (in which you're interested) is more than,
>>say, 6 FFT frequency bins away from a strong signal's center
>>frequency, use the Hanning window."
>>
>>I'm investigating speech.
>>I am externally constrained to use a sample rate of 44 khz.
>>My experimental procedure specifies looking at
>>     10 mSec, .1 Sec, and 1 Sec samples.
>>
>>My thesis statement is that "speech may be suitably characterized by 
>>total power in bands no narrower than 1/x octaves". [ My current 
>>opinion is that .3 < x < .5 ].
> 
> 
> Hi,
> 
> It sounds like you're building some sort 
> of fancy spectrum analyzer.

A spectrum analyzer was what started my train of thought.
Doubt anyone will want to use my final "thing" as one though.


> 
> 
>>Since any analysis I do will be based on a sample at least 40 bins 
>>wide, can i legitimately ignore leakage?
> 
> 
> 40 bins huh.  I'll stick my neck out and 
> say that I don't think windowing will 
> make much of a difference.

Your email the other day pointed out how I can run a test case.

> 
> 
>>[ Aside to voice recognition lurkers, I'm asking ONLY if my approach 
>>is valid in DSP terms. ;]
> 
> 
> The good news is, Rich, once you get your 
> entire process working properly, 
> you can test to see what effect 
> windowing the time samples has.
> 
> Good Luck,
> [-Rick-]
> 
>