On Sep 25, 11:18&#4294967295;am, "vivu91" <vivu91@n_o_s_p_a_m.gmail.com> wrote:
> Hi,
> I have a doubt which might be very basic. I am currently working on a
> project. In that i input a test audio signal of 1.5 seconds in which the
> actual audio is of only 0.5 seconds or so. The sampling frequency is 44100.
> I am currently using a hanning window and the pwelch command in matlab to
> find the frequency spectrum. However I am using a hanning window of size
> 128 and that gives me a resolution of only 173Hz or so. I would like to
> improve the resolution to 1hz or so. I am only interested in the
> frequencies at which the peaks occur the actual magnitude is irrelevant.
>
> I thought of increasing window size but was not sure whether that would
> improve the resolution or increase noise.
>
> Any suggestions or help along these lines would be extremely helpful.
> I tried reading through a few books all the books seem to suggest to
> improve resolution to pad with zeros. The problem for me is that I have a
> long enough duration signal but am not sure if i take a large window size
> if resolution improves or noise is added.
>
> Please help i need the solution for this as quickly as possible.
>
> Vivek

Try interpolating the data to increase the number of points and use a
much larger window. Or pad with zeros on both sides and don't use a
window at all. Generate test signals + AWGN noise to test.

Tom

>Did you help him?
>Could you help him?
>Is it possible to help the one who lacks the very very basics yet got 
>himself involved is something way above his comprehension?
>VLV
>
Hey all I am asking for is a little guidance. I am stuck in a college
without great professors and I am trying to learn everything on my own. So
I was thinking comp.dsp could help thats all! Its not like I dont know a
thing. My basics are a little confused because what we learn in college
here in India is not a great approach to strong fundamentals. Any help you
could provide would be helpful. And thanks again to all who have provided
answers. They were very helpful

>Did you help him?
>Could you help him?
>Is it possible to help the one who lacks the very very basics yet got 
>himself involved is something way above his comprehension?
>VLV
>
Hey all I am asking for is a little guidance. I am stuck in a college
without great professors and I am trying to learn everything on my own. So
I was thinking comp.dsp could help thats all! Its not like I dont know a
thing. My basics are a little confused because what we learn in college
here in India is not a great approach to strong fundamentals. Any help you
could provide would be helpful. And thanks again to all who have provided
answers. They were very helpful

VelociChicken wrote:

> "Rick Lyons" <R.Lyons@_BOGUS_ieee.org> wrote in message 
> news:leqv96l1pgqif3pqgq8rebsj6q142m4952@4ax.com...
> 
>>On Sun, 26 Sep 2010 10:54:13 -0500, Vladimir Vassilevsky
>><nospam@nowhere.com> wrote:
>>
>>
>>>
>>>vivu91 wrote:
>>>
>>>
>>>>Hi,
>>>>I have a doubt which might be very basic.
>>>
>>>[...]
>>>
>>>
>>>>Please help i need the solution for this as quickly as possible.
>>>>
>>>>Vivek
>>>
>>>If not this last demanding phrase, I might have helped you.
>>>Do you have money to pay for the solution as quickly as possible?
>>>
>>>VLV
>>
>>Hi Vladimir,
>>  Ha ha.  I agree with you.
>>
>>What's the Russian word for "manners"?
>>
>>No need to answer, I couldn't pronounce the
>>answer anyway.
>>
>>[-Rick-]
> 
> 
> He just sounded a little desperate to me, and he did say 'please.'

Did you help him?
Could you help him?
Is it possible to help the one who lacks the very very basics yet got 
himself involved is something way above his comprehension?

> Calling other people stupid, or often replying with money demands is an 
> example of good manners, I suppose?

It is not about people, it's about chickens. The best chickens are good 
at is a chicken stew.

> This is not called 'pro.comp.dsp' - if you don't want to discuss with or 
> help people, then simply don't reply.

There are other places, like alt.stupid.idiots, for example. You will be 
certainly welcomed to preach good manners there.

> Thanks.

Thanks, but no thanks  (c) Sara Palin

VLV

Rick Lyons wrote:
> On Sun, 26 Sep 2010 10:54:13 -0500, Vladimir Vassilevsky
> <nospam@nowhere.com> wrote:
> 
> 
>>
>>vivu91 wrote:
>>
>>
>>>Hi,
>>>I have a doubt which might be very basic.
>>
>>[...]
>>
>>
>>>Please help i need the solution for this as quickly as possible.
>>>
>>>Vivek
>>
>>If not this last demanding phrase, I might have helped you.
>>Do you have money to pay for the solution as quickly as possible?
> 
> Hi Vladimir,
>    Ha ha.  I agree with you.
> 
> What's the Russian word for "manners"?
> No need to answer, I couldn't pronounce the 
> answer anyway.

Same as in English. I think it is originally French word.

VLV

"Rick Lyons" <R.Lyons@_BOGUS_ieee.org> wrote in message 
news:leqv96l1pgqif3pqgq8rebsj6q142m4952@4ax.com...
> On Sun, 26 Sep 2010 10:54:13 -0500, Vladimir Vassilevsky
> <nospam@nowhere.com> wrote:
>
>>
>>
>>vivu91 wrote:
>>
>>> Hi,
>>> I have a doubt which might be very basic.
>>
>>[...]
>>
>>> Please help i need the solution for this as quickly as possible.
>>>
>>> Vivek
>>
>>If not this last demanding phrase, I might have helped you.
>>Do you have money to pay for the solution as quickly as possible?
>>
>>VLV
>
> Hi Vladimir,
>   Ha ha.  I agree with you.
>
> What's the Russian word for "manners"?
>
> No need to answer, I couldn't pronounce the
> answer anyway.
>
> [-Rick-]

He just sounded a little desperate to me, and he did say 'please.'
Calling other people stupid, or often replying with money demands is an 
example of good manners, I suppose?
This is not called 'pro.comp.dsp' - if you don't want to discuss with or 
help people, then simply don't reply.
Thanks.

Hey thank you so much for all the answers. And I am sorry it was kind of
wrong to put the thing about answer as quickly as possible. I apologize.
The problem was I was working on the project and fell sick so I was lagging
on the deadline. Sorry it was still wrong. 

Anyway thank you so much for the responses

vivu91 <vivu91@n_o_s_p_a_m.gmail.com> wrote:
(snip)

> Thank you very much for the input. However I had a doubt as to whether the
> resolution is to be calulated using fs or fs/2. Since on performing fft we
> only obtain meaningful values for upto fs/2 right? Due to nyquist
> criterion?

There is a very mysterious 2 that keeps floating around these
calculations.

OK, start with the DST and DCT (sine and cosine transform).

The sine transform (continous or discrete) has the boundary condition
that the function, f, goes to zero at the boundary.  That implies
that the basis functions (those being summed to generate f) also
goes to zero at the boundary.  Sine goes to zero every half cycle.

So, for a given transform length, T, f(0)=f(T)=0, a sine with
an integer number of half cycles will match the boundary conditions.
Because of that half, the Nth basis function, for an N point
transform, will have frequency (about) Fs/2.

The DCT (cosine transform) works in a similar way, with the 
derivative going to zero at the boundary.  f'(0)=f'(T)=0.
Again multiples of one half cycle fit the boundary conditions,
and the highest frequency is (about) Fs/2.

For the DFT (FFT) it gets more interesting.  Periodic boundary
conditions f(0)=f(T), f'(0)=f'(T)  allow for only whole cycles,
but either sine or cosine.  One can uses as basis functions
sines and cosines from 0 up to (about) Fs.  It is more usual,
though, to use those from -Fs/2 up to Fs/2.  Now it seems
to happily satisfy Nyquist, but where do those negative 
frequencies come from?  Is it all a trick to get a factor of
two where there is no other reason for it?

Since cos(x)=cos(-x) a positive frequency looks exactly the
same as a negative frequency.  For complex functions, you 
need them to allow for the imaginary part, but not for real
functions.  So, as before, only up to Fs/2.  The actual
basis functions for the DFT are exp(iwt), and again, for
a real transform, frequencies from -Fs/2 to Fs/2 are needed,
depending of the phase.

-- glen

On Sun, 26 Sep 2010 10:54:13 -0500, Vladimir Vassilevsky
<nospam@nowhere.com> wrote:

>
>
>vivu91 wrote:
>
>> Hi,
>> I have a doubt which might be very basic.
>
>[...]
>
>> Please help i need the solution for this as quickly as possible.
>> 
>> Vivek
>
>If not this last demanding phrase, I might have helped you.
>Do you have money to pay for the solution as quickly as possible?
>
>VLV

Hi Vladimir,
   Ha ha.  I agree with you.

What's the Russian word for "manners"?

No need to answer, I couldn't pronounce the 
answer anyway.

[-Rick-]

On 9/25/2010 11:02 PM, vivu91 wrote:

>>
> Thank you very much for the input. However I had a doubt as to whether the
> resolution is to be calulated using fs or fs/2. Since on performing fft we
> only obtain meaningful values for upto fs/2 right? Due to nyquist
> criterion?
>
> Vivek

Perhaps more than you need but just to put things in context:

Often we normalize on one or more of the parameters to make the 
discussion and some of the analysis independent of the absolute values 
of time and frequency.  Then, when the numbers get "real" we put the 
unnormalized values to those parameters.

Then we can talk about "40% of fs" and so forth and fs/2 might be simply 
"0.5".

I think of the parameters as:

N - the number of samples in both time and frequency if one is doing 
DFTs or FFTs.

T - the time interval between temporal samples.
(uncommonly one could define an "F" as the frequency interval between 
spectral samples but we are usually OK with 1/NT).
When normalized, T=1 is a very typical approach.

fs - the sample rate = 1/T
So, if T=1 them fs=1 as well in a normalized case.

Then:
- NT is the time duration
- 1/NT = fs/N is the frequency sample interval ... "resolution"

So, that's the answer to your question.

Note that none of this has much to do with Nyquist or "meaningful". 
That's another consideration of course but not one that affects these 
definitions.

As before, if you take a situation:
fs = 1/T
N
So the duration in time is NT then the
"frequency sample interval / resolution" is 1/NT

Now, let's append N zeros in time to get 2N samples.
Now we get:
fs = 1/T as before
2N now doubled
So the duration in time is 2NT and the
"frequency sample interval / resolution" is 1/2NT.

BUT... because, by adding the zeros we still have but a duration of NT 
seconds of nonzero signal values, we still have a resolution of 1/NT Hz 
from the perspective of information.  The frequency samples have been 
interpolated but without adding any "new" information - thus no 
improvement in real resolution.
Nonetheless this can be a handy thing to do if one is wanting to 
visualize or plot something like the reconstructed spectrum.  And, in 
fact, that can be "information" to *you*.  An example might be the DFT 
of a rectangular window.  What are its spectral spreading properties?

I hope this helps.

Fred