Questions tagged [window]

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3answers
15k views

Moving average vs. Moving median

I have read in many places that Moving median is a bit better than Moving average for some applications, because it is less sensitive to outliers. I wanted to test this assertion on real data, but I ...
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1answer
555 views

Why does the Hamming window attenuate the FFT?

I am working on a very simple voice recognition system using the msp430. In my research I've read that for real life audio signals its necessary to apply a window to the FFT data because the audio ...
1
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1answer
136 views

Non-separable, higher-order generalized cosine windows in 2D for images

Higher-order generalized cosine windows define a useful parametric family of windows functions, embedding Hamming, Hann, Blackman, Nutall, etc.: $$w(n) = \sum_{k = 0}^{K} a_k\; \cos\left( \frac{2 \pi ...
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1answer
291 views

How is the ends of a bandpass filtered signal reliable after applying the cosine taper?

A taper function decaying to zero at ends such as a cosine window is routinely applied to the signal before bandpass filtering to reduce end effects. Obviously the window alters the waveform. So, as ...
1
vote
1answer
809 views

How to Combine FFT Overlap Results?

We currently have C/C++ FFT code with Hann Window function support. For a large data (over 10,000) we want to split this into 1024 samples with 50% overlap. For each 1024 sample, we window and fft. ...
0
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1answer
124 views

Sensitiviy and Resolution in Windowing Functions

When I read the article Windowing Functions, there are two terms that are does not understanding them well, sensitiviy and resolution. I looked for this two terms on the web, And I conclude that ...
0
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1answer
97 views

Subsampling data: terminology

I'm writing software and the data reporting frequency is slower than the acquisition cycle, so effectively sub-sampling is being done. Different data types require different methods of sub-sampling ...
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2answers
316 views

Fourier Synthesis With Varying Frequencies Over Time

I'm doing some fourier synthesis by making bins of complex numbers, filling them out with the amplitude and phase information and using IFFT to turn that into time domain samples. I'm able to make ...
1
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2answers
398 views

Instantaneous magnitude

I was reading this thread: How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT? I have basically the same question, but I'm curious about more detail about the Hann window ...
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0answers
132 views

Band-pass filtering on whole signal or overlapping chunks?

I am working with a signal acquired by a pulse oximeter, i.e. a device that records the change of light intensity reflected by a specific tissue depending on its blood perfusion. Since I am interest ...
0
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1answer
4k views

Reconstructing time domain signal with Hanning window

I am currently working on a frequency domain real-time application on a digital signal processor. Currently for one time frame of my algorithm I read in time domain data into a buffer, perform a ...
-1
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1answer
421 views

FFT window corrupts signal

this is a newbie question. My goal is to create audio filter that cleans human speech from noise. I started with learning all about fft filters. At first I've created simple fft filter with ...
0
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0answers
344 views

Welch's Overlapped Method

I am measuring wind speed using a number of different anemometers. These anemometers are placed on a structure which exhibits sinusoidal motion. Thus, the signal of the anemometers contains both the ...
0
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1answer
4k views

Overlapping with flat-top window MATLAB [closed]

I am applying a flat-top window to signal because I am very interested in its actual amplitude in the time-domain. I have read that overlapping will improve results. I am using MATLAB and the ...
0
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2answers
597 views

Why are window functions used when calculating spectral estimates, really?

Having just read the rather long article on Wikipedia about window functions, I still do not see the mathematical point in using window functions when calculating spectral estimates (using e.g. Welch'...
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1answer
350 views

Will using window in Welch's method introduce artificial peak in estimated PSD?

I'd like to estimate the power spectral density of the signal attached here, the sampling rate is 100 Hz. If I don't do windowing (i.e., use boxcar window), the result seems to be a simple $1/f^2$ ...
1
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1answer
837 views

Additional prefix and suffix required when windowing an OFDM symbol?

To reduce out of band energy, it is common to apply a Raised Cosine filter to the front and back of an OFDM symbol. It is also common to overlap the windowed portions of adjacent symbols to eliminate ...