Questions tagged [window]
The window tag has no usage guidance.
101
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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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What is Frequency Resolution?
Im trying to tackle the following problem while still not having a firm idea on what "frequency resolution" means :
Suppose we sample a continuous time signal with sampling period Ts = 1/2000, and ...
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2
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Proof that the rectangular window has the best resolution
The resolution of a window is typically defined by the width of its spectral mainlobe (3dB-width or null-to-null width). It is often stated that the rectangular window has the best resolution among ...
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What window functions allow for controlling the location of nulls?
Window functions are commonly used to control spectral sidelobes. Typically there is a trade between supressing sidelobes, and maintaining the resolution of the mainlobe. A window with lower sidelobes ...
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Why is each window/frame overlapping?
I am currently reading up on some speech recognition theory.
As it speech signals usually are non stationary, but if a speech is seen in a very small time frame can it be deemed stationary, as would ...
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Can I use more than one Window on an FFT?
I was wondering if it is possible to take a signal and run it through an FFT multiple times with a range of different windows, and then combine/average the results to get a more accurate Signal ...
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Correct method for processing FFT in realtime
I am attempting to build a 'live' FFT for continuous analysis of an audio signal. I am relatively new to this, but have attempted the full thing, and then updating the graph at 20Hz refresh rate. My ...
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Hanning and Hamming Window
I am new in the field of signal processing. What's the different between Hamming and Hanning window? When we use the former and latter?
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Understanding overlapping in STFT
I understand the concept of the STFT. In order to avoid spectral leakage, you use a Hann window that overlaps by 50%. However, the problem that I have, is that the example code online does not account ...
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Window period(overlap) and FFT
How does changing the window period (i.e the number of points overlap between two frames) affect the FFT results ?
Suppose that a time series signal was converted to frequency domain by FFT with ...
- 151
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Inverse the Hanning Window [closed]
I am using the following formula to calculate the Hann values for a set of points:
$$
w(n)=0.5\left(1-\cos\left(2\pi \frac nN\right)\right)
$$
To implement this in java, I am using the following code:...
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286
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What is the LOW frequency resolution rule analogous to Nyquist?
If I'm analyzing a signal in the frequency domain, I know about the well known Nyquist criteria that the sample frequency must be > 2x of the highest component present in the signal.
However, there ...
- 151
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2
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Zero padding - High amplitude
I have a set of 512 samples that I have collected with a sensor. I'd like to apply zero padding to it, for better frequency bin resolution. However, all the tutorials I see to make this occur center ...
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2
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Hilbert transform with a sliding window
I have a input voltage signal which has disturbances present in it. I am actually discretizing the input signal into say $1300$ samples and taking Hilbert transform of the signal by taking $N$ samples ...
- 31
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Use of Tukey window and its effect on a graph
I am trying to minimize the noise in a spectrum of a variable. I am trying to to divide the time history in equal parts, to do the FFT of this time history parts and to do an average between these FFT....
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1
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Why coherence function calculation needs averaging of different segments of the signal?
I am trying to understand coherence function calculation. I am working with a non-linear system without any noise. Coherence function is defined as:
I understand that coherence is 1 for N=1, but I ...
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What is the proper way to filter out unwanted noise from accelerometers?
I'm a beginner in signal processing and have a hard time to filter out environmental noise from the floor vibration data collected using accelerometers.
I have tried using butterworth filter (IIR) ...
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257
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Fundamental misunderstanding of windowing
I believe I have a fundamental misunderstanding of windowing. I thought that windowing is applied to a signal with pointwise multiplication, then some sort of filtering is then done to it (say using ...
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upward shift in FFT windowed - attenuate fluctuation in FFT
I would like to limit the noise after the FFT. I have used this strategy:
Divide the signal in segments using a Hann window
Perform abs(FFT(segment))
Ensemble ...
- 33
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1
answer
223
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Window with optimal sidelobes for a given ENBW / frequency-resolution
Is there a family of windows which is "optimal" in terms of energy above/below a boundary, but with controllable ENBW/bandwidth? By optimal, I mean maximising energy concentration inside ...
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1
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Biorthogonal Windows
I am starting to study about the concept of biorthogonal windows and the relation to (Discrete) Fourier transform and short-time Fourier transform (STFT).
I have not found an introductionary review of ...
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How is a signal multiplied with the window functions?
How the input signal get multiplied with the window functions like Hamming, Hanning, Blackman, etc?
I have tried to multiply the input signal of $10\textrm{ MHz}$ sampled at $100\textrm{ MHz}$ using ...
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1
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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.
...
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0
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Separating out a sequence of DFTs with overlapping windows
Suppose I have a time series partitioned into $N$ equally-sized sections. Choosing some $k<N$, for each of the sections $i \in[0, N-k]$, I concatenate that section with the $k-1$ sections to the ...
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How to Calculate the Hann Low Pass Filter / Kernel for Image Processing
I'm currently studying for an exam in image processing and stumbled upon a exercise which i could not answer and my professor will not be available before the exam anymore. The exercise goes as ...
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What do I lose when I set overlap rate to a really high value in STFT
If I don't care about computational cost, is there any cons when I put overlap rate really high in STFT?
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2
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700
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Non-symmetrical DFT of real valued signal
I have a homework assignment to take the $64$ DFT of $\cos((5\pi/32)n)$ and $\cos((5\pi/64)n)$. However, for the second case I obtained DFT spectrum such that I have that famous symmetry in real part ...
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Design a FIR filter with a Kaiser window
Here is the exercise I am working on.
Use the window design method with the Kaiser window to design a linear phase high pass FIR filter of minimum order that meets the following specification:
$\...
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2
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Find the Equivalent Noise Bandwidth
I have already asked (in another thread) how to quantify (specify) the window function I have created. One figure I need it seems is the Equivalent Noise Bandwidth (ENBW) Or Noise Equivalent Bandwidth....
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2
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Interpolated FIR filter group delay
I'm trying to design a digital low pass filter with a narrow transition band. My sampling rate is 25 kHz, the cut off frequency is 60 Hz & the transition band width is 4 Hz. I'm looking for about ...
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Gaussian window and standard deviation
I am trying to figure out how to use the matlab gausswin function which constructs a Gaussian window for $N$ samples with a given standard deviation $\sigma$. The function is defined by
...
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Is an FIR filters 'transition width' frequency dependent?
I was recently brushing up on some FIR filter design and was browsing the Wikipedia page. A claim in the article caught my attention:
The main disadvantage of FIR filters is that considerably more
...
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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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2
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768
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Half Window Functions and Formulas
I am looking at implementing different window functions in an application I am making. I have found the formulas for all major symmetrical windows, however I would like to implement half windows.
...
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fft - spectral leakage from noise into target frequency?
I have an acoustic setup. A sender, emitting a clean sine signal. The receiver is far away. In the time domain, the sine is hardly visible because the noise is nearly as big as the signal. In the ...
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1
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Should zero element be considered to calculate mean when smoothing spectrogram by window?
My (mass spectrometry) spectrogram does not measure the intensity constantly. I obtain the spectrogram, for example,
...
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Why does my plot of the Blackman window not match everyone else's in literature?
I've seen the plot for Blackman window as so in a bunch of books, as on this website:
But plotting the same equation on Wolfram Alpha yields a different plot:
Why is their graph not centered around ...
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MRI reconstruction using windowing based apodization
I am trying to apply windowing to do MRI reconstruction. I have a 256 point one dimensional k-space samples which look as follows:
Here, the real part(green) is flat around 0 and the blue curve is ...
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1
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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 ...
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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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1
answer
953
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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 ...
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1
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Can I apply an hilbert transform on a signal in subsegments [windowed hilbert transform?] [duplicate]
Consider I have a signal x which has N samples, N being a very large number.
Could I create y, the analytical signal of x, by ...
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1
answer
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Multiplying a finite signal with a unity window
I have a simple question to ask:
Suppose $x[n]$ is finite and has a support for $|n|<L$
Let's denote its DTFT by $\operatorname{DTFT}\big\{x[n]\big\}(e^{j\omega})=X(\omega)$
Let's consider a unity ...
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Do we guess the cut off frequency when passband edge frequency and stop band edge frequency are given? FIR Filter design-LOW PASS FILTER
Say passband edge frequency=0.25 $\pi$
Stopband edge frequency=0.35 $\pi$
What is the cut off frequency? Do we average these 2 frequencies and write the answer or what is the procedure to find cut off ...
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minimal signal window size (length)
In order to detect a frequency component of 1 Hz with a DFT - do I need a signal window (signal in time domain) of at least 1 second length (in order to have at least 1 cycle of the desired minimal ...
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2
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Frequency Support of Window Functions
All window functions, which go from zero amplitude, up, then back to zero amplitude, are all base-band signals. Why is this? Are all functions that have this behavior always band-band aka low-pass?
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Multi Resolution STFT for audio
I am looking at trying to achieve a multi resolution STFT analysis on a log sine sweep audio measurement.
I have an impulse, and I would like to perform two different windowed length FFTs on the ...
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How to design a lowpass filter using Hamming window and sinc function
I have these three equations and have a noisy voice signal. I have to design a low pass filter of length N=1000 using hamming window technique. I have selected its cutoff frequecny 0.25 (normalized).
\...
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2
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234
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Windowing after filtering a discrete signal to get it back to its original length
What happens if you filter a discrete bandpass signal of length $N$ with a bandpass filter (Hann truncated sinc) of length $L$ and apply a window of length $N$ to the filtered signal of length $N+L-1$ ...
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Why do we not use square filters without windows? [duplicate]
This question may sound like "why do we use window functions", but it's not. So here it's:
What we currently do: If we have a function $g(t)$ and its Fourier transform $G(f)$, and a window $W(f)$ and ...
