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# Questions tagged [wavelet]

A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero.

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1 vote
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### Detecting and fixing clipped positive waveforms

I have a large number of audio files recorded using custom IOT devices. When analysing the data I noticed that a portion of them seems to have their positive amplitude ramp up, but the negative ...
• 111
10 views

### Time step (skipping) in CWT function with PyWavelets

I am using cwt function from pywavelet to perform time-frequency decomposition of a large signal (several million samples). The computational requirements for this is huge, sin it performs the ...
1 vote
24 views

1 vote
150 views

### Why are analytical wavelets said to have no negative frequency?

I have been reading about analytical wavelets and came across this definition: An analytic wavelet is a complex wavelet such that its Fourier transform is null for negative frequency. If it is a ...
1 vote
86 views

### Adding noise to ECG to mimic Electrode Motion Artifacts, Muscle Artifacts, and Baseline Wander in Python

I have clean ECG signals and I want to add noise to them. Specifically, I want the noisy signals to be closest to "real life" type of noise. Reading this paper, I noticed that the ...
• 111
38 views

### How can we prove using matlab that after each level of decomposition of a signal using DWT the frequency content is halved?

I was trying to decompose an EMG signal, which was sampled at 200 Hz, into 7 levels of decomposition using DWT. And the result is shown in the figure( only up to level 3 is shown here) However, I ...
1 vote
92 views

### How to find median position of a contour that represents a peak?

I was reading some papers on time-frequency methods of signal analysis and I am confused about one concept. The idea in these works is to plot a power spectrum in time-frequency plane and then to ...
70 views

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1 vote
88 views

### What are frequencies in a scaleogram generated using pywavelet?

I am using PyWavelet to do continous wavelet transform of a 1D signal. The pywavelet continous wavelet transform function works with this line of code: ...
• 55
1 vote
187 views

### Limited cross-correlation for multiple signals

I have $N$ signals, each of length $\tau$, with $N\ll \tau$, eg. $\tau=10^8$ samples and $N=100$. I want the $r=10$ first components of all pairwise cross-correlation for the $N$ signals. The naive ...
340 views

### Why does a signal with constant frequency have spots that changes colors at a specific value of scale (and so frequency) in the scalogram?

I am studying the Wavelet transform and I am considering this example that I took from PyWavelets documentation. The signal in time domain has the following shape: Till the value of zero on the ...
• 55
Page 5 in link: For the scaling function, it holds: $\int \phi(x)dx = 1$ or, equivalently: $\Phi(0) = 1$ How is this derived?