14
votes
What is the name of a low-pass filter that tracks rate of change?
I was able to remember how the filter works. The idea is very simple, a second low-pass filter tracks the steady-state error in the result of the first one, and it is then added to the output:
Based ...
- 683
7
votes
Accepted
Identify abrupt changes in an audio waveform
Synchrosqueezed Wavelet Transform is an option. I have developed a complete algorithm for this task, which scores 100% train accuracy and 86% test accuracy with 0.05 sec tolerance, without machine ...
- 8,815
6
votes
Estimate Sine Frequency under White Noise — simple and effective method
I wasn't going to answer this, since the question is stale. But I'm a little bit dissatisfied with Royi's answer and with the Kay algorithm as presented.
The Kay method is, at first glance, simply ...
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6
votes
What is the name of a low-pass filter that tracks rate of change?
I do not think that there's a specific name for this type of lowpass filter. There are indeed similarities between the cascade of two lowpass filters as suggested in the OP's answer, and a combination ...
- 89k
5
votes
How to measure aliasing?
Note: it's "Work In Progress", I intend to address some limitations, including "time aliasing". Interested hot visitors may wish to "Follow" the answer.
Motivating the ...
- 8,815
4
votes
Accepted
MUltiple SIgnal Classification (MUSIC) for Frequency Estimation
The second implementation takes account of the sampling frequency twice.
This line
freq_array = np.arange(-fs/2, fs/2, fs/nfft)
should be changed to
...
- 25.3k
4
votes
Identify abrupt changes in an audio waveform
One domain where continuous (complex) wavelets (CWT) are especially efficient is when you expect the 1D signals to be piecewise regular. When a signal is $C^\alpha$ by pieces, then the $\alpha$ ...
- 31.7k
4
votes
Identify abrupt changes in an audio waveform
This is more meat-and-potatoes.
An oft-used algorithm in audio is the pitch detector, which of course is attempting to accurately determine the instantaneous pitch of a note. The note is a waveform ...
- 20.1k
3
votes
Identify abrupt changes in an audio waveform
I would point on 2 approaches:
Parametric Model
You build a parametric model for the data and then apply simple change detection methods for the paraments. For instance, you may build a Kalman Filter ...
- 19.3k
3
votes
Looking for an arcsin algorithm
So we have two requirements:
Use at most 5 multiplications.
Errror is no more than 10%.
Requirement 2 means that we want to optimize (minimze) the relative error of the approximation.
Requiring 5 ...
3
votes
What is the name of this FFT technique for carrier recovery?
You can find very similar implementations as part of a "squaring loop" for carrier recovery, and this would be the closest name related to the fundamental operation provided - which is not ...
- 48.9k
2
votes
Why does the griffin lim algorithm work?
Sound is just the combination of multiple sin waves at different frequencies and phases. These phases determine how those sin waves combine together, i.e. if frequencies are resonant or eliminate each ...
- 121
2
votes
Accepted
Convex Hull Area in Pixels
It is known that OpenCV contours are not useful for quantification. For example this issue was closed without any changes, not even to the documentation. I have also seen multiple questions on Stack ...
- 2,359
2
votes
Accepted
What are the step by step actions taken in order to convert PDM data to PCM data?
Here is good intro into the topic. https://www.youtube.com/watch?v=5lH-tQw0tlU
The exact details will depend on the specific microphone, processor and application requirements. Many processors these ...
- 42.7k
2
votes
Finding start point of a curve
I believe it would be the midpoint of the resulting ramp that would be the best estimate of the actual delay, not the first instant of the output rising. That said, if we want to minimize processing, ...
- 48.9k
2
votes
Finding start point of a curve
Here's an approach I've used. It's used to enhance the upslope and suppress the remainder of the waveform, and can be efficiently implemented:
Low-pass filter your data (as you've mentioned, the ...
- 5,247
2
votes
Choosing the scaling parameters for a modem implementation
The optimum solution for where to set the Automatic Gain Control (AGC) relative to the full scale of the ADC typically allows for some clipping given the goal is to minimize the total noise ...
- 48.9k
2
votes
What is the equation I can use to create the inverse expoential graph?
Perhaps it's
$$ f(x) = 100 \cdot \big(1 - e^{-\alpha x}\big) $$
or perhaps it's
$$ f(x) = 100 \cdot \big(1 - \tfrac{1}{1+\beta x}\big) $$
or perhaps it's
$$ f(x) = 100 \cdot \big(\tfrac{2}{\pi}\arctan(...
- 20.1k
2
votes
Accepted
Measure of how well sounds fit together in a composition
I am not a big music guy but I understand audio signal processing and acoustics to a decent extent so I shall take a crack at it. There are no definitive rules or purely objective measures for ...
- 1,204
1
vote
What is the equation I can use to create the inverse expoential graph?
Sigmoid
$$f(x) = \dfrac{M}{1+e^{-kx}} $$
where:
$M$ - the asymptotic value
$k$ - controls how steep is the curve
Power and exponential function
$$f(x)=M\left(1-e^{-kx^p}\right)$$
where:
$M$ - the ...
- 11.1k
1
vote
What is the equation I can use to create the inverse expoential graph?
You're searching for an asymptotic function. The simplest asymptotic function I can think of is $y=\frac{1}{x}$:
This already looks a bit like what we want. However, we can tweak it a bit. First of ...
- 11
1
vote
What is the equation I can use to create the inverse expoential graph?
Maybe you can try the rational polynomial functions as:
$f(x)=\dfrac{a_nx^n+a_{n-1}x^{n-1}+...+a_1x+a_0}{b_mx^m+b_{m-1}x^{m-1}+...+b_{1}x+b_0}$
You can control the limit in $\infty$ with $n, m, a_n$ ...
- 81
1
vote
How to measure aliasing?
Where it matters to explicitly account for aliasing, my approach (that for context I have often used in the area of wireless communications) is using the correlation coefficient with a reference copy ...
- 48.9k
1
vote
Measures of "coincidence"?
When you say "same shape" and "coincidence" I think at symbolic meaning. I'm not sure this is what you want but if it is so you can use CNN to extract symbolic features from ...
1
vote
Identify abrupt changes in an audio waveform
I suggest you to elaborate the signal using a wavelet decomposition. If you find the correct wavelet for your task you wll see in the spectogram a band wich will expose you the cut points. This is not ...
1
vote
How do I do a point response FMCW SAR simulation?
Usually, for FMCW systems, only IF signal (beat frequency) is sampled.
The equation for the IF signal would be just the phase subtraction between the transmitted and received signal.
Again the ...
1
vote
Finding rectangle corners by using point cloud
Once you have your list of points that fall in your rectangular object, I would propose doing something like the following.
Find the best fit plane. This could be done with principal component ...
- 11
1
vote
Estimate Sine Frequency under White Noise — simple and effective method
Since @OverLordGoldDragon raised methods based on applying the DFT, I'd like to share another simple idea.
Given the DFT, if the number of bins is high enough (Zero padding if needed, choosing power ...
- 19.3k
1
vote
Estimate Sine Frequency under White Noise — simple and effective method
Summary
Possible State of the Art by Cedron in compute-limited settings, as it beats Kay and many other methods
In accuracy, Cedron is superior to Kay in nearly all settings, for both real and ...
- 8,815
1
vote
Why do we need DFT when we already have DTFT/DTFS?
To overcome the limitation of DTFT we use DFT tool. it is almost similar to DTFT but only limitation is the infinite length sequence.
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