Questions tagged [highpass-filter]
A high-pass filter is a device that passes high frequencies and attenuates frequencies lower than its cutoff frequency.
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Numeric Derivative Frequency Response
It seems quite common to use np.diff() for removing DC components of signals when plotting spectrograms.
I noticed some unexpected behaviour during analyis which ...
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Issues with ML Pattern Recognition After Bandpass Filtering
We've been working on a machine learning project for pattern recognition, using time-domain features such as kurtosis, mean, standard deviation, variance, skewness, and peak-to-peak values.
Background:...
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High pass filter with low cutoff frequency
I'm trying to design the highpass filter in Python for my accelerometer data in order to integrate them. I need to preserve low frequencies. For example, data with a sampling frequency of 2 kHz need ...
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Demonstrating linear filters on daily weather data
I have daily temperature data from some place on Earth. Apparently, the sampling frequency f_s = 1/day.
I would like to use these data to demonstrate (visually) the use of low-pass, high-pass, and ...
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Poor Attenuation With High Pass Filter
I am having issues with my implementation of a FIR high pass filter. The low pass filter has an acceptable level of attenuation in the stopband, but the high pass filter has poor attenuation in the ...
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What highpass filter is implemented in Audacity?
When I selected highpass filter effect in Audacity (an open-source audio editor), it lets me choose the cutoff frequency and the roll-off but it doesn't specify which filter type is used (IIR ...
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Get rid of DC offset by subtracting mean, but still have impulse at f = 0 Hz
I understand that there are two ways to get rid of DC offset: (1) subtracting mean of original signal in time-domain, (2) using high-pass filter. I'm trying both approaches on my data (using Matlab) ...
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digital Butterworth high pass filter
I am trying to high-pass filter a signal using a Butterworth filter, but I am getting the following results :
As in the picture, there is no signal decay.
python code:
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Is f/fL a high pass filter where fL is a low-pass version of f?
Let there be a signal f and its low pass filtered signal be fL. Then what can we say about the spectrum of f/fL ?
To be specific I am obtaining fL simply using gaussian blurring in the spatial domain.
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FIR-filter output gain
Lately, I've been doing some FIR-filter simulations as a part of a programmatic circuit design course. One task was to use different constants $b_i$ for the multiplying stage of the filter and see how ...
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Which signal corresponds to the high-pass version of the original signal?
I have wandered into the realm of signal processing and am currently focusing on learning more about filtering signals. I am currently trying to understand how to think about and solve a practice ...
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Filter amplifies frequencies at nyquist frequency. What's the purpose of such a filter?
I'm currently facing a filter that amplifies frequencies at the Nyquist frequency. The sampling frequency is $f_s = 10$ Mhz.
What's a typical application for such a filter?
This is how I generated ...
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Constraints on number of taps in a FIR filter vs. FFT length
I want to implement a FIR highpass filter for acoustic signals.
I generate the FIR using Python's SciPy code:
...
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How to choose the cut-off frequency for removing the DC components
I'm trying to remove the DC components from a signal in a static situation (there is no movement), so I'm using a high pass filter with a cut-off frequency of 0.1 Hz (since the DC components happen at ...
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Wider sharpening filter
The kernel of a sharpening filter of size 3x3 may look like
$$
\frac{1}{4}\begin{bmatrix}
0 & 1 - \alpha & 0\\
1 - \alpha & 4\alpha& 1 - \alpha\\
0 & 1 - \alpha & 0
\end{...
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Why does the derivative of an audio file act like a high-pass filter?
Code: https://github.com/echometerain/sound-derivative/blob/master/sd.py
I wrote a program which would subtract the current audio frame by the former one. Why does this act like a high-pass filter?
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High Pass Filter for Image using C++ and Python
I was assigned to optimize the HPF using C++. Fyi, the original image is 512x512.
By getting the .dat file that is produced by using Python script, I applied a 5x5 HPF on it with 2 zero-pad with ...
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How to detect and distinguish oscillations in a signal?
I would like to detect oscillations in a signal $s$ and determine the nature of the oscillations, i.e. whether they are high-frequency oscillations or not.
Edit : An example of $s$ is given below :
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How can the detail coefficients in discrete wavelet transform (DWT) be downsampled?
This question is asked with reference to this paragraph
For the high-pass filter, the frequency content lies in the range $\frac{F_s}{4} \rightarrow \frac{F_s}{2}$. There is no content in the range $...
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Why is there coherence below the cutoff frequency of two high-pass filtered signals?
I record surface EMG signals from two muscles at 1500 Hz. The following preprocessing steps are performed using basic MATLAB commands.
First, I decimate both signals to 500 Hz (Lowpass filtering ...
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How to apply Butterworth high pass filter in the frequency domain?
I have a time series of measurements which I want to high pass with Butterworth filter.
Python scipy package has a built in function for Butterworth filter (signal.butter) and I know how to apply it ...
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Implementing basic high pass filter using difference equation
For the following signal, I am trying to remove the gradual positive drift but retain the spikes using a high pass filter.
I am aware that I can use implement a high pass filter using difference ...
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strange waveform after highness FIR filter
I was trying to apply FIR filter on the ECG signal: a bandstop for 45-55 Hz for noise removal and a highpass filter for moving baseline wander. But after that, the ECG signal show strange waveform at ...
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analog filter magnitude flatness problem
I have designed an analog filter that includes a high pass filter with a cut-off frequency of 5 Hz and a notch filter with a cut-off frequency of 50 Hz.
I want to sample the output signal of the ...
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IIR Filter Stability
I have designed an inverse IIR high pass filter by inverting its transfer function B(z)/A(z) to A(z)/B(z). However, the inverse filter has a pole at z=-1.
Is this filter considered stable (marginally ...
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How to enhance thermogram image in grayscale?
I'm trying to do some image processing to improve the image below but I'm having some trouble. I already tried to do histogram equalization followed by laplace sharpening, I tried to implement a ...
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Differences in transforming a sinc FIR filter from lowpass to highpass using spectral inversion and spectral reversal
I have designed a lowpass sinc 1023 tap FIR filter with a Blackman window and this works fine.
I understand there are then two ways to transform this lowpass filter to a highpass one.
One is spectral ...
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Bio-signal discontinuity after FIR filtering
I'm filtering respiration signal. I have a signal of duration equal to 10 minutes, so I decided to divided it into period of 10 s. I filtered each epoch with FIR filter, but I have discontinuities ...
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Should we use a digital low pass or high pass filter to remove sensor bias?
Consider a continuous signal oversampled at, say $2 \;kHz$, and then system digital low pass filtered to a $100\;Hz$ frequency which is the control loop frequency. It is known that there is some bias ...
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How to implement a high pass filter digitally to remove the dc offset from sensor data
I'm trying to implement a high pass filter on sensor data to remove the dc offset. I'm aware I can subtract the mean of the data but I'm looking for a frequency domain approach. I've used the matlab's ...
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RC high pass filter differential equation
I have the question to derive:
$$RC \frac{dy(t)}{dt} + y(t) = RC \frac{dx(t)}{dt}$$
which describes a high pass filter or $CR$ circuit with $x(t)$ the input and $y(t)$ the output.
I am really ...
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High pass biquad cascade transposed direct form II low frequency accuracy
I'm quite new to DSP and I'm trying to implement high pass biquad cascade in transposed direct form II. Currently my implementation has very poor accuracy at cutoff frequencies that are less than 5kHz ...
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Highpass filter design that is better than the Moving Difference filter
The question is actually from the problem set 1.3 of the "Wavelets and Filter Banks" book (authors Nguyen/Strang).
Problem 4: Invent a Highpass filter K with 3 or 4 taps (coefficients) that ...
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Low frequency (1Hz) High pass filter
I am trying to get a useable wave from a pulse oximeter, but there is a pesky DC bias that keeps changing every now and then, so I cannot simply subtract the DC bias from it and get useable results ...
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Bandpass filter vs sequential high and lowpass filter in Matlab: weird difference
I am trying to bandpass a neural signal acquired at 20kHz between 0.5 and 100 Hz. I have tried to do it in two ways. The first way is to sequentially highpass and lowpass the signal and the second one ...
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Is there an adjective describing a filter with kernel that has zero mean?
A linear filter with a kernel that has zero mean could be thought of as a "DC-rejecting" filter. Is there a better or more commonly used adjective for such a filter?
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Why use both a high pass and a low pass filter in a Butterworth implementation for noise reduction?
I am a new to audio processing . I want to develop an application that reduces audio noise using a Butterworth filter. I found some existing code doing this, but I still do not understand the use of ...
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The magnitude spectrum of a sharpening filter
I'm trying to derive an expression for the magnitude spectrum of the following sharpening filter.
$$
g(m,n) = \delta(m,n)+\lambda (\delta(m,n) - h(m,n))
$$
where $\lambda$ is some positive constant ...
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Simulate butterworth filter with initial condition of state vector in R
I'm working in R with the packages signal and control (don't know wether these are even the best for my use case).
I have a high ...
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Is the Laplacian Filter an High Pass Filter (HPF)?
Is this kernel name as mean difference kernel or Laplacian filter?
Is mean difference just a method?
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Downsampling after a highpass filter
Question: The following sentence is not clear to me (especially why down-shift occurs). Could someone explain it please?
On the other hand, downsampling the output of the highpass filter down-shifts ...
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High pass filter not attenuating signal at start of input
I have implemented digital high pass filter with below specs:
Sampling frequency = 5333 Hz
Cutoff frequency = 10 Hz
Order = 3
We are facing problem like below:
As ...
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What is the purpose of the recurrence relation in low and high pass (audio) filters?
Newbie here. I'm familiar with time and frequency domains from math. I think I understand what low and high pass filters do, sonically. But digging into an implementation of ...
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Remove audio signal component under certain frequency in python
I want to remove all signal components under 10KHz in one audio file. Below is my code
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Problem with implementing DC offset for streaming data
I am new to the DSP world. I'm trying to run a raw input signal through a LPF, remove any DC offset, amplify the signal, and then decode the signal. The problem with my code seems to be the ...
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Are high pass/low pass filters FIR filters?
I am trying to understand the basic categories of DSP filters, and it seems that the two main groups are FIR and IIR, however I'm not sure how to categorize high pass, low pass, band pass, and band ...
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Highpass filter square wave
Generated a 1kHz square wave in Audacity and normalized it to 0dB (fs = 44100Hz):
Added a 24dB/oct high pass filter (std Audacity plug-in), cutoff frequency set to 100Hz. Result:
Zoomed version:
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3 dB cut-off frequency of first-order IIR high-pass filter
As descipbed in this great answer (thank you Matt L.), the suggested exact formula was very precise.
I need a first order high-pass with similar precision.
EDIT: (clarification)
The low-pass filter ...
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Calculating the 3dB frequency of an nth order low pass filter and nth order high pass filter
I am using the 6th order high pass filter in the C code. And the cut-off frequency selected for it is 150 Hz and the sampling frequency being used is 32000Hz. Now, I want to calculate the 3 dB ...
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Correct way to build a basic filter bank (ie. for simple multiband audio processing)?
I need to build a filter bank for multiband processing. Last time I tried I was just starting at coding/DSP so I failed and didn't get a flat spectrum out of it. I just want to know the basic ...
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