Questions tagged [frequency]
Frequency in signal processing is the number of cycles (of the signal) per second.
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What is the physical significance of negative frequencies?
This has been one of the holes in my cheddar cheese block of understanding DSP, so what is the physical interpretation of having a negative frequency?
If you have a physical tone at some frequency ...
27
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4answers
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Which time-frequency coefficients does the Wavelet transform compute?
The Fast Fourier Transform takes $\mathcal O(N \log N)$ operations, while the Fast Wavelet Transform takes $\mathcal O(N)$. But what, specifically, does the FWT compute?
Although they are often ...
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4answers
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What is meant by a system's “impulse response” and “frequency response?”
Can anyone state the difference between frequency response and impulse response in simple English?
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Image Reconstruction:Phase vs. Magnitude
Figure 1.(c) shows the Test image reconstructed from MAGNITUDE spectrum only. We can say that the intensity values of LOW frequency pixels are comparatively more than HIGH frequency pixels.
Figure 1.(...
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2answers
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FFT frequency resolution
I'm having some problems understanding the FFT. Is the frequency resolution in the spectrum calculated as
$\frac{\textrm{sampling rate}}{\textrm{number of FFT points}}$ or $\frac{\textrm{sampling ...
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9answers
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Is there an algorithm for finding a frequency without DFT or FFT?
I was looking in the Android app store for a guitar tuner. I found a tuner app that claimed it was faster than other apps. It claimed it could find the frequency without using the DFT (I wish I still ...
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2answers
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Detecting drum bpm in a noisy .wav file
I am looking for algorithm(s) to solve the following problem:
Given a noisy .wav sound capture (some wind + friction noise on the microphone), how to detect the BPM of a soft drum beat?
I have ...
0
votes
2answers
591 views
Amplitude modulation vs sampling rate?
As a sampled tone's frequency nears $f_s / 2$, amplitude modulation grows apparent:
("Actual" curve in grey; blue is what we get if taking samples (dots) "at face value"). This is ...
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1answer
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What can be meant by “bandlimited”?
This question was a source of disagreement on whether "amplitude aliasing" can occur for a signal bandlimited to below half the sampling frequency. The question was closed before the ...
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Frequency Analysis (DFT / FFT) of a Signal Without a Constant Sampling Frequency (Non Uniform Sampling in Time Domain)
I'm a stack exchange user for some time and now I'm registering to ask a simple question (I think!).
I have a vibration signal with an amplitude and time (sampling frequency not constant) in a $...
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3answers
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FFT for a specific frequency range.
I would like to convert a signal to frequency domain. The desired frequency range is 0.1 Hz to 1 Hz and the frequency resolution ...
7
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1answer
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Why does a wave continuously decreasing in frequency start increasing its frequency past the half of its length?
I'm trying to programmatically generate a wave (sine or square) with a continuously decreasing frequency.
To do so, I simply multiply the starting frequency for a decreasing value, that linearly goes ...
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4answers
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Estimation of Amplitude, Frequency and Phase of Linear Combination of Harmonic Signal Beyond the Leakage Resolution of DFT
How can I find a rough ( as accurate as possible) Amplitude of each frequency when there is spectral leakage.
Currently, I am dealing with a system that contains special leakage which seems ...
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2answers
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Frequency vector and fft
I have got a question concerning the definition of the frequency vector for an fft operation.
Generally, I work with a frequency vector, f, with power of 2 ...
4
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4answers
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Designing High Pass Filter to Remove DC Offset from a Signal
I want to design a high pass filter (f0*S/1+f0*S) in order to remove the dc offset from a signal ? (i.e. how to choose the frequency f0).
Thanks,
Hacene
Ps : the filter is for MATLAB implementation, ...
3
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5answers
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instantaneous frequency for a sum
In the literature, the instantaneous frequency for a signal $s(t)=e^{-j \phi(t)}$ is given by: $$f(t)=\tfrac{1}{2\pi}\frac{d\phi(t)}{dt}$$
This my problem: I have a signal $$u(t)=e^{-j \alpha_1 \phi(...
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2answers
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Signal Processing/FFT gives very high magnitudes for low frequencies
The script essentially pulls PCM data from the sound card and stores them in a buffer. Then I apply fft and graph it. I am looking through this blog post for some examples and ideas on how to ...
4
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1answer
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Determine fundamental period from zero crossing signal
I have got a signal which consists of zero crossings over discrete time and I would like to estimate the fundamental frequency (period) from this signal in order to remove noisy samples.
The signal ...
2
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1answer
293 views
Magnitude value of filter frequency response
Can someone help me with this problem:
Suppose we filter signals with the below pre-emphasis filter:
$$y[n]=x[n]-0.8x[n-1]$$
I have to calculate the impulse response of the filter (ok easy) and ...
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vote
2answers
184 views
OFDM sampling frequency offset
how the 4G LTE Or 5G NR OFDM measures and corrects the sampling frequency offset? if there is an algorithm using matlab please help
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1answer
57 views
Bandpass filter equivalent for amplitude
I have a signal where I am using a bandpass filter to limit the frequency range. I am also interested in filtering the remaining frequencies (after bandpass filtering) within the signal by their ...
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1answer
171 views
PLL for Phase Demodulation and Carrier Tracking
I've been playing around with using a PLL for phase demodulation and it's working pretty well. The PLL locks to the carrier and the error term is the demodulated message signal. However, depending on ...
0
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1answer
611 views
Average FFT Magnitude in bins
I am analyzing sounds of daily activities recorded by a smartphone. For example walking, getting up from bed, falling, running etc.. (one at the time).
Let’s take one them. My goal is to
convert from ...
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3answers
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What is the Gabor filter? And what are its main uses?
I'm doing research on the Gabor filter. When I Googled it, I found very long and complicated articles. Can anyone help me to find a simple explanation about it, or recommend a website or article to ...
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2answers
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How do I determine if a discrete signal is periodic or not?
I want to know how I can determine whether a series of data is periodic or not.
I want to use Fourier transform/series. My data looks either aperiodic
[111100001111000110010101010000101]
or ...
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3answers
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How can I plot frequency vs magnitude of wavelet transform?
I am running Morlet continuous wavelet transform. I have got wscalogram of signal and now I want to plot freq-magnitude like the following picture., but I don't ...
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2answers
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Amplitude of the Signal in Frequency Domain different from Time Domain
How does the Amplitude of the Signal is changed when taking the FFT of a Signal,
Have a look,
The amplitude had changed from 2 to 30,
and Here is my code for generating the above output,
...
5
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1answer
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Why should one use windowing functions for FFT?
So I just revised my pitch calculation algorithm using a harmonic product spectrum algorithm. I was just curious about why this explanation of Harmonic Product Spectrum states that you need to ...
13
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3answers
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What is the bandwidth of a (real) sinusoidal tone, and pulse?
I would like to know how to go about calculating the bandwidth of:
A constant (real) sinusoidal tone
A (real) sinusoidal pulse.
The question is as simple as that, but I am having a hard time with ...
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4answers
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Calculate and interpret the instantaneous frequency
I'm new to the principle of calculating the instantaneous frequency, and came up with a lot of questions on it. You find them all in a bullet-point list at the end of this text. The text might be a ...
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4answers
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Discrete Time Signal Property
Property:
The frequency of oscillation of discrete time sinusoids sequence increases as $\omega$ increases from $0$ to $\pi$. If $\omega$ is increased from $\pi$ to $2\pi$ then frequency of ...
5
votes
4answers
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Simple and efficient algorithm to detect frequency and phase of a sine signal
I need an algorithm to detect frequency and phase of a pure sine signal. The frequency of the input signal changes between 0 and 100 Hz.
The value of the signal gets captured with a frequency of 20 ...
5
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1answer
385 views
Understanding the $\mathcal Z$-transform
I was studying $\mathcal Z$-transforms and found pretty good material on the topic, though I feel I do not have a proper understanding of the concept. Could someone help me clarify this?
I know that ...
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2answers
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Setup frequency array properly
I've just stepped into the FFT's world since the last weeks, therefore I still don't have an clear overall idea of how to setup the frequency array.
In case of even...
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2answers
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Removing noise from audio using Fourier transform in Matlab
I'm trying to remove noise from an audio file. This audio file contains speech as well as constant pink noise. I know that I have to use the Fourier transform to convert to the frequency domain then ...
3
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1answer
398 views
How can I get the power of a specific frequency band after FFT?
I need help with my matlab code. I have recorded EEG data and now I want to analyse it in matlab. I want to find the mean power of specific frequency ranges (theta: 4-8 Hz,alpha: 8-12Hz etc.). For ...
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2answers
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How is it possible to Filter out a person's voice out of 100 of other voices?
So, I've just learned that the human voice is not a single sine wave its a bunch of unlimited Sine waves each having a different frequencies,
According to Wikipedia,
The voice consists of sound ...
4
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1answer
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Why is oversampling helpful to an anti-alias filter?
Why does oversampling make the job of an anti-alias filter easier? I don't understand the intuition on why it becomes helpful.
Isn't it economical to just keep the sampling rate at the minimal level,...
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3answers
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Fundamental frequency
Can someone help me:
I have a signal which consist of three frequencies; for example, $f_1=800\,\text{Hz}$, $f_2=1050\,\text{Hz}$, $f_3=1600\,\text{Hz}$. How can i compute the fundamental frequency?
...
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3answers
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Determining the period of a discontinuous function
I'm new to the field of DSP.
I'm trying to determine the period and shift of the function. I've tried using FFT, but haven't had much luck. Seems like it should be simple.
Signal (pastebin of ...
3
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1answer
839 views
What features describe audio signals? (Besides frequency and amplitude)
I recorded sounds with a microphone and I try to distinguish them in my Java program. The frequency works quite good, but if I look at the fourier transforms it seems like there should be more ...
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3answers
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How to compute fundamental frequency from a list of overtones?
Given a list of overtones (F1, F2, F3, etc), how do I compute the fundamental frequency? Can I do something like F2/F1=F1/F0? Is it the correct method to use?
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1answer
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Performing classification based on FFT results
It is perhaps important to start with the fact that I am a complete beginner in DSP.
I have got a number of audio recordings (of sampling rate 22 kHz) - of bird songs - which I have been trying to ...
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0answers
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How can I identify the damping of the modes in a signal by Cmor wavelet method?
I read several papers which proposed a method to identify modal parameters. such as natural frequency and damping ratio.I've tried to implement those methods by Matlab.but I couldn't get the result.It ...
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1answer
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Doppler shift in time domain?
I have some clarifications required in this topic
So initially I know that to shift a signal $X(f)$ by $f_0$ we need to take its inverse fourier transform and multiply it with a factor of $\exp(−j2\pi ...
6
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1answer
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Why can Quadrature Demodulation demod a Frequency Modulated Signal?
I use a Quadrature Demodulator in my SDR application, which is defined as:
$\angle (S_n, S_{n+1})=arctan(S_{n+1}*\overline{S_{n}})$
So practically its amplitude is the angle between two Samples $S_n$...
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3answers
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Chop out frequencies outside human hearing range
I have a bunch of audio files all sampled at 44100 Hz sample frequency. I am trying to remove all the frequencies which are outside the human hearing range (I use the following as reference: Frequency ...
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3answers
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What's the best criterion for determining a frequency peak?
I'm writing an algorithm that analyzes results of discrete Fourier transform (DFT). The algorithm should detect amplitude peaks in predefined ranges of frequencies. This is an example of such a peak:
...
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1answer
4k views
Remove a frequency and all its multiple (harmonics)
In a soundfile, I'd like to remove a frequency and all its harmonics. What is the best solution in your opinion ?
Do a loop with 20 notch filters, one after another.
// f is the fundamental ...
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3answers
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FFT Zero Padding - Amplitude Change
I'm just learning about Fourier Transforms and as an input I'm using a WAV file (Matlab) and taking one channel of it and performing a quick Fourier transform. I've zero padded the input, as I've been ...
