Questions tagged [frequency]

Frequency in signal processing is the number of cycles (of the signal) per second.

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135 views

Deciding on the FFT length for water waves in flume (wave facility)

Soon I'll be conducting experiments in a wave facility (flume) for my MSc thesis. And I would like to analyse wave spectra (amplitude and energy density). The time step (or 'accuracy') of the wave ...
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546 views

Frequency bin of the positive and negative frequency

I am using this MATLAB tutorial for Frequency-Domain Linear Regression. There is one part of code they provide, where it is necessary to determine the "frequency bin of the positive and negative ...
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A very basic question about processing high frequency signals

A standard frequency for a modern computer processor is 1-3 GHz. The frequency of a GPS signal is ~1.5 GHz. My question is how is it possible for a computer to do anything at all with a signal that it ...
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What is the bandwidth of human speech?

What is the actual frecuency bandwidth of human speech. I know there is variation for gender, age and so, but what is the general range... I seem to find different ranges. Like here http://...
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94 views

Doubling the frequency of a sound fragment in real time?

I'm given given a stream of sound, as a serie of little buffers . Is it possible to make this stream sound one octave up ? Or an arbitrary number of semitones up ? My goal is to add it to the ...
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103 views

Regressing/interpolating between quasi-periodic sinusoids

This is a cross-post (on recommendation) from CV. My problem is very simple. I currently intend on using Kriging (Gaussian process regression) to perform regression between the trajectories marked ...
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2answers
776 views

Nyquist frequency and DC

Im studying the DSP book by Steven W. Smith. On page 41 he covers the Nyquist frequency. He makes up an example by writing the following. ... consider an analog signal composed of frequencies ...
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How can I change parameters into a text string in MATLAB? [closed]

I am trying to compute the Morlet wavelet transform (cmor) of a signal, but I have to do it several times with different parameters Fb and Fc. Is there a way to automate it? For example, I have to do ...
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98 views

Digital frequency for images

From this Wikipedia link, the fastest fequency for digital frequency is 0.5cycle/sample. It can be rewritten as 1cycle/2sample. What does it mean? Does it mean that at least two pixles are required ...
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77 views

Is there a function in MATLAB similar to $\tt freqz$ but for $H(\omega)$?

I wanted to know if there's a MATLAB function that equates the frequency response, $H(\omega)$ of a system. Something similar to freqz like a ...
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59 views

Which one of these signals will be least distorted by this communication channel

So I was solving a problem that resulted in a communication channel that heavily distorts high frequency but does not significantly affect low frequency and I got stuck at figuring which one of these ...
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352 views

Why LFO should be alias-free?

I'm really tripping about this point! I try to reason with you and explain what's my trouble. Consider a scenario with Sample Rate 44100hz and a LFO square wave that will modulate some internal ...
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12k views

How to change a continuous signal to form a discrete signal? [closed]

I have a continuous signal $$ x(t)= 2\cos(200\pi t)+8\cos(250\pi t)$$ and it is sampled at 400Hz. How is this changed into the discrete time domain in order to determine the two discrete frequency ...
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Calculating maximum signal frequency knowing its sampling rate?

I was curious as to how I could calculate the maximum frequency of a signal knowing only its sampling rate (for example 125 nanoseconds). Does the sampling theorem have anything to do with it (...
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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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freqency resolution of 48khz 16bit WAV?

I was doing experetiments in Audacity,creating sine waves and trying to find out what is the smallest amount of freqency change possible,how it looks like... I found out that the super small changes ...
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1answer
36 views

i have an audio signal. i have to find whether my audio signal is from given avi scene

I have audio signal. I want to find whether my audio signal is from a given avi file . I tried using correlation and mfcc. But i'm not getting accurate output. So please help me in this.
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Discussion - Integrating Accelerometer data to Position data from Frequency domain FFT

I came across one blog who suggested to convert from accelerometer data to position data from frequency domain. Here are the steps that the original individual suggested: Remove the mean from ...
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231 views

Pilot tone frequency doubling

U.S. Broadcast FM stereo includes a $19\textrm{ kHz}$ pilot tone that needs to be frequency doubled to help demodulate the DSB stereo difference signal. How can this frequency doubling be done ...
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268 views

Lock-in amplifier

From what I have studied so far I have understood that the benefit of a lock in amp is its ability to resolve the amplitude of a signal which is deep into noise. I was wondering if the same concept ...
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1answer
56 views

How does SC-FDE modifies $E_b$ (in AWGN function)

In lot of matlab scripts of SC-FDE simulations I see $E_b = N$ (being $N$ the length of the block to be transmitted through the channel and Eb energy per bit) to generate the AWGN. I would like to ...
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707 views

Are there any cases where the negative frequencies of an FFT are used?

In performing FFTs and looking at spectra for real signals (say, taken from a sensor) we ignore the negative frequencies. I understand that the negative frequencies often reflect the positive ...
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1answer
130 views

Is there a special reason why the principal range is defined as $-0.5\le F \le 0.5$?

According to Digital Signal Processing by Ashok Ambardar, The principal range is defined as follows: Put another way, a DT sinusoid is periodic in frequency (has a periodic spectrum) with unit ...
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What is the real meaning of “frequency” for a non periodic signal?

For a non periodic signal, in the first one second the frequency of a particular amplitude (value) may be of 4 Hz, and then in the next one second it may or may not be 4 Hz. Then which value of ...
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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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261 views

Detecting frequency when frequency is not sufficiently greater than baud rate

I'm writing software this software for decoding audio samples of FSK data back to bits (ASCII, etc). The software is working really well at this point for decoding FSK when the mark and space ...
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329 views

Adaptive filter with two inputs

I have general theoretical questions: Is it true that an adaptive filter with two inputs (one normal and one delayed by the single time increment) can completely get rid of any single frequency ...
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2k views

Finding the maximum and minimum frequency of a 2D image

Suppose I transform the image into frequency domain and obtain a 2D array of complex numbers. How can I determine the minimum and maximum frequency from that array? By finding magnitude of each ...
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217 views

Are there accepted ranges of “high”, “medium” and “low” visual spatial frequency?

I have an image and have been able to quantify its power across spatial frequencies, using Python. What I am interested in doing is creating some measure of how much of the image's information is low, ...
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97 views

Low PAPR performance for Monochromatic frequency signals

I understand what is Monochromatic frequency signals from here, but could somebody kindly give a brief explanation about "why does a monochromatic frequency signal result in poor PAPR (Peak to average ...
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516 views

How to separate two signals which have same frequency and phase but generated from different positions?

How to separate two signals which have same frequency and phase but generated from different positions? For example, the EEG signals, we assume there are only two positions, position A and position B ...
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605 views

How to Map CWT to Synchrosqueezed wavelet transform?

I don't understand the mapping time-scale plane to the time-frequency plane in synchrosqueezed wavelet transform, i.e. $(3)$. You can find the paper here. For the given signal of $x(t)$ and mother ...
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1answer
964 views

How to find PSD (Power spectral density) of spatial data

I have profiled a surface, measuring the height of peaks and troughs at 0.02mm intervals. I have 1501 data points, the below listed as an example: $$\begin{align} x &= 0\,\mu\text m & y &...
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189 views

Positive and negative frequencies: how to prove they are independent?

This seems to be quite a basic question but is there some detailed proof why interference power (i.e., power spectral density) coming from the positive and negative frequencies are independent? I am ...
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330 views

Determining the Nyquist rate of signals added and multiplied together

Suppose I have a signal in the frequency domain $x(\omega)$. Suppose I know that its Nyquist rate is $\omega_0$ (and let $\omega_m$ be the its maximum frequency). I need to get the Nyquist rate of $...
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539 views

Power/Amplitude Response of a system

I am currently looking over filters and understand the frequency response of a system, e.g. a low-pass filter. However I am confused by the 'Power/Amplitude response' of a system as detailed in my ...
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213 views

Extract parameters of a single harmonic

Context I need to extract the parameters of a single harmonic in a signal. For instance if $$ x(t) = A \sin (\omega_0t + d_0) + B \sin (\omega_2t + d_2) $$ then $f(x, \omega_0) = (A, d_0)$. This ...
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How to detect decaying oscillations in a signal

I have a sampled signal which contains (among other things) some damped oscillations. From the underlying theory I have reasons to believe that it can be characterized by some specific frequencies of ...
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193 views

How do I measure frequency of an audio file into an array?

So I know how to plot fft the audio file within Matlab and a window pops up. My question is, what next? I want to know how to go about measuring the frequency(s). I have two similar audio files, of ...
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Compressing a time-domain signal in the frequency domain Matlab

I'm new to frequency domain analysis. Let's say I have a frequency domain representation from a time domain signal. What I want to do is taking frequencies with a low amplitude out of this frequency ...
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608 views

Aliasing Square Wave

I'm having a really weird issue with generating waveforms from frequencies C1 to C8. When I generate sine waves, everything sounds good; no problems whatsoever. However, when I generate a square ...
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4k views

The relationship between downsampling and frequency resolution

I am having trouble understanding a concept that I have seen in many published papers. For example, in this paper (http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082748) they wrote ...
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130 views

How can a signal have two maximum frequency components?

$x(t)$ can be exactly reconstructed from its samples at $\omega_s = 10 \textrm{ rad/sec}$. My conclusion is that the maximum frequency component in $x(t)$ is $5\textrm{ rad/sec}$. But I'm being told ...
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Sampling frequency of audio

Based on what we choose sampling frequency when sampling some song? Do we use Nyquist–Shannon sampling theorem, or maximum sampling frequencies are pre-defined, so it will never come to aliasing ...
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5k views

What is the difference between a'mixer' and a ' multiplier' used in modulation process?

I am not sure if it is valid to conclude that a mixer produces a difference/sum of frequencies at output ,while multiplier produces multiples of frequency at its output. I am keen to know how far I ...
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791 views

Difference between these frequency response curves

I am thinking about a simple mass-damper system response. Most single DOF systems show a frequency response plot that looks like this: Note how increasing the damping ratio always reduces the output ...
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314 views

EEG signal processing with sampling frequency

What is the relation between sampling frequency and the frequency of the signal after sampling? For example sampling frequency is 100 Hz, that is the signal contain maximum frequency of 50 Hz. Then ...
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Why does resampling change the frequency range?

I am currently working on a set of .wav files which, unfortunately, do not have the same sampling rate - I need to resample them for the purpose of feeding them to a neural net. So - using Sox I ...
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How to remove 50 Hz frequency noise from a PCM file?

Are you kind to tell me the odds or the means by which should I grab a clean signal with the $~50 \mathrm{Hz}$ hum removed using just programming? I managed to make a program in Visual-C that ...
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1answer
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No of samples 4mega samples per second,using 8 bit ADC,V p_p is6V. calculate frequency and peak power

This place has been great in helping me to understand my online image and signals class! I've moved on to another question and wanted to see if I'm correctly grasping the subject. The next question ...

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