# Questions tagged [frequency]

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

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### Frequency identification as a convex problem

Suppose I have two time series, $x(t)$ and $y(t)$: $x$ is the output of a sine wave generator, and $y$ is the generator's frequency setting. Given a training set of $(x, y)$ pairs, Is it possible to ...
839 views

### Impact of modulation index in FM

If I have the spectrum of a FM modulation, does the frequency of the carrier disappear when the modulation index is too big? Does the amplitude of any side band depend from the modulation index? And ...
109 views

### How to add the noise covariance matrix of my measurements to tmy 1D kalman filter?

So I am new to kalman filters. This is my first experience with it. I have some measurements but sometimes due to external factors those measurements become totally wrong (hence the peak when you run ...
349 views

### Detecting a low frequency cue in audio recording

I am hoping to find a linux program or library for a language like perl or python (open to ...
106 views

### Why the bandwidth of the system with the minimum-order observer is higher than the full-order observer?

In Ogata's Modern Control Engineering (5th Ed., page 786) it says: The bandwidth of the system with the minimum-order observer is higher than that of the system with the full-order observer, ...
484 views

### Identify the frequency spectrum of an audio file by using matlab [closed]

I need to identify the first few harmonics of a audio file by cancelling the noise of the specific signal. So I have partitioned the signal into 1024 Hz sample blocks and then took the FFT values of ...
3k views

### What is the difference between phase noise and frequency noise?

I'm reading Audoin and Guinot's The Measurement of Time: Time, Frequency and the Atomic Clock, and ran across a confusing an interesting passage (Section 5.2.5, pp 72-73): The physical origins of ...
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### Reduce impact of outliners for frequency analysis by increasing signal length?

I am working on a project to detect drivers drowsiness with EEG signals. I am using the frequency values retrieved by FFT. I have some outliners (artifacts) in my signals, which I don't want to remove ...
1k views

### 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 ...
429 views

### Sampling and the creation of multiple images at integer multiples of the sampling frequency

From what I thought I learned about sampling is that when you draw a sampled signal in the frequency domain, you can show copies or "images" of that signal at integer multiples of the sampling ...
512 views

### Guitar String frequency

I'm making a guitar tuner for iOS.Due to the fact I'm Beginner I'm struggling a bit to gather all the resources and information about it. I know the theory like ( correct me if I'm wrong ) :- First I ...
267 views

### Finding frequency of data given in time domain

Think there is an analog signal source and we are recording it with a data logger. Sampling rate isn't important in here. We know the analog signal is 0 mV when time 0 and goes to 1000mV in 1000 ...
30 views

### Frequencies from unsorted data

I have a 2D samples f(x,y) = z in a circle (disc). Values x, y are not generaly uniform, but they can be resampled. Is there ...
82 views

### Correcting for Doppler shifts at the speed of sound for a 800 MHz signal

I'm working with a system which is planned to reach velocities of about 340m/s. It's likely that we'll be using a frequency around 800 MHz for rx and tx. At these speeds, supposing a fixed source, the ...
254 views

### Identify fundamental frequencies in short-period waveform

Maybe I'm being stupid and failing to see something here... I need to analyse a signal over a relatively short time period (~1-2 cycles for the lowest frequency, perhaps 20-30 cycles for the highest ...
682 views

### Distribution of energy in frequency bands

On my wav-file (music), I do a short-time Fourier transform (STFT). I have spectrum, which spans from $0\textrm{ Hz}$ to $f_s/2$. I took out the range between $1$ and $1000\textrm{ Hz}$, which I ...
526 views

### Find the dominant low frequency

I have this signal, with an arbitrary x-axis, and I want to find the (visually) dominant frequency of the signal. There may be a high frequency component, but I'm interested in the component with a ...
25 views

### Does frequency shifting double needed bandwidth? [duplicate]

Suppose we have a low pass signal and it's spectrum is like this: If we define bandwidth as the difference between signal minimum and maximum frequencies, above picture says that the signal has a ...
559 views

### why human voice is band limited while it's time limited?

According to Wikipedia, time-limited signals can not be band-limited and vice versa. Also we know that human voice is band-limited and has frequencies from $50\textrm{ Hz}$ to $4\textrm{ kHz}$. So ...
115 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 ...
445 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 ...
328 views

### 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 ...
21k views

### 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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### 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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### 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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### 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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### 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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### 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 ...
56 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 ...
255 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 ...
6k 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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### 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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### 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 ...
206 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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### 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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### 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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### 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 ...
90 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 ...
1k views

### Frequency Analysis 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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### 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 ...
228 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 ...
1k 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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### 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, ...