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Questions tagged [frequency]

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

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2answers
3k 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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122 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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911 views

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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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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1answer
465 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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1answer
289 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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1answer
661 views

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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2answers
1k views

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
4k views

Calculating a signals frequency when given the number of samples

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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2answers
411 views

Capturing the sampling rate from a basketball being dribbled

I'm taking an online image and signals class and the structure is absolutely horrible. I'm wondering if you can provide me hints, or tips to solving the below question. I'm not looking for an ...
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2answers
106 views

Will decorrelating an audio signal help reduce interference patterns at low frequencies?

In live sound it is common to have a left/right sub-speaker configuration, which will produce an strong interference pattern in the audience area based on listener/sub-speaker locations. If the left/...
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2answers
682 views

How to pick a sampling frequency for Matlab fft

I am recording vibration data using an adxl335 accelerometer.I have ~50ms delay before i save a reading from this sensor so most probably each second i have ~20 readings. I verified that by checking ...
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1answer
117 views

Signal response in Frequency Hz from angular frequency

I have a filter whose respose I have in angular frequency. ...
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2answers
1k views

Audio frequency modulation algorithm

I have a digital audio signal (float samples). I need to apply the Vibrato effect to a signal. "Vibrato" is no common term, but it is the same as the frequency modulation. So, I need to modulate my ...
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1answer
985 views

VIbrato (pitch variation) function

I'm looking for an algorithm for Vibrato audio effect for a cross-platform C++ program of audio processing. Now I use the realization from Chaotic-DAW sources. The problem is that Chaotic-DAW has a ...
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2answers
192 views

What are the implications of resampling the derivative of a signal with a higher frequency than the original signal?

Suppose I have a digital signal measured with sampling time, $T_s=1$ sec. If I take it's derivative, it will, naturally have $T_s=1$ sec. But what are the implications if I re-sample this derivative ...
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1answer
162 views

What does pre-emphasis $\alpha=1$ will do to a signal?

I am trying to understand pre-emphasis equation. $$ y[n]=x[n]-\alpha x[n-1]$$ Where $\alpha = 0.95$. My question is what does it mean if $\alpha = 1$?
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1answer
278 views

Find Natural Frequency $\omega_n$

You are testing a new device to determine its characteristics. You find the magnitude of its frequency response shows a peak at 500 Hz, and the measured overshoot of the step response is 40% of the ...
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1answer
235 views

how to find breakpoints of a signal based on the frequency of the signal

There are 4 cos signals with 10,20,30 and 100 Hz each. The main signal is the sum of those 4 and I have to create a low pass filter, on the main signal for the frequency's > 50 Hz. ...
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3answers
109 views

Resonance and Pitch classes

Suppose we denote the frequency of the note $\textbf{C}_{0}$ by $f$ then we know that $f,2f,3f,...$ are all resonating frequencies. However the frequencies $2f,4f,...,2^{m}f$ belong to the same pitch ...
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225 views

Is the book wrong? — How to sketch frequency response obtained from H(z)?

This question is directly related to digital signal processing, so I am asking here. How to sketch frequency response obtained from $H(z)$? I'm adding an example and its solution below. I did not ...
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42 views

Find unknown broadcast frequency

I'm very new to this stuff, so please excuse the dumb sounding terminology. I'm trying to capture the data from my elster smart hydro meter. How can I find its frequency (I know its between 902 and ...
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1answer
551 views

Relation between bandwidth and data rate

I have trouble understanding the following from wikipedia - Bandwidth (Signal Processing) A key characteristic of bandwidth is that any band of a given width can carry the same amount of ...
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3answers
2k views

Are there libraries for extraction of sound wave features?

I am looking help for my project for which I need C++ (or any other language) libraries useful for extraction of sound wave features like frequency, loudness, pitch and orientation. Using these ...
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1answer
181 views

Find minimum sampling rate of non-ideal notch filter

Old test problem: "You have been asked to design a real-time digital filtering system that eliminates a band of frequencies between 20 and 30 MHz but preserves everything else. The system uses an ...
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3answers
4k views

sampling rate for band pass signal

The sampling frequency for band pass signal which is having frequency from 4 kHz to 6 kHz(rectangular shape from 4 to 6 kHz), can I prefer the sampling frequency of 12 kHz(2*the highest frequency ...
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409 views

Determining frequency deviation FM

I am trying to understand the concept of frequency modulation. As written in Wikipedia, if I have a signal containing information $x_m(t)$ and I want to transmit it using frequency modulation, I need ...
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1answer
104 views

Sample Frequency - Recommended Practical Nyquist, Lower Used by majorities appications

Doubt1: What is the Lowest Sampling Frequency used by majorities sound applications. Is there limited frequency sampling lower than 8KHz In C/C++? Comment In Java I haven't detected any problem, but ...
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63 views

Retrieve frequency value of an 2D frequency spectrum

How do you retrieve the values of the frequency component occurring in a 2D freq spectrum? I have this, and if I wanted to know the values of the white dots. what should i do ? I apolgize ...
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1answer
48 views

Find the frequency of a pole (Discrete Form) [closed]

I am studying a Notch filter. I found its Transfer Function (in Z) and its poles. How can I find the frequency of theses poles (which corresponds to the cut-off frequency)? Thank you very much for ...
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1answer
88 views

Obtaining power spectral density without having knowledge about frequency bandwidth or sampling frequency of the signal in Matlab?

Is there a way to plot PSD of a signal which show true frequency amounts ( not normalized one) without having knowledge about frequency bandwidth or sampling frequency of the signal in matlab ?
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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 ...
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2answers
143 views

What is a note?

That simple. What is a note in digital signal processing? Is it a single value of y[n] in a system with a difference equation e.g. ...
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2answers
87 views

Given a real signal, increase modulation frequency

Lets say I receive the signal $$x(t)\cos(\omega_c t)$$ and I want to change the the carrier frequency $x(t)\cos(1.001\omega_c t)$ How can this be done? If I modulated it with a complex exponential, ...
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1answer
182 views

Why is discrete cosine preferred to FFT in neuroimaging GLM

High-pass filtering is often used in neuroimaging data analysis. Commonly, whenever a general linear model is fitted to the data (as for instance in statistic parametric mapping) a number of columns ...
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97 views

phase locked loop

I have seen that to get the phase angle of a signal, we have to use PLLs. this PLL is modeling in order to get the phase angle about one frequency, which is the free running frequency of the VCO. If ...
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2answers
1k views

Calculate Min/Max value of multiple sine waves added together

So I feel like this should be possible, I'm just not sure how to do it. Let's say I'm generating a signal with a sample rate of 10K samples/second. Then let's say my signal is comprised of X number of ...
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0answers
54 views

Using K-Space Filtering to Filter by Speed

I want to read waves with an electret consender microphone that are slower than the speed of sound, and I figure it would make those waves easier to identify if I could process out all waves moving ...
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1answer
49 views

Frequency of a DFT term

I've been wrestling with this question for way too long. I appreciate any insight you can offer. Thanks. If the $9$-point sample sequence $x(n)$ represents a time domain signal sampled at $48\...
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1answer
2k views

How to Flip Spectrum Around DC?

Is it possible to flip a signal's spectrum around DC? I have a simple spectrum that I made up (MATLAB code): ...
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2answers
7k views

How to calculate the frequency of a signal without knowing the sampling frequency using Matlab

I have a signal and I am using Matlab command pwelch to calculate the frequency of the signal, but the frequency I obtained is changed as I change the sampling frequency. For example, when using ...
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2answers
5k views

Frequency Shifting in MATLAB

I am currently attempting to demodulate an audio file using MATLAB. After taking the fft of the signal, I receive this: After some more coding, I found the following values: Fs = 44100; Window ...
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0answers
82 views

Filtering with filters without even or odd symmetry in the fourier domain

I am doing a project where I have to use the fourier domain for convolution. I have been reading Digital Image processing by Rafael Gonzalez but I unsure about one thing, and I could not find anything ...
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1answer
526 views

Why is the magnitude of the second component of my FFT spectrum always the largest one?

While working with FFT, I have a strange case with a current experimental setup. I am working with beat frequencies (intermediate frequency output) and using a standard FFT algorithm (complex to ...
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0answers
106 views

Curve fit for fft dplot

I have data from accelerometer (time domain) and convert it to fft using Fourier Transform. However, I need to do the curve fit to the plot. Can somebody share with me the coding.I don't know how to ...
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0answers
418 views

Very high SNR BPSK modulation

I am using BPSK modulation to modulate a signal in continuous time (making rectangular waveform, multiplying by a carrier). The channel is band-limited and frequency-selective, and has the following ...
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1answer
928 views

Real-time frequency recognition in python

I'm a newcomer to signal processing, so forgive my ignorance. I'm working on a project in Python that will play a .wav file and pick out the dominant frequency as it plays. I've found a few examples ...
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4answers
9k views

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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1answer
56 views

Cannot recreate a simple Nyquist series in Matlab

a Nyquist series should look something like {...-1, 1, -1, 1, ... }, which i think means it is a sine wave sampled at the peaks and valleys exactly. Now, given a sampling rate of 48 Hz, the Nyquist ...
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3answers
421 views

Zero-frequency response of an IIR transfer function

I have a question about the zero-frequency (DC) response of a IIR filter. The coefficients of the 3rd order IIR filter are as follows, ...