Questions tagged [frequency]

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

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110 views

Time-varying waveform

My situation is as follows: i am trying to generate a waveform the hard way, by constructing the samples one by one and then saving the result to a .wav file using Python. When the frequency is ...
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If low frequency travels longer distance, why our speech is not travelling longer distance?

It is know that low frequency signals travel longer distance that of high frequency signal. If so, our speech signal is low frequency signal, why it is not travelling further?
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Cepstrum, peak picking

I try to obtain fundamental frequency from cepstrum. I decide to use peak picking algorithm, which pick maximum value of the Cepstrum (c) with sampling rate fs. ...
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1answer
379 views

Pitch Detection: HPS not working

I'm trying to code the HPS (harmonic product spectrum) algorithm and the problem I'm facing is that using my guitar, the fundemental frequency (Here it's 82Hz) just isn't there, so is the 5th Harmonic ...
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1answer
384 views

Sampling bandpass signal with spectral replications

I want to clear my thinking on how to approach problems of the type characterized below. I guess what we want to do is select a sample rate of a sufficient size such that this signal can be fully ...
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1answer
77 views

resonance demodulation for bearing faults [closed]

Can someone explain me how are the different frequency bands useful for detecting bearing faults using resonance demodulation?
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467 views

Doppler shift using PLL

I am trying to apply phase lock loop to calculate phase shift due to doppler effect and finally calculate the doppler frequency($\Delta f$). I am assuming that the received wave is of the form, $r(t) =...
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1answer
4k views

Sampling frequency of modulated signal

A very naive question... A signal with bandwidth of 20 MHz is modulated using a carrier of 1 GHz. What will be the sampling frequency? I was asked this question during an interview. I answered 2 GHz ...
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1answer
992 views

How to transmit voice signal and receive on radio?

I want to transmit data like radio stations do. Like radio stations broadcast music and etc. using frequency, so I am also curious to know about it that actually how it works. I also want to make ...
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1answer
2k views

How can I reduce noise errors when detecting DTMF with the Goertzel algorithm?

Thanks a lot to whoever downvoted my question for no good reason. I wrote an implementation of the Goertzel algorithm in JavaScript and made a demo that detects DTMF dial-tones. You can find the ...
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2answers
2k views

Algorithms for finding fundamental frequency based on ACF result

I am developing a software for fundamental frequency tracking. For this purpose, I have designed a function which calculates autocorrelation over the signal and a second function which, based on ...
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1answer
161 views

Lowest frequency within pitch detection in polyponic sound

I perform some tests where I run cepstrum pitch detection algorithm over polyphonic sound. Result shows that there is almost always occurrence of lowest frequency of tones played simultaneously. I ...
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1answer
3k views

Upsample data using FFTs. How is this exactly done?

I am basing my question on this post here, because I would like additional details on it, as I have not had any success in re-creating it. I would like to simply learn, in no uncertain terms, how to ...
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4answers
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given a mixture of two signals, how to separate it to its base components?

I have a signal that contains two components. How can I separate it two its two components in matlab? Please note that the location and shape of components are different in each experiment and we do a ...
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862 views

bearing frequency detection

I am working on bearing faults detection. I am doing the following steps: signal->mean zero->high pass->hilbert->y->fft->cepstrum of y. my code is: ...
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Adequate representation of frequency domain amplitude/magnitude of FFT of a signal

I'm quite new to the subject and am having fun playing around with the FFT. What I am currently doing is trying to sample an audio signal and display its frequency spectrum at the same time. This ...
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3answers
103 views

Connection between filter equation in frequency domain and difference equation in time domain?

I know that the frequency response of a filter is described by equation: H(w) = 1-1.176*e^(-jw) + e^(-j2w) , where w is the angular frequency. Then in time domain ...
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70 views

Frequency contour cross-correlation

I'm trying to segment (or extract) different calls from a spectrogram. My current method, calculates a threshold value (variance) and then using RMS can detect voiced/unvoiced signals: $$ Thres = (1 -...
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1answer
113 views

Standard representation of FFT of an Image?

Statement 1 : When we take DFT of an image matrix, we get DFT co-efficient matrix. What does the DFT Co-efficients tells about the image? (For example, take the 1st co-eff in the DFT matrix, what ...
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2answers
284 views

Why we need Frequency and Time information at the same time

The big disadvantage of a DFT is that it has only frequency resolution and no time resolution. This means that although we might be able to determine all the frequencies present in a signal, we do not ...
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109 views

Calculating hertz / kHz

Over the past few weeks, I have been working on a problem of segmenting an audio file containing some bat samples. I have now successfully come up with a moderate algorithm to do this. I am trying ...
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1answer
47 views

Frequency filtering - Audio

Sound are digitalized in computers as an archive with its intensity amplitude at the given time. I want to ask a very simple question about frequency filtering. How it's done, if there's no frequency ...
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4answers
2k views

Why does the high frequency component of an image contain more noise?

I am working with wavelet transforms. When we apply a discrete wavelet transform to an image, it decomposes into four components named the approximation component, thevertical component, the ...
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2answers
220 views

make a threshold frequency based on percentage of frequencies less than that?

Using MATLAB signal processing toolbox, I have created signals like dirichlet, chirp and etc and and obtained their fourier and cosine fourier transform. Now I want to find the frequency where for ...
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1answer
105 views

Understanding Hertz

This question is in two parts, both related in some way or another. Suppose I have a signal where the sample rate is 44100 and compute a normal 1D DFT on this signal. The size of this signal is ...
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2answers
228 views

Estimating the amplitude of a particular frequency

I am relatively new to DSP and have been reading a lot on the internet. I have a couple of questions. I have a signal in the form of a function $$ f(x) = A_0 + A_1 \cos(\omega_1 x) + A_2 \cos(\...
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Understanding Spatial Frequency of Images (using matlab)

I wish to isolate a crosswalk from its surrounding, and I thought that as crosswalks have a repetitive pattern of thick white stripes, I might be able to isolate them by measuring their frequency ...
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1answer
134 views

How to derive a rate (e.g. water dripping) from an audio file

I want to learn how to go about analyzing some audio files I have acquired. Let's say the files contain some sort of repeating sound (e.g., water dripping), and I want to derive the pattern of the ...
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How to estimate the frequency at certain time of linear sine sweep?

experts. I have a question concern "linear sine sweep". Here is the equation of linear sine sweep(from Wikipedia Chirp). $$ x(t) = sin\biggl[ 2\pi( f_0 +\frac{f_1-f_0}{2T}t)t\biggr] $$ where, $...
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1answer
313 views

The impulse response, $h(t)$, of a system

I have this differential equation $$ y''(t) + y'(t) + y(t) = x(t) - 3x'(t) $$ I found the system response of the system: $$ H(f) = \frac{1 - 6\pi fj}{(2\pi fj)^2 +2\pi fj+1} $...
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2answers
169 views

Generating a sound where end frequency is 1/2 of the start frequency

I am very very new to signals, and I am trying to generate sounds based on some parameters from a database. So, the database stores the following: startFrequency endFrequency startAmplitude ...
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1answer
481 views

Find “base” frequency of pulse wave

I have some samples that are read from a square pulse wave and I'm looking for a way to find the characteristics of this wave. It's a pulse wave, let $T_1$ be the non-pulse duration and $T_2$ to be ...
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4answers
399 views

How to find period/envelope that is larger than sample size?

Mercury's distance from the solar system's barycenter (in kilometers) can be approximated as: ...
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276 views

Solving linear system and find impulse response

I have this linear system that is defined by the differential equation $$ y''(t) + 4y'(t) + 5y(t) = 2x(t) + 3x'(t) $$ with x(t) the input and y(t) the output. I'm asked to find two things:...
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639 views

Frequency domain confusion

I'm a bit confused with some details about frequency domain or studying systems with Laplace and Fourier analysis. Let's say we have a system with a transfer function $H(s)$ with no poles and zero's ...
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2answers
218 views

What is an octave? It is said to be eight, but I cannot see the eight anywhere

When I searched for octave, I listened to the fact that if you take an octave band the lower cutoff is double the upper cutoff. Where is this name octave coming from, that is, where does the figure ...
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1answer
179 views

How to decipher this Microphone sensitivity Chart for Choosing a SPL meter

I have a mic having sensitivity chart as below which has relative dB on y-axis showing 1V/0.1Pa what does this convey how to read my mic's sensitivity a document on microphone sensitivity from ...
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2answers
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HPS Algorithm for detecting the fundamental frequency of a guitar string

When you plucked on a string, the string is vibrate and except the fundamental frequency, there are an integer multiple of the fundamental frequency, which are the harmonics. I know that the HPS ...
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1answer
189 views

Magnitude of intermodulation distortion products?

Assuming I have a set of frequencies $\mathbf F$, and I pick 2 frequencies $f_1$ and $f_2$ randomly from the set, generate sine waves for them, and pass the signals through a non-linear distortion ...
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98 views

DFT detemine frequencies

I am just begining learning about DFT and I am bit unsure on what is happening mathematically during DFT. I've sampled a signal , a sine wave sin(1000*2*pi*t). And performed DFT to calculate the Ck-...
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1answer
488 views

Frequency and damping estimation with Prony method?

I have a sinusoidal time domain signal with few damped exponential components. i.e. ...
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124 views

What is difference between Signal frequency and data rate

I read somewhere the below two line and got confused what is the actual difference between the two line. These two lines are related to CAN 1.Maximum Signal frequency used is 1 Mbit/sec 2.Typical ...
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How are the time scales of an exponential decaying autocorrelation related to the duration of peaks?

I'm reading a biology article (full text here) that analyzed the variation of a cell parameter over time at different stimulus intensities (calcium concentration). The frequency of peaks increases at ...
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1answer
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Time shifts and change in phase

My question here is in regards to implicit information/terminology. Basically, whenever we say that "a shift in time means a change of phase in fourier space", is it implicit that the shift is ...
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2answers
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Bandpass Filter Implementation in C

I've been googling for a while and came across the audio cookbook and Bjorn's blog explaining it further Link Here. Background info: I've modified the rtl-sdr open source code to tune to a VOR ...
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4answers
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Estimate frequency and peak value of a signal's fundamental

How can I find out frequency and peak value of a signal's fundamental? Please do consider the following: The peak value of some harmonics might be higher than that one of the fundamental The ...
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190 views

Reducing frequency of a signal

I have a signal that I want to make it sound like a whisper. This is probably better than using a voice conversion system, but I was just want to do some experimenting before. I was thinking maybe ...
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2answers
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How does one know how many times to downsample in Harmonic Product Spectrum?

I have been working on a Harmonic Product Spectrum Algorithm. Now, all the literature I've read about the subject tells me to downsample an N amount of times. How does one determine what this N value ...
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1answer
248 views

What is the frequency of $\cos x -\sqrt 2\cos\sqrt 2 x$?

Question Considering that $1\over{2\pi}$ is the frequency of $\cos x$ and also of $\cos x - 2\cos 2x$, what is the frequency of $\cos x - \sqrt 2\cos\sqrt 2 x$? Thoughts Perhaps "frequency" isn't ...
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766 views

Using Doppler velocimetry with digital signals such as Bluetooth

I have found several sources describing how to use Doppler velocimetry/anemometry to measure the Doppler shift with analog signals, but i cannot find much about using this method for digital signals ...