The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.

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estimating frequency spectrum from power spectrum

I am passing white noise of known variance through filter, and I get the ouput signal.I estimate the filter response from PSD of the output. Is the following code correct when implemented in matlab? ...
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23 views

Is it possible to calculate the variance of signal in real time implementation?

In communication system, when we received some signal which contain our message of known variance sigma_s which is corrupted in noise of unknown variance. If I need the variance of the signal in ...
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2answers
20 views

Phase spectrum range

I computed spectrum analysis of sine wave (without windowing and zero-padding) and I got plots as follows: As far as I know they are correct. When I learnt about DSP, I got the huge problem with ...
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1answer
18 views

Predict auditory masking with a crude estimation?

If I had a vector containing the spectral centroid, spread, skewness and kurtosis (all normalised) of an audio clip and found the distance between it to the same kind of vector of another audio clip. ...
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6 views

Spectrum density estimation in R. Plot scale

I used spec.pgram to estimate the spectrum of a sequence. It gives a plot, I wonder what exact does it plot? It is not spec in the return value it is not log of that, it is not log10 of that. I fail ...
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2answers
50 views

Frequency spectrum of signal - Matlab

Here is the code I use to plot a function in frequency domain in Matlab: ...
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1answer
33 views

Average spectrum representation - SonicVisualiser

I try to have a signal (speech) represented in time and frequency domain (waveform, spectrum and spectrogram). I use Sonic Visualiser and for spectrum representation it shows an analysis at a given ...
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3answers
112 views

How to estimate the period of a pulse train?

I am trying to find the period of a pulse train like signal. I have reviewed the following questions but I did not find a clear-cut answer to the problem, 12892, 16502, 6260. I do not know the ...
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11 views

What is the best way to detect audio drops (audio level drops irregularly) in a video?

While recording a video, due to some problem in microphone (like low battery ) audio level go down inconsistently (voice____Voice__), I am trying to figure out an solution for this, is there any way ...
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1answer
33 views

What is the Sound of a Solution to the Wave Equation?

What is the sound of a solution $y(x,t)$ to the Wave Equation $\frac{\partial^2y}{\partial t^2}=c^2\,\frac{\partial^2y}{\partial x^2}\enspace$? To be clear, I don't look for a solution of the Wave ...
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45 views

How to define cyclic frequency for cyclostationary signal in terms of signal parametrs?

I am trying to detect cyclostationary signal. For that it is required to know its cyclic frequency. But I am unable to figure out how it can be related to signal parameter. Is it possible to define ...
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1answer
44 views

Detect repetitive units within signals

I have several signals that consist of repetitive units. In the figure you'll clearly see the variability of the signals, that increases top down. The first signal is super repetitive and units are ...
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3answers
72 views

How to add pitch-shifted version of signal to itself?

I want to write an algorithm to add pitch-shifted version of audio signal to itself (like Electro-Harmonix POG does). And I need to do it in realtime. How to implement it? My guess is: break signal ...
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1answer
58 views

Increasing the number of points in the frequency spectrum

I have an image with few pixels in length and height. For this image I calculated the two dimensional Fourier transformation. What I got for the frequency spectrum in one direction was a very ...
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1answer
32 views

Do I need an overlapping in STFT if I want to play the signal back?

I want to write an algorithm to implement a pitch-shifter, like in this article: http://www.guitarpitchshifter.com/matlab.html. And I need to do it in realtime, not with a signal already defined ...
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0answers
29 views

Computational model for spectrum analyzer - how to model resolution?

I'm trying to model a spectrum analyzer which may be used experimentally for visualizing the spectra of signals. I have a numerical data signal with excellent resolution (...
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27 views

Spectral centroid range between 0.45 to 0.5, almost doesn't react to mic input

I am implementing some feature extractors in Swift for an application. One of these features is Spectral Centroid. For some reason I keep getting values ranging between 0.45 and 0.5, and these don't ...
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23 views

Determining the point in a temporal signal when a periodic behavior begins to occur

I'm a newcomer to digital signal processing, so I'm looking for some general advice and direction on this problem I have. I have a signal like that shown below. Starting around x=40000, you can see a ...
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12 views

Extract features from video based on temporal frequency

Situation is as following: there is a video, 2d sequence of frames, each of which contains still picture of beating heart, or some other oscillating object. Also each picture contains some features, ...
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1answer
66 views

Measuring frequency response range of piezoelectric disc

How can I measure the frequency response range of a piezoelectric disc below. I don't have an oscilloscope but I do know how to program in matlab / octave I was thinking of creating a swept signal ...
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4answers
395 views

Difference between DC component and zero frequency component of signal

We know that Fourier Transform of a signal exists if it is absolutely integrable and it exists for periodic signals if impulse functions are allowed. If we consider the fourier transform of ...
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1answer
44 views

How to find transfer function looking bode plot

I have some Bode plot (only in amplitude) as these: Now, I must to find their transfer functions, in particular the exact value of their zeros and poles. It is clear that their are a low pass ...
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3answers
165 views

How can I automatically identify and remove a fundamental frequency and all of its harmonics?

I have some microscopy data that is contaminated by a heartbeat artifact that I'd like to remove. The data consists of a large time series of images captured at ~60Hz. Here's a small example clip in ...
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2answers
105 views

How to know if a audio file is real lossless using its spectrogram?

I need to know if a certain audio file is real lossless and not a transcode (i.e. lossy converted in lossless, but lossy at the end). I was told there was a way to do this by creating a spectrogram of ...
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44 views

How to plot Full spectrum with negative frequencies

I'm trying to do frequency analysis on signal of a rotating shaft. The signal is generated in two measurement planes i,e X-position and Y-Position. I was able to use fft and transform into frequency ...
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2answers
128 views

What is meant by *sampling* in terms of the *sampling theorem*?

Let $y:\left(-\frac T2,\frac T2\right)\to\mathbb{C}$ be a square integrable function. The Fourier coefficients of $y$ are $$\underline{Y}(k):=\frac ...
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79 views

Sampling theorem and signals explained to a mathematician

Let $f:\left(-\frac T2,\frac T2\right)\to\mathbb{R}$ for some $T>0$. The Fourier coefficients of $f$ are $$\left\{\begin{matrix}a_0&=&\displaystyle\frac ...
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1answer
67 views

Strange phase spectrum from stft

I've tried to implement STFT in functional way in Python. I've got code such as below: ...
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32 views

Square signal: from a period histogram to a frequency analysis

I have a dataset of square waves (with periods slightly varying from the nominal one) and I read the times between edges with a PIC microcontroler, so I can obtain a histogram of periods. The data ...
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38 views

Applying a custom filter to FFT results?

I think I am missing something here and I do not quite understand why. Background: I am collecting quadrature signals from a software defined radio. There are two signals, the I, and the Q which is ...
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1answer
106 views

Removing periodic noise from image using Fourier transform

I'm trying to get rid of some periodic flicker noise through post-processing of the recorded images. The reason for these artifacts is that the electronic rolling shutter of the camera reads each line ...
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1answer
96 views

Formulas to plot Frequency Impulse Response Coefficients

I made this question newbie:Plotting FFT and Impulse Response Coefficients, using Java I have the IRC: Impulse Response Coefficients: $h(k), k = 0, 1,.., N-1$ Low Pass: ...
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1answer
29 views

Is a negative Es/No for an SCPC RF signal possible, and what would such a value signify?

I apologize if this isn't the correct Stack on which to ask this question, but it seemed like the best fit. I've tried to Google an answer, but I haven't been able to find anything that applies ...
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159 views

How to plot the amplitude spectrum of the Ricker wavelet in MATLAB?

I have the following MATLAB code and I would like to plot the Ricker wavelet both in time domain and frequency domain. I would like some help because I am getting amplitude greater than one for the ...
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92 views

Using only positive frequencies in fourier domain, How will it affect the ifft?

I am going to do some kind of transformation and transform a data to another domain, and again back to the first domain. For this, I take a fourier transform of the data and separate the positive part ...
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26 views

How to transform one graph to a spectrum?

Recently, I studied a paper called "What Does Your Chair Know About Your Stress Level? It can be download at the link below. ...
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0answers
26 views

How to measure spectrum envelope in matlab

I would like to measure the energy change of the spectrum envelope of a wav file like 20hz - 40 hz and plot a graph like this in matlab: Sorry I have no knowledge about signal and would like someone ...
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21 views

What does it mean compute spectra of Center of Press?

Recently, I studied a paper called "What Does Your Chair Know About Your Stress Level? It can be download at the link below. ...
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3answers
90 views

Normalization purpose in signal processing

What is the purpose of normalizing the signal? If we have two signals on hand, how is it used when comparing these two signals?
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1answer
60 views

For a standard second order transfer function, what is the equivalent time domain significance of $\zeta>0.707$?

In frequency domain $\zeta>0.707$ implies no resonant peak in frequency response. But I am unable to correlate what is the exact time domain effect of this? If $\zeta=0.707$ acts like an ...
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2answers
39 views

fundamental question regarding bandwidth

What I've learnt so far is that, if we change a time-domain signal into frequency domain, its bandwidth shows the range of frequency of radio waves that required to generate such signal. However, for ...
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1answer
44 views

What is the distance metric in dynamic time warping?

I am reading the lecture slides from this site http://luthuli.cs.uiuc.edu/~daf/courses/CS-498-DAF-P/Lecture%2018%20-%20Time%20series,%20DTW.pdf In slide 24, the lecture suggest using metric of the ...
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78 views

Confusion in the spectrum of FSK modulated signal by using matlab fskmod module

I want to do a comparison of power spectral density of BFSK, 4FSK and 8FSK by using matlab baseband module "fskmod".Following is ...
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0answers
65 views

How to, efficiently, identify telephone number from the key pressed data audio file?

A very common homework question. You are given an audio file(.wav) which has the recording of the keys pressed during a telephone call. You have to identify the telephone number from this audio file ...
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169 views

Detect Frequency of Incoming Audio on Raspberry Pi

I've been lurking around these forums for a while and they've been a great help to me in the past. However, I've been researching this problem for the past 2 days or so and can't seem to find a ...
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1answer
61 views

Downsampling fft results to a graphics display

I'm new to dsp. I've got a complex signal that was sampled at 192kHz then an fft of 16384 bins created. This now needs to be plotted on a graph for a real time spectrum display. The problem is if ...
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1answer
77 views

Help on implementing an IIR filter

I am new to signal processing and and having difficulty understanding how to implement an IIR filter. The reference is athttp://www.dxatlas.com/rocky/Advanced.asp in the Band scope section. It ...
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13 views

Suppose we have the following data. How can we calculate the channel capacity and R?

A channel has a bandwith of 5MHz. If signal strength to spectral noise density S/N0 is 107 Hz, calculate the channel capacity C and R. The problem is that I can use Shannon-Hartley theorem because ...
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1answer
25 views

Is there any tool to anlyze audio specturm of a song and give the average visually ?

I have a lot of songs I made over the 20 years and was thinking it would be interesting to see how the overall EQ changed on the various songs I made. Any tool out there to help me with something ...
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1answer
69 views

why upsampling contracts the spectrum?

I'm trying to understand why Matlab function upsample causes contraction in the spectrum, like the following figure shows. Also showed in mathwork online document. enter link description here ...