Questions tagged [signal-analysis]

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2
votes
4answers
15k views

Measure the SNR of a signal in the frequency domain?

How do you measure the SNR of a sinewave in the frequency domain? (Assuming no filtering.) Suppose: $$x(n) = s(n) + n(n)$$ Create the signal (nCycles of a sinewave) in MATLAB...: ...
4
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2answers
2k views

Extracting audio track to determine the song beat

I'm completely new to this field. Perhaps I'm calling it by a wrong name, but I want to analyze an audio track and retrieve a timestamp to beat mapping. Is there an open source 3rd party library ...
3
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2answers
2k views

Effects of DC offset on a signal

What are some of the reasons why DC offset is considered undesirable for a timeseries signal other than wastage of power during transmission ? Specifically, How does it cause spectral leakage and out ...
0
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1answer
87 views

Expected value of coupled signals is zero

Suppose there are two vector signals, $u$ and $v$, which are functions of time. Given, $E[uv^T]=0$, what is the physical significance of this statement. For clarity, assume $u$ and $v$ are noises in a ...
-2
votes
1answer
43 views

What happens to the fourier transform of sample result of $30kHz$ sinusoidal signal when sampled with sample frequency $44.1KHz$?

As the title says,w hat happens to the fourier transform of the sample output of $30KHz$ when sampled with sample frequency $44.1KHz$? I do not get how alias can appear, because fourier transform of ...
0
votes
1answer
475 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 ...
1
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1answer
2k views

Why do we need to normalize a WAV file before calculating the FFT?

I am trying to calculate the FFT of a signal stored in a WAV file using SciPy. I found a solution here, but it seems like we need to perform this step before the FFT: ...
-1
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1answer
249 views

BCI project using EEG signals

I want to make a BCI project, based on EEG signals, to control a robot using the brain's P300 wave. I have read a lot of papers, which give me a wide knowledge on how to deal with those signals, but ...
-1
votes
1answer
407 views

Confusion when applying Hamming window to signal

I am writing some code which takes a signal of length $n$, and processes it in 20 ms chunks with 5 ms of overlap... So basically I have a buffer of 20 ms worth of sampled data, and I am trying to ...
1
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1answer
305 views

Question on Chebyshev filter

What does the output signal look like when you insert $2000 Hz$ square pulses to chebyshev filter with parameters: (Matlab syntax). I tried to do it like this but I don't understand where it goes ...
1
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0answers
104 views

Removing the mean in finding PSD

Does removing the mean value of the signal effect the estimation of power spectral density(PSD)? If it effects, how? What is the advantage we can get by removing the mean of the signal in estimating ...
1
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1answer
89 views

What is the use of the Welch lower bound when k > 1?

The Welch lower bound on the maximum cross-correlation (inner product) of $m$ vectors, each of $n$ elements, is given by $c_{max} = f(m, n, k)$ (eg, see Wikipedia Welch bounds). It is always assumed ...
2
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1answer
211 views

Regarding Bode plots; $H(s)$ and $H(j\omega)$

In circuit analysis, I understand the use of Laplace Transforms to obtain the impedance of a linear RLC circuit, ie transforming from the time domain to the frequency domain. In most texts I have seen ...
0
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0answers
18 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 ...
0
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2answers
191 views

“Perfect waveform” for cross-correlations?

I am well versed in cross-correlations, as my masters thesis heavily relied on them for music classification and beat detection. So this question focuses more on the signals that I am running an ...
1
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1answer
70 views

How to apply “Substitution Method” in Difference Equations?

How to get the value of $y_p(n)$ using substitution method? What exactly do we need to substitute to get the value?
1
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1answer
621 views

Speech recognition using mfcc and neural network [duplicate]

I am doing the project on speech recognition.I have implemented both the mfcc features and neural network.I am a bit confused in joining the two blocks.For example i have three different words with ...
1
vote
1answer
879 views

Find similarity of sound signal

So I was working on a program to comparing the similarity between the pronunciation of a word, First I got the audio file, and I use FFT on it to get the amplitude over frequency array, then I just ...
1
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1answer
662 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 ...
0
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0answers
46 views

Calculating the modulation based on the coordinates in the constellation diagram

A constellation diagram has points at the following coordinates: (2,2), (2,-2), (-2,2), <...
0
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2answers
3k views

Merits of “Zero-Phase” Zero Padding

I understand the reasons for zero-padding a finite signal before FFT. However, I was reading this book (http://www.dsprelated.com/dspbooks/sasp/Zero_Phase_Zero_Padding.html) where the topic is Zero ...
-2
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1answer
560 views

FFT on Hamming Window Function [duplicate]

I want to apply Hamming window function the Audio sample then find out its fft.. ...
0
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0answers
62 views

comparing different signals

I have some noise measurements and 4 different models that can generate a similar noises using estimated parameters from the real measurements. To compare the estimated noises I calculated the PDF, ...
2
votes
2answers
225 views

Detecting sound inside a sound

I was searching on the Internet hopelessly about some materials regarding detecting a sound in another sound. Say, I've got a recorded short sound (which may be anything, fragment of speech, fragment ...
0
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1answer
1k views

Feature vector for MFCCs

I am working on a project, for which I am finding the onset times of an audio and then extracting the MFCC coefficients for all the times. Thus if I have n onset times, I would have n feature vectors,...
1
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1answer
738 views

Does Wav format supports writing complex values

I have a sine tone, doing some math, and finally gets an harmonically accumulated sine tone in complex numbers. I do want to preserve the phase information of imaginary part on the other end, which ...
1
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1answer
327 views

How to learn MUSIC algorithm?

I was actually preparing for my semester project and decided to take up Frequecncy estimation.I ll directly come to the point that I want to know how should I learn MUSIC algorithm. How do I start it? ...
0
votes
1answer
642 views

MSK signal recoverd though FM Discriminator?

I am attempting to write a FFSK (differentially encoded MSK) modulator. I have found and implemented a demodulator that works with sample data taken from a radio of a FFSK signal. The demodulator ...
-1
votes
1answer
188 views

Accumulator with decay?

I am using an accumulator in the form of X + [Y-1], X plus the unit delay of the output. Is there an accumulator that follows this form, but will fall to 0 over time, similar to a differentiator?
0
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3answers
225 views

Could multiple echo reflections be combined to improve signal to noise ratio?

I am working on a system processing ultrasonic echo reflection. The transmitter creates a short ultrasonic pulse and the receiver analyses the reflection. If I send two pulses (back to back or with ...
1
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1answer
118 views

Characterising a system from its input and output

I have 2 data sets sampled at regular intervals which represent the input and the output of a system. A quick analysis of the plots shows the following: There is a proportional factor between the ...
1
vote
3answers
248 views

Study Signal Processing

I'd Like to ask two questions : What is the difference between studying Signal processing (both Deterministic and statistical) in Department of Electrical Engineering versus Department of Mathematics ...
-1
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1answer
205 views

Q and I part in QAM

I have one confusion in QAM about in-phase I and quadrature Q part, i.e. do they transmit identical data or not? For e.g. if i have 11001001 as a byte to be transferred, so will 4-QAM separate it like?...
2
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2answers
2k views

Can the order of filtering and downsampling be exchanged?

Say for example, I have a signal with maximum frequency at 600Hz, and I originally oversampled it at 2000Hz. Afterwards I was only interested in frequency less than 500Hz. I guess I could first filter ...
1
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2answers
8k views

Negative dB signal to noise ratio

Is it common to find systems having signal to noise ratio (SNR) less than 1 i.e. noise is more than signal? I am currently working with SNR of -5db to -20db. And how useful is it to work with sensor ...
1
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2answers
81 views

how can i get to know the frequency of a speech signal?

What is the actual meaning of frequency? what if the signal is aperiodic?? In general, we say that frequency means the repeatition of an event in unit time. But what about a speech signal? how can we ...
2
votes
0answers
735 views

Extracting the phase of a jittering sine wave using python

The background: I conducted an experiment where I rotated an object (with three-fold symmetry) many times and recorded the projection of the object. I should be able to tomographically reconstruct ...
0
votes
1answer
366 views

understanding discrete-time convolution in LTI systems

I'm trying to understand the discrete-time convolution for LTIs and its graphical representation. standard explanations (like: this one) start with the idea of decomposing an input signal $x[t]$ into ...
0
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1answer
245 views

converting block diagrams with delays to equations

given this block diagram: can someone please clarify how to interpret the second delay (the one prior to $Y$)? to convert this block diagram into a simple equation, I interpret the diagram as: ...
1
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0answers
1k views

In a signal there is a peak, I want to find the start of the peak and the end of the peak

I want to the start time and end time for the peak shown below. The start and end are shown by the marked circles in the fig As there are number of such plots and want to know start and end time for ...
-1
votes
1answer
269 views

Describing Function for non-symmetric Saturation Model

Let's talk about a standard saturation model: with bounds $bound_{lower}$ and $bound_{upper}$. So in this example the output $y$ will be: \begin{equation} y(u) = \begin{cases} bound_{lower} ...
1
vote
1answer
48 views

How to decode speaker gender from spoken transcript

I have 20 audio recordings (raw format) of people reciting the same ~50 word transcript. I would like to use audio signal analysis to decode speaker gender from audio recording. Intuitively, it ...
1
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0answers
72 views

Interpolation methods for radar and acoustic imaging and potential pitfalls

A) What are the most common methods used to remap data for current generation imaging radars and acoustic sensors? B) What are some of the pitfalls in these methods? For example, in the past, at ...
1
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1answer
122 views

When was the time-frequency analysis invented?

It seems there are several papers from the seventies but backtracking from the references gets quickly difficult. Who calculated for the first time a time-frequency representation of a signal?
0
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1answer
58 views

Time shift — two interpretations

In their textbook(Example 1.1), Oppenheim and Willsky provide the following method for obtaining $g(t)=x(-t+1)$ from $x(t)$ : Replace $t$ with $-t$ in $x(t+1)$. In other words, advance the signal by 1 ...
4
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1answer
24k views

How to calculate Signal-To-Noise Ratio

I am doing some analysis in python working with a photodiode. The signal is more or less periodic with some phase shifting in certain areas that give rise to faster or slower periods but overall still ...
1
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0answers
106 views

How to replace Hadamard Product and Column wise addition with new Matrix operation?

Let $$ A= \begin{bmatrix} a_{1,1} & a_{1,2} & a_{1,3}\\ a_{2,1} & a_{2,2} & a_{2,3}\\ a_{3,1} & a_{3,2} & a_{3,3}\\ \end{bmatrix} $$ and $$ B= \begin{...
0
votes
1answer
82 views

Time Invariance

I cant understand this when I have a system thar compress the input as follows $$y(t)=x(2t)$$ Now to check for time invariance now I should input $x(t)$ to get $$y_1(t) = x(2t)$$ Then I should input $...
1
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1answer
320 views

minimum frequency in periodic components

Suppose we have the following signal model $y(t) = A_1\sin(\omega_1 t+\phi_1) + A_2\sin(\omega_2 t+\phi_2) + ... + A_p\sin(\omega_p t+\phi_p) + z(t)$ When we are sampling at sampling frequency $f_\...
2
votes
2answers
3k views

Preprocessing audio signal for neural network classification

I need to identify certain features of the audio signal recorded from microphone in stethoscope. These sounds are only samples i've found, but the final signal will be probably a bit noisier (maybe ...