Questions tagged [signal-analysis]

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2answers
623 views

Determine if two signals are the same?

I'm pretty new to signal processing. My data is the $(x,y,z)$ acceleration of someone walking with a smartphone in his/her pocket. Goal Given two signals, determine if it's from the same person ...
3
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0answers
366 views

Linear Frequency Cepstral Coefficients, is Filter bank needed?

I am working on my master thesis on acoustic pattern recognition and have a question to the calculation of cepstral coefficients. I understand the step with a filter bank in MFCC calculation, it is ...
3
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1answer
167 views

Overlapping power-of-cosine windows with constant weight

I would like to refer you to a relevant question I posed on the Math StackExchange: A generalisation of the Pythagorean trigonometric identity. As can be seen from the question and the answer, what ...
3
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0answers
119 views

Preserve scale during PCA

I have two signals, I've done a Principal Component Analysis and separated my signals, I get one with noise and one with signal. . ...
3
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2answers
163 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 ...
3
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0answers
218 views

Segment/Idenfication of signal from a spectrogram

I have the following Spectrogram of a signal: Essentially, in this signal, I know there is one point of interest (between 60-80) and between the the particular frequencies. I could, potentially ...
3
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2answers
379 views

How to Extract Nonorthogonal PCA Principal Components

My problem is essentially a 'blind source separation' problem. I have 3 non-orthogonal sources (or basis functions) and $N$ random linear combinations (mixes) of said sources. My problem is to obtain ...
3
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0answers
160 views

understanding discrete wavelets

I was reading section 4.3.3 from chapter 4 of "A Wavelet Tour of Signal Processing", "...Let $\bar{f}(t)$ be a continuous time signal defined over $[0,1]$. Let $f[n]$ be the discrete signal obtained ...
3
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0answers
2k views

How to convert raw pulse sensor data into actual pulse?

I've built a simple device, which sends readings from a pulse sensor to a PC. I get these data: What technique or algorithm can I use in order to calculate the pulse rate (beats per minute) from ...
3
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0answers
56 views

Intuition of Location on the Conic Axis TDOA solution

In an old paper "A New Approach to Geometry of Range Difference Location", there is a mathematical derivation that does not include any mention of the relationship to the underlying problem. In the ...
2
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4answers
3k views

What does the exponential term in the Fourier transform mean?

We know that Fourier transform $F(\omega)$ of function $f(t)$ is summation from $-\infty$ to $+\infty$ product of $f(t)$ and $e^{-j \omega t}$: $$ F(\omega) = \int\limits_{-\infty}^{+\infty} f(t) \ e^...
2
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3answers
305 views

Can use of Fourier transform be minimized completely with the help of Laplace and Z transform?

Fourier transform has different types like continuous Fourier transform (CFT), Discrete time Fourier transform (DTFT) and Discrete Fourier transform ( DFT). CFT can be used in case of continuous ...
2
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3answers
429 views

Computer exercises and solutions in signal processing

I am very interested in this question and can literally not find anywhere a simple answer, so apologize in advance if it does not fit well this community. I am looking for either an online resource ...
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 ...
2
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4answers
14k 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...: ...
2
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3answers
2k views

“Fourier Transform can localize signals in frequency domain, but not in time domain.” — What does it mean in layman's terms?

I was studying the introduction to wavelets and its benefit over the frequency domain. I said that: Fourier analysis can't localize signals both in time and frequency domain. Fourier analysis can ...
2
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1answer
4k views

Time-frequency representation of sound signal using Matlab

I am currently doing a project on sound signal processing by using MATLAB. I have a problem regarding creating the command line so that I can get a graph containing frequency by its time. But this ...
2
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6answers
35k views

Simplest way to implement FIR filter in C/C++

What's the simplest way to implement a FIR filter in C/C++ ? (I don't want to have to use a third-party software like Matlab or Octave in order to compute the coefficiens because I have to use ...
2
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3answers
2k views

How to get fundamental frequency of a signal using autocorrelation?

I am trying to get the fundamental frequency of a signal that only has a single pitch. I coded out the autocorrelation function using FFT and already got the autocorrelation result. Unfortunately, I ...
2
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3answers
162 views

Detect valleys of a signal

I have raw values that are coming directly from a sensor (on the fly). These values are coming from a wearable sensor installed on a cows neck. When the cow ruminates (meaning that it chews food that ...
2
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1answer
285 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 ...
2
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2answers
2k views

How to quantify asymmetry of a signal?

I'm looking for a suitable measure in order to quantify the asymmetry of a signal. I've read this: Detect signals degree of imbalance and this: How to measure the agreement between to curves? but I ...
2
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2answers
1k views

How do I perform the sifting process in empirical mode decomposition?

I am programming a voice activity detection algorithm and I found a paper that recommends the use of HHT. I have been trying to program it and understand how to calculate $m1(x)$, but the shifting ...
2
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1answer
7k views

Use Butterworth and Chebychev filters

I need to calculate frequency response, phase response and apply to signals the Butterworth, Chebychev1 and Chebychev2 band-pass filters. I'm developing in C++ with Qt, and I'm looking for algorithms ...
2
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2answers
77 views

Periodicity of sum of discrete signals

In my lecture slides for school and from this website here "The sum $z[n] = x[n] + y[n]$ of periodic signals $x[n]$ with fundamental period $N1$, and $y[n]$ with fundamental period $N2$ is periodic ...
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2answers
3k views

How do I find the fundamental period of the given signal?

I am having a problem in finding the fundamental period of the signal $x(t)$ given below: \begin{align} x(t) &= 2\cos\left(\frac 45 \pi t\right)\sin^2\left(\frac{16}{3} t\right)\\ &= 2\cos\...
2
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4answers
113 views

Can you recommend an efficient encoding algorithm for sound with long periods of silence?

As a side personal project, I'm coding an Android application that I plan to use to record the sounds of our first baby. I'm kind of new to the world of Android development and sound processing, so ...
2
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3answers
104 views

Weighted Sum of Auto Correlation - Lower Bound

Given a vector $ v $ with elements $ {\left\{ {v}_{n} \right\}}_{n = - \infty}^{\infty} $ and denoting $ {v}_{n}^{\left( k \right)} = {v}_{n - k} $, namely, a shifted vector by $ k $ elements (Mind ...
2
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1answer
89 views

Beginner's book in signal processing with practical examples on fault detection in electrical motors

I'm an electrical engineering graduate and I'm working on condition monitoring for electrical motors and generators. My goal is to improve reliability of electric rotary machines in such way, that any ...
2
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2answers
101 views

Mathematically speaking, is a “signal” a function or the set of outputs from a function

In engineering it is well known that we abuse the notation of a function $f: A \to B$ with the image of that function $f(t) = \left\{y \in B\mid f(t) = y, t \in A\right\}$ When we say: let $f(t) = \...
2
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1answer
134 views

adjust mean of signal using exponential

I have discrete signals whose values are between 0 and 1. I wish to post-process such a signal such that the mean of its values equals 0.5, yet keeping maximum and minimum values 0/1 intact. ...
2
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4answers
3k views

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 ...
2
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1answer
381 views

Very first values of y[n] in an IIR filter

I use a simple biquad IIR filter : ...
2
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1answer
115 views

$\lim \limits_{a \to 0} \frac{1}{a}[u(\frac{t}{a}+\frac{1}{2})-u(\frac{t}{a}-\frac{1}{2})]= \delta(t) $

It would be very helpful if someone could provide the intuitive reasoning and mathematical proof for: $$F_a(t):=\frac{1}{a}\left[u\left(\frac{t}{a}+\frac{1}{2}\right)-u\left(\frac{t}{a}-\frac{1}{2}\...
2
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1answer
1k views

Determining if the given system is LTI

Problem Given the compound system below, with the input $x(t)=\operatorname{sinc(t)}$, the output of A is $y(t)=\operatorname{sinc(2t)}$ and the output of B is $z(t)=\operatorname{sinc(t)}$, ...
2
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2answers
162 views

How to perform downconversion using a DSP

I read that to perform downconversion, first, I need to generate a sine wave with the same phase and frequency as the transmitter's and then multiply the signal received by the generated sine wave. I ...
2
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1answer
500 views

Signals cross-correlation

I am trying to measure phase difference between two received waves which are recorded by two separate PC's (microphones). The two PC's starts recording at the same time, then I make a sine wave sound ...
2
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1answer
160 views

Definition of energy of a signal

I was wondering why the energy of a signal is defined as $$E=\int_{-\infty}^{\infty}|x(t)|^2dt$$ I mean, I know that it is a definition, but is there a physical reason for it being defined like that?...
2
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2answers
318 views

Fourier Transform of infinite sum

I'm looking at last year's exams, and I found an exercise I can't solve: (Roughly translated) Consider $x(t)=\sum\limits_{k=1}^{+\infty}\left(\frac{1}{2}\right)^k \cos(k2\pi t)$ the input to a LTI ...
2
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3answers
232 views

Separating a signal into its constituent components

First off, I apologize for possibly incorrect use of jargon, as I am new in this area. I have a type of signal that I am assuming can be described by an arbitrary number (let's say $n$) of basis ...
2
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1answer
1k views

Estimating Filtered Noise Variance

Assuming I have samples of a colored noise. I know the empirical Variance of those samples. I also know the bandwidth of the filter which colorized the noise (Only the bandwidth, not the actual filter)...
2
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1answer
5k views

Determine the optimum receiver and the corresponding $P_{eM}$ for an AWGN channel

I have a source that emits $M$ equiprobable messages, which are assigned signals $s_1, \dots,s_M,$ that are equidistant by $a$. That is, if we plot the $s_k$ signals in a horizontal axis they are dots ...
2
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1answer
30 views

Is there any way that we can perform speech recognition without using Fourier transforms?

I am trying to research about speech recognition and why everyone uses Fourier transforms in going about the topic. I know that we get information related to the frequency of each sound uttered which ...
2
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1answer
86 views

What is discrete angular frequency?

I am currently reading a paper about speech enhancement. The paper uses Spectral Subtraction Method. On that section, The paper stated that ω is the "discrete angular frequency index of the frames" ...
2
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2answers
74 views

how is this method of proving shift invariance correct

I got this answer from here. But i don't know how this method is correct. Until now to prove shift invariance what i did was : step 1: delay output and write it in terms of input. step 2: delay input ...
2
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1answer
519 views

Comparing multiple signals for similarity

I have multiple (between 2 and 100) signals and need to determine when a significant number diverge from the rest. We're exploring machine learning techniques, but we also want tackle this as a signal ...
2
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2answers
198 views

Measuring vibrato rate of a sung note

I'm doing a project where I need to measure the rate of vibrato cycles in a sung note under various conditions. The stimulus will be a several-second-long audio sample of a held a capella note with ...
2
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1answer
473 views

Exponential decaying step response in LTI System

I'm attempting to better understand the relationship between step responses, impulse responses, and convolutions. Say that I have a system where if I apply a constant input, my output decays from a ...
2
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2answers
162 views

Find the transfer function of the difference between IIR and FIR filter

I am using a filter following equations from papers. It is basically the difference between exponential moving average and simple moving average. $$L[n]=\frac{1}{\alpha_L}f[n]+\left(1-\frac{1}{\...
2
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2answers
538 views

DFT of real sinusoids - why sum over -$N/2$ to $N/2-1$ as opposed to $0$ to $N-1$?

I'm going through a Coursera course on signal processing, and we're just introduced to DFTs. We are told that if you have a complex sinusoidal signal $x[n]$ where $n=0,1...\ N-1$, its DFT is given ...