Questions tagged [signal-analysis]

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1answer
69 views

Determing the frequency of a signal with a sample at a time [closed]

How to determine the frequency of a signal with a value of the sample and value of the time instant the sample was taken ?
3
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5answers
15k views

Percentage difference between two signals

Apologies in advance for what I imagine is a simple question, however I can't work out how to do this. I have two signals of the same type but with different sensor types, the figure below will give ...
3
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2answers
10k views

What is the difference between a one dimensional and a two dimensional signal?

If a signal depends on only one variable then we call it one dimensional, and if a signal depends on two variable we call it a two dimensional signal. But when we represent an one dimensional signal, ...
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2answers
1k views

Matching two audio inputs (signals) [duplicate]

this is for an application in which passwords are stored in the form of audio inputs . In order to provide user access , the password(in audio form) will be matched with already stored password(audio ...
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3answers
32k views

What is the difference between linear and non-linear filters?

How a mean filter is called as linear filter and a median filter is called as non linear filter? I understand how a mean and median filter operates, but I was not able to relate with the term linear ...
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1answer
106 views

recognizing words in a sentence

I want to know that what features might be needed for recognizing a word i a sentence exactly? I guess the routine for recognizing the word in a sentence is ganna follow this: 1-calculate voiced and ...
3
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1answer
2k views

Large Laplacian Spatial Filter on EEG?

I want to know that why large laplacian spatial filtering is done on EEG signals? I tried a lot but could not find material on LLSF. And what is meant by spatial filter ( in context of Digital Signal ...
0
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1answer
668 views

Estimating device height from 3-axis accelerometer data (possibly by supervised learning)

I'm trying to estimate the height of my device using an cheap integrated Freescale accelerometer. First, I estimate the earth direction when measured acceleration is close to 1g, then I project the ...
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1answer
139 views

FFT of 2 D images

Branching off from this question - https://dsp.stackexchange.com/questions/6020/mapping-the-value-of-a-sample-in-a-2-d-dft-to-cycles-pixel, I have a few more questions related to 2D FFT of images. I ...
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2answers
389 views

Need to learn wavelet, suggest steps and resources [closed]

I am looking for a good introduction to wavelets and wavelet transforms. that covers the following: Vector Spaces – Properties– Dot Product – Basis – Dimension, Orthogonality and Orthonormality – ...
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1answer
240 views

STFT Time Variance - Threshold

This is a follow up question to: Segment/Idenfication of signal from a spectrogram My main goal is to identify (segment) all of the calls from a given signal. The signal looks like the following (...
3
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0answers
221 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 ...
2
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1answer
205 views

Gesture recognition from analog sensor value

Not sure if this is the right place for my question but let me give it a try. I have a very simple analog sensor (piezo transducer) which is attached to a microcontroller. I'm using this sensor to ...
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0answers
460 views

Analyzing an undersampled recording from an antenna with matlab?

I'm trying to analyze the power spectral density of a signal recorded from a Ham radio antenna. The signal is about 30 seconds long, recorded at a 48 kHz sample rate. The frequency is center frequency ...
3
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3answers
260 views

How to determine, calculate and plot a probability distribution for a given set of numbers?

A device is rotating with a particular wind speed and producing such pulse frequencies in a minute: ...
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1answer
216 views

How to extract the maxima and minima of a noisy period input signal

I have a (rough) known period sine wave coming in, held in an array, with superimposed noise. I need to find and count the maxima and minima (in C). Any suggestions or algorithms? The signal has ...
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1answer
96 views

Two-dimensional wavelet analysis

Could you tell me why wavelets without scaling functions can't be used for two-dimensional analysis? What is the role of scaling function?
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0answers
64 views

Common mode noise from two ADC results

I am sampling two sinusoidal analogue signals that are phase separated by $\frac{2\pi}{3}$, and there appears to be a significant amount of common mode noise in my samples. What, if any approach can I ...
0
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1answer
257 views

Change of bin magnitude when phase of signal changes when doing FFT?

I am working on an implementation in which I need to apply an FFT to determine which of 4 frequencies are present in a signal. I am doing a 64 point FFT on a buffer which only is partly filled (the ...
1
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1answer
240 views

How can a zero-padded length n signal be truncated to n coefficients from which a signal can be reconstructed?

A wavelet transform is defined for infinite length signals. Finite length signals must be extended in some way before they can be transformed. I know that periodic replication and zero padding are ...
1
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1answer
490 views

Calculating an incoherence property from sub-optimal sampling patterns

EDIT (after comments and subject matter review) CS is based on a choice of a sensing basis $\Phi$ relative to a representation basis $\Psi$. Using an "Incoherence Property" $\mu$ that measures the ...
3
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2answers
4k views

Compressive Sensing - Incoherence Property

Compressive Sensing is built on 2 properties: 1) the sparsity of the representation basis relative to the sampling basis and 2) the incoherence between the singular vectors from each of the 2 bases in ...
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2answers
244 views

Examples of mixture of 'almost periodic' signals/data in nature or practice

I am working on algorithms to separate mixtures of 'almost periodic' signals. One such example is composite ECG consisting of maternal and fetal signal. Can anyone help with examples of such signals?...
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1answer
135 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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2answers
365 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 ...
3
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2answers
382 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 ...
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1answer
706 views

cceps (complex cepstrum) function in Matlab

My doubt is in regards to the usage of the function cceps in Matlab. The function is giving me the cepstrum for the entire speech signal of 3 or 4sec. This works ...
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0answers
207 views

Use of USRP SDR to process sonar?

I have ordered a USRP kit to do radio signal processing in software. Is there a way to use the same device to process sonar data? What would I do upconvert the sonar to 50 MHz?
3
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3answers
3k views

Why do we get ripples in the frequency spectrum of a chirp, and how do I remove it?

The ripples in the amplitude spectrum of a linear spectrum is undesirable. I desire to obtain a flat spectrum response. Hence, how can I remove these ripples? Also, which factors (like time bandwidth ...
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 ...
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1answer
182 views

Turn your guitar to MIDI and Guitar Synthesizer

I don't know if this question is related to DSP, but I'll give a chance. Introduction: These days there are a Guitar Synthesizers which allow the guitarist to play another instruments like: brass, ...
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3answers
1k views

How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT?

My understanding if a frequency in my signal doesn't line up exactly with a bin, it is smeared over a few bins to the right and left. How can the instantaneous magnitude be determined? (do I have to ...
2
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1answer
1k views

Short term energy signal explanation

I'm trying to calculate the short term energy of a digital signal in python, using a rectangular window, but don't understand the basics of how this works, a pointer to any good explanation would be ...
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3answers
2k views

Compressive Sensing Incoherence Principle

As people acquainted with Compressive Sensing would know, incoherence and sparsity are two main principles. I've been reading about compressive sampling and developed an interest into the topic. What ...
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2answers
2k views

Zero-padding in STFT

I a recent topic, it has been told that zero-padding in the STFT can improve it, and avoid some circular convolution related things. Here is my Python code for STFT : ...
3
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3answers
2k views

Filtering with STFT

I have sucessfully implemented a STFT (+inverseSTFT with perfect reconstruction of original signal, with overlap add, etc.) in order to work on audio files. Using this STFT / iSTFT framework, I have ...
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1answer
230 views

Audio fingerprinting - 2D (time - frequency) filter / Energy differences

I am trying to implement the algorithm described in this paper. However, I am having trouble understanding the last part where I need to find the energy differences of bands. In another paper, this ...
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2answers
664 views

how were DTMF frequencies determined exactly and how can I extend them?

I've been playing with DTMF frequencies and the Goertzel algorithm, and would like to know exactly HOW the DTMF frequencies were determined. I understand that they were chosen such that none of the ...
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1answer
164 views

What kind of discrete convolution is this?

Let x[n] and y[n] be defined for n=0,1, ..., N-1. This (for example with Python's scipy fft ...
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1answer
23 views

How to detect if the given signal is Data or Clock signal type?

I have the edge information of the signal. I need to find if it's a Clock or Data type signal without iterating through all the points in edge vector... Please provide your valuable inputs
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1answer
75 views

How to identify stable deltas in a noisy signal

This is a problem I have had to deal with in several different contexts now. Given a real time signal which you expect to act as a noisy step function (periods of stability separated by quick changes ...
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0answers
147 views

Can ICA be applied to solve BSS problem in frequency domain?

I'm recently doing research on EMI, and I want to seperate the mixing signals. However, the data given is in frequency domain. As I have used ICA to solve blind source separation problem in time ...
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1answer
167 views

Detecting presence of music in ambient sound

I am hoping to create an application that would listen to ambient sound and detect if music is being played. It is not important to identify the music being played; just detecting that some music is ...
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2answers
2k views

Discretized CWT vs. DWT vs. FWT vs. MRA

By reading some books about wavelets, it seems that Discretized CWT is not the same thing as DWT. Can we give a classification of Discretized CWT vs DWT vs FWT etc. ? A few remarks : All I read ...
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1answer
890 views

understanding time constant meaning in signal processing

from my DSP book,i am reading that exponential signal $x(t)=e^{-a*t}$ has some time constant value $c$ let say if $e^{-a*t}=e^{-t/c}$ which means that $a=1/c$,but i want to understand what is ...
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1answer
3k views

Convolution of a signal by itself properties [closed]

I'm studying for a test and I can't really explain this question very well. If we convolve a signal by itself, will it have the same properties (time-invariant, linear, stable, casual)? I know how ...
1
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1answer
88 views

Theoretical question on Fast Fourier

I have a question regarding Discrete Fourier Transform and Discrete Time Fourier Transform. Suppose that we have a sequence $x(n)= \{1,2,3,3,2,1\}$. So is it possible to reconstruct the Discrete ...
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2answers
3k views

scipy.signal.wiener for audio processing

Does some have an example of what a Wiener filter (that can be used directly with scipy.signal.wiener) can be useful for, in sound processing (it seems that such ...
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1answer
232 views

Most accurate method of Voice Activity Detection?

What is currently the most accurate Voice Activity Detection algorithm with high levels of background noise? I would also appreciate if it does not require any manual calibration. Bonus points for ...
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2answers
149 views

How to do a spectral fade out?

I'd like to do a fade out of a sound in a few seconds, but in a "spectral way", with a special curve : (here x-axis is time, y-axis is frequency from a few hz to 20khz). All the part "to be removed"...