Questions tagged [averaging]

Averaging is a signal processing technique applied in the time domain, intended to increase the strength of a signal relative to noise that is obscuring it.

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Optimizing Spectrogram Parameters

I'm looking for references that explain the trade-offs between more averages with shorter fft sizes or longer fft sizes with fewer averages when generating a spectrogram to perform energy detection of ...
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49 views

Downsampling by block averaging

Many spectroscopic detectors used to study light absorbance as a function of time. These detectors cab sample data at 160 to 250 Hz. There is an option of choosing lower sampling rates such 80, 40, 20,...
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73 views

Spectral averaging without phase information

In the context of signal averaging to reduce uncorrelated noise: Is it possible to perform signal averaging from just the magnitude spectrum of certain signals? Or that would only work if we know ...
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Smoothing of Log Data Plots in Octave

I have some frequency based data that I'm plotting with Octave's semilogx that looks like this: The amplitude of peaks does not increase with frequency over the linear scale. But with a log scale, ...
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170 views

Why is Error Vector Magnitude (EVM) measured as an RMS value?

I do understand Voltage/Current measurement of a Sine Wave is in RMS, as average yields a zero, and RMS gives a true 'DC equivalent' value. But I do not understand why an EVM measurement could be in ...
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Why does signal averaging reduces noise levels by more than $\sqrt{n}$?

I have an electrophysiology signal, which is time-based. It basically measures neural activity in the form of potential differences over time. The noise in this signal is assumed to be a random ...
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How to deal with noise near saturation

If I have a noisy signal which I know is approaching the saturation limit of my sensor, then the measurement will sometimes be saturated. It seems that if I try to estimate the true data by averaging ...
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402 views

Why averaging in Spectral magnitude domain not in complex domain to estimate spectrum of a process

Consider we need the magnitude spectrum of the signal. Signal is recorded in $N$ trials to a certain stimuli. Signal varies from each trial because of noise. So, to estimate the actual magnitude ...
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Lowpass : What is wrong with average filtering?

The question is : What is wrong with averaging as low pass filter ? The details : I want to lowpass filter a signal to downsample it. The constraints are : I have no RAM available and I work in ...
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Time synchronous averaging - MATLAB

I have a time domain signal that corresponds to a vibration signal of a machine. I have a second signal that corresponds to a tachometer signal (There is a pulse every one revolution of the shaft). I'...
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201 views

Is there an equivalent time-domain operation to the spectrum averaging in Welch's method?

In Welch's method a time-series is segmented and then the subsequent FFTs of the segments are averaged. Is there an equivalent time-domain operation? I guess doing the the Welch estimate and ...
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Removing the Multiples of Decrease and Increase in a Spike

I have a signal shown below. I got this signal from a glove, where I want to detect the movement of a finger. What I am planning to do is to threshold the signal, so I can get a binary signal ...
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is there upper limit on averaging window size for images?

An amateur question. I take an image and average pixels over a window 3 by 3, thus obtaining a smoother image. Then I increase the averaging window size - obtain an image with even less details, but ...
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99 views

Why is it necessary to average signals with filters?

As someone who is new in working with filters, why do signals need to be averaged? What are the advantages, by performing filters on signals? As I know, there are different types of filters for ...
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331 views

Averaging over bins in frequency domain

I have a sound file with a computed spectrogram from 0 to 8000 Hz (spanning about 5 octaves). The spectrogram has 128 logarithmically spaced frequency bins. How can I reduce the number of bins so that ...
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94 views

On number of samples needed

Suppose we get $m+1$-bit signed noise samples $n_i$ with magnitude of noise as high as $m$ bits. Does averaging say $m\log m$ samples suffice to get average of $n_i$ to magnitude within few LSBs? ...
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Bit accuracy improvement versus sample averaging

Supposing we have multiple samples of a scaled signal $x$ given by $y_i=a_ix+n_i$ where $n_i$ is AWGN how does the bit accuracy of estimation of $x$ improve with averaging of samples $y_i$ (number of ...
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RMS averaging in spectrum analyzers

While studying spectrum analyzers I ran into the concept of RMS averaging as a mean to reduce dispersion of data without affecting power spectral density (PSD). What is not really clear to me is how ...
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What is the intuition of “averaging is a low pass filter”?

As I know, the shape of a low pass filter in time and frequency are as follow: But how averaging work like a normal function in time domain? Is there any intuition in it?
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Is it correct to subtract two signals acquired over different times and trials to remove the common signal in them?

I have two signals that represent the response of a neuron under two different conditions. Signal 1 (S1): response to Stimulus A Signal 2 (S2): response to Stimulus A+B The response to stimulus A is ...
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146 views

Generalized/Power means in DSP

Generalized/power means may be used to construct moving-average filters with different properties than regular one which is based on arithmetic mean. This observation seems to be trivial - even ...
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2k views

Exponential weighted moving average time constant

I think it is an easy question but I am stuck. I want to derive that $$ \alpha = -e^{\frac{-T}{\tau}}\,. $$ Can someone provide me with an answer? [EDIT] Sorry guys, this was really a senseless ...
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Averaging multiple FFTs in matlab

I have multiple, real, audio signals which I am taking the FFTs. Although they don't come from the same recording, those signals represent the same thing (biologically). I was told that I could ...
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How to derive the results that averaging $N$ signals yields a $\sqrt{N}$-fold increase in signal-to-noise ratio?

If I have understood correctly, averaging $N$ noisy independent segments or signals increases the signal-to-noise $\sqrt{N}$-fold. How does one derive this result?
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734 views

Averaging Different Length Speech Signal

I have around 10 wav audio files all containing same word spoken i.e. 'Hello' but all having different length. So lets say 1st file when loaded consist of 20000 samples, 2nd of 15000, 3rd of 18000 ...
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How to average coherences estimated using Welch's method in MATLAB

I'm trying to estimate the average coherence of discontinuous snippets of a signal in MATLAB. For Welch's spectrum estimates, the following works: ...
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669 views

Is there an algorithm for second order filtering of data where the filter frequency is not known a priori?

It is well known that a moving average algorithm done in the time domain is equivalent to a filter with frequency response $\mathrm{sinc}(\omega\tau)$ where $\tau$ is the averaging time. (see this ...
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346 views

Slow sampling of signal and averaging over n periods

Can one in theory achieve as high accuracy as needed by sampling a sinusoidal signal over n Periods? Is there a formula that connects the signal frequency (f), sampling frequency (fs), periods (P) and ...
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How do I average frequency spectra?

How did letter d.) become letter e.)? How do we perform this averaging process? Its clear the averaging the signal causes some noise to be reduced.
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Weight vector of an exponential moving average?

With weight vector I mean the vector with weights that you have to multiply the observations in the window that slides over your data with so if you add those products together it returns the value of ...
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What is averaging and how can it be done?

I'm studying about the analysis of (mainly) fMRI and EEG data. Multiple times it's mentioned that to reduce noise, you can use averaging, but nothing more detailed than that. There never is literally ...
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Does the determination of the ergodicity of a signal force any changes in methodology?

In mathematics, the term ergodic is used to describe a dynamical system which, broadly speaking, has the same behavior averaged over time as averaged over space. -from wikipedia From the perspective ...