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1answer
65 views

why multiply grayscale images by 256

I am a newbie in image processing. in an open source code for convolution neural networks, the author is multiplying a gray scale image from MNIST dataset by 256. Please can any one tell me why? ...
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0answers
70 views

Correctly scaling Power Spectrum and Correlation Function of Galaxies from Mock Catalogues

I'm currently writing a code to compute the two-point correlation function of a set of galaxies. As I work with a loooot of galaxies, it was suggested to me not to do it in real space, but to compute ...
-1
votes
1answer
64 views

The concept of normalized frequency

This question has already been asked and answered, but the motivation behind the use of normalized frequency units still evades me. The Discrete Time Fourier Transform $$X(\tilde{ \omega }) = \sum_{n=...
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0answers
16 views

Estimating a distribution of feature of sound based on a factor

I am currently working on creating a model of sound of inside of a car based on speed. To be specific, making a Gaussian distribution of MFCC(13 dim) for each speed, i.e. car running at 30 kmph, ...
0
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1answer
44 views

What information does the abs(normalized_image - normalized_quantised_image) carry?

Given a grayscale image X2 And its (under)quantised version with 3 bits depth X3 What information does the abs(X2_normalized - X3_normalized) carry?As an example ...
0
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1answer
111 views

Pole zero plot, normalizing frequency response plot?

I'm asked to plot the frequency response (amplitude) given a specific pole-zero diagram. $$ H(z) = H_0 \frac{\prod\limits_{m=1}^{M} (z - q_m)}{\prod\limits_{m=1}^{M} (z - p_m)}$$ $$ H(e^{i\omega}) =...
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0answers
32 views

How to calculate Normalised PSD?

I have calculated psd of a signal using periodogram. I followed this guide. ...
0
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0answers
28 views

Calculate RMSE and DTW before or after signal normalization

I want to calculate RMSE and DTW of clear speech signal and noisy speech signal. Im normalizing signal using division by max possible value (for 16bit audio its 32756) to have signal in range [-1;1]. ...
0
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1answer
141 views

Normalization of a signal with respect to another signal

Imagine that I gave one signal (call it master signal) with respect to which I would like to normalize all the others. How should I treat it mathematically? Any ideas?
1
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1answer
106 views

Design a filter which passes all frequencies except $\omega=\pm\frac{\pi}{2}$ and plot its pole-zero diagram

Also draw its normalized frequency response. What is the ROC? This has to be done in z-plane so there must be two poles at $+i$ and $-i$ since they cannot be included in region of convergence. Is my ...
0
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0answers
105 views

What would you call a power spectrum which has been normalized to another

Let's say I have the FFT derived power spectrum of a signal measured at time 1 ($P_{xx,1}$) and of the same signal measured at time 2 ($P_{xx,2}$). If I want to demonstrate how the frequency content ...
0
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0answers
305 views

How to normalize the noise power spectrum (NPS)

I have calculated the noise power spectrum (NPS) according to this formula: I would like to normalize it in order to get the NNPS. However, the definition that I have found is that the NPS is divided ...
0
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0answers
142 views

cross spectral power density calculation and normalization

I'm currently calculating average magnitude squared coherences for a whole set of pairs of time series, using a combination of the pwelch and cpsd functions in Matlab. However, I would like to `...
2
votes
1answer
151 views

Making audio clips comparable in terms of RMS

I have a challenging question on how to normalize several audio clips so that they are comparable (similar) in RMS but without the clips clipping (having values over -1 and 1). Is there a systematic ...
0
votes
1answer
99 views

Methods of scaling FFT power

I wanted to know what are the well-known methods of scaling the FFT power of a signal? I am referring to EEG signal but this should apply to all signals I guess. I need to plot the powerspectrum/PSD ...
0
votes
1answer
155 views

Normalizing audio waveforms code implementation (Peak, RMS)

I have some audio data (array of floats) which I use to plot a simple waveform. When plotted, the waveform doesn't max out at the edges. No problem - the data just needs to be normalized. I iterate ...
1
vote
1answer
58 views

Normalization of signal against reference

I am trying to figure out if there is any standard way of normalizing a sequence such as a time series against a reference sequence. I am not an expert on signal processing but I was hoping someone ...
1
vote
1answer
285 views

FIR filter Gain of 0dB at Passband Frequency

I have designed a FIR pass band filter. The impulse response looks good and on applying this on my input data, the filter works as desired. Now I have a requirement in my system to have exact $0$ dB ...
2
votes
1answer
799 views

normalized sum of squared differences

I want to search for a patch in a region of image, and I will use the normalized sum of squared differences. I know that the sum of the squared differences is: $SSD = \sum {\left(F - I\right)^2}$ ...
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0answers
553 views

Normalizing FFT by N or sqrt(N) in MATLAB

I did FFT of a signal in MATLAB. But now I am confused how to normalize it. Whether it should be $N$ or $\sqrt{N}$ where $N$ is the length of the signal. On this forum thread, one said to do it with $\...
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0answers
36 views

Frequency Normalization [duplicate]

How can I normalize 60Hz?, I need to design a Suppressor Band Filter with Matlab's fir1() method, that cancel 60Hz band. I tried this: ...
4
votes
2answers
75 views

Factor $|a|^{-1/2}$ in definition of mother wavelets

The mother wavelet is defined as $$\Psi_{a,\tau}(t) = \lvert a\rvert^{-1/2}\Psi\left(\frac{t-\tau}{a}\right)\tag{1}$$ in which the factor $$ \lvert a\rvert^{-1/2}\tag{2}$$ is supposed to serve ...
1
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1answer
396 views

Magnitude response and DFT normalization

Suppose I have an FIR denoted h that represents the impulse response of a system. Using MATLAB syntax (for convenience and brevity), What does ...
0
votes
1answer
528 views

Normalization of an image in MATLAB [closed]

If I have an image whose range is from $-18.3667\cdot10^{-5}$ to $9.3127$, how could I normalize it on the same gradient so that they fall between a specific range, say fro $0$ to $255$?
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1answer
1k views

Signal normalization

I have some questions about what is normalization. The obvious way to do that is x_max = max([max(x), abs(min(x))]); x=x-mean(x); x_norm=x./x_max; Can somebody ...
1
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2answers
139 views

How to choose the “best” measurment (from a given set) as input for a kalman filter?

Problem: For an object tracking scenario with multiple objects and multiple tracks, I want to choose the "best" assignment object<->track. Therefore, I need a parameter indicating how suitable an ...
1
vote
1answer
500 views

Obtaining normalized matrix for the Haar Wavelet Transform

I've been reading this article: http://aix1.uottawa.ca/~jkhoury/haar.htm which explains the Haar Wavelet Transform. At a certain point, the author says: ... Since the transformation matrix $W$ is ...
0
votes
1answer
846 views

How can I sample a signal at 4 samples per cycle?

I am in Chapter 5 of "Understanding Digital signal processing" 3rd edition by Richard G. Lyons. I am stuck with Section 5.4. In order to get the bandpass filter centred at $F_s/4 \mathrm{Hz}$, I need ...
0
votes
2answers
257 views

Dynamic range compression - Need pseudo algorithm for normalizing a signal

I have a signal that is NOT an audio signal (but looks like an audio signal - probably you can even "play" it). I would like to amplify the signal in regions where its amplitude is low. In very rare ...
1
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0answers
241 views

Moving signal power normalization

I am using matched filters using GNU Radio to extract from noise a CW Morse signal. The filter actually performs pretty well in various SNR environments. My problem is that the threshold upon I decide ...
1
vote
1answer
735 views

DFT normalization for amplitude estimation

After an interesting recent answer, I'm doing some research on proper DFT normalization for sinusoidal peak estimation. It's clear that to get the correct amplitude from DFT peaks we need to normalize ...
0
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0answers
572 views

How to normalize audio data for feature extraction

I recorded the same piece of music from different instruments and I want to compare their timbre by means of feature extraction. As you can see from the image, the recording is composed of different ...
0
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1answer
115 views

Adjust the power of a digital signal to a given value

I have two signals: $x(n)$ is a white-noise signal with a given variance, $y(n)$ is the sum of white noise plus a sum of sinusoids. $$ x(n) = v_1(n) $$ $$ y(n) = \sum_{i=1}^{q} [ a_i \cos(\omega_i n) +...
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2answers
307 views

How do I normalize accelerometer signals values to an relative scale?

Different smartphone devices have accelerometers manufactured by different manufacturers. Say I want to categorize vibrations recieved from various devices into one of the following scales : ...
1
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0answers
100 views

Cepstrum: subtracting the mean vs. dividing by the variance

In cepstral speech analysis, it is relatively easy to understand why subtracting the mean removes any "channel" effects (including that of recording equipment and the vocal tract). There is a good ...
3
votes
1answer
8k views

Normalization of a signal in MATLAB

I have a signal in MATLAB s = randn(1,1e6); that is normalized in the following way: s = s/sqrt(sum(abs(s .^2)) / 1e6); I ...
1
vote
1answer
139 views

In speech recognition applications, how are different voice amplitudes handled? (i.e loud vs. quiet tones)

I am doing some research related to real-time voice/hotword recognition engines. In most current implementations, input is divided into frames (overlapping or not), and audio features are extracted ...
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0answers
168 views

Spectral Whitening: Approches

Given the absence of information about the algorithms of spectral whitening functions in software packages: How many ways do you know for doing spectral whitening? What are the differences?
1
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2answers
3k views

Contrast stretching Equation problem

How to determine $a$ and $b$ in this equation. I know how to determine $c$ and $d$ by looking at the intensity histogram. But what about $a$ and $b$? $$P_{out}=(P_m -c)\left( \dfrac{b-a}{d-c} \right)...
0
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1answer
1k views

When do we normalize data in audio processing?

Lets assume we have a simple audio processing flow with preprocessing, feature-extraction and classification. Where and why do we normalize the data? I know the purpose of normalizing the data in ...
0
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0answers
386 views

What is the difference between “preprocessing” and “normalization”?

I am currently writing my bachelors thesis about on-line handwriting recognition. In this context, there are different methods to make the input data more useful to classifiers / to make learning ...
1
vote
1answer
1k views

Obtaining power spectrum from ACF, FFT using Matlab and FFTW

I am using Matlab R2012b 64-bit on Windows 7 in order to estimate the power spectrum of a simple signal that is: $$\cos(10t) + \sin(20t) $$defined in the time interval from 0.0 to 10.0 Here is what ...
0
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0answers
87 views

Normalisation of delay-addition comb filter implementation

I'm trying to write a tempo detection algorithm for analysis of audio samples. I'm roughly following the approach described in Scheirer, the first stages of which give me some very nice beat onset ...
0
votes
2answers
769 views

Fourier transform of a normalized vector

I was expecting that when I take (for example, in MATLAB), s2 = fft(s1/norm(s1)), the norm of s2 is not equal one, norm(s2) $\neq$ 1. I cannot figure out why this is! Can anyone shed light on this?
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2answers
432 views

Normalisation of different length signals

I have a collection of audio files of subjects sleeping, which have different lengths, ranging from 8 hours to 10 hours. I want to detect when a snore occurs in them. First of all I want to ...
2
votes
2answers
367 views

Precalculate the Normalization of a filter size

If we have an Image I and a Gabor filter created at specific size and orientation, assume that is 11x11. I saw some persons who normalize the size of the filter, ...
0
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1answer
207 views

Normalise data which has peaks

Some methods #1 YData = YData / max(abs(YData)); #2 ...
16
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3answers
5k views

Why are magnitudes normalised during synthesis (IDFT), not analysis (DFT)?

In most examples and FFT code that I've seen, the output (frequency magnitudes) of the forward DFT operation is scaled by N -- i.e. instead of giving you the magnitude of each frequency bin, it gives ...
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3answers
6k views

Why normalize the data set before applying Direct Linear Transform

Direct Linear Transform (DLT for short) is a method of homography estimation, it solves the overdetermined linear system via SVD $$Ah=b$$to find a solution $h$ under constraint $\|h\|=1$. Actually it ...
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0answers
179 views

when trying to nomalize a power plot , do we normalize it after converting it to db scale or before it?

I have two power plots. I am trying to normalize it for comparing them . So , do we normalize it after converting to db scale? or do we normalize the power as such?