Questions tagged [signal-analysis]

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3
votes
1answer
963 views

Why do we read that Hilbert transform can be used for envelope detection?

We can often read that Hilbert transform is useful for envelope detection (e.g. Hilbert transform to compute signal envelope?) I have done some tests with various soundfiles, and ...
2
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4answers
4k 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 ...
3
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1answer
6k views

Concept of Orthogonality and Orthonormality

Please explain me the concept of Orthogonality and Orthonormality. I understand that the mathematical definition of orthogonality between two vectors is that their dot product is zero. It means that ...
1
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2answers
1k views

How does one know how many times to downsample in Harmonic Product Spectrum?

I have been working on a Harmonic Product Spectrum Algorithm. Now, all the literature I've read about the subject tells me to downsample an N amount of times. How does one determine what this N value ...
0
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1answer
697 views

Signal processing using panda board

I'm an absolute beginner. I'm doing a project that involves estimating the time delays between the sound signal arriving at different microphones in an array (the project is a bit complicated but I'll ...
4
votes
1answer
886 views

Envelope of a signal via Convex hull / Edge detection

Is there a method in order to compute some sort of edge detection / convex hull of a signal x[n] (in orange here). Here of course the orange signal is not convex ...
1
vote
1answer
505 views

Has this Principal Component Analysis (PCA) been done correctly?

I have a set of 3D data points, indicated by the blue color in the picture below. I then project them onto the x-y plane, i.e. setting z values of all the points to 0, shown by the yellow color below....
1
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1answer
258 views

Symbol rate offset estimation

I am confused between symbol rate offset, symbol timing offset and sampling clock offset. Can anyone tell be the difference between these terms.
1
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0answers
645 views

What is the best pitch (frequency detector) for a Voice Activity Detection Algorithim?

I am programming a Voice Activity Detection algorithm. After researching several methods, I implemented a simple method that determines whether or not the person is speaking based off the RMS of the ...
0
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1answer
1k views

Envelope follower not smooth enough

With the following code, I get the "envelope" of a sound signal. However in the "envelope" there are small oscillations (high frequency) : it is not smooth enough... I imagine that it's possible to ...
0
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1answer
49 views

How to determine degree of polarization in time domain!

I know there are methods to determine the degree of polarization of multi-dimensional signals, say [Bx(t), By(t)] -> DOP(f). Is there any way to extract a DOP for given vector time series in the time ...
2
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1answer
415 views

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

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

Using fft in matlab to retrieve input signal magnitude

I am trying to understand how you use an FFT in matlab to measure/retrieve the magnitude of the input signal. For my understanding I have put this script together, creating a 15Hz sine wave with a ...
0
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2answers
347 views

Logarithmic Scale Question

I just have a small theoretical question that buggers me to be honest. I have a sound file that I found its spectrum on linear and on logarithmic scale. Alright, I have done this, it's a plain ...
4
votes
1answer
154 views

Guess the frequency response of a filter with little information

I have a processing unit that does a nice EQ filtering on soundfiles. The only thing I can do is : I give the original .wav file, and the processing unit gives me back the filtered .wav. I have no ...
0
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0answers
184 views

Constant phase for each frequency?

FFT of some signal $x$ has two parts: $|x|$, which is the magnitude spectrum and $arg(x)$, which is the phase spectrum. I want each frequency to have the same phase. Is there a way to accomplish this?
1
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3answers
2k views

Draw a frequency response graph from a simple equation

How is it possible to draw an audio frequency response graph (x-axis : freq from 20 to 20 000hz, y-axis : dB) from a simple equation like y[n] = x[n] - x[n-486] ...
1
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2answers
1k views

IIR issues when order is high

Thanks to all the people who helped me here, I finally achieved to implement a notch filter (*), with coefficients given by : http://www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html When I do order=...
4
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2answers
2k views

Audio Signal Separation - Identifying Interest points

I asked this question here: Audio Separation of .wav signal but it wasn't clear, so, here is my second attempt: First off, assume that I have a .wav file containing a sentence as follows: "My name ...
0
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1answer
186 views

How to distinguish between recorded and a live vocal signals?

Is it possible to detect if a sample of human voice by smartphone/computer(44Khz) is sourced from another electrical device or originated from a human being I ...
2
votes
1answer
179 views

Detect signals degree of imbalance

I have got this question: let's suppose that I have three signals, representative of the same variable, but taken on three different component of a same device; in my case, three load signals, ...
0
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2answers
8k views

Scale signal to a given range [closed]

Is there a function in MatLab to scale a given signal to a specific range, like how soundsc does it with the input? I have to signals, one is a ...
0
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2answers
785 views

Audio Watermarking in MATLAB - How to choose frames to embed in?

Hello I am working on audio watermarking in MATLAB and am trying to choose specific frames of the audio signal where the watermark will be embedded. Through research, I have read that the best way to ...
1
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2answers
698 views

Classifying this signal in dimension and number of channels

The question is: "Weight and height measurements of a child taken every month" Classify this signal as: one/multidimensional single/multichannel I'm not understanding how this can be described as ...
3
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0answers
161 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 ...
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0answers
114 views

understanding windowed fourier ridges

I am studying windowed Fourier ridges for my project. I know that it computes the instantaneous frequencies and amplitudes from the spectrogram. But I don't really know how it relates to signal ...
7
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1answer
3k views

Magnitude-squared Coherence calculation inconsistence

I have to calculate the magnitude-squared coherence (MSC) between two signal. However, using a routine that uses only one taper (or no tapers at all) my result is always 1, despite the signals are ...
0
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1answer
183 views

Add harmonics to a FFT decomposed signal

i would like to add even harmonics from the data of FFT of a signal. How do i do that ? do i have to search for higher magnitude frequencies then add the $2f$ then $4f$ etc ? I understand how to do ...
1
vote
1answer
334 views

Inverse filtering

There is an example of inverse filtering in my textbook which I don't fully understand. Given the two filters v(t) = (1,-0.5) and w(t) = (-0.5,1). The inverse of these filters are given by: for v: ...
2
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0answers
249 views

Is there any problem with my FFT method?

I am trying to analysis a system by Fourier Transform. my system has 3 dominant modes. (1,0.05) (0.51,0.01),(0.46,0.01) the pairs are defined as (freq,damping_ratio) I've got those result with ...
2
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0answers
1k views

Calculation of the correlation of two sinusoidals

First of all I apologize for the long question. I am working with a 3-axis accelerometer and a 3-axis gyroscope and I need to calculate the correlation between the different signals (acceleration in x,...
0
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1answer
331 views

Find the time lag for a wave

suppose that we have a wave which has some peaks in some indexes like 2,12,25,... and otherwise zero. I want to extract the time lag or lags between peaks of a signal. could anyone help me ?
4
votes
1answer
2k views

What is the meaning of a Nyquist diagram in a vibration signal

I need to analyze some vibration data from accelerometers (g-Hz) but I don't quite understand the meaning of each component that the registered signal contains. Basically it is Magnitude and Phase. I'...
3
votes
1answer
128 views

Right algorithm for fourier transform on physical heights

I have data from a LIDAR unit that I would like to get the spectral density of. Unfortunately, the only thing I remember from my Fourier analysis class are the methods that I know will not work. The ...
0
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2answers
207 views

Is there any way to differentiate between impulses?

I have a set of signals consisting of impulses at different instant of time i.e. its not a continuous signal. What I want is a mathematically intuitive way to distinguish between any two such signals? ...
0
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1answer
490 views

Complex Cepstral Transform on Audio in MATLAB

Hello I am trying to computer the Complex Cepstral Transform of an audio signal. I am using wavread to get an array of data type double precision. However, when I ...
2
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0answers
111 views

Complex Cepstral Transform and Audio Watermarking

I am doing research in audio watermarking and have come across the paper that uses the complex transform to embed the watermark in order to improve the robustness and inaudibility of the embedded ...
1
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1answer
113 views

Is my accelerometer precise enough?

I have a device with an accelerometer and I want to make it as precise as possible (using algorithms). Currently no DSP algorithm is running - I am reading values as they are. I've made 3 tests - in ...
2
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0answers
167 views

How much is the chance for a pure mathematician (geometer) to get a postdoc in imaging if he switches fields after Ph.D. and apply for one? [closed]

Before I start my question, I should probably mention that this question might not be the right question to ask here, but I tried academiabeta, and stackoverflow, but without getting any to-the-point ...
2
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0answers
115 views

Voice sample prediction scheme

I have some telephone voice audio with occasional "blips" in the audio. The blips appear to come from an IP link buried in the PSTN (this is a conceptual explanation, so don't worry about things like ...
2
votes
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)...
3
votes
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 ...
4
votes
2answers
381 views

Sum of sines sound wave using microcontroller

I need to produce a signal which contains only several frequencies, for example, 17KHz, 17.2 kHz,17.6 kHz. The components I'm using are microcontroller (PIC16F1783 by microchip) which works at 80 kHz ...
1
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0answers
2k views

Prony method for frequency estimation in matlab

i am interested if where can i find matlab code for Prony method for frequency estimation.there is pdf article about prony https://www.google.ge/#site=&source=hp&q=prony+method+for+...
0
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1answer
150 views

How did Scientists Capture First Images of Molecules Before and After Reaction?

"Using a state-of-the-art atomic force microscope, the scientists have taken the first atom-by-atom pictures, including images of the chemical bonds between atoms, clearly depicting how a molecule's ...
2
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1answer
562 views

Gain function calculation (frequency response)

Define moving average process $y_t := 0.5 x_t + 0.5 x_{t-1}$ where $x_t := e^{i2 \pi t}$. Its frequency response is then: $$H(f) = 0.5 + 0.5 e^{-i2\pi f}$$ Recall that the frequency response in ...
2
votes
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
votes
2answers
1k views

Possible to break out complex WiFi signal?

Is it possible to break out the i and q of a complex WiFi signal? If I have a laptop with a standard WiFi card in it, could I break out the i and q in analog, or upon sampling in an FPGA via digital ...
12
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2answers
12k views

How do I determine if a discrete signal is periodic or not?

I want to know how I can determine whether a series of data is periodic or not. I want to use Fourier transform/series. My data looks either aperiodic [111100001111000110010101010000101] or ...
0
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1answer
127 views

doing sine regression to recover the paramters from a given signal

I have a discrete signal. I want to do sinusidal regression to estimate the parameters such as amplitude,phase, frequency etc It is important to note I only have the signal values and ...