The frequency spectrum of a time-domain signal is a representation of that signal in the frequency domain.
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1answer
33 views
Programming language for sound manipulation
Having had little experience in PHP, I moved to C++ in-order to create a spectrogram, I wanted to create probably the simplest/easiest one for my first project, so easy infact I don't need ...
0
votes
1answer
28 views
What is an “annason” (VLF whistler)?
I am watching the following video on software defined radio and at the beginning the narrator points out some "whistlers" on the spectrum display and says maybe they are caused by an "annason". He ...
2
votes
2answers
39 views
Frequency response of system with feedback and feedforward co-efficients?
For seismological application, I am playing with an elliptical filter, and once I have both sets of feedback and feedforward co-efficients, how do I make it so that I can plot the frequency response ...
0
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0answers
24 views
FFT of chirp function with varying amplitude [closed]
I have a output that uploaded as image1 or ( http://testybab.blogspot.com/2013/06/fft-peoblem.html ). actually, i should take a Fast Fourier Transform of this output but i got exactly twice of ...
0
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0answers
22 views
Spectrum analyser and resolution bandwidth
For the preliminary part of a lab I had to do, I was asked the following question:
I get how to do 1.1, but with 1.2, I really don't get what's going on; I really would've thought that the ...
4
votes
1answer
54 views
Spectral analysis of positive signals
Suppose that I have a sensor that can acquire samples $X[k]$ of the Fourier transform of an unknown signal $Y[t]$. An example is MRI, where the acquired data is in $k-$space. Now suppose that the ...
2
votes
1answer
132 views
Spectrum of a zero-order-hold signal
What does the spectrum of a sampled signal look like if one uses a zero-order-hold?
There is some information in:
Sampling theorem and Dirac comb, but I am wondering, how to apply this in practice.
...
0
votes
1answer
37 views
Square of Frequency characteristic of the system
What does $|H(j\omega)|^2$ in $20 \log_{10}|H(j\omega)|$ mean?
Is it some ratio of energy or power? And why? How to derive it?
I'm sorry for curtness of my questin.
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3answers
132 views
Basics of frequency spectrum for onset detection using FFT
I'm pretty new on signal processing and I've been reading a lot the last days in order to understand a little about it. But still there are things that I'm not sure if I got well. Sorry if I don't use ...
2
votes
2answers
48 views
CDMA : Calculating M from m1 * w1, m2*w2, etc M as Walsh Code, M as Orthogonal COde
I have these values,
m2 = 1 -1 -1 1
w2 =-1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1
Im about to multiply m2 with w2
Should i multiply m2 with all of w2
(1 * -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 ...
3
votes
1answer
61 views
Spatial and temporal frequency of a wave
I've sampled a propagating wave so that I know its amplitude at several equidistant points on a line, and at several points in time. That is, I have this discrete function:
...
5
votes
5answers
263 views
Why do we use window in time domain rather than do FFT modify the spectrum and than inverse FFT
I thought that DSP would be done by using FFT of portions of a signal, modify the samples that result from FFT (since they represent the spectrum of our signal + noise) and remove any unwanted signals ...
3
votes
3answers
100 views
How to compute fundamental frequency from a list of overtones?
Given a list of overtones (F1, F2, F3, etc), how do I compute the fundamental frequency? Can I do something like F2/F1=F1/F0? Is it the correct method to use?
-3
votes
1answer
67 views
frequency domain vs cosine wave amplitude
Hey guys, what is the difference between b.) and c.)? Why do we need each of them?
Excrept from: http://www.dspguide.com/ch8/5.htm (scroll below)
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2answers
99 views
How to determine a very low frequency signal?
I have a noisy signal with frequency between 1/3 and 1/5 of the sampling window.
DFT has a very low resolution for low frequency components, what is the best way to find the frequence?
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votes
1answer
48 views
Format location from LPC magnitude
I am confusing when I find the lpc roots magnitude, f1=0.9313, f2=0.9308, f3=0.91 and f4=0.95 but when I look at LPC envelope the f1 is higher than f4 in term of magnitude in dB.
Could anybody explain ...
2
votes
3answers
92 views
OFDM coarse freq estimation
I am trying to read OFDM synchronization paper by Schmidl and Cox. The math is slightly overwhelming.
What is the formula that they use in implementation that distinguishes between coarse estimation ...
3
votes
2answers
65 views
What is the theoretic difference in the ways to compute the spectrogram?
I have noticed that the spectrogram for a audio signal is often calculated in different ways when the result from the DFT is transformed into real numbers; some tend to compute $|k|$ or $|k|^2$ while ...
3
votes
0answers
55 views
Question on spatial sampling for non-linear and/or non-uniform arrays
I am a little confused as to how to compute the nyquist criterion for a sensor array that is not linear, and/or non-uniform. For the linear, uniformly spaced case, the spatial nyquist is delimited by ...
1
vote
1answer
53 views
Frequency vector and fft
I have got a question concerning the definition of the frequency vector for an fft operation.
Generally, I work with a frequency vector, f, with power of 2 ...
1
vote
1answer
80 views
Frequency resolution and timestep in DFT
I am learning DFT and I am not sure I understand it correctly. I am just going to write out the process of DFT and I am asking you to tell me if I am thinking the right way.
Suppose we have a ...
2
votes
1answer
126 views
Spectrum of OFDM with raised cosine window
I'm having trouble implementing OFDM with a raised cosine (RC) window in Matlab. I know how to generate an OFDM signal and how to show its spectrum, I just don't know how to generate the window ...
2
votes
1answer
177 views
Amplitude and phase spectrum in MATLAB
I have a little problem with the subject Theory of signal. We were told to make amplitude and phase spectrum of cosinus in MATLAB, but we don't have results nor materials from our teachers, so we have ...
2
votes
1answer
75 views
how do windowing functions not distort the signal?
I'm trying to gain a better understanding of windowing functions, but so far I can't tell why they're used. As an example, I'm familiar with the Hamming Window:
$ w(k) = 0.54-0.46cos( ...
4
votes
1answer
89 views
Constant Magnitude Chirp across audio band (Parseval's Theorem?)
I want to excite a loudspeaker with a constant magnitude chirp that sweeps across all frequencies in the audio band. I downloaded a test file from this website to start with.
I plot the log magnitude ...
0
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0answers
17 views
How do you calculate/compute/determine the spectral coverage of a frequency spectrum?
I'm comparing frequency spectrum of FSK, ASK, QPSK, and MSK. And I'm asked which has the least and greatest spectral coverage. Could someone enlighten me on how to get it?
3
votes
1answer
103 views
What tranform can I use to “zoom” in a specific portion of a signal's spectrum?
If I recall correctly, there is a variation of the DFT that can be used to analyze a specific band of the spectrum of a signal. How is it called?
3
votes
0answers
66 views
What is the proper way to select the time-bandwidth product when doing multi-taper spectral estimation?
Frequently programs for calculating the spectrum of a signal using the multi-taper method require the user to specify the time-bandwidth product.
What considerations must be made when selecting the ...
2
votes
2answers
136 views
How to predict the spectrum of an aliased/folded signal without looking at the FFT?
This seems like a trivial concept but I just can't get the hold of it. I have a signal with two complex sinusoids having frequencies -25MHz and 17MHz. Currently it is being sampled at 64MHz so I get ...
2
votes
0answers
57 views
Calculating a filter's attenuation at a certain frequency from the Q-factor
I'm using the Web Audio API to make a graphic EQ with four BiQuad filters; a highpass, two bandpass and a low pass:
You can see each node representing each filter's frequency. It's working nicely ...
1
vote
1answer
166 views
DFT as convolution question
I have tried to make this question as readable and consistent as possible. The short of it, is that I am trying to ascertain how one gets from the math equation shown, (which I understand), to the ...
2
votes
1answer
176 views
Finding the Amplitude spectrum of a FM signal
My textbook have a question p.360 problem 6.26 is like this
Consider the signal $v(t) = 8 cos (2\pi [10^5 + 4 sin(5 \times 10^3 t)]t)$. And Please Draw the amplitude spectrum of $v(t)$
So, The ...
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1answer
96 views
How do I find the power of a specific frequency at a specific sample of a discrete time varying signal?
EDIT:
First off let me explain that I understand that frequency makes no sense for a single sample. What I am actually talking about is the power spectrum within a short time window around a specific ...
3
votes
0answers
51 views
What are the uses of those three types of wavelet transformations?
In my studies of wavelets, there appear to be 3 different families of them:
The Continuous wavelet transform
The Discrete wavelet transform
The Redundant wavelet transform
They are all based on ...
5
votes
2answers
129 views
Pisarenko Harmonic Decomposition
I'm attempting to code Pisarenko's method for some time-series data that I have.
I've had a look at a couple of papers, which explain in detail the theory behind it, but I'm having some trouble ...
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0answers
51 views
Recover High Frequency Loss in a Simulated Power Spectrum
I'd like to ask a theoretical question about power spectra.
In MATLAB, by means of a particular approach, I'm trying to generate a Gaussian variable which embodies a particular power spectrum.
The ...
2
votes
1answer
150 views
Scalogram (and related nomenclatures) for DWT?
My understanding of the scalogram is that, for a particular row, the scores of the projection of the input signal with the wavelet at a particular displacement is shown. Across rows, the same thing ...
2
votes
2answers
90 views
check power spectrum
my question is quite straight-forward to be grasped and handled.
I have an 1D array, F_11 representing a target power spectrum. It is sketched in the following ...
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2answers
123 views
eliminate signal A from signal B
i have 2 audio signals, both available in time and frequency domain:
A: Noise
B: Noise(A with minor variations) + Additive sounds (C)
i want to eliminate Signal A from B to leave only C.
C is for ...
5
votes
3answers
254 views
Common methods of transmitting digital data through an extremely noisy audio signal?
I am developing software for transmitting data from a computer to a mobile device using audio. Specifically, from the computer's speaker to the device's microphone. (I am developing both the sender ...
2
votes
2answers
127 views
Extract frequencies from PCM signal
I have an PCM (pulse-code modulation) signal. If I want to work out the frequency of a sample $ x $ long, I count the number of peaks/troughs of the sample, and divide by $ x $. The equivent dB of ...
1
vote
1answer
119 views
increase of encoding rate increases bandwidth?
I came across this paragraph in an article about signal processing.
Addition of redundant bits for improving the error probability leads to bandwidth expansion of the
transmitted signal by an amount ...
2
votes
1answer
131 views
How to find the envelope of a wide-band signal?
I would like some feedback on possible techniques that one may use to determine the envelope of a broad-band time domain signal. I have heard anecdotally, that it is not as straight-forward as it ...
0
votes
0answers
35 views
are there any tools available that will output audio spectrum as raw data?
Is there an app or script that will output raw text data representing an arbitrary number of bands in the audio spectrum of an input file like a .wav or .mp3 to make the data equivalent of a ...
7
votes
1answer
202 views
Ultrasound pulses and reflection problems
I am building a whiteboard to track the position of its pen. I have n ultrasound receivers placed on the periphery of the whiteboard, and an ultrasound emitter in ...
0
votes
1answer
62 views
Commenting frequency spectrum of a sampled data
the question below asked in my latest signal processing exam. I have no idea about it and i could not find any solution in literature. Could you please help me finding out the answer. Actually i ...
3
votes
2answers
944 views
A Simple Lowpass Filter Behaving so Strangely
I don't know much about filter design. After reading a few articles on wikipedia I am playing with filter design and I see something weird and would like some help in understanding what exactly is ...
4
votes
3answers
141 views
Harmonic errors in acoustic instruments
If a note has a fundamental frequency of 100Hz, then its second harmonic is located at 200Hz and its tenth harmonic is located at 1000Hz. But for acoustic instruments, the harmonics will not occur at ...
1
vote
1answer
50 views
Vestigial Filter problem?
I have been stuck on this question for a while now. It has to do with vestigial sideband.
I wasn't sure if I should be dividing $H(\omega)$ graph values by 2 because only the positive side of the ...
2
votes
2answers
230 views
When negative frequencies cannot exist in practice, why do we calculate power in negative frequency?
Suppose a signal with two-sided power spectral density $N/2$ is passed through an ideal LPF having cutoff frequncy $B\,\mathrm{Hz}$. The output power is equal to $N/2 \times 2B = NB$ Watts. Why not ...
