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# Abs Fft

32 Threads found on edaboard.com: Abs Fft

## Which formula to process fft audio file ?

Hello, In the audio processing field, after applying fft on a sound signal, sometimes, engineers use 10*log10(abs(value)) and some others just sqrt(i**2 + j**2) to get the amplitude of frequencies. Why one instead of the other ? Thanks, Larry

## fft spectral analysis in mat lab

Hi, Set the range for 'n' (as we are in discrete time domain), say n = Compute values for the given signal x in the above taken range. For spectral analysis, compute fft using fft(signal, N) and plot the abs value to get magnitude spectrum. Let me know if you need the code.

## 10x or 20x in calculation the ADC sample sequence in decibel

hi, I have adopt the ADS5560 for sampling, and the sample sequence is expresses as X in matlab. Then I want to calculate the power/energy spectrum in decibel, I have a problem whether to choose 20 or 10 as the multipy coefficient, i.e., 20*log10(abs(fft(X)) or 10*log10(abs(fft(X)) thanks to all. --yakex

## how to decompose a signal into its complex exponentials

I am having a periodic impulse train of N=5 y=ones(1,5) i want to decompose it into complex exponentials by writing a matlab code. Can anybody guide me how to write a matlab code the aswer of code should be same as of builtin command stem(abs(fft(y,5))) thanks a lot

## pitch profile detection

I have written the cepstral method to determine the pitch of a voice signal which is much simpler. =wavread('/home/..specify where your speech signal is located...'); %determination of cepstral coefficients f=fft(x); f1=abs(f); f2=log(f1); f3=ifft(f2); %finding the strongest cepstral coefficient pitch=max(f3); display(pitch); Hope it

## THD + N Calculation of a sine wave in Matlab

Here are the steps which I normally follow: 1. Choose sufficient number of points of output signal. I usually take points, k such that n = (log k) / (log 2), where n is an integer. 2. Take fft of k. 3. Take abs value of the step-2 result. 4. Multiply each element of step 3 by itself. e.g. step4 = step3.^2 5. The max point available fro

## to Design a suitable system to eliminate this noise and output the pure signal

plzzzzzz help me i dont now what its wrong in my m file ///////////////////////////////////////// =wavread('NoisySignal.wav'); figure(1) plot(x) Ts=1/fs; y=fft(x); y=Ts*fftshift(y); f=-fs/2:fs/length(y):fs/2-fs/length(y); figure(2) plot(f,abs (y)) x1=.4*(hardlim(f+3050))-.4*(hardlim(f+2950)); figure(3) plot(f,x1)

## FFT scale to frequency conversion!

Hello All, Please solve my problem, I want to find fft plot for a 50 Hz and 5V sinusoidal signal. So I tried the following code.. fm=50; fs=150; N=512; t=0:1/fs:100; y=sin(2*pi*(fs/fm)*t); F=fftshift(abs(fft(y,N))); k=(-N/2:N/2-1)*(fs/N); plot(k,F); grid on; But I tried something but, I never (...)

## Not getting the same signal after FFT and IFFT in Matlab

you are making the following transformation:ifft(abs(fft(waveform2)))instead of: ifft(fft(waveform2))The abs function changes the fft of waveform2...

## FFT of given signal in matlab

Try, t=0:Ts:10; y=x1+x2+x3; plot(t,abs(fft(y)));

## frequency spectrum using matlab

how to get frequency spectrum of EEG signal using matlab?abs(fft(x)) is not giving good plot

## Matlab Simulink spectrum of a signal

Hi, i want to see the spectrum of the output in a pll. In order to do so, i have put 5 blocks in series: the first is the Zero-Order-Hold (its sampling time is more than twice the main frequency of the output), the second is a Buffer, the third is the fft block(having fft length equal to that of the buffer), the fourth is the abs block and (...)

## [Urgent] Matlab DFT Strange result

If you change the line: m=abs(y); to m=abs(y2); then the fft plot will go from -Fs/2 to Fs/2. Thus you'll see the DC component in the middle of the plot, and you wanted signal on either side of the DC signal.

## How to get the values of signal frequencies that was loaded from wav file to variable

You need to know the sampling frequency, Fs. Then you can plot the spectrum as follows: =wavread('sound.wav'); N=length(x); X=fft(x); f=(0:N/2-1)*Fs/N; plot(f,abs(X(1:N/2)))You might have to adjust the vector sizes, using floor if your number of points is not even, but I hope you get the point...

## How do you convert from frequency to time domain??

Yeah I tried that already but for some reason it's not coming out right. This is my code thus far: Fs = 0.01; % sampling frequency T = 1/Fs; %sample time N = length(data); %length of signal t = (0:N-1)/N; % define time t = t*T; % define time in seconds realData = data(1,:); imagData = data(2,:); FinalData = realData + 1i.*imagData; f

## Novice at Matlab. Need some help

Have a good slap: plot (abs(Y1)) ;-) The fft returns an imaginary number (magnitude an phase).

## Need Matlab code for finding SNR via Hspice output

N = 2048; cycles = 67; fs = 1000; fx = fs*cycles/N; LSB = 2/2^10; %generate signal, quantize and take fft x = cos(2*pi*fx/fs*); x = round(x/LSB)*LSB; s = abs(fft(x)); s = s(1:end/2)/N*2; % calculate SNR f = /N; sigbin = 1 + cycles; noise = ; snr =10*log10( s(sigbin)^2/sum(noise.^2) );

## ECG using matlab - help with FFT

I got the samples of various arrhythmias and i took the fft of it using matlab.. Its found to be different... The dominent frequencies are found to be varying for various arrhythemia which i understood while plotting its abs value... Is it possible to extract those dominent frequencies??? that is frquency with max value...

## How to use Windowed FFT for Harmonics Analysis

x=5sin(2*pi*50*t)+3sin(2*pi*100*t) W=hann(length(x)); Data=x.*W; figure; f=(sampling_freq)*linspace(0,1,Nfft); plot(f,abs(fft(Data,Nfft))); grid on; Is this what you are looking for?? HTH, -- Ashwini

## How toobtain a phase map using Matlab

Hi, I am trying to obtain phase and amplitude images by using Fresnel tranform. In my matlab program, I call the saved image (acquired by a CCD), use fft and ifft to recontruct the image field (x2) at different z distance values. I create the amplitude image by using command Intensity = abs(X).^2; where (...)