Im trying to extract the frequency peaks of an FFT in order to synthesis the original using additive synthesis.

Ive tried using the findpeaks function and using the location values however these do not seem to be in Hz how would i go about converting

Here is my code

p = 2^nextpow2(N);
x = fft(y,nfft)/p; % performs fft of clip
forx = fs/2*linspace(0,1,nfft/2+1);
X = 2*(abs(x(1:nfft/2+1)));
[peakval, locval] = findpeaks(X,fs,'minpeakheight',1.8*10^-5);

%% add synth
Freqs = locval;
Xs = zeros(length(Freqs),length(time));

for i=1:length(Freqs)
    %Xs(i,:) = singen(Freqs(i),fs,time);
    Xs(i,:) = sin(2*pi*Freqs(i)*time);
end

x = sum(Xs);
x = x./max(abs(x));

soundsc(x)

Answer 1

[Ridwan Alam]

findpeaks() returns the indices of the input signal where the peaks were found. you have to use the frequency range to convert those locations to Hz.

x = fft(y,nfft)/p; % performs fft of clip
freq_range = fs*(0:(nfft/2))/nfft; 
X = abs(x(1:nfft/2+1));
X(2:end-1) = 2*X(2:end-1);
[peakval, locval] = findpeaks(X,'minpeakheight',1.8*10^-5);

Freqs = freq_range(locval);
...
    

Hope this helps.