Find peaks not working on my data set

I am trying to find the first 5 peaks in the PSD plot of an acoustic signal. While I do not have any bugs in my code, it is not finding actual peaks and looks more like arbitrary locations. I will paste my code below:

M = movmean((PSD), 50);

[maxpks, maxloc]=findpeaks(PSD(1:2000),'MinPeakDistance',195,'MinPeakHeight',-50,'NPeaks',5);

figure(1)
plot(fp,PSD)
hold on
%O=2*f %%convert to octaves so the slope is in dB/octave
plot((maxloc), maxpks, 'r*')
hold off
sortpks=sort(maxpks);
[j,h]=size(sortpks);
J= [sortpks(j),sortpks(j-1),sortpks(j-2), sortpks(j-3), sortpks(j-4)]; %first five peak 

ML = maxloc(j-4:j); %first five peak location
ML=(ML)'; %%convert to octaves so the slope is in dB/octave
figure(2)
plot(ML,J,'r*')
 Fit = polyfit(ML,J,1); %linear regression 
 yfit = Fit(1)*ML+Fit(2); %equation of line 
 hold on
 plot(ML,yfit,'g-')
 slope=Fit(1)%spectral tilt

The picture above is a zoomed in version of figure 1 and it is just not detecting the peaks I need. Thank you in advanced for any help!

Answer 1

[Steve Eddins]

I suspect the issue is with the x-coordinates that you are using to plot the peaks. You are plotting the peaks against the indices returned by findpeaks, but you are plotting PSD against x-coordinates in the variable fp. So, intead of this:

plot((maxloc), maxpks, 'r*')

Try this:

plot(fp(maxloc), maxpks, 'r*')

[Ashlyn McCann]

Yes! thats what it was! thank you

[Steve Eddins]

Great! If this answer worked for you, can you go ahead and accept it?