Plotting wav sound file onto graph

Hey I am trying to plot a wav file in the time domain that I recorded from my own microphone onto a graph in matlab, I am reading in the file using audioread, and when I am plotting it, I am getting this weird orange superimposition over my graph. However, when I am using an audio clip from online and plotting it, it seems to be completely blue. What is the difference between the blue and the orange graphs? Is the orange portion ambient noise from my microphone? Here is my code   %filename is where I am getting the sound wav file from on my cpu, [y,Fs] = audioread(filename); %sound(y,Fs); size(filename); length(y) whos y; whos Fs; TotalTime = length(y)./Fs; t = 0:TotalTime/(length(y)):TotalTime-TotalTime/length(y); plot(t,y) Also as a follow up question, when I am going about finding the fft of these two waveforms, is it as simple as the following statements. nfft = fft(y); F = 1./t; plot(F,y)