How to amplify the noise on a recording?

Question

Fourier transform

There is a recording that was recorded in conditions with an open window, no matter how much background sounds are heard, like a car passing by and so on, how to amplify them? I removed the voice on the recording, only noise remained, but it is not clear what nature.
Here is the program code:

clc;
clear;
[flute,Fs] = audioread('record.mp3');
%sound(flute,44100)
plot(flute)
f=fft(flute);
%ff=abs(f);
hist(f)
count=0;
for i=1:1775856
    if f(i,1)>1 || f(i,1)<-1
        f(i,1) = 0;
        f(i,2) = 0;
        count=count+1;
    end
end
count
y=ifft(f);
audiowrite('record2.wav',y,44100);