Sin wave spectrum shows multiple frequency I am very new to DSP, so excuse my ignorance.

Using Audacity, I generated a sine wave of:


frequency 440Hz
amplitude: 0.8   
duration: 1 minute


Now when i plot the spectrum for this sine wave, I get an image like this:



This is really surprising for me. 

I was expecting a single surge at 440 Hz for the pure tone. But this is entirely different.
Sure this is not anything to do with noise. Right ?

My question

How can the spectrum of a pure tone have so many frequency components in the spectrum. 

What obvious am I missing ?
An FFT only results in a single component (plus its complex conjugate and some tiny numerical noise) if the single pure real sinusoid input is of a frequency whose period is an exact integer submultiple of the FFT size.  A rectangular window makes any "leakage" into other non-adjacent bins even worse.

But the length of the FFT you have specified is 512, which is not an exact multiple of the period of your signal (which is 44100/440 = 100.227273).