You're right, there's really no distinction between double and single letters on here. Which is wrong, there should be a distinct difference. Also rsc55 is right, hair is capelli. Capello isn't a word. But yes, you're right about the pronunciation. Unfortunately if we were going to report it every time we heard it, we'd be reporting nearly every question :P
I can't really speak in this particular case (because I haven't heard capello said by this computer speaker)...
But in my past experience of Italian, the way I always heard the difference between double and single consonants in Italian was in the sound of the preceding vowel (not in the sound of the actual consonant/s). The vowel always sounded longer to me with a single consonant.
Cappello - "cap - pel - lo" (very short first vowel)
Capello - "ca - pel - lo" (long first vowel compared to above)