Stichting Club Alfa Romeo Bezitters

I had exactly the same problem, very quiet around my house early morning and the beeps sound horrendously loud.

If your still looking to deactivate the alarm beeps then use the following for a 147

UK = 2, Holland = 4 (no beeps)

The operating mode can be changed by diagnostic instrument or the following manual procedure:

set the ignition key to Key-On;
activate the hazard warning flasher
press the rear fog light control button and hold it down
using the ignition key, carry out the following sequence in strict order: Key-Off (for less than 2 s), Key-On (for less than 1 s), Key-Off, starting from the Key-On state, always holding down the rear fog light button.
at the end of the sequence, the siren emits 5 beeps to indicate the activation of programming.
release the rear fog light switch and press it again the same number of times as the desired mode (each press gives a feedback beep)
If the button is pressed for an invalid number of times (e.g. greater than the number of available operating modes), the siren emits 5 beeps and is cancelled and the country code is not changed:

set the ignition key to the Key-On position within 10 s of the last press on the rear fog light button.
the siren emits the same number of beeps as the number which indicates the selected operating mode: each beep lasts 1 s and is followed by a 0.5 s pause.
at the end of the beeps, set the key to the Key-Off position: the BC is programmed in the new operating mode.

Hope this helps keep the peace.