property volume_multiplier : 1.2

tell application "Airfoil"
	set all_speakers to (get every speaker)
	repeat with this_speaker in all_speakers
		set curr_volume to get volume of this_speaker
		set (volume of this_speaker) to (curr_volume * volume_multiplier)
		if (volume of this_speaker) is 0 then set (volume of this_speaker) to 0.1
	end repeat
end tell