Some well-known vendors APC, Belkin, Tripplite, regarding disabling or muting, turning off the annoying alarm and here are the responses:

– Belkin: The only UPS that we have that carries that feature is our UPS for home audio. Part number AP30800. There is a
switch on the back of the unit that can be shut off.

– APC: You can disable the battery alarm by using the management software in all APC back-UPS. You have to install the management software and set the disable battery backup alarms at all time. Once you set this setting, you can disconnect the communication cable. The setting will not change until you changed the settings.

– TrippLite: All of our LCD UPS have alarms that can be permanently muted. Please take a look at out Smart1000, 1200 and 1500LCD UPS.

– CyberPower UPSs have an option in the included software to disable the audible alarm in the event of a power outage. This option sticks even if the UPS is subsequently disconnected from the PC.

We will try a few other manufacturers and post back.