Custom Alarm for One Sensor

Greetings,I would like to have an alarm setting to just one sensor. We want the sensor on our basement door (seldom used) to be in Alarm mode all the time, no matter what mode the rest of the house is in. We have the open alert set with a chirp tone, but that is too soft to hear in all cases. It seems that adding a "sound alarm" on/off option that goes with the open and closed alerts for each sensor in the Alarm Devices menu should be possible. Thank you.