Does the Ultrasonic Fence raise alien aggression?
The summary states:
The Ultrasonic Fence is a defensive structure which prevents alien lifeforms from invading the space around your cities, creating a passive, non-aggressive barrier between yourself and the neutral alien lifeforms.
A non-aggressive barrier in my understanding will not alter the alien aggression in any way, so your free to use it and not get a load of angry aliens knocking on your door.