This is one of he more complicated behavior issues, as there are many contributing factors as to why your cat might become aggressive to other cats in the house.
Without detailed information from you I can only guess what some of the causes might be:
Intruder - There might be temporary inter cat aggression between two resident cats who have co-habitated peacefully in the past, brought on by the sights and smells of a stray, or maybe even a kitten or cat you are fostering. This is called "redirected aggression".
Smells - Unidentified smells may lead a cat to reaffirm their territory with "territorial aggression".
Sounds - Cats are sensitive to very high frequencies - hearing ranges of cats extend two octaves above ours into the ultrasonic spectrum. Ultrasonic bug repellant devices have been known to drive a cat "crazy", even on the "pet safe" settings. It is better to seek an alternative pest control solution if you have pets in the home.
Upbringing - If your cat is being introduced to another cat for the first time and it has been hand-reared (not around other cats), it will not be able to recognize the cat as the same species and may not be able to tolerate socializing with them.
Fear - Something is causing your cat to be fearful and it is expressing it with "fear aggression".
Play - "Play aggression" happens when a cat was not taught how to play with other cats (and humans) safely in it's developmental stages. It is possible to correct this with proper guidance and training.