creating mood
audio is importamt for film and programmes because it can create an atmostphere for the world around the character. for example if there is ambient sound effects playing or objects banging then its more likely to be a horror film.
creating meaning
sound can also help to create a feeling or emotio. this type of sound or music used has to match the mood of the video. for example if its a joyful scene then the music should be up beat and happy.
using audio to create illusion in the auiences mind.
an auditory illusion is an illusion of hearing the sound equivalent of an optical illiustion. this wasa quote from wikipedia.