The document discusses using sound effectively in movie trailers. It provides examples from films like Inception and Prisoners that use sounds like electronic thuds and ticking clocks to build tension and urgency. Short trailers need sound to convey the same information as longer films. Certain sounds can help set the tone, like upbeat music for a teen drama versus dramatic music for a thriller. The document also discusses using recognizable soundtracks to remind audiences of other similar films. However, sounds and music cannot be used without permission and must be royalty-free if obtained from other sources. The document advises researching royalty-free sound options on sites like freesound.org and GarageBand.