Radio trailer conventions.

After researching the insidious and paranormal activity trailers, a few key conventions became clear. the main ones being; an eerie non diegetic soundtrack to create a scary mood. also, quick, unexpected blasts of noise get the audience jumping, a sign of what is in stor should they watch the film. and finally a crescendo is often used to build up tension and again, imply what is in store should they see the film.