In a haunted house, the special effects can turn a stroll through a living room into a scream-fest. While an amusement park budget isn't necessary to create hair-raising chills, smart planning is key. Often the best way to get a visceral reaction is to alter your guests' senses with a surprising combination of sight, sound and smell. Keep in mind the age of the audience who will be attending the house; you don't want crying kids and angry parents on your hands.
Lighting is one of the fastest ways to alter a room's mood. Walk a guest through a pitch black room with just one light source -- even a candle or flashlight -- and the most natural setting becomes spooky. Using colored paper, cloth swatches and plastic gels, change a bright white overhead light into blood red or dark blue. Combining black lights with glowing paint or dye make a prop or wall decor appear otherworldly.
Projectors can add a face to a tree or a set of eyes on a house. Inside, the combination of a computer, plexiglass and a pre-recorded floating head create a "Pepper's Ghost" effect, similar to what's used in professional Halloween displays.
Sounds and Shivers
Scary sounds are particularly effective when combined with surprise. Haunted house guests might walk in anticipating a recorded scream and dragging chains, but a realistic-sounding dog growl or crow caw might be a little more disturbing. Using live actors for sound effects can be the most shocking since the effect won't sound canned.
When utilizing recorded sound, wire the room so the sound source isn't obvious. A stereo system can be re-purposed, with speakers hidden underneath lampshades or inside props. Wire motion sensors to trigger shocking squeals or install a pressure plate switch that unleashes the swoosh of an imaginary spear flying through the air. The right image can capitalize on a good sound. Combine the horn from a loud train with a cardboard cut-out locomotive and a bright back light. Aim the train directly toward a guest to cause shivers and screams.
Shadows and Fog
Turn a grey, unfinished basement into a dungeon with a spectral cloud billowing through it. Cut holes in a plastic garbage can; place vacuum cleaner hoses in the can; fill the can with dry ice, and attach a fog machine to feed fog through the tubes in the garbage can. The result boosts the amount of fog coming out of the machine. Use the manufacturer's safety precautions when working with dry ice and keep children away from it.
To conjure the scent of a graveyard or crypt, use natural scents such as dirt and potting soil. Place pots of the soil in strategic spots throughout the basement.
Bring the Props to Life
Combine a prop with a live actor. Adorn a wall with a variety of different masks, and have one of them suddenly come "alive" and talk. Build a cardboard or wooden box to house a "disembodied" head that taunts and terrifies. Sculpt the shrunken head and the masks out of papier-mache and paint them when the paper is completely dry. Build dummies using a combination of newspaper-stuffed clothing and papier-mache heads. Position a few dummies in the lawn; when one of them gets up and follows the guests, expect several yelps.