Sounds like magic

The magic effect

Three matchboxes lie on a table. You pick up the middle one and shake it. You can clearly hear that it contains some matches rattling round inside. You pick up and shake the other two, and it’s clear they are empty. You then move the boxes round, and ask your spectator to follow the filled box. At the end of the movements they are to say which box has the matches. They select a box, you shake it, and they are wrong - you can show the matches are in another box. You can repeat the trick too. Every time, however closely they watch, they can never find the box with the matches.

Magic or secret audio misdirection?

Follow that sound!

This is a sound version of the classic crooked game of 'find the lady', where a queen and two other cards are mixed and you're asked to find the queen. Called the 'three card monte', it's been used to fleece people out of cash for centuries. How it works is another story, but let's look at the matchbox version, where find the lady becomes find the matches.

Hearing a handy secret hint

This needs a secret setup: three EMPTY matchboxes on show. Yes, they are all empty, so where does the sound of the matches rattling come from? It's a fourth, concealed matchbox, with a few matches in it to make plenty of noise, and you hide it attached to your wrist with a rubber band, under your sleeve on your non-dominant hand. If you're right handed your non-dominant hand is your left and vice versa. Selecting the non-dominant hand to hide the rattler means that you can naturally pick up the empty boxes with your dominant (normal) hand and shake to show they are empty. When you want the matches to be in any of the boxes, you pick the box up with the other hand, the hand with the hidden rattler on its forearm, and shake away. Suddenly, there be matches.

Sounds local

The human ear is very good at detecting the location of sound. Two ears give stereo and the time delay between the sound reaching your left and right ears allows our brains to calculate the position of the source of the sound. The shape of your ear is also evolved to help determine the location of a sound. The reflections of sounds within the pinna (the visible outer part of the ear) bounces the sound wave around and helps determine the height of a sound source.

The art of ear fooling

Your ear is good, but not that good. The hidden rattler sound is so close to the visible empty box you're shaking, plus you're telling your punter that the matches are in the box. The expectation that the matches are there is so strong that any small location errors are ignored. In effect you 'hear' the matches within the empty box. The rest of the trick is just about presentation. When swapping the empty boxes, do it so that perhaps they could have missed something: move them around, perhaps stack them up, make some suspicious-looking move. In short, give them a reason to believe they were mistaken. Then show them that their careful powers of observation were lacking each time: the matches aren't where they expect them to be.

Well that much is true at least!