[Note: Portions of this project are excerpted from the article “Auditory Illusions” in Make: volume 31, by Michael Mauser, a retired engineer and science teacher. ]

Perhaps you’ve heard of optical illusions, but did you know you could create auditory illusions? Explore your sense of hearing by creating weird sound tricks and effects.

Necker_cubeUse Audacity (, a powerful, free audio editing software program to create a verbal transformation, or audio wordplay.

Some words when repeated start to sound like different words, as our brains shift interpretation of where the words start and end. For example, say can be perceived as ace, and rest can be perceived as tress or stress.

This audio illusion is called verbal transformation, and it’s similar to the visual flip-flop you experience with an illusion like Necker’s cube (right.)

Project Steps

Download Audacity.

Go to to get your free copy of the software.

Take a look at Audacity’s control panel and corresponding functions. If you need help understanding anything in the instructions below or with the program in general, check out Audacity’s resources page: 

Loop-Play to blur words.

Record yourself saying “rest.”

Trim the recording down to just the word.

Loop-Play the word to hear the transformation.

Try the same thing with “say” and “tress.”

Say it in song.

Record yourself reading a short phrase such as “free audio editing software.”

Use Loop Play to hear it repeated.

After a short while, it will sound like you’re singing the phrase instead of reading it.

Psychology professor Diana Deutsch reported on the first formal investigation of this illusion in 2008. Hear an interview with her on Radio Lab:

Make an audio palindrome.

Now record yourself saying “Mom say yes” several times.

Select the track and then choose Effect → Reverse from the menu.

Play the result and you’ll hear something like your voice saying “say yes Mom.”

Both mom and say yes are audio palindromes, a series of sounds that sound the same in reverse.

A written palindrome is a set of letters that reads the same forwards and backwards, like “TAHITI HAT” or “A MAN, A PLAN, PANAMA!” or “TACOCAT” or “Mr. Owl ate my metal worm.” But just because the letters are the same, the sounds may not be.

Try recording different words and then reversing them and putting them up against one another in the track to make a true (nonsensical) audio palindrome.

Go one step further.

Think about how sound influences your experience of something visual.

Use your auditory illusions to enhance a video, play, or stop-motion animation. How wacky can you make it? How does the sound change how you feel about the visuals?

To explore the science behind visual and audio illusions, check out the websites of Michael Bach ( and Diana Deutsch (

Show them off Make a video that includes

your auditory illusion as the soundtrack,

and share it on the Google+ Maker Camp


Try the other effects from the article.

Binaural Beat: “It only exists in your brain.”

Phantom Rotating Tone: “It sounds like it’s moving.”

Franssen Effect: “Sound from nowhere.”

Haas Effect: “Sound that seems to vanish.”

Deutsch’s Octave Illusion: “Flipping reality.”

Fractal Sound: “The same at twice the speed.”