Even though only piano notes are being played,

if you know the song, you'll start to hear the lead singer's voice and the words being sung.

I swear, what you're hearing is 100% digital piano simply matched to the frequency of the original song and not mixed with real vocals.

And yet, you can hear the words.

This speaking piano shows a similar phenomenon.

It's hard to make out what it's saying, but as soon as words are on screen, you begin to hear it talking.

Hearing is all about perception, after a soundwave hits your ear, it's transformed into signals for your brain.

But your brain gets so many external signals that it can't process it all at once and so it uses context to craft what you're hearing.

You hear the lyrics because the brain uses the information it already has to understand the world around you.

which is why if you've never heard the song, it will sound like nonsense.

But, even without words, we sometimes hear things that aren't there.

Take this jumping transmission tower, for example.

Around 20% of people will actually hear a thud each time it lands in a fenomenun known as visually evoked auditory response.

Do you hear it?

It's a type of synesthesia which is when the senses like hearing and sight get crossed in the brain.

Expectation is also playing a role here

A 2006 study scanned the brains of participants who were told they'd eventually hear a sound

as they were listening to the silence and expecting to hear something, the auditory cortex was activated in the same way as when you were actually listening to sound.

So, do you hear it now?

Our brains are pretty good at filling in the gaps, like in this audio clip.

The state governors met with their respective legislatures convening in the capital city.

But, now, listen to it with the cough removed.

The state governors met with their respective leg_latures convening in the capital city.

There's literally a full syllable missing.

But with the cough, people tend to hear the entire word.

The state governors met with their respective legislatures convening in the capital city.

This illusion is known as "temporal induction".

Your brain fills in information to make sense of the world.

Now, listen to this rhythm.

Sounds like it's getting faster, doesn't it?

The thing is, it will seemingly get faster forever if I let it continue to play.

This is known as the "Risset rhythm" in which a beat starts relatively slow and starts to speed up,

but, as it gets faster, beat 2 starts at exactly half the speed and they increase in speed together.

Eventually, the faster one fades out as the slower one fades in, and the loop continues.

But, your brain can't pick up the subtlety and, as a result, it sounds like it's speeding up forever.

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