The Allassonic Effect

When the bottom of a ceramic cup filled with boiling water and a heap of instant coffee is tapped at regular intervals the pitch of the sound heard slowly increases over time.

The effect takes its name from "allasso", the Greek root for to change, and "sonus", the Latin word for sound.

In the past the effect has been referred to as the "Hot Chocolate Effect" but the phenomenon is found to occur in many instances beyond the humble cup of hot cocoa. It can even be heard when the base of a pint of beer is tapped after having sprinkled some table salt into it!

Category:

Entertainment

Tags:

• physics
• demonstrations
• experiments
• allassonic
• sound
• hot
• chocolate
• effect
• changing
• pitch

[RyuDarragh]

After a while, the dissolving crystals in the powder have finished dissolving and the change in pitch stops. As crystals of sugar, salt and other substances dissolve, they form ionic lattices in the liquid as the concentration changes. The effect changes the speed of sound in a liquid.. which changes the resonance, thus changing the pitch.

[BreakFreeze]

try this...just after pour hot water to a glass with coffee powder, stirr it then drink it till finish...try to slap your stomach at regular interval..sounds nice too..aaaaarghhhh!

[Andy3650]

@spolida allakso is how it sounds when its said by a greek

[UnderManiac]

how many times do you tap the bottom of the cup before it breaks, spewing hot coffee all over the place?

[spolida]

Not sure if the word allaso is the ancient Greek word for change but the current/modernversion is spelled allakso. I wonder who came up with this word

[Axgoodofdunemaul]

Holy shit, I've been wondering about this for years. HOWEVER I always notice the effect when I clink the the rim of the cup with my spoon, and there are no dissolving crystals in the tea. I've always assumed that the effect was caused by the tea (having been circularly stirred) gradually losing its angular momentum and therefor not climbing so high on the sides of the cup. I'm too lazy but somebody else immediately investigate this before it's too late! The future of humanity is at stake!

[hhairball9]

but why does it happen?!...

[amannvig]

@BreakFreeze stupid u are

[LaSaro888]

Thats why my cup exploded, hit the resonance. :)

[OldSchoolSkill]

Wave mechanics 101.

F= v / lambda.

Entrained bubbles retard transmission of sound in a liquid.

The pitch is actually a standing wave inside the cup.

As bubbles dissolve, sound travels faster, making

frequency rise because;

Frequency (f)

is equal to the speed (v) of the wave

divided by the wavelength. (lambda)

F= v / lambda

[flamedramon02]

Does it HAVE to be instant coffee?

[flamedramon02]

Well someone went to Yale