The noise meter widget displays the noise level picked up by your device's microphone, and plots it over time. It currently works only on chrome. The noise levels are measured in decibels.

We often talk and complain about noise. Now we have a chance to quantify it, and make it a subject for math talks.

Are noise levels objective or subjective?

Noise, which is defined as unwanted, unpleasant sound, is subjective by definition. Turns out we find some frequencies to be more annoying than others, and sudden sound level changes to be more annoying than smooth ones. Several noise measurement standards have emerged based on research on what the human ear perceives as noise. The noise meter here is based on the ITU-R 468 standard.

Did you know:

• So far, all classes the noise meter was introduced to responded by shouting. Is your class any different?
• I once made a deal with my class that if they keep the average noise level below some number, they won't get any homework. That was a typical 'The operation was successful but the patient is dead' case. Everyone was completely occupied in making sure everyone else is being quiet.
• Decibels are a logarithmic unit, so doubling the power of source of noise doesn't double the measured level, but increases it by about 3.
• How does the noise level change when you move a source of noise closer or farther away from the microphone?