No More Noise!: How Cotton Density Affects Sound Level in Earmuffs

Voiceover

Presenter(s) Information(s)

Mary Fernandez

Abstract or Description

Earmuffs are hearing protection devices that shield the inner ear from intense sound energy. When I used earmuffs with foam in them to block out everyday sounds at home, I noticed that noise was still getting through! I wondered if a common household material like cotton would block out sound effectively in earmuffs, so I tested different cotton densities. My hypothesis was that if I use cotton balls (10 grams), a washcloth (15 grams), and a flour sack dish towel (20 grams) to decrease sound in a pair of earmuffs, then the flour sack dish towel will block out the most sound because its greater mass will absorb more noise. I set up this experiment by attaching an ear cup to a bubble-wrapped acrylic tube holding a smartphone with a sound meter app. I played a tone from a speaker outside of the ear cup and recorded the maximum decibel level for each cotton density. The data showed that the less densely packed cotton reduced sound more effectively than the more densely packed cotton. My hypothesis was not supported, because the less densely packed cotton worked the best.