ADVERTISEMENT
See Inside February 2005

Reducing a Roar

Whining jet engines pummel airline passengers with a mind-numbing 75 to 80 decibels of noise. Subways, trains and speeding cars also assail riders with a relentless howl. Putting on simple headphones and cranking up a compact-disc player to drown out the din just adds to the ear-pounding volume.

Deep earplugs or earmuffs like those worn by factory workers typically reduce the racket by 15 to 25 decibels, but they are uncomfortable and do not allow wearers to hear the audio from an airplane movie, music channel or their own music player. Noise-reduction headphones can help. The most advanced models, priced around $300, are made from structural materials that passively block higher-frequency noise (above about 200 hertz). They employ electronics and a speaker to actively cancel lower-frequency sounds, which are otherwise difficult to stop. A microphone inside each muff senses sound waves that make it through the outer ear cup, and a speaker creates pressure waves that cancel them. If desired, music can then be piped in at a comfortable level.

This is only a preview. Get the rest of this article now!

Select an option below:

Customer Sign In

*You must have purchased this issue or have a qualifying subscription to access this content


It has been identified that the institution you are trying to access this article from has institutional site license access to Scientific American on nature.com.
Click here to access this article in its entirety through site license access.

Rights & Permissions
Share this Article:

Comments

You must sign in or register as a ScientificAmerican.com member to submit a comment.
Scientific American Holiday Sale

Give a Gift &
Get a Gift - Free!

Give a 1 year subscription as low as $14.99

Subscribe Now! >

X

Email this Article

X