In the Know #27

January 31, 2008


Dictionary.com's Word of the Day

irascible \ih-RASS-uh-buhl\, adjective:
Prone to anger; easily provoked to anger; hot-tempered.


In the news:

- John McCain wins the Florida primary.

- Rudy Giuliani and John Edwards drop out of the presidential nomination race.


Today in History, according to Wikipedia:

1606 - Guy Fawkes (pictured) is executed for plotting against Parliament and James I.

1876 - The United States orders all Native Americans to move into reservations.

1961 - Ham the Chimp travels into outer space.


Today's Famous Births:

1797 - Franz Schubert (pictured), Austrian composer

1872 - Zane Grey, American Western writer

1919 - Jackie Robinson, American baseball player, the first African-American player in Major League Baseball, 6-time All Star

1931 - Ernie Banks, American baseball player, 10-time All Star

1941 - Dick Gephardt, American politician

1947 - Nolan Ryan, American baseball player, 8-time All Star

1970 - Minnie Driver, British actress, Good Will Hunting

1981 - Justin Timberlake, American singer, "What Goes Around...Comes Around" and "My Love"


Trivia
Today's Category - per request, Neptune...the planet, not the trident-wielding god


~ Neptune (pictured as seen by Voyager 2) is the eighth planet from the sun, located beyond the asteroid belt and is one of four Jovian planets, the gas giants.

~ Neptune's circumference is 3.8 times bigger than Earth's with 57.7 times more volume, but it is only 17.1 times as massive as Earth.

~ A year on Neptune lasts 164.8 Earth years.

~ A day on Neptune lasts only 16.1 Earth hours.

~ Mean temperature is between 55K (-361 F) and 72K (-330 F) depending on altitude.

~ The atmosphere of Neptune is composed mostly of hydrogen and helium.

~ The apparent magnitude of Uranus varies from 8.0 to 7.8 at its brightest, making it visible only with magnification.


I always wondered...
...how noise-canceling headphones works...

In order to understand how noise-canceling headphones work, one must first understand how sound waves work. A sound wave is composed of crests and troughs which, respectively, represent compressions (positive pressure) and rarefactions (negative pressure) of air. When graphed, a sound wave is seen as a sine wave.

Destructive interference is what makes noise-canceling headphones work. Destructive interference occurs when crests meet troughs, or vice versa, in opposing sound waves. Alternatively, if crests meets crests and toughs meet troughs, constructive interference - or amplification - occurs (constructive and destructive interference pictured). So all that needs to happen in order for sound cancellation to occur is to reproduce a sound wave in the opposite direction and 180 degrees out of phase from the original sound wave. To visualize this, imagine two identical trains on the same track, traveling at the same speed, but towards each other. When the trains collide, neither will continue traveling along the track, instead they will "cancel each other out"...though quite violently in this example.

Active noise-canceling headphones utilize a microphone, a circuit board (which analyzes sound waves and creates the opposite wave), and a speaker. The speaker is aimed away from the ear and transmits the out of phase sound waves, which practically destroys all sound waves coming toward the headphones.

["Noise-canceling headphones" reference: How Stuff Works]
[All references from Wikipedia.org unless otherwise noted]