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May 24, 2012
Jeff Jacoby: The peace process battered Israel's reputation
Michael Muskal: 'Pro-choice' position hits record low, according to poll
Chris Farrell: Are We in a Tech Bubble?
The Kosher Gourmet by Penelope Wall: PHILLY CHEESE STEAKS --- hold the steak!
May 23, 2012
Tony Pugh: More private colleges offering tuition discounts
Mary Beth Franklin: How to Choose the Right Annuity for You
Tina Susman: The wig wasn't enough: Man gets 13 years for posing as his dead mom
The Kosher Gourmet by Emma Christensen:A simple way to do fish right
May 22, 2012
Warren Richey: Can US group challenge overseas surveillance act? Supreme Court to decide
Thomas M. Anderson: Walking Away From a Mortgage
The Kosher Gourmet by Megan Gordon: Enjoy a celebration of the most rich and layered flavors: Black bean, sweet potato and quinoa chili
May 21, 2012
Mark Clayton: Cybersecurity: How US utilities passed up chance to protect their networks
Howard LaFranchi: NATO summit: Who will foot the bill for long-term Afghanistan security?
Chris Farrell : Earn Dividends in Emerging Markets with This WisdomTree ETF
Stephen Whiteside, Ph.D. : Mayo Clinic Medical Edge: Social anxiety disorder --- or just shy?
Guy Jackson : Victim's father regrets death of Lockerbie bomber
The Kosher Gourmet by Mario Batali: Famed chef's veal shoulder farsumagru: A festive meat course for late spring
May 18, 2012
Rabbi Berel Wein: Striving: The People of the Book's Book for (All of) the People
Steven Goldberg: 5 Great Stock Picks and the Exchange-Traded Fund that Owns Them
Mary Pickett, M.D.: Ask the Harvard Experts: Don't be forced into gluten-free lifestyle based merely on a doctor's false-positive test
The Kosher Gourmet by Carolyn Malcoun: DIY healthy lunchbox treats: HOMEMADE FRUIT BARS for kids and brown-bagging adults alike
May 17, 2012
Warren Richey: Teacher fired for being unwed and pregnant can sue religious school, court rules
Josh Mitnick: Netanyahu's 'centrist' coalition is already proving it's anything but
Steven Goldberg: Earn Dividends in Emerging Markets with This WisdomTree ETF
Amina Khan: Research links coffee to lower death rates
The Kosher Gourmet by Faith Duran : Cheesy Potato Breakfast Casserole with Cheddar and Sun-Dried Tomatoes
May 16, 2012
Carmen Terzic, M.D., Ph.D. : Mayo Clinic Medical Edge: A variety of exercises can help improve balance
Melissa Healy: National strategy on Alzheimer's disease aims to halt it by 2025
The Kosher Gourmet by Joyce White : GOODNESS GRACIOUS: GREENS! 4 winning recipes that are no longer just for down-home folks (Includes expert tips & techniques)
May 15, 2012
Kristen Chick: Obama administration resumes arms sales to Bahrain despite serious unresolved human rights issues. Activists feel abandoned
Pat Mertz Esswein: Homes are now affordable again and mortgage rates are low. What you need to know before you buy
Kathy Kristof: Our Practical Investor Fights Inflation with These 6 Investments
Sue Hubbard, M.D.: The Kid's Doctor: Lactose intolerant young child? Check again
The Kosher Gourmet by Kathy Hunt: Spread a Little Excitement with EXOTIC CONDIMENTS (4 RECIPES)
May 14, 2012
Lisa Gerstner: How to Protect Your Identity, Finances If You Lose Your Phone
Harvard Health Letters: Heart disease and dementia
The Kosher Gourmet by Megan Gordon: MANGO COCONUT OAT MORNING MUFFINS are a bright but hearty delight
May 11, 2012
Jessica L. Anderson: Get the Best Deal on a Used Car
Jett Stone: Forget face-lifts and fake knees. Scientists have seen the fountain of youth --- and it's broccoli
The Kosher Gourmet by Chef Mario Batali: The famed chef's vegetable dish that tastes true to the season: FAVAS AND SUGAR SNAP PEAS WITH POTATOES AND TARRAGON
May 10, 2012
Sergei L. Loiko: Putin sends warning to U.S., NATO in Victory Day speech at Red Square
Mary Rourke: How being a 'mentch' got Vidal Sasoon his start and fighting in Israel's War of Independence provided him with confidence and a strong sense of his own identity
Jeff Bertolucci: Get Home Phone Service for Less Than $10 a Month
The Kosher Gourmet by Betty Rosbottom: Gleaming with its golden, crimson, and snowy white hues, this silken smooth and creamy STRAWBERRY ORANGE TRIFLE looks impressive, but is easy to prepare
May 9, 2012
Sharon Palmer, R.D. How you can reduce your risk -- or delay -- chronic diseases associated with aging
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Jewish World Review
How CDs work
By
Marshall Brain
http://www.JewishWorldReview.com | (MCT)
In 2007 we are celebrating an important event - it's the 25th anniversary for the CD, also known as the compact disc. In 25 years CDs have become ubiquitous, to the point where we take them completely for granted. But inside a CD you find both an amazing amount of technology.
To understand just how profound the effect of the CD has been, it is helpful to look back at the two reigning technologies in the early 1980s: The vinyl LP and the compact cassette. You may recall just how bizarre the vinyl LP was. An aficionado would have a massive turntable with little black and white markings along the edge so that he could calibrate the speed of the turntable with a strobe light. The turntable rested on big vibration-dampening pads to try to keep any spurious vibrations away from the turntable. The tip of the tone arm was measured with a sensitive scale to minimize its pressure in the record's groove. The LP itself was sprayed with an anti-static gun to cut back on dust. And even with all this technology, the first thing you heard from any vinyl disk was hiss. With the cassette the story was the same: the tape stretched, it flaked, it broke, it jammed.
Enter the compact disc. Because of its digital nature, its sound quality was amazing compared to vinyl or tape. It also eliminated hiss once and for all. Things like dust, fingerprints and small scratches didn't matter. The sound did not degrade over time as it did with vinyl or tape. And normal heat levels, as in a locked car on a hot summer day, didn't cause any problems. And there was an added bonus - over time, compact discs became incredibly inexpensive to produce. How inexpensive? So inexpensive that AOL could afford to mail out billions of them.
The thing that is so amazing about a CD is its simplicity. A CD is basically a mirror. The mirror is made out of a tough, clear plastic disc. A microscopic layer of aluminum is coated onto the plastic to create a mirror surface. To store the CD's data, the mirror has millions of tiny blemishes on it. When a laser hits the CD's aluminum surface, it either reflects cleanly off the mirror or scatters off a blemish. A computer inside the CD player interprets the reflections and scatterings as the ones and zeros of the computer binary code, and reassembles the ones and zeros into music (or data). That is the essence of a CD.
The process of making a music CD goes something like this. The songs of the CD are recorded using a microphone. The microphone picks up vibrations in the air. Those vibrations can then be digitally sampled. For a CD, a device called an analog-to-digital converter (ADC) samples the vibration pattern 44,000 times per second. Based on the intensity of the vibration pattern at the moment it is sampled, the ADC assigns a number between -32,767 and 32,768. Approximately 158 million of these ADC samples make up all the music on a 60-minute CD.
Now these 158 million numbers are turned into ones and zeros. Things like track information and error correcting codes are added. All the ones and zeros are placed end to end to formed a single microscopic spiral track that is about three miles long. This track is placed on a metal mold - a tiny bump on the metal represents a one, and a tiny flat area represents a zero.
To make a CD, liquid plastic injects into the mold and it picks up the pattern of microscopic bumps and flats. Once the plastic comes out of the mold, a layer of aluminum coats the bumps and flats on the plastic. The flats reflect a laser perfectly, while a bump scatters a laser beam. To read the CD, all the CD player has to do is read the ones and zeros, reassemble them into numbers and run the numbers through a digital-to-analog converter. Out comes music.
You can see why CDs are so inexpensive to produce. Each CD is nothing but a blob of liquid plastic injected into a mold, along with a milligram of aluminum. A coat of lacquer protects the aluminum and holds the CD label. There really is nothing to a CD.
In the early 1990s, music companies sold more than 440 million cassette tapes per year. Last year, the number had fallen to 700,000. That shows you just how thoroughly the CD has dominated the musical landscape. Of course, the days of the CD are now numbered - compact discs will be replaced by digital music players that use only the music's data, without any need for the plastic and aluminum.
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Previously:
How the Edsel worked
How Stinger missiles work
How hybrid cars work
How sharks work
How mosquitoes work
How diesel engines work
How water towers work
How the Dawn mission works
How Kassam rockets work
How the North American Eagle works
Why aren't we flying to work?
How tofu and soy milk work
How Colony Collapse Disorder works
How airbags work
How the U.S. income tax works
How gum works
How caffeine works
How Daylight Saving Time works
How a cruise missile works
How snow making works
© 2007, How Stuff Works Inc. Distributed by McClatchy-Tribune Information Services.
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