How long audio cd

When the Compact Disc Digital Audio standard came out in , there was a curious fact about it: It was 74 minutes long. Not 60 minutes. Or an even 70 minutes. And it was all one deaf man's fault. The fault of a deaf man and one of the best musical compositions ever written—one that gives me goosebumps every time I listen to it on my big honking Denon reference headphones: The Symphony No. Picture this: The s, the greatest rock era of them all.

Plus, disco. The exact year: It was also the year in which Philips and Sony were working on the first audio CD standard.

Philips wanted a Both were enough to fit any of those vinyls, the smaller size capable of storing 60 minutes of bit 44, Hz stereo music. But that wasn't enough. He had agreed to endorse the CD at the Vienna press conference where they would announce the company's prototype. But he had one condition: that the new technology could allow listeners to hear the whole of Beethoven's Ninth Symphony without interruption.

There are a couple of different versions of the story - one says that it was Sony President Norio Ohga who held the Ninth symphony in such high esteem that he insisted that the work would be able to fit onto a CD in its entirety.

But whichever version is true, Beethoven's last symphony is at the root of one of the most important inventions of the modern music industry. You see, the legend isn't demonstrably false, it actually appeared as a question on Who Wants To Be A Millionaire , but it wasn't just old Beethoven who was calling the shots on this new tech.

Philips engineer Kees A. Schouhamer Immink writes that Philips were pushing for the CD to be close in size to the cassette tape, whereas Sony were pushing for a slightly larger 12cm disc, partially because they knew that Philips already had a factory capable of producing Eventually the maximum playing length was set at 74 minutes, 33 seconds, and in his grave Beethoven breathed a sigh of relief - modern consumers could now hear the whole Ninth Symphony in all its glory.

This testing for R discs is in the preliminary stages, and much more needs to be done. ROMs are generally mass-produced and contain music, video, computer applications, or interactive games. ROM disc longevity is determined by the extent to which its aluminum layer is exposed to oxygen. Oxygen, including pollutants, can migrate through the polycarbonate layer or the hard lacquer layer CD label side and edge , carried in by moisture.

Oxygen or moisture can more easily penetrate through scratches, cracks, or delaminated areas in the label. Oxygen can also be trapped inside the disc during manufacturing, although manufacturing improvements have reduced the likelihood of this. If left in a very humid environment, moisture-and oxygen-will eventually reach the aluminum, causing it to lose its reflectivity.

The normally shiny aluminum, which resembles silver, becomes oxide-dull and much less reflective, like the color of a typical aluminum ladder. The combination of high humidity and increased temperatures will accelerate the oxidation rate. The life expectancy of a ROM disc therefore depends on the environmental conditions to which it is exposed over time.

Generally, it is best to keep ROM discs in a dry, cool environment. Other contaminates, however, such as inks, solvents, and pollutants, have the potential to irreversibly penetrate and to deform, discolor, or corrode the disc, causing permanent reading problems for the laser.

The tests are generally performed by manufacturers, and the discs are usually categorized by the metal and dye types used in the disc. These discs use gold, silver, or a silver alloy for the reflective layer instead of aluminum as in ROM discs. Gold will not corrode but is expensive. Silver is more reflective and cheaper than gold but is susceptible to corrosion if exposed to sulfur dioxide, an air pollutant that can penetrate the disc in the same way oxygen can-with moisture.

Manufacturers use various silver alloys to help inhibit silver corrosion, and most R discs available today use a silver alloy reflective layer. The chance of silver corrosion from exposure to sulfur dioxide is less than the chance of aluminum oxidation caused by high humidity. With proper storage, these discs will outlast the technology.

R discs use a dye-based layer organic dye for recording data. The organic dye used in the data layer of R discs degrades naturally but slowly over time.