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@The standard that CD records is decided, "Sampling frequency 44.1kHz and bit depth 16bit and stereos of number 2.0ch of channels". And, the capacity of CD becomes 700MB. Let's calculate how many minutes it is possible to record.
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@First of all, the sampling frequency is understood.How many times a second is the sampling frequency must to be recorded the sound?That is, if it is 1000Hz once a second if it is 1Hz, it is 1000 times a second. There is no necessity for division into the place where man cannot judge it though it becomes a sound that the more it increases it, is the smoother. Therefore, it is 44.1kHz. That is,
44.1kHz = 44100Hz = It is said that the sound of 44100 times a second will be recorded. |
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@Next, about the bit depth. The bit depth is tomorrow how much information on the sound can be recorded is said. It comes to be able to record the difference of a sound that the more greatly, is the more detailed. Most sounds can be covered if there is depth of 16bit. By the way, because the unit named bit is general when assuming the unit of capacity and doesn't exist, it converts it into 2B(byte).
¦8bitPB |
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@Then, music CD is recorded 44100 times a second how much capacity is necessary at one second, and 2B becomes one record with 44100Hz~2B=88200B because it needs it. To record with the stereo (each right and left), it becomes 88200B~2=176400B. |
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@Then, 700 millionB (M is the sixth power of ten)176400B=3968 second comes because it is the CD1 piece 700MB. That is, it will be possible to record for 66 minutes by a simple calculation. It is necessary to calculate however, it calculates roughly like this though it actually becomes a little different value because it is necessary to temper with data for error correction etc. with 1MB=1024KB. |
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