PULSE-CODE MODULATION

Pulse-Code Modulation

Pulse-Code Modulation

When sound is been recorded on the tape or been transmitted via telephone, then it is transformed into electrical wave. It is described “analog” audio, because of the electrical signals are an analogue of a sound that shaped it. On playback, the electrical signals are transformed back into resonance. In a digital audio, THE other step is supplemented in which electrical signals are transformed in digital data series in 0's and 1's for the purpose of storage space or broadcast. There are quite a few ways to do this, however the most commonly used system is known as Pulse Code Modulation .

Two variables are essential to convert analog to digital hearing data: bit depth and sample rate. Bit depth may determine the distance between maximum and minimum sound volume. For example, in the system a bit, the possible values are zero and one, until the sound is off or on at full volume. With extra bits, the levels of possible double, so the 16-bit system (the standard for CD) has more than 65,000 possible levels, and the 24-bit (standard DVD) is over 16 millions of possible levels. Higher resolution is generally little thought to correspond to the superior sound quality. However, higher resolutions need more storage space and more bandwidth to transmit 24-bit file is 1.5 times larger than the 16-bit file. The compromise between sound qualities and storage spaces are go through by specifications of digital audio styles.

The sampling rate indicates that several thousands of times per second (kilohertz, or kHz) digital audio system takes the snapshot of the analog signal. Think of the sampling rate as the frames of the film: By itself, each border appears as still image, but by projecting the number of still images, conceived the illusion of movement. The ...