Its typical values are one for mono systems two for

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: n transforms an analog input (such as voltage) into a series of numeric representation by digitization. D/A conversion is the reverse process of A/D conversion. It transforms a sequence of discrete numbers back into continuous analog signal. Figure 19.3 shows the role of A/D and D/A converters in the acquisition and playback of analog signals by a computer system. A multimedia computer system capable of processing audio information requires a sound board (or sound card), which is equipped with A/D and D/A converters. In addition to performing the basic function of A/D and D/A conversions of audio signals, a sound board is generally also equipped with the following features: 1. It has a connector for speakers or headphones to allow users to listen to sound recordings. 2. It has a MIDI input port to input sound from an external MIDI device (such as an electronic keyboard or drums), a MIDI output port to output recorded sound to the MIDI device, and a MIDI synthesizer to translate the information transferred between the computer and the musical instrument. MIDI (Musical Instrument Digital Interface) is an international standard developed for digital music that determines the cabling, hardware, and communications protocol needed to connect a computer with electronic musical instruments and recording equipment. 3. Most sound boards also have a volume control knob to allow users to control sound volume according to their taste. Digital Audio Quality The quality of digital audio is characterized by the following three parameters: 1. Sampling rate. Analog-to-digital conversion transforms an analog signal into a series of numeric representation by digitization. Digitization is composed of sampling and quantization. Sampling take; snapshots of the analog waveform at certain points in time, and the sampling rate determines how often the analog signal is digitized. According to Nyquist theorem, the sampling rate must be at least twice the highest frequency component of the analog waveform to reproduce the signal optionally. The higher the sampling rate, the truer the sound. Sampling rate is measur...
View Full Document

This document was uploaded on 04/07/2014.

Ask a homework question - tutors are online