Sound quality Standard
The so-called sound quality, refers to the transmission, processing audio signal fidelity. At present, the industry recognized sound quality standards are divided into 4 levels, that is, digital laser turntable Cd-Da quality, its signal bandwidth is 10, FM broadcast FM quality, its signal bandwidth is 20hz, amplitude modulation broadcasting am quality, its signal bandwidth is 50hz; The voice quality of the telephone, the signal bandwidth is 200. It can be seen that the sound quality of digital laser discs is the highest, and the voice quality is the lowest. In addition to the frequency range, people often use other methods and indicators to further describe the different uses of sound quality standards.
For analog audio, the more frequency components of reproducing sound, the smaller the distortion and interference, the higher the sound fidelity, the better the sound quality. For example, in communication science, the level of sound quality is measured in terms of distortion, signal-to-noise ratio, and so on, in addition to the frequency range of audio signals.
For digital audio, the more components to reproduce the sound frequency, the smaller the BER, the better the sound quality. Usually use the digital rate (or storage capacity) to measure, the higher the sampling frequency, quantization bit number, the more the number of channels, storage capacity is greater, of course, fidelity is high, sound quality is good.
Sound category features different, sound quality requirements are not the same. such as, the fidelity of voice quality is mainly embodied in the clarity, the truth, the reappearance of the plane sound image; The sound fidelity requirements are higher, and the creation of the space acoustic image is mainly embodied in multi-channel analog stereo surround sound, or virtual dual channel 3D surround sound and other methods to reproduce the original sound source image.
The use of the audio signal is different, and the quality standard of compression is not the same. For example, the telephone quality of the audio signal using Itu-Tg? 711 Standard, 8kHz sampling, 8bit quantization, rate 64Kbps. AM broadcast using ITU-Tg 722 Standard, 16kHz sampling, 14bit quantization, code rate 224Kbps. High Fidelity stereo audio compression standard is jointly developed by ISO and ITU-T, Cd11172-3mpeg audio standard is 48kHz, and 1kHz, 32kHz sampling, each channel digital rate 32kebs, suitable for Cd-Da CD-ROM.
The requirement of sound quality is too high, the equipment is complex; Generally with "enough, not waste" as the principle.