A method of measuring distortion noise in digital audio equipment

An experimental system, developed to measure the dynamic characteristics of digital audio systems, can measure dynamic distortion as little as a 16-bit quantized noise-level with high accuracy. The system eliminates a certain frequency range from the test-signal, and the rest of the signal is fed to the equipment under test. Any output appearing in the eliminated frequency range is taken as distortion produced by it. It is measured and the amount of distortion may be represented by the ratio of this measured level to the original signal level in the eliminated frequency range. No special test-signal is needed, and program such as those stored in conventional analog tape recorders can be used. Thus, the performance of audio equipment can be measured under operational conditions with real program signals.