Abstract
The nonlinearity to be allowed in sound transmission systems is usually found experimentally. For this purpose a group of persons is proposed to find (by listening to a program) the grade of nonlinearity at which distortion is noticeable. The resulting data may depend on the hearing sharpness of these people, on the sequence of the experiments, on the form of nonlinearity, frequency band, and transmitted program. Therefore the value of such data is limited. Distortion hearing thresholds for various programs and forms of nonlinearity were measured. In a single experiment for a group of people they are distributed in a good agreement with the Gaussian law. A method of computing the nonlinear distortion audibility was developed. The transmitted signal is considered to be a stationary oscillating process with normal distribution law. The probability for the nonlinear products to exceed the hearing threshold which is influenced by the main transmitted signal (masked) was computed. Calculation for a constant amplitude spectrum signal and transmission system with a frequency band 100–5000 cps. and various distortion factors was done. The probability of noticing second-order nonlinear products for a distortion factor = 3% was found to be 0.035; as for a distortion factor = 5% nearly 1/7 to 1/5 of the whole program may be spoiled by nonlinear effects.
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