Energy accountancy concept

Abstract

The study of noise sources on an engineering level calls for a good working knowledge of machinery mechanics, structural vibration, energy absorption or damping, and fluid mechanics as well as acoustics. The acoustic output is effectively a remainder term associated with inefficiency in one or many of these processes. Due to uncertainties existing between various subjects, new mathematical techniques used to obtain exact calculations of cause and effect cannot be exploited. It is the contention of this paper that mathematical methods dealing with special simplified cases should be associated with a systems analysis which is strong in concept and universality rather than in detail. The energy accountancy system is intended to be such, not specifying the details of how each component is studied, but how they are linked together. It is based on the idea that noise occurs only when compressibility occurs in the flow near to a body or flow, and that in noisy machines this can be equated to the high‐acceleration portions of the motion. It uses an energy balance approach which allows one to ignore the exact modal vibratory front except where necessary, as well as ignoring coupling and directional effects. It looks at a single machine impact and adds a repetition effect, because a large number of high‐frequency modes arise from the sharp accelerations which can only be dealt with statistically. Thus while SEA can and is used in some of the terms in the “energy accountancy equation,” the method is not dependent upon this.