ISO 532 – Living and working with alternative loudness standards

By its very nature, standardization claims to set unique rules and procedures, thus aiming unique, i.e. comparable and reproducible results. Also, to be effective, the standard and the underlying approach need to be broadly accepted by the addressed user community. To come up with such general agreement it is typically required that a “best” approach, covering all relevant applications of interest, has been established. If this does not apply, the existence of alternative standards in parallel may offer a way out. The revision process of ISO 532 “Acoustics – Methods for calculating loudness” showed that it was not possible to prove and agree on a single “best” approach. Acknowledging the legitimate demand of applicative continuity, the member bodies of ISO TC 43 “Acoustics” therefore decided to maintain the given situation by specifying two alternative approaches again. With reference to existing national standards (DIN 45631/A1 and ANSI S3.4), these are the Zwicker approach in an extended version for time-varying sounds and the Moore/Glasberg approach for stationary sounds at first. Based on a review of the revision process and a summarizing justification of the resulting decision, the discussion of practical and theoretical consequences of the renewed dualism will outline the chances for broader applications of loudness calculations. However, this dualism also establishes the commitment to thoroughly identify and seize the chance for final unification of the standard.