Computer sound quality: Masking, loudness and prominence

Abstract

Computers and business equipment were one of the first applications for standardized sound quality metrics. Various product specifications (emanating primarily from Europe) defined criteria for A-weighted sound pressure and sound power levels as well as the absence of prominent tones and impulsive noise. Standards such as ISO 7779, ANSI S12.10 and ECMA 74 have provided the means for assessing these quantities. Of particular interest at the moment is the prominent tone, for which there are two accepted metrics: tone-to-noise ratio and prominence ratio. Experience has shown that both metrics occasionally fail to track listeners perception of the prominence of tones or tonal complexes. An alternate prominence analysis is constructed based on psychoacoustical factors, using a method proposed by Zwicker for identifying the loudness of any sound masked by another. The accepted metrics are compared and contrasted with the masked loudness method using carefully selected test cases.