Progress in calculating tonality of technical sounds

Noises with tonal components, howling sounds, and modulated signals are often the cause of customer complaints when emitted from technical products. The perception and evaluation of sound events containing such components has become increasingly important, e.g., in the field of vehicle acoustics for the assessment of tonality due to alternative drives. Furthermore, Information Technology (IT) devices and products such as hard disk drives may emit tonal sounds. Despite their very low sound pressure levels, such noises are unwanted and should preferably be avoided or masked. The psychoacoustic parameter tonality was introduced in order to quantify the perception of tonal content. However, existing methods for tonality calculation show problems when applied to technical sounds. Recently, a new approach to tonality calculation based on a hearing model was presented by Sottek, Kamp, and Fiebig. In accordance with recent research results, the calculation of tonality is therein performed upon the basis of the partial loudness of the tonal content. This paper presents model validations exploiting the results of new listening tests using bandpass-filtered noise signals with varyingly steep filter slopes and model improvements, especially in order to adequately indicate the perceived tonality of technical sounds with low sound pressure levels.