Interspeech'2005 - Eurospeech
Three different scales which have been used to measure perceived prominence are evaluated in a perceptual experiment. Average scores of raters using a multi-level (31-point) scale, a simple binary (2-point) scale and an intermediate 4-point scale are almost identical. The potentially finer gradation possible with the multi-level scale(s) is compensated for by having multiple listeners, which is a also a requirement for obtaining reliable data. In other words, a high number of levels is neither a sufficient nor a necessary requirement. Overall the best results were obtained using the 4-point scale, and there seems to be little justification for using a 31-point scale.
Bibliographic reference. Jensen, Christian / Tøndering, John (2005): "Choosing a scale for measuring perceived prominence", In INTERSPEECH-2005, 2385-2388.