Rating the dieselness of vehicle noise using different psychoacoustic methods

Modern diesel engines meet the demand for high power-engines while strict emission regulations have to be fulfilled. Therefore, diesel engines entered vehicle segments where the expectations on the sound quality are exceptionally high. Sound Quality and fuel efficiency are often conflicting goals during the development of a diesel engine. The typical sound character of diesel engines, the so called Dieselness, is an indicator for the overall Sound Quality of the vehicle noise. Hence, it is desirable to rate the Dieselness of engine sounds. Sounds emitted by gasoline- and dies el-powered vehicles in idle condition were rated in psychoacoustic experiments using different methods. First, the method of line length was used as direct scaling procedure to get ratio ratings of the relative Dieselness of the vehicle noises. Second, a direct ranking of the noises has been done with the Random Access method where subjects had to rank the sounds according to their Dieselness. Third, in a paired-comparison test the participants had to judge which of two sounds had more Dieselness, resulting in an indirect scaling. These methods are compared regarding the time the experiments took and the resulting ranking respectively scaling.