Comparison between global loudness and loudness change ratings for increasing sounds

Loudness change has been recently studied for tones with linearly varying levels. The published results by different authors revealed that direct ratings of loudness change for increasing sounds are higher compared to decreasing sounds. Interpretations of the results were different between Neuhoff’s (1998) and Teghtsoonian et al’s (2005) studies. The latter ones showed that judgments of loudness change were affected by the intensity at the end of the increasing sounds whereas Neuhoff claimed for a bias for rising sounds. Other studies by Canévet et al (2003) and Susini et al (2007) did not show any significant difference when judgement of loudness change were obtained indirectly by computing the ratio between estimated loudness at the beginning and the end of the sweep. On the other hand, direct judgments of the global loudness in the study by Susini et al revealed also that the judgments were affected by the end loudness of the increasing sounds. The assumption of the present article is that direct ratings of loudness change in Neuhoff's study are confounded with a global impression of loudness. Thus, three experiments were performed in order to test this methodological assumption. In the two first experiments, indirect and direct estimation of loudness change of increasing levels of synthetic vowel sounds and1-kHz tones for several ramp ranges of either two sizes (15, 30 dB) were obtained by magnitude estimation respectively for two groups of 16 participants. In the third experiment, a third group of 16 participants estimated the global loudness of the same stimuli also by magnitude estimation. Results of the first experiment reveal a difference between indirect and direct estimations. Indirect estimations are significantly different for ramp sizes of 15 and 30 dB and are independent of the end level, whereas direct estimations are not. In addition, direct estimations of loudness change show the same trend than the global loudness estimations according to the end level. These results suggest, as assumed, that direct ratings would rather measure a global impression of loudness than a loudness change.