Human Dimension of the Soundscape: From Individuals to Society - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 115

Fig. 5.4 Framework representing the complexity of the soundscape where the acoustic and
psychoacoustic approach is constrained by a variety of sonic sources, their direction, proximity,
evolution in time, level of dominance, and position in foreground or background from the listener
(Reproduced with permission from Jennings and Cain 2013 )
Loudness is the most fundamental of auditory sensations.
The unit of loudness is the sone : the ratio scale referenced against the sensation
produced by 1 kHz sine tone with a sound pressure level of 40 dB. This parameter is
not considered as a robust auditory scale or data representation. Loudness has an
inherent dependency on frequency content.
Loudness is affected by the dominant frequency of the signal, the signal band-
width, and the signal duration.
Sharpness (or brightness) is one of the most important features of timbre. This
model describes how a sound is “sharp,” “harsh,” or has “an edge.”
The unit of sharpness is the acum , referenced to a band of noise centered on
1 kHz at a level of 60 dB.
Roughness is the sensation caused by a quite rapid amplitude modulation within
auditory filters.
The unit of roughness is the asper , which is referenced to a 1-kHz tone at 60 dB
with 100 % amplitude modulation at 70 Hz.