Information Technology Reference
In-Depth Information
8.5.1.1.
The issue
From a general point of view, the study of auditory perception is concerned with
quantities and units representative of what humans perceive when they are subjected
to an auditory stimulus (percept). These units - assembled under the general term of
auditory attributes - can cover simple notions that it is possible to link to physical
units directly calculable on the auditory signal (intensity, duration, etc.) via the
intermediary of basic metrological approaches, which globally relate to the domain
of psychoacoustics. They can also cover more complex notions linked to the nature
of the information contained in the sound (mentioning the source, judgment of
value, etc.) that require more exploratory approaches, belonging to the field of
experimental psychology.
These approaches respectively summarize the two main mechanisms of
processing sensory information, which are mentioned in Chapter 29 of [SEA 07]
from a general point of view and developed in [MCA 93] on issues more particularly
linked to sound:
- bottom-up processing guided by attributes of the auditory stimulus;
- top-down processing guided by prior knowledge acquired about the auditory
stimulus (culture, expertise, etc.).
The particularity of these approaches resides in the fact that, with a few
exceptions, there is no tool for measuring - and therefore predicting - these auditory
attributes, other than the human ear and the processing that is then done by the
cerebral system. Their knowledge and the understanding of their links with the
auditory stimuli considered therefore inescapably go via experimental procedures
involving listening and judgment tasks carried out by people (called “subjects” or
“participants”), whose methods are explained hereafter.
8.5.1.2.
Classic methods
Classic methods involve psychophysics (and more precisely psychoacoustics)
and are more generally one-dimensional, i.e. they try to establish a direct and
qualitative relation between an auditory attribute (perceived unit) and a physical
sound property (physical unit, also called acoustic descriptor) in order to result in a
formula such as:
Ψ
= f(
φ
), where
Ψ
represents the perceived unit (psychological)
and
the acoustic unit (physical). The most common methods were ordered and
categorized by Susini in [SUS 11] according to the following taxonomy:
φ
- indirect methods:
- the
threshold method
that consists of measuring a threshold of the
perception of a unit which can either be absolute or differential, leading in the
