Page 98 - The Master Handbook Of Acoustics

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THE EAR AND THE PERCEPTION OF SOUND

fullness of tone blend
liveness intimacy
sonority shimmering

What kind of an instrument measures warmth or brilliance? How
would you devise a test for definition? Progress, however, is being
made. Take definition for instance. German researchers have adopted
the term deutlichkeit, which literally means clearness or distinctness,
quite close to definition. It can be measured by taking the energy in an
echogram during the first 50 to 80 milliseconds and comparing it to
the energy of the entire echogram. This compares the direct sound and
early reflections, which are integrated by the ear, to the entire rever-
berant sound. This relatively straightforward measurement of an
impulsive sound from a pistol or pricked balloon holds considerable
promise for relating the descriptive term definition to an objective
measurement. It will be a long time before all of these and a host of
other subjective terms can be reduced to objective measurements, but
this is a basic problem in acoustics and psychoacoustics.
There comes a time at which meter readings must give way to obser-
vations by human subjects. Experiments then take on a new, subjective
quality. For example, in a loudness investigation, panels of listeners are
presented with various sounds, and each observer is asked to compare
the loudness of sound A with the loudness of B or to make judgments
in other ways. The data submitted by the jury of listeners are then sub-
jected to statistical analysis, and the dependence of a human sensory
factor, such as loudness, upon physical measurements of sound level is
assessed. If the test is conducted properly and sufficient observers are
involved, the results are trustworthy. It is in this way that we discover
that there is no linear relationship between sound level and loudness,
pitch and frequency, or between timbre and sound quality.

The Precedence Effect

Our hearing mechanism integrates sound intensities over short inter-
vals and acts somewhat like a ballastic measuring instrument. In sim-
pler terms, in an auditorium situation, the ear and brain have the
remarkable ability to gather all reflections arriving within about 50
msec after the direct sound and combine (integrate) them to give the
impression that all this sound is from the direction of the original