|Hardly anybody would evaluate
a sound with closed ears.
However, this is still common practice for con- ventional
acoustic and vibration measurements. Recordings with conventional
measurement microphones are not suited for an aurally-
accurate evaluation of an acoustic scenario, because substantial
acoustic information such as the spatial array of sound
sources and the selectivity of sound perception gets lost.
In particular, the three-dimensional locating of sound
sources and the influence of the acoustic signal through
the human auditory apparatus are substantial parts of
the normal aural impression.
|A human is able to locate a sound
source in three dimensions, i.e. in the horizontal plane (1)
and in the median plane (2).
The locating takes place automatically by means of delay and
level differences of the acoustic signal at both ears because
the outer ear causes a direction-dependent filtering of the
sound signal. The filter impact results from a modification
of the sound waves diffusion through attenuation, deflection,
reflection and resonance of the sound waves. Geometry and anatomy
of the head and shoulder unit as well as the influence of the
pinna play a decisive role. Based on this locating capability
of the human auditory apparatus it is possible for humans to
select single sound sources from background noise.
Binaural hearing cannot be simulated by simply using two measurement
microphones as "ear replacements". Only after having taken the
acoustic filter characteristics of the head and ears into account,
do aurally-accurate, unaltered recordings become possible. In
many respects the human auditory system is different from the
properties of conventional sound sensors. On the one hand, very
complex signal processing takes place in the auditory apparatus,
which captures the amplitude distribution and the spectral and
temporal structure of the acoustic signal. The listener perceives
a comprehensive, holistic impression of an acoustic event. On
the other hand, man possesses only a very short acoustic memory.
With the artificial head measurement technology from HEAD acoustics,
it is possible to conduct aurally-accurate recordings of acoustic
signals and to save them. The playback of an artificial head
recording generates the same aural impression as if the listener
had heard the sound event directly.
Thanks to the true-to-original recording and playback of arbitrary
sound incidents and their digital archives, the system makes
comparative and aurally-accurate evaluations of different sound
situations possible. And because the artificial head technology
is compatible with conventional measurement technology, subjective
and objective sound field analyses can be combined in one investigation.