Philips HP1500 - Manual (Page 7)

Advanced technologies used in HP 1500
The HP1500 makes use of several advanced technologies.
Principle of determining the direction of sound
People can determine the localization of sounds through the perception of
differences in intensity – so called Interaural Intensity Difference (IID) – and
through time differences – so called Interaural Time Difference (ITD).
IID is about the fact of sounds being louder as they are closer to the ear
and being louder in case they have a non-obstructed path to the ear.
ITD is about the fact that in most cases sounds will arrive earlier in time at
one ear than at the other.
In fact it is the environment itself that greatly impacts the sound before it
reaches our ears. Reflections and absorption all will influence the sense of
distance and direction we associate with a sound.
Combining IID and ITD will allow the brain to determine the direction of
sounds only in a rough way. It is in through the combination of IID and ITD
and the way sounds are filtered because of the structure of the pinna
– the outer ear – that allows to brain to accurately localise sounds.
•
Depending on how a sound wave hits the pinna, it will be emphasized
or suppressed.
• Depending on how a sound wave hits the pinna, reflections within the
pinna are created, altering the phase relationship within the spectrum of
the sound wave.
• And also: higher frequencies are more affected by the pinna than lower
frequencies.That’s why our brain can easily locate higher frequencies,
rather than lower frequencies.
ENGLISH 7
0912HP_EU 09-12-2003 12:12 Pagina 7