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Appendix 5: Microphone placement strategy when creating ARC Zones
As is discussed in
, it is possible to create
settings for different
ARC Zones
(or
listening areas). This is done by
placing a microphone in three different
locations within the zone and
performing an ARC measurement at
each position. This section gives some
recommendations regarding where to
place the microphone for the
measurements.
18.1
General information
18.1.1
Background noise
It is important to ensure that
extraneous background noise is kept to
a minimum during the measurement
procedure. This does not only include
mid-range frequencies (e.g. speech)
but also low-frequency noise.
Therefore, for example, it is
recommended that air conditioning
systems be turned off, and the
measurements are performed during
low-traffic hours. This is because, in
some cases, the measurement may
interpret background noise as artefacts
of the room’s acoustical behaviour.
(For example, the process may result
in reduced bass in the loudspeakers if
a truck was idling outside the room
during the measurement procedure.)
18.1.2
Microphone
Orientation and Holder
The microphone should be securely
held (e.g. on a camera tripod or
microphone stand), pointing upwards
as is shown in Figure
Figure 18.1:
Recommended micro-
phone orientation.
It is not recommended that the
microphone be hand-held due to the
length of the measurement procedure
and the fact that the microphone
should not move during the
measurement. Extraneous noise
caused by holding the microphone may
also affect the measurement accuracy.
18.1.3
Height
If the ARC measurement is for only one
listener who never changes position
(e.g. never “slouches” in the listening
chair), then the height of the
microphone should be roughly the
same as the height of that person’s
ears, typically 100 – 120 cm above the
floor.
Figure 18.2:
Recommended micro-
phone placement height for one listener
shown in gray.
If the ARC measurement zone is
intended for more than one listening
position, or for listeners of different
heights, then it may be beneficial to
change the vertical position of the
microphone for the three
measurements. For example, set the
centre microphone position at
ear-height, the front-left position
slightly lower (10-20 cm), and the
back-right position slightly higher
(10-20 cm). This will provide the
calculation with additional information
regarding the effects of room modes in
the vertical dimension that may
benefit listeners of different heights.
18.1.4
Doors and Windows
Doors and windows in the listening
room should have the same position
during the measurement as when the
room will be used for listening. So, if
you normally listen to music with the
doors closed, then they should also be
closed during the measurement
procedure. This is because opening a
door or a window can have a
significant effect on the acoustical
behaviour of a listening room.
If doors may be opened or closed for
different listening situations (e.g. patio
doors leading from the living room to
the outdoors) then two different ARC
Zones should be created separately for
the two different scenarios.
18.2
One listening position
If an ARC Zone consists of only one
listening position, it is recommended
that the three microphone positions
are:
•
the location of the listener’s
head, as shown in Figure
•
on each side of the listening
position (approximately 30 cm to
either side of the listening
position). One placement should
be slightly forward
(approximately 20 cm) and the
other should be slightly behind
(approximately 20 cm).
As mentioned above, the microphone
should be placed roughly at ear-height.
Figure 18.3: Recommended ARC micro-
phone placements (in red) for a single
listening position.
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