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Chapter 24
Building Acoustics
Airborne sound insulation
General
When airborne sound insulation between rooms is
measured, one of the rooms is designated the source
room and the other the receiving room. A stationary
sound field is generated in the source room by a suit-
able loudspeaker.
If a facade is measured, the loudspeaker is placed
outdoors and the outside of the building is then acting
as the source room. The description made here refers
to the sound insulation between rooms, but may also
be adapted to the measurement of facades.
Noise excitation
The measurements require broadband or band filtered
noise to be used for the excitation. The noise may
be generated by the instrument if option 10, Noise
generator, is installed. Sometimes it will be convenient
not to have a cable between the instrument and the
loudspeaker for the excitation. This may be achieved
by using a radio-transmitter for the noise signal or to
use a power amplifier with an internal noise generator
such as the Nor280. Another alternative is to play a
music-CD with recorded noise.
Measurement of sound level
As stated in the standards, the spatial average of the
sound level in the room is required. For survey meas-
urements this may be achieved by measuring the lev-
el while moving the sound level meter (microphone)
around in a figure-of-eight trajectory. Recommended
measuring time is 30 seconds. For the engineering
method point by point measurements has to be applied
and the instrument will calculate the averaged level.
The level measurements may be performed in the
normal mode of operation and stored for later process-
ing, or alternatively, the measurements may be start-
ed from the calculation menu when the results are
required for the calculation.
Measurement of reverberation time
For a survey measurement according to ISO 10052,
the corrections for the acoustic absorption may either
be based on measurement of the reverberation time or
based on estimation based on room type, type of sur-
face and furniture. Both methods are implemented. For
engineering measurements according to the ISO 16283
series of standards, the reverberation time has to be
measured.
If a measurement is required, the reverberation
measurement may be performed in the reverbera-
tion mode of operation and the result stored for later
processing (MODE 2. Rev.). Alternatively, the meas-
urement may be started from the calculation menu
when the result is required for the calculation.
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