User`s manual

RTU [s]. Reverberation time evaluated from a user defined dynamic range; refer to
15.3 acoustical parameters settings. See also below the correlation coefficient
R associated with RTUser.
R(RT). Each reverberation time estimation (RT20, RT30 and RTU) has associated a
negative number which is the correlation coefficient R showing how closely the
corresponding decay curve fits a straight line. A value of -1 gives a perfect linear
fit. When the correlation coefficient is smaller than -0.95 the RT value
should be viewed with suspect as the decay curve may not be
sufficiently linear; direct inspection of the decay curve with markers
should be carried out.
15.5 NOTES ABOUT ACOUSTICAL PARAMETERS MEASUREMENT
This paragraph gives some guidelines that should be followed while executing the
measurement of the impulse response of rooms; what said here should be
considered together the general procedure that is described in chapter 10 for
executing MLS measurements.
The sound source shall be as omni-directional as possible. Maximum
acceptable deviation from omni-directionality should not be higher than ±1dB up to
500Hz, ±3dB at 1kHz, ±5dB at 2kHz, ±6dB at 4kHz when excited with octave
bands noise and measured in a free field.
Regarding measurement positions it is important to execute an adequate number
of measurements with different source and receiver positions to characterize the
entire room. For large auditoria a number of measurements from 6 to 10 in
dependance of the number of seats (from 500 to 2000) should be carried out.
The microphone should be placed at a height of 1.2m above the floor at audience
seat locations to be representative of listener’s ear height.
206 15 ACOUSTICAL PARAMETERS