Dynaudio AIR 15, Reference Manual

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Appendix: Acoustics
Dynaudio Professional AIR reference manual – 2014-09-28 121
Surround Sound Forum
Surround Sound Forum is a German interest group
composed of the VDT (Verband Deutscher Tonmeister;
Association of German Sound Engineers), the
Institut
für Rundfunktechnik (IRT) and the Schule für Rund-
funktechnik
(SRT). The SSF has prepared calibration
guidelines, which are generally accepted in Europe.
They specify three test signal, which are recorded at
-18 dBFS (RMS).
Signal (only in one channel) PPM level
t < 0,1 ms
PPM level
t < 10 ms RMS level Sound pressure
level SLOW Sound pressure
level SLOW
[dB] [dB] [dB] [dB] [dB(A)]
1 kHz sine -18 -18 -18
Pink noise 20 Hz to 20 kHz -9 -13 -18 82 78
Pink noise 200 Hz to 20 kHz -11 -15 -20 80 78
SMPTE
The corresponding SMPTE standard (RP155) uses
a standard of -20 dBFS for the reference level. Here,
the C-weighted sound pressure level of a 500 to 2 kHz
noise signal ends up at 83 dB.
Calibration of cinema systems
In a cinema, the listeners are sitting far from the moni-
tors. Presumably, the majority sits in the diffuse sound
field. Attempts are made to establish a diffuse sound
field from the surround monitors. Accordingly, when the
sound pressure is measured inside the cinema or in a
mixing theatre, it must be averaged over many differ-
ent measurement locations. The typical basis for the
majority of the standards is measuring at four or more
locations. If there are different areas for the audience
(for example main floor and balcony), measurements
should be made in at least four locations in each area.
Before these measurements can be made, the sys-
tem’s frequency response must also be in order.