The correct level of presentation is important for all kinds of auralisation in order to be as realistic as possible. The method applied in ODEON is approximate, aiming at the A-weighted sound pressure level to match that of the calculation result of the same simulation. A pink noise signal is applied for the calibration. The trick is to create modified versions of the input signals used for auralisation in such a way that the input signals have the same A-weighted level. In order to ensure a proper calibration it is necessary to know the sound power level of the sound source used as input for the auralisation. This can be difficult in some cases and may be the major source of uncertainty in the calibration. Next step is to look at the room simulation that produces the auralisation, and to choose a source-receiver combination to be used for the calibration. The relation between the sound power of the source and the sound pressure level in the receiver position is a result of the room acoustic simulation. The third step is to replace the anechoic recording to be used for the auralisation with a pink noise signal that is more suited for the calibration, and to note the level difference introduced by this shift of input signal. Finally, it may be advantageous to apply a correction to the calibration signal in order to get a calibration level that is convenient for the purpose, e.g. 80 dB.