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The sound strength, or level, is defined as
(5)
where h10(t) is the free-field response of the (assumed omni-directional) source at a distance of 10 m, filtered in the same way as the impulse response itself.
The upper integration limit in the numerator is taken as the truncation point determined in the decay curve formation, or the end of the impulse response, according to the integration option specified. If compensation for truncated energy is calculated, this is taken into account as well to increase accuracy.
The reference level is:
(6)
There are various ways of specifying or estimating the reference level, and this is governed by the choices in the direct energy options dialog. The method is common for strength (G) and late lateral strength (LG).
The dialog shown below is displayed.
First select what type of strength you wish to compute. Select in the list shown below
Each selection will display an explanation as shown in the dialog above. It should be noted that the ISO 3382 standard requires a fairly elaborate calibration measurement of the sound source to provide the reference energy at 10 m. Only the option ISO3382 Strength gives the possibility of obtaining G-values according to the ISO 3382 recommendations.
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