The Noise tab (figure 95) contains all the information specific to the noise modelling of this turbine type and includes the following fields:
•Total sound power level at source [dB(A)]. This is the overall A-weighted sound power level at the turbine nacelle as calculated from a noise test near the ground.
•Octave band sound power levels [dB(A)]. These are the sound power levels broken down by octave. This information is used to estimate turbine noise attenuation by octave.
If you do not have data for the 31hz or 16khz bands then you can leave them as zero or even put them as -999 (as zero dB is not the absence of noise). Using the grid interface below it is possible to add sound power levels at multiple different hub height velocities. If only one wind speed is entered, then these values will be used throughout. If two or more wind speeds are entered, then sound power levels will be linearly interpolated between these wind speeds and outside the range then the sounds power levels at the closest wind speed value will be used. The wind speed values here do not need to match the wind speed values used in the noise model.
It is generally assumed that the input sound power levels, and the corresponding output sound pressure levels, will be A-weighted. This means that the absolute octave band levels have been adjusted to account for the way the human ear perceives noise. ISO9613 is intended to be used with A-weighted sound power levels and absolute sound power levels can be easily converted. If, for some reason, unweighted decibels are entered in this dialog, the output should be considered to be also in unweighted decibels.