- Limit output to frequency range given by fLower and fUpper (if supplied)
- Enable noise models to be run outside of $FOAM_CASE directory
  - if relative paths are used, $FOAM_CASE is prepended to the noise
    dict and input file names
- Enable output to be customised, e.g.

    // Optional write options dictionary (all default to 'yes')
    writeOptions
    {
        writePrmsf  no;
        writeSPL    yes;
        writePSD    yes;
        writePSDf   no;
        writeOctaves yes;
    }