In a noise-measuring set, a noise weighting based on an amplitude-frequency characteristic that is flat over a frequency range that must be stated. Note 1: Flat noise power is expressed in dBrn (f1 - f2) or in dBm (f1 - f2. ) Note 2: "3-kHz flat weighting" and "15-kHz flat weighting" are based on amplitude-frequency characteristics that are flat between 30 Hz and the frequency indicated.