The C-weighting characteristic is realized by two low-frequency poles at frequency f1, two high-frequency poles at frequency f4, and two zeros at 0 Hz. With these poles and zeros, the power response for the C-weighting characteristic, relative to the response at the reference frequency fr of 1 kHz, will be down by D2 = 1/2 (approximately –3 dB) at fL = 101.5 Hz and fH = 103.9 Hz.