Every person is having different audible, due that result are not very favorable with Head Phone. Go for Digital Null Detector Headphones are one of the simplest and most commonly used balance detectors in AC bridges. They consist of a pair of earphones connected to the bridge circuit. When the bridge is balanced, the null point is reached, and no current flows through the headphones, resulting in silence. Impedance : Lower-impedance headphones require less power to deliver high audio levels.