Audio transformers are designed to operate within or beyond the audio frequency range. For example, in high-fidelity circuits, the frequency range might be from 10 Hz to 30, 000 Hz or higher. Typical applications are input, output, and impedance matching transformers. There are several important design parameters to consider: frequency response, impedances, power level, total harmonic distortion, value of DC in windings, hum-reduction level, longitudinal balance and insertion loss.