Comparison of nonlinearities between different earphone models is not directly possible due to their different sensitivities and the high dynamics in the transducer's frequency response. Also, nonlinearities are highly dependent on the level of the excitation signal. An approach to overcome these differences and allow for fair comparison is proposed. The method is based on filtering commonly used stimuli like pink sweeps with a linear correction filter. This filter is obtained by a measurement at low input levels where the transducer shows linear behavior. The nonlinear response is then measured at different levels and THD is computed. In this way the non-linearity or different transducers can be compared directly. Some examples demonstrating the performance of consumer grade earphones are presented and discussed. The results show that nonlinearities mainly appear for low frequency excitation.
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