Estimating human hearing thresholds using potentials that follow sinusoidally amplitude modulated (SAM) tones

Binaural sinusoidally amplitude modulated (SAM) tones were used to evoke potentials from the scalp that followed the modulation envelope. It is examined whether this amplitude-modulation following response (AMFR), with modulation frequencies near 40 Hz, can be used to estimate frequency-specific hearing thresholds by two methods: (1) decreasing sound intensity until the AMFR could no longer be evoked and (2) linearly extrapolating the amplitude-intensity function to a zero volt response. Both methods yielded estimates that were within 15 dB of the behavioral threshold. A method that could identify bilateral sensitivity differences of about 20 dB was also developed. This involved comparing AMFRs to binaural SAM tones when their envelopes were in- or out-of-phase. Threshold estimates suggest that the AMFR may be an effective tool for assessing hearing thresholds across the audiometric range of frequencies