Two-Point Method for Measuring the Temporal Modulation Transfer Function

The temporal modulation transfer function (TMTF) has been proposed to estimate the temporal resolution abilities of listeners with normal hearing and listeners with hearing loss. The TMTF data of patients would be useful for clinical diagnosis and for adjusting the hearing instruments at clinical and fitting sites. However, practical application is precluded by the long measurement time of the conventional method, which requires several measurement points. This article presents a new method to measure the TMTF that requires only two measurement points.

Experiments were performed to estimate the TMTF of normal listeners and listeners with hearing loss to demonstrate that the two-point method can estimate the TMTF parameter and the conventional method. Sixteen normal hearing and 21 subjects with hearing loss participated, and the difference between the estimated TMTF parameters and measurement time were compared.

The TMTF parameters (the peak sensitivity Lps and cutoff frequency fcutoff) estimated by the conventional and two-point methods showed significantly high correlations: the correlation coefficient for Lps was 0.91 (t(45) = 14.3; p < 10) and that for fcutoff was 0.89 (t(45) = 13.2; p < 10). There were no fixed and proportional biases. Therefore, the estimated values were in good agreement. Moreover, there was no systematic bias depending on the subject's profile. The measurement time of the two-point method was approximately 10 min, which is approximately one-third that of the conventional method.

The two-point method enables the introduction of TMTF measurement in clinical diagnosis.