The Temporal Modulation Transfer Function (TMTF) for normally-hearing children and adults using a bandpass noise carrier

A psychophysical method often employed to measure sensitivity to sound envelope fluctuations (temporal acuity) is to determine a listener’s sensitivity to sinusoidal amplitude modulations of a sound as a function of modulation frequency (the temporal modulation transfer function; TMTF). The TMTF has a low-pass characteristic and its cut-off frequency is a measure of temporal resolution (Viemeister, 1979). Studies of the developmental trajectory of the TMTF (e.g., Hall and Grose, 1994) indicate that whilst the thresholds for the detection of modulation are uniformly higher across both low and high modulation rates in children than in adults, the derived cut-off for the function does not vary between children aged 4-5 years and adults. This suggests that although temporal resolution appears to be adult-like by 4-5 years of age, children remain less sensitive overall to modulation detection than adults. The goals of these experiments were to determine how sensitivity to modulation detection changes as a function of age and also with presentation mode (headphones and loudspeakers). Loudspeaker presentation was included to develop baselines for later comparison with children using hearing aids and cochlear implants. Three experiments have been conducted. All experiments used an octave-wide noise-band carrier impressed with sinusoidal amplitude modulation. In the first and second experiments the subjects were children aged between 5 and 14 years old and the third experiment was carried out with adults. In the first experiment the TMTF was measured in 45 children with stimuli centre frequencies(CF) of 1,2 and 4 kHz via headphones. In the second experiment the TMTF was measured at a centre frequency (CF) of 2kHz in 53 children via loudspeaker. In the final experiment TMTFs were measured at CFs of 1 and 2kHz with 6 adults, via headphones and also via loudspeaker. The results showed that the youngest group of children (5 to 6 years) were less sensitive to modulation detection than the older children. Even by 14 years old the children were less sensitive to modulation detection than adults. The TMTF measured via loudspeaker indicated that sensitivity at high rates of modulation was reduced. Acknowledgements This work was funded by Deafness Research UK