Time-efficient measures of auditory frequency selectivity

Abstract

Objective: The objective of this study was to compare two recently proposed methods for fast measurements of psychophysical tuning curves (fast-PTCs) in terms of resulting tuning curve features and training effects.

Design: Fast-PTCs with swept-noise (SN) and gated-noise (GN) maskers were measured at signal frequencies of 500, 1000, 2000, and 4000 Hz. The effect of amplitude modulating the signal in the GN condition was evaluated. Two PTC runs were obtained for each condition to assess training effects.

Study sample: Eight normally-hearing young adults participated in the study.

Results: The SN and GN methods resulted in similar estimates of frequency selectivity when training effects were considered. Amplitude modulating the tone in the GN method reduced the effect of training. On average, SN-PTCs were most repeatable compared to the two other methods and they were not affected by training. Estimation of the shift in the PTC tip frequency was not affected by the measurement method or training effects. Fast-PTC methods resulted in similar estimates of tuning as compared to published notched-noise data.

Conclusions: The SN method and the GN procedure with amplitude modulated signals allowed for time-efficient estimation of frequency selectivity that was unaffected by training.

Fig. 1

An example of a fast PTC (thin line) smoothed with the LOESS algorithm with smoothing parameter α set at .25 (bold line).

Fig. 2

The PTCs collected with the SN-PTC, GN-PTC and GN-AM-PTC methods for subject NH18. The filled squares indicate the probe level and frequency. Data for the first run are shown.

Fig. 3

Mean equivalent rectangular bandwidths (ERB) derived from the data collected using SN-PTC (squares), GN-PTC (circles), and GN-AM-PTC (triangles) methods for run 1 as a function of the signal frequency. Data points are offset slightly for clarity. Error bars represent ±1 standard deviation.

Fig. 4

Mean shifts in the tip frequency of the PTC (in percent of signal frequency) for the SN-PTC (squares), GN-PTC (circles) and GN-AM-PTC (triangles) methods (run 1) as a function of the signal frequency. The total represents the global mean across f_signal for a given method. Data points are offset slightly for clarity. Error bars represent ±1 standard deviation.

Fig. 5

Mean Q_ERB for SN-PTCs obtained in run 1 (squares). The Q_ERBs of auditory filters derived with the simultaneous masked notched-noise paradigm are shown for comparison: the thick solid line corresponds to Glasberg and Moore's predictions (1990) and the dashed line with diamonds was replotted from Fig. 7 (signal level of 10 dB SL) of Oxenham and Shera (2003). Data points are offset slightly for clarity.