Self-report and long-term field measures of MP3 player use: how accurate is self-report?

OBJECTIVE: This study was designed to evaluate the usage patterns of portable listening device (PLD) listeners, and the relationships between self-report measures and long-term dosimetry measures of listening habits. DESIGN: This study used a descriptive correlational design. STUDY SAMPLE: Participants (N = 52) were 18-29 year old men and women who completed surveys. A randomly assigned subset (N = 24) of participants had their listening monitored by dosimetry for one week. RESULTS: Median weekly noise doses reported and measured through dosimetry were low (9-93%), but 14.3% of participants reported exceeding a 100% noise dose weekly. When measured by dosimetry, 16.7% of participants exceeded a 100% noise dose weekly. The self-report question that best predicted the dosimetry-measured dose asked participants to report listening duration and usual listening level on a visual-analog scale. CONCLUSIONS: This study reports a novel dosimetry system that can provide accurate measures of PLD use over time. When not feasible, though, the self-report question described could provide a useful research or clinical tool to estimate exposure from PLD use. Among the participants in this study, a small but substantial percentage of PLD users incurred exposure from PLD use alone that increases their risk of music-induced hearing loss.

Failure to unlearn the precedence effect.

Studies of the precedence effect using two binaural clicks have shown that listeners' ability to discriminate changes in the interaural time difference (ITD) of the lagging click is much poorer than that for the leading click [e.g., Zurek, J. Acoust. Soc. Am. 67, 952-964 (1980)]. This difference is thought to reflect an auditory process that suppresses directional information from the lagging sound and attributes greater perceptual weight to directional information contained in the leading one. A report by Saberi and Perrott [J. Acoust. Soc. Am. 87, 1732-1737 (1990)] suggested that listeners can "unlearn" this suppression of the lag's directional information after training with an adaptive psychophysical procedure involving 100 reversals and extremely small step sizes. Here, an attempt was made to find a similar effect using psychophysical procedures that are more common to precedence studies. Eight subjects were rigorously trained on the precedence task using either a blocked procedure or an adaptive procedure to vary ITD. Listeners showed no sign of unlearning. After 9-31 h of participating in the task, all subjects maintained high lag just-noticeable differences (jnd's) and low single source jnd's. This failure to train away the precedence effect (as manifested in discrimination suppression) suggests that directional information contained in the lagging source is not easily accessed. Several possible explanations for the discrepancies between the present study and Saberi and Perrott's finding are discussed.