Extended high-frequency thresholds in college students: effects of music player use and other recreational noise

Abstract

Background: Human hearing is sensitive to sounds from as low as 20 Hz to as high as 20,000 Hz in normal ears. However, clinical tests of human hearing rarely include extended high-frequency (EHF) threshold assessments, at frequencies extending beyond 8000 Hz. EHF thresholds have been suggested for use monitoring the earliest effects of noise on the inner ear, although the clinical usefulness of EHF threshold testing is not well established for this purpose.

Purpose: The primary objective of this study was to determine if EHF thresholds in healthy, young adult college students vary as a function of recreational noise exposure.

Research design: A retrospective analysis of a laboratory database was conducted; all participants with both EHF threshold testing and noise history data were included. The potential for "preclinical" EHF deficits was assessed based on the measured thresholds, with the noise surveys used to estimate recreational noise exposure.

Study sample: EHF thresholds measured during participation in other ongoing studies were available from 87 participants (34 male and 53 female); all participants had hearing within normal clinical limits (≤25 HL) at conventional frequencies (0.25-8 kHz).

Results: EHF thresholds closely matched standard reference thresholds [ANSI S3.6 (1996) Annex C]. There were statistically reliable threshold differences in participants who used music players, with 3-6 dB worse thresholds at the highest test frequencies (10-16 kHz) in participants who reported long-term use of music player devices (>5 yr), or higher listening levels during music player use.

Conclusions: It should be possible to detect small changes in high-frequency hearing for patients or participants who undergo repeated testing at periodic intervals. However, the increased population-level variability in thresholds at the highest frequencies will make it difficult to identify the presence of small but potentially important deficits in otherwise normal-hearing individuals who do not have previously established baseline data.

Figure 1

A. Average EHF thresholds measured from current subjects at frequencies from 8–16 kHz closely matched the RETSPL sound levels identified as normal hearing threshold level in ANSI S3.6 1996 Annex C. Figure 1B. EHF thresholds measured from current subjects tested at frequencies from 8–16 kHz were consistent with those reported by Schechter et al. (1986; mean and SD for subjects ages 16–20 years old, from their Tables I and II), Green et al. (1987; mean and SD for 37 subjects ages 18–26, from their Table II), Stelmachowicz et al. (1989; mean and SD for 160 subjects ages 10–19, from their Table I), and Frank (2001; mean and SD for 100 subjects ages 18–25, from his Table I).

Figure 2

Factors that may influence thresholds include ear (2A,2B), gender, (2C,2D), and age (2D,2E). Ear. For these 87 subjects, small but statistically reliable differences were detected for right versus left comparisons at 4 and 6 kHz (2A), with no differences in pure-tone average threshold at 0.5, 1 and 2 kHz (LFPTA), 3, 4, and 6 kHz (HFPTA), or 10, 12, 14, and 16 kHz (EHFPTA) (2B). The thresholds defined as “0-dB HL” in the ANSI standard are plotted for comparisons purposes in Figure 2A, and pure-tone average thresholds are plotted using the dB HL convention (2B). Gender. Small but systematic differences were observed when males were compared to females, with males having poorer hearing at 0.5, 3, 4, 6, 10, and 12 kHz (2C). The effect of gender was observed for HFPTA comparisons, but not LFPTA or EHFPTA (2D). Age. There was a small but statistically reliable elevation in threshold at 8 kHz as a function of age (2E). Deficits did not extend to PTA comparisons (2F).

Figure 3

A. There was no relationship between pure-tone-average threshold and number of noise sources reported by the subjects. Figure 3B. There was no relationship between thresholds at individual EHF frequencies and number of noises sources reported by the subjects.

Figure 4

A. There was a statistically reliable relationship between PTA threshold and long-term use of a music player device, defined as greater than 5-years of device use, using the EHFPTA metric (average threshold at 10, 12, 14, and 16 kHz). Figure 4B. Single frequency comparisons revealed statistically reliable differences at 10 and 14 kHz. Group differences at 12 and 16 kHz were not statistically reliable at the α=0.05 level. Figure 4C. Average PTA thresholds at EHF frequencies were reliably worse in those subjects that used their devices in noisy backgrounds (p<0.05). Figure 4D. Single frequency comparisons revealed statistically reliable differences at 12, 14, and 16 kHz. Figure 4E. Average PTA threshold for low frequencies (0.5, 1, 2 kHz) was reliably worse in those subjects that could not hear others speaking to them (p<0.05) with a similar trend observed for conventional high frequencies (3, 4, and 6 kHz: HFPTA p=0.055). Figure 4F. Single-frequency comparisons revealed statistically reliable differences at 1, 2, 3 and 4 kHz.