Temporary threshold shift after impulse-noise during video game play: laboratory data

Abstract

Objective: Prevention of temporary threshold shift (TTS) after laboratory-based exposure to pure-tones, broadband noise, and narrowband noise signals has been achieved, but prevention of TTS under these experimental conditions may not accurately reflect protection against hearing loss following impulse noise. This study used a controlled laboratory-based TTS paradigm that incorporated impulsive stimuli into the exposure protocol; development of this model could provide a novel platform for assessing proposed therapeutics.

Design: Participants played a video game that delivered gunfire-like sound through headphones as part of a target practice game. Effects were measured using audiometric threshold evaluations and distortion product otoacoustic emissions (DPOAEs). The sound level and number of impulses presented were sequentially increased throughout the study.

Study sample: Participants were normal-hearing students at the University of Florida who provided written informed consent prior to participation.

Results: TTS was not reliably induced by any of the exposure conditions assessed here. However, there was significant individual variability, and a subset of subjects showed TTS under some exposure conditions.

Conclusions: A subset of participants demonstrated reliable threshold shifts under some conditions. Additional experiments are needed to better understand and optimize stimulus parameters that influence TTS after simulated impulse noise.

Figure 1

Sound levels shown here were measured using a Brüel & Kjær Type 4153 Artificial Ear in combination with PULSE spectrum analyzer with levels sampled at 0.125 sec (1/8 sec) intervals. Variability within a given stimulus condition is a function of the challenges inherent to accurately capturing peak SPL for brief impulse-like signals. The individual acoustical signal was routed from a Tucker-Davis-Technology RX6 to a stereo receiver (Onkyo TX-8555) that controlled signal amplitude, which ranged from 88 dB peak SPL (Figure 1A) to 108 dB peak SPL (Figure 1C) using 5 dB increments, and 111 dB peak SPL (Figure 1D) to 117 dB peak SPL (Figure 1F) using 3-dB increments. Approximately 20 seconds are shown for each stimulus level; the presentation rate varied as a function of the rate at which the Wii^® zapper was triggered during the acoustic measurements. Presentation was triggered by subject response using the Wii^® zapper. The sound spectrum for a single impulse is shown in Figure 1G, and the detailed time sample for a single impulse is shown in Figure 1H.

Figure 2

There was no reliable effect of game play on pure-tone air conduction thresholds at either 2-min or 15-min post game play; the average change in thresholds was less than 5 dB regardless of exposure condition. Data were collected for 52 different exposure conditions (see Table 1). Exposure conditions shown here include the three highest test levels (2A–2C: 111 dB peak; 2D–2F: 114 dB peak; 2G–2I: 117 dB peak). The highest number of impulses presented within each sound level are shown (2C, 2F: 3200 shots; 2B, 2E: 1600 shots; 2A, 2D: 800 shots; 2I: 200 shots; 2H: 100 shots; 2G: 50 shots). Data are Mean ± S.E., to illustrate confidence with respect to the mean change.

Figure 3

Within subjects exposed to a given noise condition, there was significant individual variability. Individual subjects are plotted in panels 3A–3J, one subject per panel. Panels are sorted such that subjects with smaller changes are followed by subjects with larger changes. Subjects were followed until complete recovery was observed; subjects with larger threshold shifts were followed for longer periods than subjects with smaller shifts, based on time to recovery. The longest post-game monitoring interval was 2 hrs 15 mins (Figure 3J).

Figure 4

There was no reliable effect of game play on distortion product otoacoustic emission (DPOAE) amplitude 15-min post game play. Data were collected for 52 different exposure conditions (see Table 1). Exposure conditions shown here include the three highest test levels (4A–4C: 111 dB peak; 4D–4F: 114 dB peak; 4G–4I: 117 dB peak). The highest number of impulses presented within each sound level are shown (4C, 4F: 3200 shots; 4B, 4E: 1600 shots; 4A, 4D: 800 shots; 4I: 200 shots; 4H: 100 shots; 4G: 50 shots). Stimulus conditions are identical to those in Figure 2; subjects are the same in Figures 2 and 4. Data are Mean ± S.E., to illustrate confidence with respect to the mean change.

Figure 5

Within subjects exposed to a given noise condition, there was little individual variability with respect to changes in DPOAE amplitude. Individual subjects are plotted in panels 5A–5J, one subject per panel. Panels are sorted such that subjects with smaller changes in thresholds are followed by subjects with larger changes in thresholds, based on the data shown in Figure 3. Subjects are the same in Figures 3 and 5. However, only the DPOAE data from the most vulnerable ear are shown.