Sound Level Measurements in Berthing Areas of an Aircraft Carrier

Background Personnel assigned to aircraft carriers work and live in environments where hazardous noise areas and hearing recovery spaces such as sleeping areas are in close proximity to one another. Hazardous noise exposure occurring during on-duty time periods and elevated noise levels during off-duty periods in sleeping areas may be prohibiting adequate hearing recovery, thus potentially leading to hearing loss and may lead to adverse effects on sleep, leading to crew-member fatigue. This investigation characterizes Equivalent sound level (Leq) and standardized octave band center frequency noise levels according to berthing (sleeping) area location during flight operation and nonflight operation time periods on a US Navy aircraft carrier. In addition, the investigation compares noise measurements in sleeping areas to noise levels associated with auditory rest and poor sleep quality and quantity. Methods Noise levels were measured in berthing areas aboard a US Navy Nimitz-class aircraft carrier during a routine at-sea period. Sixty noise measurements were taken in eight sleeping locations. Leq in decibels ‘A’ weighted (dBA) and noise levels from 16 to 16 000 Hz in (dB) were measured during flight operations [Leq (flt ops)] and nonflight operations [Leq (nonflt ops)]. Leq was also measured according to sleep area shipboard locations of forward (FWD) Leq (FWD), middle (MID) Leq (MID), and rear (AFT) Leq (AFT). These data were compared to the 70 dBA American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for effective quiet areas. In addition, these data were compared to noise levels associated with hearing loss and sleep parameters. Statistical analysis was conducted with R version 3.5.2 using an alpha level of 0.05. Results Leq (flt ops) in sleeping areas was a statistically significant (P < 0.05) 6.4 dBA higher than the Leq (nonflt ops). Leq (FWD) and Leq (MID) in sleeping areas was a statistically significant (P < 0.05) 15.2 and 15.0 dBA higher, respectively, than the Leq (AFT) noise levels. Mean noise levels at standardized center (1/1) octave bands were highest between 500 and 4000 Hz, ranging from 65.2 to 69.8 dB. A total of 72% of all area Leq measurements exceeded the 70 dBA ACGIH TLV classified as effective quiet to allow for temporary threshold shift recovery. All noise measurements exceeded the World Health Organization’s noise threshold where adverse effects on sleep begin. Discussion/Conclusions Results suggest that sleeping area location in close proximity to relatively high noise sources and activities occurring on an aircraft carrier (i.e. flight operations) increase noise levels in sleeping areas. These findings raise serious concerns since high noise exposures both on duty and during off-duty/sleeping periods may inhibit auditory recovery from hazardous noise exposures. In addition, results suggest noise levels in sleeping areas are high enough to evoke negative sleep effects.

The Sensitivity of Adolescent School-Based Hearing Screens Is Significantly Improved by Adding High Frequencies

High frequency hearing loss (HFHL), often related to hazardous noise, affects one in six U.S. adolescents. Yet, only 20 states include school-based hearing screens for adolescents. Only six states test multiple high frequencies. Study objectives were to (1) compare the sensitivity of state school-based hearing screens for adolescents to gold standard sound-treated booth testing and (2) consider the effect of adding multiple high frequencies and two-step screening on sensitivity/specificity. Of 134 eleventh-grade participants (2013–2014), 43 of the 134 (32%) did not pass sound-treated booth testing, and 27 of the 43 (63%) had HFHL. Sensitivity/specificity of the most common protocol (1,000, 2,000, 4,000 Hz at 20 dB HL) for these hearing losses was 25.6% (95% confidence interval [CI] = [13.5, 41.2]) and 85.7% (95% CI [76.8, 92.2]), respectively. A protocol including 500, 1,000, 2,000, 4,000, 6,000 Hz at 20 dB HL significantly improved sensitivity to 76.7% (95% CI [61.4, 88.2]), p < .001. Two-step screening maintained specificity (84.6%, 95% CI [75.5, 91.3]). Adolescent school-based hearing screen sensitivity improves with high frequencies.

Research Directions for Examining Hazardous Noise at the Theater

Hazardous noise in workplaces is a leading cause of preventable hearing loss among American workers. Traditionally, studies of hazardous noise have been conducted in industrial and manufacturing settings. However, there exists a void in research concerning the prevalence of hazardous noise and the means by which HF/E experts can work to mitigate hazardous noise in less commonly researched settings, such as movie theaters. In this paper, I illustrate and discuss why hazardous noise should be investigated in this setting and highlight relevant research questions associated with investigating noise in theater environments.