Noise-Induced Hearing Loss and its Prevention: Current Issues in Mammalian Hearing

The perception of ultrasonic vocalizations by laboratory mice following intense noise exposures

Noise-induced hearing loss interacts with age, sex, and listening conditions to affect individuals' perception of ecologically relevant stimuli like speech. The present experiments assessed the impact of age and sex on vocalization detection by noise-exposed mice trained to detect a downsweep or complex ultrasonic vocalization in quiet or in the presence of a noise background. Daily thresholds before and following intense noise exposure were collected longitudinally and compared across several factors. All mice, regardless of age, sex, listening condition, or stimulus type showed their poorest behavioral sensitivity immediately after the noise exposure. There were varying degrees of recovery over time and across factors. Old-aged mice had greater threshold shifts and less recovery compared to middle-aged mice. Mice had larger threshold shifts and less recovery for downsweeps than for complex vocalizations. Female mice were more sensitive, had smaller post-noise shifts, and had better recovery than males. Thresholds in noise were higher and less variable than thresholds in quiet, but there were comparable shifts and recovery. In mice, as in humans, the perception of ecologically relevant stimuli suffers after an intense noise exposure, and results differ from simple tone detection findings.

Preclinical prospects of investigational agents for hearing loss treatment

INTRODUCTION

: Hearing loss has a high prevalence, with aging, noise exposure, ototoxic drug therapies, and genetic mutations being some of the leading causes of hearing loss. Health conditions such as cardiovascular disease and diabetes are associated with hearing loss, perhaps due to shared vascular pathology in the ear and in other tissues.

AREAS COVERED

: Issues in the design of preclinical research preclude the ability to make comparisons regarding the relative efficacy of different drugs of interest for possible hearing loss prevention or hearing restoration. This has not slowed the advancement of candidate therapeutics into human clinical testing. There is a robust pipeline with drugs that have different mechanisms of action providing diverse candidate therapies and opportunities for combination therapies to be considered.

EXPERT OPINION

: Much of the preclinical research literature lacks standard study design elements such as dose response testing, and lack of standardization of test protocols significantly limits conclusions regarding relative efficacy. Nonetheless, the many positive results to date have supported translation of preclinical efforts into clinical trials assessing potential human benefits. Approval of the first hearing loss prevention therapeutic is a major success, providing a pathway for other drugs to follow.

On the definition of noise

Urbanization has exposed people to extreme sound levels. Although researchers have investigated the ability of people to listen, analyze, and distinguish sound, the concept of noise has not been clearly articulated from a human perspective. The lack of knowledge on how people perceive noise limits our capacity to control it in a targeted manner. This study aimed to interpret the definition of noise from the public perspective based on a grounded theory approach. Seventy-eight participants were interviewed about noise, and four categories of perceived understanding of noise were identified: challenges, definitions of noise, opportunities, and action. As one of the challenges, urbanization is associated with increased noise levels around the human environment. In terms of definition, perceiving sound as noise is considered to be a result of the complex and dynamic process that includes sound, the environment, and humans. Sound and humans interact with the environment. In terms of opportunities, noise may have positive roles on certain occasions, dispelling the misconception that noise is exclusively negative. In addition, we found that noise perception has gradually shifted from noise control to noise utilization. In terms of action, noise can be controlled at the sound sources, susceptible target groups, susceptible behaviors and states, locations, and times where noise is perceived with high frequency. In this study, we investigated several aspects of noise, ranging from noise control, soundscape definition, and 'soundscape indices' (SSID) integration and application. Our findings provide an additional basis for developing better definitions, control, and utilization strategies of noise in the future, thereby improving the quality of the sound environment.

Occupational Noise on Floating Storage and Offloading Vessels (FSO)

The purpose and scope of this paper are to provide guidance of the potential impacts of being subjected to high level noise recorded on 1st generation (30 years old) floating storage and offloading vessels (FSO) in sector offshore. The international community recognizes that vibroacoustic impacts from commercial ships may have negative consequences for both humans (worker's) and marine life, especially marine mammals. As regards the effect of noise on human health, there are legal requirements imposing the noise exposure control on personnel working on ships. The acceptable noise exposure standards are established in European Union Directive 2003/10/EC (2003), the NOPSEMA Regulation (2006), the Maritime Labor Convention (MLC) guidelines (2006), and the recommendations of the International Maritime Organization IMO contained, e.g., IMO MEPC.1/Circ.833 (2014). These regulations inform employers and employees what they must do to effectively protect both the marine environment and the health and life safety of workers employed in the maritime industry offshore. This study also presents an analysis of the results of noise measurements carried out on exemplary 1st generation FSO units.