No abstract

Anew automated method termed as 'NewEarly Warning Test (NEWT)' has been designed to provide automatic auditory threshold monitoring in individuals exposed to high noise levels. The NEWT method is incorporated inside an active communication earplug called Quietpro®, which has high attenuation characteristics for background noise. The NEWT measures auditory thresholds using at wo-peep pure tone stimulus. The aim of the present study wast oe stablish the calibration values required for the NEWT method by comparing the deviations in the thresholds obtained in the NEWT against standard pure tone audiometry (PTA ). Sixteen subjects (twenty-eight ears)with normal hearing participated in this study.Auditory thresholds were measured using the NEWT and PTAfor frequencies of 1, 3, 4and 6kHz. It wasobserved that there wasnosignificant difference in inter-subject variability.Because this inter-subject variability also included intra-subject variability,results suggested that the NEWT method had at least not anyh igher intra-subject variability than the PTA. Results of the present study will be used to calibrate the NEWT method, which helps in regular monitoring of hearing status in individuals exposed to noise. These results might have important implications to further evaluate the NEWT method on various groups of population having different degrees of hearing loss.

During the development of an intelligent hearing protection and communication system the attenuation of two different earplugs were measured. Both earplugs were measured separately and in combination with earmuffs. Foam earplugs and custom-moulded silicone earplugs were both used. The hearing protection system in question is able to measure the ear canal with respect to leaks. If a leak is detected, the system will warn the user.The measurements show that the foam plug gives higher attenuation than the silicone plug at all frequencies, but particularly at frequencies below 2 kHz. It has a steadily increasing attenuation from 30 dB -43 dB over the frequency range 125 Hz -8 kHz. The silicone plug attenuates around 26 dB, from 125 Hz -1 kHz. Above this range, the attenuation increases to approximately 40 dB. With extra earmuffs added, the attenuation is 40 dB or better at all frequencies except 125 Hz, and the two plugs offer nearly identical protection.The results show that the mean and standard deviation of the attenuation for the foam earplug is as good as for an optimally fitted earplug. In the case of the silicone earplug, the mean attenuation is comparable to a typical custom earplug, but the standard deviation is better than comparable earplug. This finding is a result of the leakage control acting as a 'supervisor' in the fitting of the earplugs.

The ideal hearing protection device (HPD) should ensure a safe level of noise exposure while at the same time providing a high degree of situational awareness. This paper describes the core elements of a digital signal processing based HPD representing such a comprehensive approach to hearing protection. A set of features has been designed to offer optimal protection. First, a built-in automatic sealing control warns the user if the appropriate passive attenuation is not achieved. Second, the hear-through functionality ensures that the user is not overprotected such that situational awareness is compromised, while at the same time the level of the reproduced sound is kept within safe limits. This functionality is combined with instantaneous impulse compression. Further adding to the HPD scheme, digital active noise reduction is used for the attenuation of low-frequency sound. Based on the performance characteristics of any given HPD, traditional approaches to noise exposure control use some highly uncertain estimates of the HPD attenuation, often including de-rating schemes. The HPD described here, on the other hand, offers the option to monitor in-ear noise exposure. This offers an additional barrier against noise induced hearing loss by warning the user in situations where he is approaching over-exposure from noise.

Objectives/Scope: The objective of this research project is to study the connection between noise exposure and possible hearing damage. A key feature in the project is QUIETPRO, an active hearing protection device manufactured by Honeywell. Methods, Procedures, Process:QUIETPRO is an in-the-ear hearing protection device, HPD. It features among other things a special test routine that is activated after the earplugs have been fitted into the ear canal. Improper insertion is detected. A warning signal is given unless sufficient protection has been verified. The noise levels at the eardrum and outside the earplug are logged continuously throughout the working day. The actual noise dose the user has been exposed to is calculated in real time, and an audible alarm signal is activated if the dose exceeds a pre-set limit. QUIETPRO also features an automatic hearing test that can be activated on demand for instance before and after a working day. The test is simple and fast (typically 2 minutes duration) and it is self-administered. Data from the hearing test together with stored noise exposure data is uploaded to a database at the end of the working day. Results, Observations, Conclusions:The system has been used for some time at two Statoil offshore installations. Personnel exposed to especially high noise levels, typically 100-110 dBA and above (heli-deck crew and maintenance personnel doing sand blasting and needle picking) have been using QUIETPRO regularly. This paper will present examples of performance data and demonstrate how the exposure and audiometry data can be used to detect the onset of a hearing damage at a very early stage.