Objective: To investigate the effects of personal listening device use on hearing in young listeners.Methods: Conventional frequency audiometry (0.5-8 kHz) and extended high-frequency audiometry (10-20 kHz) were performed on 120 personal listening device users and 30 normal-hearing young adults. Results:The hearing thresholds in the 3 to 8 kHz frequency range were significantly increased in the personal listening device listeners. The frequency range of the increased thresholds became broad as the exposure duration was increased. Impaired hearing was detected in 14.1% (34 of 240 ears) of ears (> 25 dB HL in one or more frequencies in 0.5-8 kHz). The hearing thresholds of extended high-frequency audiometry in personal listening device users could also be increased even if their hearing thresholds in conventional frequency audiometry were normal. Conclusion: Our results suggest that long-term use of personal listening devices can impair hearing function The data alsoindicate that extended high-frequency audiometry is a sensitive method for early detection of noise-induced hearing loss. SOMMAIRE Objectif: Investiguer les effets du baladeur sur I'audition des jeunes. Methodes: Par audiometrie conventionnelle (0.5-8 kHz) et de hautes frequences (10-20 kHz), nous avons mesure I'audition de 120 utilisateurs de baladeur et 30 jeunes adultes normaux. Resultats: Les seuils d'audition entre 3 et 8 kHz etaient significativement eleves chez les utilisateurs de baladeur. L'dtendue des frequences affectees s'elargit quand la duree d'exposition augmente. L'audition de 14.1% (34 sur 240) des oreilles etait affect^e (> 25 dB HL dans au moins une frequence entre 0.5 et 8 kHz). Le seuil des frequences plus elevees pouvait aussi etre affecte meme si les frequences conventionnelles etaient normales. Conclusion: Nos resultats suggerent que I'utilisation a long terme de baladeurs peut affecter I'audition. Ces donnees indiquent aussi que I'audiometrie etendue aux hautes frequences est une methode sensible pour la detection precoce de la surdite induite par le bruit.Key words: conventional frequency audiometry, extended high-frequency audiometry, noise-induced hearing loss, personal listening devices 7 t is well known that exposure to occupational noise can induce noise-induced hearing loss (NIHL). Recently, attention has turned to nonoccupational or recreational noise that can also induce hearing loss. Although there are many possible sources of potentially hazardous leisure noise, much attention has focused on the effects of personal listening devices (PLDs), such as a Walkman cassette player, a CD player, and an MP3 player.Recent years have seen an increase in the use of PLDs, and many studies have raised concern over their effects on hearing. It has been shown in many reports that the use of a PLD has damaging effects on hearing. Wood and colleagues and Katz and colleagues reported that the maximum available sound pressure levels from a stereo headphone were 124 and 128 dBA, respectively.'"^ Fligor and Cox reported that free-field equ...

Salicylate, one of the most widely used drugs, produces at repetitive high doses reversible tinnitus and hearing loss. Neural correlates of hearing loss have long been established, whereas they remain elusive for tinnitus. The average spectrum of electrophysiological cochleoneural activity (ASECA), a measure of spontaneous auditory nerve activity, was monitored in guinea pigs over weeks of salicylate administration. Auditory nerve compound action potential (CAP) was also recorded to monitor acoustic sensitivity. In the first days of treatment, ASECA decreased acutely during hours after salicylate administration; after several days this decrease could be reduced. Over weeks of treatment the level of ASECA increased progressively. No change in CAP threshold was observed. The ASECA decrease induced by a contralateral broadband noise remained unchanged. At the end of treatment, acoustic tuning of ASECA showed a partially decreased sensitivity. After cessation of treatment the ASECA level returned progressively to initial values. In control animals delivery of an ipsilateral acoustic noise could reproduce the ASECA increase observed in long-term salicylate-treated animals. This white noise was of moderate sound pressure level and it elevated slightly CAP thresholds at high frequencies. These data provide evidence for salicylate-induced ASECA alterations without changes in CAP thresholds, in accord with clinical reports of tinnitus being the first subjective sign of salicylate ototoxicity. The similarities in occurrence, development, reversibility, frequency content, and acoustic level support the idea that ASECA changes, which indicates alterations of spontaneous eighth nerve activity and reflects the presence of salicylate-induced high-pitch tinnitus.

This article describes a comprehensive microstructural characterization of an inertia friction welded joint between nickel-based superalloys 720Li and IN718. The investigation has been carried out on both as-welded and postweld heat-treated conditions. The detailed metallographic analysis has enabled the relation of hardness profiles across inertia-welded alloy 720Li to IN718 and morphological changes of the precipitates present. The work demonstrates that inertia friction welding (IFW) 720Li to IN718 results in a weld free of micropores and microcracks and no significant chemical migration across the weld line. However, substantial differences in terms of grain structure and precipitation phase distribution variations are observed on each side of the dissimilar weld. The high c¢ volume fraction alloy 720Li exhibits a wider heat-affected zone than the mainly c¢¢ strengthened IN718. Alloy 720Li displays only a small hardness trough near the weld line in the as-welded condition due to the depletion of c¢, while c †-strengthened IN718 shows a soft precipitation-free weld region. Postweld heat treatment (PWHT) of the dissimilar weld at 760°C, a typical annealing temperature for alloy 720Li, results in an overmatch of the heat-affected zone in both sides of the weld. The comparison of the as-welded and postweld heat-treated condition also reveals that IN718 is in an overaged condition after the stress relief treatment.

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