High-frequency air conduction audiometry. Testing of a new low impedance circumaural transducer system in normal young persons

Extended high-frequency audiometry in patients with acoustic trauma

OBJECTIVES

The aim of this study was to examine extended high-frequency (EHF) hearing in patients with acoustic trauma.

DESIGN

A prospective, case-control study in a group of soldiers with acoustic trauma caused by shooting practice during basic training.

SETTING

Tertiary referral centre.

PARTICIPANTS

A total of 39 young soldiers hospitalized for hearing loss and tinnitus following exposure to weapon impulse noise were studied. Conventional audiometry in the frequency range 0.25-8 kHz and EHF audiometry in the frequency range 9-20 kHz were performed, both on admittance and before discharge. Thirty healthy recruits of similar age and sex were used as controls.

MAIN OUTCOME MEASURES

Pure-tone threshold changes documented by conventional and EHF audiometry.

RESULTS

The most significant differences in pure-tone thresholds on initial testing were found in the frequency range 0.25-11.2 kHz, and especially in the 4-8 kHz region. Reduction in thresholds across most frequencies was observed after treatment, although recovery was partial in most cases.

CONCLUSIONS

The EHF audiometry adds no significant additional information to conventional pure-tone audiometry in assessing and monitoring noise-induced hearing loss.

Temporary threshold shift in military pilots measured using conventional and extended high-frequency audiometry after one flight

Noise of such a high level that it can result in hearing deterioration is an inherent characteristic of military flying. Susceptibility to hearing impairment was studied using 51 Finnish Air Force military personnel as subjects. The test persons flew missions on a British Aerospace Hawk 51 advanced jet trainer, Boeing F-18 Hornet, Mikoyan & Gurevich MiG-21bis and Saab 35 Draken interceptors, and a Valmet Redigo turboprop liaison aircraft. The duration of noise exposure was one flight mission, which varied from 30 to 60 min. Noise doses and levels were measured using a miniature microphone at the inlet of the ear canal, while a second microphone was located at the level of the subject's shoulder. Hearing thresholds were measured before each flight using conventional (0.125-8 kHz) and extended high-frequency (EHF) (8.20 kHz) audiometry. The measurements were repeated as soon as possible after the flight. The study showed that the pre-flight threshold levels of the subjects were good. Both conventional and EHF audiometry revealed statistically significant temporary threshold shifts (TTS) at several frequencies and with all aircraft types involved. The changes were, however, minor. The risk of noise-induced hearing impairment at the studied exposure levels is, in all probability, rather small. The role of extended high-frequency audiometry would be in research, and it might be performed for flying personnel upon entering service and every fifth year thereafter.

Extended high frequency audiometry in pre-school children

Since adequate and reliable earphones are now available and standards have been established, clinical audiometry can be performed at extended high frequencies (EHFs). In the present study, 47 preschool children (aged 4-7 years) were examined with EHFs (8-16 kHz) using the new Sennheiser HDA 200 earphone. The hearing thresholds correspond to those of other studies; the median thresholds and range increase with increasing frequency. The medians and quartiles were: 10 kHz: 25 (5-35) dB(SPL), 11.2 kHz: 35 (20-40) dB(SPL), 14 kHz 40 (30-50) dB(SPL) and 16 kHz: 50 (40-60) dB(SPL). The hearing thresholds could be more reliably determined in the older children (> 5 years) and were 5 dB better than in the younger ones (< 5 years). Thresholds in the 10-12.5 kHz range correspond to those of adults but are more sensitive by 5-12 dB in the 14-16 kHz range.

A pilot investigation of high-frequency audiometry in obscure auditory dysfunction (OAD) patients

The diagnosis of obscure auditory dysfunction (OAD) has been an elusive one, based primarily upon reports of poor speech perception in noise by the patient. Basic audiometric testing reveals hearing within normal threshold limits and it is thought that there may, in part be some subtle psychoacoustic and/or central auditory deficits causing this phenomenon. The use of high-frequency audiometry (HFA) as a test of subclinical cochlear damage has been well documented, especially to monitor the early effects of noise exposure and ototoxic drugs. However, it has not been used in the diagnosis of OAD patients. This study examines the use of HFA as an aid to the understanding of OAD pathophysiology. HFA was conducted on nine OAD subjects, each matched to two controls. Results indicate an elevated threshold amongst all frequencies (10-20 kHz) in OAD patients with significant differences occurring at 10, 14, 16 and 20 kHz. It could be postulated that OAD in fact, is the product of an ultra-high-frequency hearing impairment and its psychoacoustic sequelae. Furthermore, HFA may be a useful inclusion in a diagnostic test battery for OAD status. However, the degree to which it can be used may be limited due to the large intersubject variability in HFA thresholds in the normal population. It is suggested that further investigations into the ultra-high-frequency hearing abilities of OAD patients should be completed in the future.