The Audioscan: a high frequency resolution audiometric technique and its clinical applications

Abstract

The Audioscan is a form of high definition audiometry based on iso-hearing level frequency sweeps, which was developed by Meyer-Bisch in 1990. Compared with traditional tone audiometry, it sweeps across the preset frequency range at a predetermined sweep rate and provides a continuous audiometric curve. Because the device has a maximum frequency range of 125-16 000 Hz with 64 frequencies per octave, the Audioscan method can, theoretically, give 64 times as many values as fixed-frequency audiometry, which may give greater accuracy and sensitivity. An advantage of this is its capacity to detect mild audiometric deficits such as narrow notches situated between the frequencies normally tested. These may represent very limited auditory lesions, at a stage when they cannot be detected by routine audiological methods. Thus, the Audioscan method can give not only a detailed audiometric curve, but also provide important indicators of mild auditory dysfunction. The Audioscan device (e.g. Essilor model) is commercially available for clinical purpose. It is a software-based system, which can also be used for pure tone audiometry and Békésy audiometry. This paper reviews the general aspects of the Audioscan technique and current applications for detecting auditory dysfunction. This would be valuable to provide some guidelines on the Audioscan assessment, and contribute to a clarification of the clinical application of Audioscan and facilitate further research.

The characteristics of Audioscan and DPOAE measures in tinnitus patients with normal hearing thresholds

“…The significance of Audioscan notches has been confirmed for detection of hearing deficiency in the screening of noise-induced hearing impairment, in carriers of genes for hearing impairment (Meredith 1991;Zhao et al, 2002), for example King-Kopetzky syndrome, in which an individual complains of difficulties in understanding speech in the presence of background noise but has normal hearing thresholds on pure tone audiometry (Zhao & Stephens, 1998).…”

“…Detailed information can be found in previous publications Zhao et al, 2002;Zhao and Stephens, 1998). A brief description of its principle and procedure is summarised as follows:…”

“…This may reduce subjects' concentration level and, consequently, produce unreliable results. A systematic review by Zhao et al (2002) suggested that Audioscan notches were found less frequently in a group of subjects when tested with faster sweep rates than at slower sweep rates, and the test-retest reliability of hearing thresholds obtained from Audioscan was affected by sweep speed, with the reliability at the slower sweep speed being slightly better than that at a faster sweep rate. In a recent study of test-retest reliability and validity of the Audioscan using a fast sweep rate (15 s per octave), the results showed that 86% of participants had hearing threshold variability within 5 dB at most frequencies except at 1,500 Hz (80%) and 4,000 Hz (81%), while more than 90% of participants had variability of hearing threshold of less than 10 dB at all frequencies (Ishak et al, 2011).…”

“…Based on a systematic review of the Audioscan test and its clinical application (Zhao et al, 2002), only one previous tinnitus study by Sirimanna et al (1996) has included the Audioscan test within the test battery. These authors recruited 26 tinnitus patients who had PTA thresholds less than 25 dBHL at frequencies of 0.25 to 8 kHz and who were able to match their tinnitus to pure tone.…”

“…One suggestion is that a normal hearing threshold on pure tone audiogram does not prove normal auditory function (e.g., König et al, 2006;Sirimanna et al, 1996;Weisz et al, 2006;Zhao & Stephens, 1998). Other hypotheses include minor cochlear dysfunction or abnormality beyond cochlear level (e.g., Shiomi et al, 1997;Thabet, 2009;Zhao F et al, 2002). For example, Jastreboff's theory of discordant dysfunction of outer hair cells (OHCs) and inner hair cells (IHCs), indicates that a different level of dysfunction, where damage to OHCs is greater than IHCs is a possible peripheral mechanisms that can trigger tinnitus 4 (Jestreboff, 1990).…”