Comparison of Clinical and Traditional Gap Detection Tests.

Temporal resolution refers to the ability of the auditory system to respond to rapid changes in a sound stimulus over time. This ability is important for speech recognition, where the listener must process temporal information at varying rates. For example, variations in the speech envelope contain lexical and syntactic information; segmental cues such as gap duration provide information about phoneme identity; and subsegmental information derived from the periodic vibrations of the vocal folds conveys voice pitch and sound quality. Good temporal resolution may also support use of dips in the level of background noise to assemble segments of the target speech, a feature which has been shown to be important in speech-in-noise recognition (e.g., Bernstein and Grant, 2009; Rosen et al., 2013). If temporal resolution is important for speech recognition, it may be one factor contributing to variability in communication ability among patients. Temporal resolution may decrease with sensorineural hearing loss and with age, but not every older patient with hearing loss demonstrates reduced temporal resolution (see Reed et al., 2009 for a recent review). Individual testing could ensure appropriate characterization of temporal abilities, which could then be used to guide auditory rehabilitation. For example, work by Gatehouse et al. (2006) found that temporal resolution ability influenced the benefits of fast- or slow-acting hearing aid compression. There is also evidence that therapy that focuses on improving temporal processing (for those listeners in which temporal processing is impaired) can improve speech recognition (Merzenich et al., 1996; Vatanabe et al., 2014). Accordingly, the ability to measure temporal resolution in a time-efficient way is necessary if those measures are to be considered in treatment decisions. Various measures have been proposed to assess temporal resolution. We focus here on gap detection, which is relevant to speech recognition and relies on a well-validated paradigm. The listener’s task is to detect a brief temporal gap that separates two successive stimuli. The test is commonly within-channel, such that the stimulus that precedes the gap has the same spectrum and duration as the stimulus that follows the gap. Classic methodologies reported in the literature provide precise estimations of the shortest-perceivable gap, but can be time consuming compared to alternatives designed for a clinical environment. They also require specific equipment and software that must be set up and maintained, calibrated, and validated with reference to published norms. To facilitate testing in a clinical environment, several tests have been developed. These include the Random Gap Detection Test (Keith, 2000), the Adaptive Test of Temporal Resolution (Lister et al., 2006), the Auditory Fusion Test (McCroskey and Keith, 1996), and the Gaps-In-Noise Test, or GIN (Musiek et. al., 2005). We focus here on the GIN, which has gained some acceptance in clinical use (e.g., Gilani et al., 2013; Sirow and Souza, 2013). The GIN consists of a compact disc recording administered via a clinical audiometer. Stimuli consist of a six-second burst of broadband noise which contains zero to three silent gaps. Gap durations range from 2-20 msec. The listener’s task is to press a button each time a gap is heard. A second track audible only to the audiologist uses brief tones to alert the audiologist to the gap points. The test is scored as the lowest gap duration where a listener correctly identifies at least 4 (out of 6) gaps, and in overall percent correct across all gap durations. The GIN is a clinically feasible measure of temporal resolution in the adult population (John et al., 2012; Shinn et al., 2009). Somewhat surprisingly, there have been no published comparisons of gap thresholds from the GIN to those obtained from a psychophysical gap detection measure. Indeed, a common-sense view suggests that GIN thresholds might not reflect “pure” gap thresholds. The GIN must introduce some uncertainty, because the listener is unsure as to when to listen for each gap, and because scoring relies on audiologist judgment as to how close a response needs to be following the gap to be scored as a correct response. The participant also needs to have sufficient motor skills to press a button quickly in response when they perceive a gap. In contrast, the traditional gap detection paradigm allows for a higher level of certainty due to its use of a defined interval and typically an adaptive procedure. If the GIN is to be used to assess temporal resolution in the clinic, it would be useful to know how closely it approximates more traditional gap detection tests. Accordingly, we undertook a comparison of the GIN to a psychophysically-based measure. Speech-in-noise testing was included to explore its relationship to temporal resolution. Both younger and older adults were recruited to support generalization of findings to a clinical population. The GIN is considered both in terms of the data obtained, and in the practicality and usefulness of the test in a typical clinic.