Development of an adaptive low-pass filtered speech test for the identification of auditory processing disorders

Abstract

Objective: One type of test commonly used to examine auditory processing disorders (APD) is the low-pass filtered speech test (LPFST), of which there are various versions. In LPFSTs, a monaural, low-redundancy speech sample is distorted by using filtering to modify its frequency content. Due to the richness of the neural pathways in the auditory system and the redundancy of acoustic information in spoken language, a normal listener is able to recognize speech even when parts of the signal are missing, whereas this ability is often impaired in listeners with APD. One limitation of the various versions of the LPFST is that they are carried out using a constant level of low-pass filtering (e.g. a fixed 1 kHz corner frequency) which makes them prone to ceiling and floor effects. The purpose of this study was to counter these effects by modifying the LPFST using a computer-based adaptive procedure, and to evaluate the performance of normal-hearing participants of varying ages on the test. Methods:In this preliminary study, 33 adults and 30 children (aged 8 to 11 years) with no known history of listening difficulties were tested. The University of Canterbury Adaptive Speech Test (UCAST) platform was used to administer a four-alternative forced-choice adaptive test that altered a low-pass filter (LPF) to track the corner frequency at which participants correctly identified a certain percentage of the word stimuli. Results: Findings on the University of Canterbury Adaptive Speech Test -FilteredWords (UCAST-FW) indicated a significant maturational effect. Adult participants performed significantly better on the UCAST-FW in comparison to the child participants. The UCAST-FW test was reliable over repeated administrations.Conclusions: An adaptive low-pass filtered speech test such as the UCAST-FW is sensitive to maturational changes in auditory processing ability.

Characteristics of Pediatric Performance on a Test Battery Commonly Used in the Diagnosis of Central Auditory Processing Disorder

“…This may be most relevant in the case of LPFS, as the filters applied to the stimuli on Willeford's version of the test tend to vary quite a bit from other versions of LPFS tests. In addition, some recent studies of children's performance on LPFS measures have suggested that adaptive LPFS tests that look at how much redundancy is needed to achieve a certain percent correct criterion may be a better indicator of monaural low redundancy deficits (O'Beirne et al, 2012;Rickard et al, 2013). Specifically, these studies have shown that children with central auditory processing issues tend to require a low-pass filter setting that is higher in frequency to achieve criterion when compared with children without deficits.…”

The Effect of Increased Cognitive Demand on Auditory Processing Assessment

“…In practice, the vast majority of clinical tests of AP are nonadaptive and assess performance at a single level of difficulty only. Thus, the ability of such tests to optimally engage a participant and to avoid effects of fatigue, boredom or discouragement depends on the difficulty level chosen by the developers of the test and on the homogeneity of test ability of the target population (O'Beirne et al, 2012). In an adaptive test, the level of difficulty of each trial is dependent on the participant's response to one or more previous trials (Leek, 2001).…”

Psychophysical and behavioral peripheral and central auditory tests

“…Filtering using a 500-Hz cut-off frequency with an 18 dB per octave rejection rate or a 1000 Hz cut-off has been recommended for clinical use (Wilson and Mueller, 1984). LPFS tests are available on the Veterans Administration compact disk (Veterans Administration, 1992), an Auditec of St. Louis recording (Wilson and Mueller, 1984), SCAN:3A and SCAN:3C (Keith, 2009a, b), and the University of Canterbury Adaptive Speech Test (O'Beirne et al, 2012). Stimuli are presented at 50 dB above the PTA (i.e., 50 dB SL re PTA).…”