While it is well documented that signal-to-noise ratio (SNR) affects the hearing impaired, the impact of reduced SNR is also significant for a child with normal hearing. This is especially true for children who may have an auditory processing disorder (APD). The “routine” audiologic battery administered by audiologists typically does not include a screening tool to identify SNR loss, which may lead to further evaluation of an APD. The purpose of this case study is to demonstrate the value of including a screening tool for early identification and aid in the implementation of a recovery plan. A favorable SNR aids auditory figure ground discrimination, that is, the ability to identify sounds in the presence of background noise. A child with normal hearing but struggling with auditory figure ground discrimination may not be able to filter out background noise to focus on important speech cues, potentially leading to learning disabilities. When you link auditory figure ground problems and poor classroom acoustics with other higher-level weaknesses, such as language delay, attention deficit, impaired intellectual function, or another learning disability, it creates an even greater challenge for the child. If the pediatric audiology test battery does not include a hearing-in-noise screening tool, there is a good chance that auditory figure ground discrimination issues will go undetected. An abnormal score on a speech in noise screening score may indicate potential problems with auditory figure ground discrimination, which would then lead to a recommendation for an APD evaluation, as well as management strategies.
This case demonstrates the utility of including a screening tool, specifically the Bamford-Kowell-Bench Speech-In-Noise (BKB-SIN) test, in the pediatric test battery as an option to identify underlying auditory figure ground discrimination problems. A five-year-old male was evaluated in our clinic for an audiological assessment. His parents reported that he had trouble hearing at a distance, locating sounds and regulating the loudness of his voice. They also reported that the child received therapy because of a language delay. Audiological tests at the time indicated normal hearing at 250-8000 Hz and excellent word recognition at 45 dB HL in each ear. In addition, tympanometry revealed normal middle ear function and 12 frequency diagnostic otoacoustic emissions were present, excluding bilateral cochlear dysfunction. At that time, an APD evaluation was delayed due to factors that may have contributed to the low scores, such as low cognitive ability, developmental factors, and other non-auditory processing influences. Therefore, it was recommended to continue the language therapy and return within a year for audiological monitoring.
The child returned at the age of 6 years and 10 months for a follow-up audiological evaluation. According to the parental report, therapy was discontinued as he was no longer eligible for in-school services, although he was reported to have continued problems with language and hearing at a distance, especially when background noise was present. Audiological tests were unremarkable with one exception; the BKB-SIN, which was not filled in at the first evaluation, showed a slight amount of SNR loss. Given his parental history and BKB-SIN score, an APD evaluation was recommended.
Results from the APD test battery, which consisted of subtests to evaluate binaural separation, binaural integration, auditory figure ground/auditory closure, auditory discrimination, and temporal processing, demonstrated a global deficit. Specifically, deficiencies were seen in four of the five subtests, with a noticeably lower score on the auditory figure-ground subtest compared to the other subtests. In addition, a clinical evaluation of Language Fundamentals screening was performed as part of our standard battery. The child scored borderline low on concepts, following directions, and understanding spoken paragraphs. This deficit pattern suggested that the weaknesses identified in the APD test battery were likely secondary to the previously identified language delay and/or a combined auditory processing disorder/language delay.
Based on the results of the evaluation, recommendations have been categorized under environmental adaptations, remediation activities and compensating strategies. In addition, a repeated comprehensive language assessment was recommended. Finally, it was advised that the child return to our facility within one year for repeat testing to check for maturation and/or effects of recovery.
This case supports the need to include a screening tool for SNR loss as part of the pediatric audiological evaluation. One of those instruments, the BKB-SIN, was able to detect an SNR abnormality in a child with normal hearing. While the traditional pediatric audiology test battery allows the audiologist to diagnose a hearing impairment using an ideal listening environment, adding the BKB-SIN simply provides objective measurements of how a child is performing in complex, realistic listening conditions. Abnormal findings not only lead to recommendations for further testing, such as an APD evaluation, but they also further support the need for an assistive listening device or environmental changes.