Abstract
Working memory—the ability to process and store information—has been identified as an important aspect of speech perception in difficult listening environments. Working memory can be envisioned as a limited-capacity system which is engaged when an input signal cannot be readily matched to a stored representation or template. This “mismatch” is expected to occur more frequently when the signal is degraded. Because working memory capacity varies among individuals, those with smaller capacity are expected to demonstrate poorer speech understanding when speech is degraded, such as in background noise. However, it is less clear whether (and how) working memory should influence practical decisions, such as hearing treatment. Here, we consider the relationship between working memory capacity and response to specific hearing aid processing strategies. Three types of signal processing are considered, each of which will alter the acoustic signal: fast-acting wide-dynamic range compression, which smooths the amplitude envelope of the input signal; digital noise reduction, which may inadvertently remove speech signal components as it suppresses noise; and frequency compression, which alters the relationship between spectral peaks. For fast-acting wide-dynamic range compression, a growing body of data suggests that individuals with smaller working memory capacity may be more susceptible to such signal alterations, and may receive greater amplification benefit with “low alteration” processing. While the evidence for a relationship between wide-dynamic range compression and working memory appears robust, the effects of working memory on perceptual response to other forms of hearing aid signal processing are less clear cut. We conclude our review with a discussion of the opportunities (and challenges) in translating information on individual working memory into clinical treatment, including clinically feasible measures of working memory.
Highlights
Binary Mask-Based Noise Reduction Processing With respect to binary mask-based NR processing, Ng et al (2013) conducted a study where they tested both ideal and non-ideal versions of this algorithm
Data analyses revealed a main effect of working memory capacity on recall, with better memory being related to longer working memory capacity
Outcome measures included the dual-task paradigm used previously as well as subjective ratings of listening effort and overall preference. This time, working memory capacity was unrelated to speech understanding and did not interact with NR processing either
Summary
Working memory—the ability to process and store information (Daneman and Carpenter, 1980; Miyake and Shah, 1999; Baddeley, 2000, 2012)—has been identified as an important aspect of speech perception in difficult listening environments. A number of empirical studies have supported this view, showing working memory capacity to be more strongly related to speech in noise than to speech in quiet (see Akeroyd, 2008; Besser et al, 2013 for reviews). This relationship has led to calls for including measures of working memory in diagnostic protocols (Weinstein, 2015), or in treatment planning (Remensnyder, 2012). Individuals who present with a range of communication difficulties will likely benefit from an understanding of the cognitive (and sensory) factors that influence their communication abilities It is less clear how working memory should be applied to practical decisions, including the selection and fitting of hearing aids.
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