Thomas Lunner

Research Area Manager / Adj. Professor

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Cognitive Spare Capacity is the residual cognitive capacity once successful listening has taken place. Aggressive noise reduction schemes and directional microphones may release cognitive resources in challenging ‘cocktail party’ listening conditions.

In this study a dual-task paradigm was used to show that binary-mask noise reduction processing enhanced short-term memory for hearing-impaired listeners with high working memory capacity.

  • Cognitive Spare Capacity
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Testing dual-task word recall with aggressive noise reduction

The effect of hearing loss on cognitive load is suggested by studies demonstrating that under conditions where auditory perception is difficult (i.e., hearing loss), greater cognitive resources are dedicated to auditory perceptual processing, to the detriment of other cognitive processes such as working memory (WM). The cognitive effort attendant to successful recognition can draw on resources that would otherwise be available for sentence comprehension and for encoding words in memory.

Can noise reduction schemes improve memory outcomes?

In cooperation with Linnaeus Centre HEAD, we tested an ‘aggressive’ binary-mask noise reduction scheme (Wang et al., 2009; Boldt et al., 2009) on 26 hearing-impaired listeners with moderate symmetrical sensorineural hearing loss. Cognitive spare capacity was assessed with a dual-task paradigm requiring the last word of each of eight successive HINT (hearing in noise test) sentences to be remembered.

The primary task was to repeat the last word of each sentence; the secondary task was to recall as many previously repeated words as possible after the end of the eighth sentence. Test conditions included 4-talker babble interfering noise, both with and without noise reduction. Working memory performance was assessed by the reading span test


For hearing-impaired listeners with good WM capacity (reading span), noise reduction signal processing released WM resources. There were indications of working memory being overtaxed for participants with low WM capacity. Binary-masking noise reduction helped to free up cognitive resources, thereby enhancing memory task performance in the four-talker babble background for hearing-impaired listeners with high working memory capacity.

Further reading

Wang D, Kjems U, Pedersen MS, Boldt J.B, Lunner T (2009). Speech intelligibility in background noise with ideal binary time-frequency masking. Journal of the Acoustical Society of America, 125(4) p. 2336-2347.

Boldt JB, Kjems U, Pedersen MS, Lunner T, Wang DL (2008). Estimation of the Ideal Binary Mask using Directional Systems. Proceedings of The 11th International Workshop on Acoustic Echo and Noise Control (IWAENC), Seattle, WA.

Sarampalis, Kalluri, Edwards, Hafter (2009). Objective Measures of Listening Effort: Effects of Background Noise and Noise Reduction. Journal of Speech, Language, and Hearing Research, 52, p. 1230-1240.

Ng EHN, Rudner M, Lunner T, Pedersen MS, Rönnberg J (under review). Improved cognitive processing of speech for hearing aid users with noise reduction. International Journal of Auduiology.

Rudner M, Ng E, Ronnberg N, Mishra S (2011). Cognitive spare capacity as a measure of listening effort. Journal of Hearing Science, 1(2), p. 1-3.

Studies at Linnaeus Centre HEAD

Three PhD studies on Cognitive Spare Capacity were hosted at Linnaeus Centre HEAD and co-supervised from Eriksholm Research Centre. The three different measures of CSC for research and clinical use are being developed by:

Elaine Ng: "Hearing aid settings - Signal processing skill". Using the free recall task (Ng et al., under review); sets of eight HINT sentences were presented in quiet or in background noise, with and without noise reduction (Wang et al., 2009). Final words were repeated after each sentence and recalled after each set (c.f. Sarampalis et al., 2009).

Sushmit Mishra: "Sick and tired of listening". In the CSCT (Mishra et al., 2010) Swedish two-digit numbers were presented audiovisually (AV) or as audio only (A) in sets of 13 and recalled in accordance with instructions inducing differential memory and executive load.

Niklas Rönnberg: "The Auditory Inference Span Test (AIST)". Developing a test for cognitive aspects of listening effort for speech comprehension (Rönnberg et al., 2011). The ability to recall the content of sentences was tested at three different levels of cognitive load, represented by three different types of questions about the content of the sentences.

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    Effects of hearing aid signal processing on cognitive outcome measurements