Disentangling the contribution of head shadow, loudness summation, and binaural unmasking to spatial release from masking in children

Segregating target speech from noise is crucial for children’s ability to communicate effectively in everyday environments. Past research clearly shows that when target sources are spatially separated from maskers, compared with target-masker being co-located, children as young as 2–3 years old demonstrate improved speech understanding. This effect is known as spatial release from masking (SRM). Generally, studies have used free-field or dichotic listening; hence, the contributions of head shadow, loudness summation, and binaural unmasking to SRM are unknown in children. This study aimed to quantify these factors in virtual auditory space. By varying the target-masker spatial configurations (co-located versus separated) and ear conditions (monaural versus binaural), speech understanding benefit was defined as improvement in the signal-to-noise ratio to achieve an accuracy of 50%. Results from 29 children with normal hearing (6–15 years old) show that head shadow cues are dominant in providing benefit, followed by binaural unmasking. Loudness summation, through increased intensity by listening with both ears, provided little to no benefit. No age effects were found. Results also suggest a re-balancing between cues depending on listening strategies adopted by children. For example, children who relied more on binaural unmasking received less benefit for speech understanding from head shadow. [Work supported by NIH-NIDCD.]