4.3 Spatial Release from Masking
Several studies regarding SRM in adults and children with NH have been
published [13,14]. The results were highly diverse due to numerous
factors, including task setting, master stimuli type, number of
competing sounds, and similarity in voices producing target and
competing speech [15]. In addition, the age at which SRM fully
develops is undefined. Some researchers indicated that SRM became stable
earlier in childhood (4–6 years) [16,17], while others have
reported that SRM was adult-like at 12 years of age [18]. This study
suggests that for NH children aged 7 to 12 years, SRM continued to
change, as a significant relationship was observed between age and SRM.
However, the specific age at which SRM plateaus was not defined due to
the narrow age range of participants.
BCDs facilitate the alleviation of HSE to improve speech perception
ability, especially when the speech signal is presented from the hearing
field of the poor ear [6]; however, during this process, real
binaural hearing cannot be restored because the device could not provide
real auditory stimulus to the deaf ear [15]. This explained why the
average aided SRM for SSD group was statistically improved neither in
SeparatedS0NNH condition nor the
SeparatedS0NNH condition. When being unaided in the
SeparatedS0NNH condition, SRMs were not detected in most
SSD patients. This was the most challenging hearing condition for
patients with SSD, as the SSN presented from the NH ear interfered with
the fronted speech signals. When the SSN was presented in the
hearing-impaired ear in the SeparatedS0NSSD condition,
all paediatric SSD patients showed SRMs. This hearing condition was
historically considered the optimal listening condition for SSD, as the
HSE prevented the SSN located at the SSD side from disturbing the speech
recognition ability of the NH ear. Theoretically, it was assumed that
BCDs would increase SSN interference with the healthy ear. Fortunately,
there was no difference between the unaided and aided SRMs,
demonstrating their hearing adaptation to the newly aided BCDs.