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Influence of background noise level on speech reception in normal und hearing impaired personsCluster of Excellence „Hearing4all“
18 April 2018 (online)
The aim of this study was to determine the relationship between hearing loss and speech reception threshold (SRT) at different fixed background noise levels using the Oldenburg Sentence Test (OLSA). In a previous study, ears with various hearing abilities were tested at a fixed noise level of 65 dB SPL. With this setting, SRTs in noise could be determined for an average hearing loss below 45 dB HL (PTA). Above this PTA, SRTs were affected by hearing disability in quiet. The present two-center study investigated the effect of different noise levels on speech reception.
SRTs were determined monaurally with headphones using the standard noise of the OLSA (Olnoise) at different levels and a standard adaptive procedure converging to 50% speech intelligibility. At the Hörzentrum Oldenburg, 41 ears were tested in quiet and with fixed noise levels of 55, 65, 75, and 85 dB SPL. At the Medical University Hannover, SRTs in quiet were determined at fixed noise levels of 65, 85, and 95 dB SPL in 52 ears. In total, data from 93 ears with hearing losses ranging from 0 to 90 dB HL PTA were obtained.
For all noise levels, two domains with a linear dependence between SRT and PTA could be identified. For PTAs lower than the respective noise level minus 20 dB HL, the SRTs increased with slopes of approximately 0.09 dB SNR/dB HL. For higher PTAs, the identified domain included heterogeneous data, thus the noise level specific regressions differed in slope.
The OLSA can be applied to a wide range of hearing losses. Preliminary results indicate that for real speech in noise testing, the selected background noise level should be at least 20 dB higher than the PTA. Otherwise, the SRT will be influenced by a reduced hearing ability in quiet.