Comparison of acceptance of background noise and speech reception threshold in quantifying the hearing aid directivity benefit

Abstract

Hearing aid directivity benefit was compared as improvement in acceptance of background noise and speech reception threshold (SRT). Forty adult subjects were tested wearing binaural hearing aids in omnidirectional and directional listening conditions. Acceptance of background noise was determined by having subjects select their most comfortable listening level (MCL) for a story delivered from a loudspeaker (0). Next, speech babble was added (180) and the subjects selected the maximum background noise level (BNL) which was acceptable while listening to and following the story. The MCL minus the BNL yielded the acceptable noise level (ANL), all in dB. The difference between the ANL for the omni-directional and directional conditions is the directivity benefit. The SRT was determined by delivering spondaic words (0) at the subjects MCL. Next, speech babble was delivered (180) and adjusted until the subject could repeat 50% of the spondees. The difference between the SRT for the omni-directional and directional conditions is the directivity benefit. Mean directional benefit, ANL=3.50 dB and SRT=3.60 dB, were not significantly different. The individual ANLs and SRTs were significantly correlated (r=−0.36, p=0.002). The ANL procedure appears to be a viable tool for quantifying hearing aid directivity benefit. [Work supported by NIDCD (NIH) 3 RO1 DC 05018-01S1.]