FreeHear: A New Sound-Field Speech-in-Babble Hearing Assessment Tool.

Pure-tone threshold audiometry is currently the standard test of hearing. However, in everyday life, we are more concerned with listening to speech of moderate loudness and, specifically, listening to a particular talker against a background of other talkers. FreeHear delivers strings of three spoken digits (0-9, not 7) against a background babble via three loudspeakers placed in front and to either side of a listener. FreeHear is designed as a rapid, quantitative initial assessment of hearing using an adaptive algorithm. It is designed especially for children and for testing listeners who are using hearing devices. In this first report on FreeHear, we present developmental considerations and protocols and results of testing 100 children (4-13 years old) and 23 adults (18-30 years old). Two of the six 4 year olds and 91% of all older children completed full testing. Speech reception threshold (SRT) for digits and noise colocated at 0 degrees or separated by 90 degrees both improved linearly across 4 to 12 years old by 6 to 7 dB, with a further 2 dB improvement for the adults. These data suggested full maturation at approximately 15 years old SRTs at 90 degrees digits/noise separation were better by approximately 6 dB than SRTs colocated at 0 degrees. This spatial release from masking did not change significantly across age. Test-retest reliability was similar for children and adults (standard deviation of 2.05-2.91 dB SRT), with a mean practice improvement of 0.04-0.98 dB. FreeHear shows promise as a clinical test for both children and adults. Further trials in people with hearing impairment are ongoing.