Loudness recruitment is an abnormally rapid growth of perceived loudness above the hearing threshold that slows to normal growth as the intensity of the signal increases. Recruitment is common in sensorineural hearing loss and in simulated hearing loss with noise masking. This study looked at possible differences in loudness recruitment with age, noise level, and frequency. Participants from two age groups were tested. Group A included participants aged 18 to 30 years and Group B included participants aged 50 to 75 years. Participants practiced the Alternate Binaural Loudness Balance (ABLB) test without noise present. They then repeated the tests with masking noise. Tests were completed with two different noise levels (50 dB SPL and 70 dB SPL), and two different test tone frequencies (1000 Hz and 2000 Hz). Participants identified loudness matching points to reference intensities of 20, 40, 60, and 80 dB HL. Participants completed 3 trials at each intensity level. Difference scores of the intensity of the loudness matching point minus the intensity of the reference tone were computed and analyzed statistically. An analysis of variance (ANOVA) for repeated measures fails to show significance for between-subjects effect for age, within subject effect for frequency, and trial. An ANOVA for repeated measures shows significant within subject effect for noise and for intensity. The 70 dB SPL noise level shows greater difference scores and a steeper loudness matching function slope than the 50 dB SPL noise level. The greater difference scores and steeper slope are expected due to the higher hearing threshold created with the higher noise level. As the intensity level increases, the difference score decreases. The decrease in difference scores with increasing intensity levels shows the presence of loudness recruitment. The results of this study suggest the use of masking noise in order to measure recruitment is an acceptable simulation. Age alone does not account for changes in loudness recruitment. Therefore, recruitment measurement with noise masking may be a potential marker of early auditory dysfunction.



College and Department

David O. McKay School of Education; Communication Disorders



Date Submitted


Document Type





loudness matching function, loudness recruitment, normal hearing, simulated hearing loss, age, noise masking, frequency