Open-plan offices are common in the tertiary sector, yet occupants often complain about noise, particularly from co-worker conversations. This issue can differently affect normal hearing people and those with presbycusis. This study therefore examines the impact of mild hearing loss (the onset of presbycusis) on performance in open-plan offices, focusing on the effect of irrelevant speech. An analysis of the decrease in performance on serial recall task as a function of speech-to-noise ratio was carried out with young, normal-hearing subjects under two auditory conditions: with and without a hearing loss simulator, as well as with hearing-impaired elderly subjects. Participants were exposed to five speech-to-noise conditions and silence. Subjective intelligibility was also measured. The results showed a minor, non-significant difference in decrease of performance between normalhearing and hearing-impaired participants. The hearing loss simulator produced results comparable to those of the older group, validating its efficacy.