ABSTRACT This study investigated the effects of noise from building mechanical systems with tonal components on human task performance and perception. Six different noise conditions based on in-situ measurements were reproduced in an officelike setting; all were set to approximately the same sound level (47 dBA) but could have one particular tonal frequency (120 Hz@ 235 Hz@ or 595 Hz) at one of two tonal prominence ratios (5 or 9). Thirty participants were asked to complete typing@ grammatical reasoning@ and math tasks plus subjective questionnaires@ while being exposed for approximately 1 hour to each noise condition. Results show that the noise conditions that had tonal prominence ratios of 9 were generally perceived to be more annoying than those of 5@ although statistically significant differences in task performance were not found. Other findings are (1) that higher annoyance/distraction responses were significantly correlated with reduced typing task performance; (2) that the noise characteristics most closely correlated to higher annoyance/distraction responses in this study were higher ratings of loudness followed by roar@ rumble@ and tones; and (3) that perception of more low frequency rumble in particular was significantly linked to reduced performance on both the routine and cognitively demanding tasks.