Disturbances of communication in noisy environments may be identified sooner in patients with sensorineural hearing loss when speech audiometry is performed using fluctuating rather than stationary background noises. In the present study, the factors determining the loudness of fluctuating noises were examined using psychoacoustical procedures. The results indicated that loudness of fluctuating noises was best represented by the same percentile loudness N15 or percentile level L15. This is the value that is reached or exceeded in 15% of the analysed measurement time. The percentile level L15 or the percentile loudness N15 may be used to measure the level of noises with identical spectra. However, subjective loudness is approximated only by the percentile loudness N15 if the stationary and the fluctuating noises are spectrally different.