We used free-field audiometry to investigate the loudness perception of unilateral high-frequency tinnitus in 16 "normal-hearing" ears by comparing the results with loudness scaling in 20 normally hearing ears without any tinnitus. Narrow-band noise signals at four different frequencies from 500 to 4000 Hz were employed. The parameters used included the slope m of the loudness function and the level Lm (corresponding to the loudness perception of "medium loud") as well as the suitability of fit (delta FIT). The results showed that in subjects with tinnitus the slope of the mean loudness level tended to decrease at 4000 Hz. The dynamic range of ears affected by tinnitus was restricted for stimulation with noise signals at 1000, 2000 and 4000 Hz. The parameters of delta FIT fitted to the loudness functions were increased in the whole frequency range of 500-4000 Hz, indicating that loudness scaling was not as reliable for normal hearing ears when influenced by tinnitus. Tinnitus masking was based on the finding that external sound could change tinnitus loudness. Our results showed that the loudness perception of external sound was influenced by tinnitus. This change in loudness perception seemed to be not restricted to the frequency range of the tinnitus.