At high frequencies the change in the sensitivity is more abrupt, with sensation ceasing entirely around 20 khz. The threshold of pain increases in the top octave also. The ability to make loudness judgments is compromised for sounds of less than 200ms duration. Durations longer than 200ms do not affect loudness judgment, beyond the fact that we tend to stop paying attention to long unchanging tones. The threshold of hearing for a particular tone can be raised by the presence of another noise or another tone.
White noise reduces the loudness of all tones, regardless of absolute level.
If the bandwidth of the masking noise is reduced, the effect of masking loud tones is reduced, but the threshold of hearing for those tones remains high. If the masking sound is narrow band noise or a tone, masking depends on the frequency relationship of the masked and masking tones. At low loudness levels, a band of noise will mask tones of higher frequency than the noise more than those of lower frequency. At high levels, a band of noise will also mask tones of lower frequency than itself. Better results are obtained if the stimuli are similar complex tones, which makes sense since there are more active points along the basilar membrane to give clues.