A decade has passed and it would be interesting to know how many people have reproduced the results detailed in the abstract. I gave it a quick read and at first glance it looks like an impressive experiment:
Hearing thresholds for pure tones between 16 and 30kHz were measured by an adaptive method. The maximum presentation level at the entrance of the outer ear was about 110dB SPL. To prevent the listeners from detecting subharmonic distortions in the lower frequencies, pink noise was presented as a masker. Even at 28kHz, threshold values were obtained from 3 out of 32 ears. No thresholds were obtained for 30kHz tone. Between 20 and 28kHz, the threshold tended to increase rather gradually, whereas it increased abruptly between 16 and 20kHz.