DESCRIPTION:
Experience the auditory equivalent of an optical after-image. Heaphones recommended.

Thanks to Jim Griffiths for telling me about Xqicker Tones and emailing me the Physics Review Letters paper (available here: http://itb.biologie.hu-berlin.de/~kempter/Publications/2003/PhysRevLett/franosch_prl_2003.pdf)

The broadband noise with a spectral gap was generated in Daqarta, free software available here: http://www.daqarta.com/


ANSWER:
The 2nd Zwicker Tone should be lower in pitch than the first.