Illusory continuity of tones

An ascending tone is interrupted by a noise burst, but is perceptually continuous.

The illusory continuity of tones is the auditory illusion caused when a tone is interrupted for a short time (approximately 50ms or less), during which a narrow band of noise is played. The noise does, however, have to be of a sufficiently high level to effectively mask the gap, as can be seen in the audio example found here. Whether the tone is of constant, rising or decreasing pitch, the ear perceives the tone as continuous if the 50ms (or less) discontinuity is masked by noise. Because the human ear is very sensitive to sudden changes, however, it is necessary for the success of the illusion that the amplitude of the tone in the region of the discontinuity not decrease or increase too abruptly.

Most probably, this happens because of the way that the human ear adapted to filter out the background noise from signals (visual, acoustic, tactile,...) in order to show one signal disturbed by noise as one event, not several. (A longer change in the signal could mean a different event.)

References

• Warren RM, Wrightson JM, Puretz J (1988). "Illusory continuity of tonal and infratonal periodic sounds". Journal of the Acoustical Society of America 84 (4): 1338–42. doi:10.1121/1.396632. PMID 3198869.