Page 194 - Master Handbook of Acoustics

TABLE 10-1 Auditory Critical Bands

These examples tend to confirm the observation that in large spaces (long delays) comb filters are
inaudible, whereas they often are very troublesome in small spaces (short delays). Also, critical
bands are much narrower at low frequencies, suggesting that comb-filter effects are more audible at
low frequencies.

The relative coarseness of the critical bands suggests that the ear is relatively insensitive to the
peaks and nulls resulting from a 40-msec delay (see Fig. 10-7C). Therefore, the human ear may not
interpret response aberrations such as timbral changes resulting from 40-msec combing, or combing
from longer delays. On the other hand, the combing resulting from the 0.5-msec delay (see Fig. 10-
7A) could be delineated by the ear’s critical band at 1,000 Hz, resulting in a perceived timbre of the
signal. Figure 10-7B illustrates an intermediate example in which the ear may be marginally able to

analyze the 8-msec combed signal. The width of the critical bands of the auditory system increases
rapidly with frequency. It is difficult to imagine the complexity of the interaction between a set of
critical bands and a constantly changing music signal, with diverse combing patterns from a host of
reflections. Only carefully controlled psychoacoustics experiments can determine whether the
resulting differences are audible.