basic function of the PARC is to equalize bass anomalies in the
room, commonly referred to as room modes. The most prominent
bass anomalies occur when two parallel walls (or floor and
ceiling) excite a particular frequency (an axial mode). The
distance between the two walls determines which frequency is
excited. The most problematic, or highest amplitude, is
generally ½ of a wavelength between two walls. The way to
calculate the distance is: ½ * speed of sound / distance between
walls = Frequency The speed of sound is 1130 feet per second.
Thus a room with 17 foot spaced walls would have a frequency
bump at: 565 / 17 = 33.2 Hz. This is considered the first mode
between those two walls. The second mode is for a full
wavelength, which would be at 66.4 Hz. The third mode would be
at 3/2 wavelengths, or 99.6 Hz. Each mode has lower amplitude
than the previous mode. However, imagine a room where the length
is 2 times the width. In this example 34 feet long. The first
mode for that room is at the same frequency of