Equalization and mode cancellation both reduce bass resonance ringing despite different mechanisms

Evidence

Figure 14.33 is especially interesting as it shows the time-domain performance of two methods of attenuating a room resonance: equalization of one sub and mode cancelling using two subs (1 and 2 in Figure 14.32(a)). These energy-time curves illustrate the amplitude vs. time events at the frequency of resonance (0,1,0), seen above. The data are not perfect because the filter used to isolate these events in the frequency domain has a decay time of its own, but the differences between the curves are valid. In this comparison the curves have been adjusted so that they all exhibit the same peak sound levels. In reality the equalized and mode-cancelled curves would start at lower levels, thereby adding further assurance of reduced audibility. Figure 14.32(b) and (c) show a 9 dB reduction in amplitude due to the equalization, to which the increased decay rate is an added improvement. … Both the equalization and cancellation treatments reduce the build-up interval and the ringing, but they behave differently in their interactions with the prevailing sound field. In both cases it is not difficult to hear the improvement in bass uniformity and temporal definition. — Toole, Floyd E, Sound reproduction- the acoustics and…, 1638

Categorization

• XREF: Ties to the tone-burst waveforms of Figure 5.4 (build-up/decay of resonant energy) mentioned in the passage, and to Section 9.4 loudness halving per 5 dB cited in the next paragraph.