Tuned resonators cancel duct fan noise without blocking airflow

Evidence

This is accomplished by tuning the resonator to a frequency just below the expected sinusoidal component of hum from a fan, for example. The sound reflection works while letting air pass freely by, the primary purpose of the duct. The rooms downstream of the resonator are then much quieter. — Eric J. Heller, Why You Hear What You Hear- An…, 1263

Categorization

• XREF: Concrete application of the anti-phase cancellation mechanism central to the reader’s ‘why we hear what we hear’ question.