In the early 80s, engineer Vic Tandy was working in a supposedly haunted lab when he broke into a cold sweat, hairs on the back of his neck standing on end. Out of the corner of his eye, he noticed an ominous grey shape drifting slowly into view. Terrified, he went straight home.
Tandy discovered that source of his discomfort was a 19hz standing wave, caused by an extractor fan. 19hz is in the range known as infrasound, below the range of human hearing (20hz). Low frequencies in this region can affect humans and animals in several ways, causing discomfort, dizziness, blurred vision (by vibrating your eyeballs), hyperventilation and fear, possibly leading to panic attacks. 19hz standing waves have since been discovered in many a ‘haunted’ building.
Prior to an attack, a tiger’s roar contains frequencies of about 18hz, which might disorientate and paralyse their intended victim. Is this the sound of fear itself?