Sound Effects

Low frequency noise is common in urban environments, and has physiological and psychological implications.

For healthy adults the range of hearing is often quoted as extending from 20Hz to 20,000Hz. ‘Low frequency noise' is the term used to describe sound energy in the range from about 10Hz to 200Hz. It spans the infrasonic and audible ranges. Infrasound is specifically used to describe sound energy below 20Hz.

Low frequency noise may be produced from many artificial sources like automobiles, rail traffic, aircraft, industrial machinery, artillery and mining explosions, wind turbines, compressors, and ventilation or air-conditioning units and household appliances such as washing machines.

Low frequency noise can evoke particularly strong reactions in some groups of people. Reported effects include annoyance, irritation, unease, stress, depression, fatigue, headache, dizziness, palpitations, nausea, disturbed sleep and increased cortisol levels. Low frequency noise from ventilation systems can disturb rest and sleep even at low sound levels (This could explain why I lie awake sometimes in hotels trying to shut out the noise of the central air-conditioning system). Although exposure to low frequency noise in the home at night causes loss of sleep, there is evidence that low frequency noise under other conditions induces drowsiness.

As people cannot consciously detect infrasound, it can cause them to have unusual experiences. Infrasound has been reported to cause unexplained feelings of awe or fear in humans.

A low frequency noise can be heard by one person and not by another because people’s hearing sensitivity varies from one individual to another. Consequently it may annoy one person but not the other.

Earplugs are not an adequate solution.

A review of published research on low frequency noise and its effects is available at the Defra website. More research papers on low frequency noise are also available on the website.