More and more people are exposed to low frequency noise in their homes, which are supposed to be a safe space. Even at very low levels, this noise is perceived as disturbing, especially in quiet areas. And even when legal noise limits are met, people feel disturbed, and some describe a deterioration in their health. Such situations can lead to protracted disputes with neighbors and a significant reduction in the quality of life.

Noise pollution is caused by the increasing density of settlements and traffic and by the use of more and more equipment, often in a decentralized fashion, such as heat pumps, ventilation systems, small wind turbines, micro combined heat and power units, or robotic lawn mowers. A population that has become increasingly sensitive to environmental influences in recent years is confronted with rising noise levels. In particular, people are noticing noise pollution more often.

Humans hear sound with frequencies between about 20 hertz (Hz) and 20,000 Hz. Sound below 20 Hz (known as infrasound) is perceived only at much higher volumes than, for example, music or speech. At the same time, humans cannot accurately distinguish between different types of low frequency sound, which is why they generally perceive low frequency sound as “humming” or vibrations.

The best way to avoid humming equipment is to address the problem early, preferably in the design phase. In the European Union, manufacturers are required to declare noise emission levels for most equipment. This means that you can compare noise emission levels before you buy. As well as choosing the right equipment, it is also important to choose the right location. As few people as possible should be disturbed during operation.

Typical residential area where low frequency noise sources have been installed in stages – shown as gray circles. The colored areas illustrate the low frequency noise that can become annoying.
1 Original – 2 As of 2016 – 3 Forecast for 2030

For existing installations, local authorities can order improvements on a case-by-case basis, for example, if the equipment is not state of the art or if the installation is poorly sited. However, retrofitting to reduce low frequency noise is technically very difficult and costly, and involves measures such as relocating equipment or building complicated enclosures around the entire equipment. Measures such as soundproof windows help against “normal” noise in the audible range, but are usually useless against low frequency humming.

The German Environment Agency (UBA) is currently investigating the technical and legal framework conditions and possible further courses of action in a research project entitled “Detection and Assessment of Low Frequency Noise in Residential and Surrounding Areas.” Interim results of the ongoing project have been compiled in a guideline: a first approach to raise awareness of the growing problem and to identify conflict solutions.

A practical guideline:
Free download from the German Environment Agency: Tieffrequente Geräusche im Wohnumfeld
Press release of the German Environment Agency: Heat pumps and the like: low frequency hum annoys a growing number of people