Infrasound

Source/Presence:

Infrasound is generated both naturally and by artificial sources.

Natural triggers include, for example, wind, storms, gales, ocean waves, waterfalls, earthquakes, and volcanoes.

Technical sources of low-frequency sound and low-frequency noise include, among others, large engines, rotors, generators, compressors, transformers, ventilation systems, heat pumps, industrial facilities, traffic, airplanes, loudspeaker systems, and blasting operations.

Machines, building services, or poorly decoupled systems can also cause humming, oscillations, and vibrations.

Since low frequencies travel long distances and can cause structural elements to vibrate, infrasound occurs not only outdoors but also in indoor spaces, residential environments, workplaces, and technical facilities.

Limit values:

Unlike many chemical air pollutants, there is no single, universally applicable limit value for infrasound.

The assessment typically depends on frequency and is influenced by factors such as sound pressure level, frequency spectrum, measurement location, duration of exposure, time of day, and the surrounding environment.

In Germany, low-frequency noise exposure is assessed using, among other things, the TA Lärm and the DIN 45680 standard. This assessment takes into account not only the volume but also the frequency range in which the exposure occurs.

For this reason, proper acoustic measurement is particularly important, since traditional dB(A) values often provide only limited insight into low frequencies, low-frequency noise, infrasound, and possible fluctuations in atmospheric pressure.

Consequences:

Below the perception threshold, based on current scientific knowledge, no proven negative health effects have been demonstrated.

However, if infrasound or low-frequency sound is perceived, it can be annoying, overwhelming, or unpleasant.

Common sensations include a feeling of pressure, ringing in the ears, a sensation of vibration, the room seeming to sway, or a noise that is difficult to pinpoint.

At noticeable or very high levels, these can lead to difficulty concentrating, sleep disturbances, fatigue, headaches, discomfort, or stress reactions. At extremely high sound pressure levels, hearing pain or hearing damage is also possible.

Note:

Measurements are important because infrasound and low-frequency noise are often not clearly audible, yet they can still be perceived as a noise nuisance.

Sensors such as the air-⁠Q sensor help measure infrasound, visualize sound events, track changes in noise levels, identify temporal patterns, and pinpoint potential technical sources of noise.

Measurement is especially useful when the discomfort occurs only at certain times or may be related to building systems, traffic, ventilation, heat pumps, or other sources.

This makes it easier to classify anomalies and compare them with environmental factors such as air quality, atmospheric pressure, CO₂, VOCs, temperature, or other measured values.