Low-frequency noise and humming: specialist research.
Low-frequency noise is sound with a frequency below 100 Hz. It is perceived as a constant hum, drone or rumble. Particularly burdensome because it is difficult to locate, poorly attenuated by standard building constructions and not heard by everyone. The source can be hundreds of metres away.
Schedule free consultationWhy is low-frequency noise so difficult?
Low frequencies have a long wavelength (at 50 Hz almost 7 metres). They bend around obstacles, penetrate constructions that block higher frequencies, and are amplified by resonance in enclosed spaces. A room can amplify the noise through standing waves, making it louder in certain corners than in other places of the same room.
Common sources of hums
Heat pumps and AC compressors (50-100 Hz). Nearby transformer stations. Industrial fans and compressors. Truck engines idling in a car park. Sewer pump stations and pumping installations. Sometimes even wind turbines kilometres away. In some cases it concerns the electricity grid (50 Hz mains frequency).
Our specialist measurement method
Standard sound measurements cover the range from 50 or 100 Hz. For low-frequency noise we extend the measurement down to 20 Hz with special measurement equipment and longer measurement times. We perform a 1/3 octave band analysis to identify the exact frequency and compare it with the assessment curve for low-frequency noise (NSG guideline). Systematic source investigation through measurements at different locations and times.
Solutions for low-frequency noise
Low-frequency noise is difficult to insulate. Standard measures (plasterboard, mineral wool) barely work at frequencies below 100 Hz. Effective solutions require considerable mass (thick concrete, sand filling) or specific resonance absorbers. Sometimes the only solution is to address the source itself. We calculate in advance which measure is feasible and effective in your situation.
Consultation or direct quote
Schedule a free consultation or request a direct quote via the form. We respond within one business day.