Speaker
Description
Since 2021, the Styrian provincial authority has received an increasing number of complaints concerning low-frequency noise immissions. By March 2024, 46 complaints had been registered, of which eight cases were investigated in detail through night-time third-octave-band measurements following DIN 45680. A-weighted sound pressure levels inside affected dwellings were typically below 15 dB, corresponding to very quiet indoor conditions. One of the eight cases, an air-source heat pump in a pure residential zone, exceeded the DIN 45680 reference values for significant annoyance, while two further complaints were attributable to immissions in the audible range rather than to actual low-frequency components. To account for individual differences in low-frequency hearing sensitivity, the assessment was complemented by comparison with statistical hearing-threshold curves derived using ISO 389-7 and ISO 28961 (1 % and 10 % percentile thresholds) and by evaluation of the G-weighted infrasound level. In most cases, the measured spectra lie well below the extended assessment criteria, indicating that low-frequency noise is unlikely to be the cause of the complaints. These observations suggest that the unusually quiet conditions in the affected dwellings themselves may contribute to the reported perceptions.