Projects from our assessment practice.

For a flat in which recurring low-frequency noise was perceived, a preliminary acoustic investigation was carried out based on event-triggered recordings made by the residents, documented in parallel in a noise log. The recordings were evaluated by spectrogram and one-third-octave analysis and examined for tonal components and recurring patterns, and compared with the hearing threshold according to DIN 45680. The recording system used was characterised beforehand against a Class 1 sound level meter, and the frequency-dependent measurement deviation was compensated mathematically.

For a wooden roller coaster in a German theme park, an acoustic investigation compared the noise emissions of the original track system with a newly installed steel rail profile. Reference and follow-up measurements were used to determine and compare the relevant sound emission parameters, a one-third-octave frequency analysis and the impulsiveness of train pass-bys before and after the conversion. In addition, sound propagation and level decrease with increasing distance were evaluated in order to derive representative level values.

For a planned self-service laundrette on the ground floor of an inner-city residential building, an acoustic noise forecast was prepared as part of the permit procedure. Based on the sound power levels of the machines and the building physics, it was demonstrated that the TA Lärm immission guideline values are reliably met in the flat above and at the outdoor receiver locations. The required noise control measures, including a suspended acoustic ceiling, were dimensioned from the results.

For the planned installation of four air-to-water heat pumps at several apartment buildings in a dense residential area, an acoustic forecast according to TA Lärm was prepared to rule out harmful environmental effects at the surrounding receiver locations. The assessment was carried out as a detailed propagation calculation according to DIN ISO 9613-2, applying the maximum sound power levels plus manufacturing tolerance and tonal penalty. As unregulated full-load operation exceeded the night-time guideline value at several receiver locations, a low-noise night mode was derived with which the immission guideline values are reliably met at all receiver locations.

For a software office, an acoustic investigation according to TA Lärm was carried out after a tonal noise, described as a “hum”, was noticed in the offices, originating from the rooftop photovoltaic system with inverter. As the installation and the protected rooms are structurally connected, the indoor immission guideline values according to section 6.2 of TA Lärm were applied and checked by measurement. In addition, a one-third-octave analysis assessed the low-frequency noise exposure and prominent tones according to TA Lärm 7.3 in conjunction with DIN 45680.

Following a complaint from a neighbour, the building authority required proof that two unpermitted air conditioners, retrofitted on the gable of a residential building, comply with the TA Lärm immission guideline values. Based on the manufacturer's data and the local conditions, the noise immissions at the relevant protected receiver locations on the neighbouring property were determined and assessed. The investigation served to clarify on a technical basis whether the units cause unreasonable noise nuisance for the neighbourhood.

For an owner-occupied flat above a bar, an acoustic investigation was carried out after low-frequency noise, vibrations and information-bearing components such as music and voices were perceived as considerably disturbing, especially at night. As the bar and the flat are structurally connected, the indoor levels were measured and assessed against the indoor immission guideline values of TA Lärm no. 6.2. In addition, the low-frequency components were evaluated according to DIN 45680, the peak levels were assessed, and the structural sound insulation was appraised according to DIN 4109.

For a cultural centre with an indoor loudspeaker used to broadcast prayers, a noise measurement according to TA Lärm was carried out to assess the effects on the surrounding neighbourhood. Airborne sound measurements were taken at several representative receiver locations in the surrounding mixed-use area with protected residential use, using a substitute measurement point for one inaccessible location. The investigation served to establish whether the installation complies with the relevant immission guideline values under typical use.