Max Brahman –

1/2-22 Kirkham Road West, Keysborough
Melbourne, victoria 3173

Ulrich Gerhaher
Helmut Bertsch
Sebastian Wiederin

Popular version of 4pEA7 – Bringing free weight areas under acoustic control
Presented at the 185th ASA Meeting
Read the abstract at

Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.

In fitness studios, the ungentle dropping of weights, such as heavy dumbbells at height of 2 meters, is part of everyday life. As the studios are often integrated into residential or office buildings, the floor structures must be selected in such a way that impact energy is adequately insulated to meet the criteria for airborne noise in other parts of the building. Normally accurate prediction of the expected sound level for selection of optimal floor covering, can only be achieved through extensive measurements and using different floor coverings on site.

To be able to make accurate predictions without on-site measurements, Getzner Werkstoffe GmbH carried out more than 300 drop tests (see Figure 1) and measured the ceiling vibrations and sound pressure level in the room below. Dumbbells weighing 10 kg up to packages of 100 kg were dropped from heights of 10 cm up to 160 cm. This covers the entire range of dumbbells drops, approximately, to heavy barbells. collection of test results is integrated into a prediction tool
developed by Getzner.

The tested g-fit Shock Absorb superstructures consist of 1 to 3 layers of PU foam mats with different dynamic stiffnesses and damping values. These superstructures are optimized for the respective area of application: soft superstructures for low weights or drop heights and stiffer superstructures for heavy weights and high drop heights to prevent impact on the subfloor. The high dynamic damping of the materials reduces the rebound of the dumbbells to prevent injuries.

Heat maps of the maxHold values of the vibrations were created for each of the four g-fit Shock Absorb superstructures and a sports floor covering (see Figure 2). This database can now be used in the prediction tool for two different forecasting approaches.

Knowing the dumbbell weight and the drop height, the sound pressure level can be determined for all body variants for the room below, considering the ceiling thickness using mean value curves. No additional measurement on site is required. Figure 3 shows measured values of a real project vs. the predicted values. The deviations between measurement and prediction tool are -1.5 dB and 4.6 dB which is insignificant. The improvement of the setup (40 mm rubber granulate sports flooring) is -9.5 dB for advanced version and -22.5 dB for pro version of g-fit shock absorb floor construction.

To predict the sound pressure level in another room in the building, sound level should be measured for three simple drops in the receiver room using a medium-thickness floor structure. Based on these measured values and drop tests database, the expected frequency spectrum and the sound pressure level in the room could then be predicted.

The tool described makes it easier for Getzner to evaluate the planned floor structures of fitness studios. The solution subsequently offered enables compliance with the required sound insulation limits.

Figure 1, Carrying out the drop tests in the laboratory.
Figure 2, Maximum value of the ceiling vibration per third octave band as a function of the drop energy
Figure 3, measured and predicted values of a CrossFit studio, on the left only sports flooring without g-fit Shock Absorb, in the middle with additional g-fit Shock Absorb advanced and on the right with gfit Shock Absorb pro, dumbbell weights up to 100 kg
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