In apartment buildings it is quite normal to be able to hear sounds from the flats of the neighbours. Most noises cannot be avoided. But of course tenants do not have to accept all disturbing noise sources. Noise sources such as loud televisions, music systems and screaming children or barking dogs can be very exhausting. If the own room is no longer usable, because the noise from the neighbour dwellings is too large, noise nuisance is present.
Usually tenants can complain or call the police. But what can tenants do if, for example, the neighbour's television is already too loud at room volume? In clairaudient apartment buildings it can happen that you notice more of your neighbours than you would like to. Then complaints or calling the police won't help. Perhaps, however, the sound insulation of the walls can be improved, especially if there is a leak.
In this application example we show how measurements with the Acoustic Camera can help to reduce noise pollution in rented flats with a high hearing level. In this case, the noise nuisance is due to the bright hearing between two flats. The tenants of both apartments want to improve the sound insulation and reduce the bright hearing. For this purpose, acoustic measurements are carried out on the wall between the apartments.
The transmission measurements were carried out on a drywall between bedroom (room 1) and living room (room 2). For this purpose, a reference sound source was positioned in one of the rooms, while a measurement with the Acoustic Camera was carried out in the other room (see Figure 1).
In one measurement, beside the reference sound source children's cries were used. The microphone array Ring48 AC Pro with a diameter of 75 cm was used. This array allows two-dimensional beamforming measurements up to a lower cut-off frequency of 400 Hz.
Leaks in the sound insulation can be identified on an acoustic image. An acoustic image shows the sound sources as a color map above the optical image. Figure 2 shows an acoustic image in the NoiseImage software. You can see that the maximum sound pressure level and the dynamics of the acoustic map are shown on the sidebar. The dynamics refer to the difference between the minimum and maximum amplitude. Relevant measurement information such as sampling rate, integration time, frequency range, focus and algorithm used can also be found on the bottom. In the spectrogram you can see, that the frequency range between 400 Hz (lower frequency of the array) and 2 kHz was selected to localize the leakage (see Figure 3). The reason for this is that a clear transmission can be seen in the spectrum up to 2 kHz and the amplitude is hardly dependent on the frequency. From 2 kHz, however, a sharp decrease in amplitude is visible.
First, measurements were carried out in the living room (room 2). Figure 4 shows a spectral photo of the measurement result. Three sound sources are visible. The location of the transmission is clearly visible as the largest sound source. The crying child in the bedroom (room 1) is clearly audible during the measurement and the sound source is visible in the spectrogram (Figure 5). Also in the bedroom (room 1), a linear source with two hotspots on the acoustic photo can be identified (see Figure 6). The increase of the sound source in the corner probably results from an additional wall reflection.
The clear transmission could be localized at the slit at the top of the wall. For constructional reasons, the gap between wall and ceiling is nessecary. The gap has already been acoustically sealed. However, the measurement with the Acoustic Camera shows, that this sealing does not function continuously (well). From the living room side, a leakage in the sealing was found on the left side, while from the bedroom side it has been localized on the right side. Apart from this point, no other leakage points were identifiable in the sound insulation of the wall.
The Acoustic Camera helped to locate problematic leakage spots in the acoustic sealing. Now, important actions can be taken. Sealing the leakages leads to increased sound insulation and thus to noise reduction in both apartments. The noise pollution in the room can be efficiently reduced as a result of the measurement with the Acoustic Camera.
