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M. Liˇ canin et al.
turned off, the residual noise level at positions 4, 5, and 6 were in the range between
54.6 dB and 55.3 dB. After the analysis of the measurements, a decision has been
made that noise control should provide at least 8 dB of noise attenuation and as a
result, match the residual noise level. Another reason is the acoustical zoning of the
Belgrade, which is an ongoing process. By reducing more than 8 dB of noise, this
will satisfy the day noise limits of the most strict acoustical zones [5].
After the noise level evaluation, using the construction blueprint of the technical
room, the entire object has been made in 3D in a 1:1 ratio so different engineering
solutions can be visually exploited.
3 Simulation of the Acoustic Barrier
Traditional one segment barrier would not satisfy the need of HVAC air supply, and
can potentially create the overheating of the units. To solve this problem an investigation of the multi-segment barrier has been considered. During in situ measurements,
it has been observed that there is a possibility to redirect some of the noise energy
to a longer path. This will naturally attenuate the sound energy without a negative
influence on the nearby buildings. Area where noise could be redirected is highly
influenced by traffic noise from the nearby busy street. This has been tested in the
simulation.
Segmented noise barrier has been analyses in COMSOL Multi-physics. It is
composed of absorption metal perforated panels angled at the 25°. Figure 3 shows
the simulation results without barrier, and with barrier included.
Results are presented at frequencies of 100 Hz (Fig. 3—top), 500 Hz (Fig. 3—
middle), and 1 kHz (Fig. 3—bottom). As can be seen, when the barrier is placed,
more noise energy is contained inside the technical room where chillers are placed.
This is especially visible at the middle to high frequency.
Besides observation of the sound propagation, another simulation has been
performed using the Raytrace method (Fig. 3).
As mention before, some of the noise has to redirect to the longer path and
simulation has been used for evaluation of the geometry of the segmented barrier.
In Fig. 4, results have been presented in a way that the left portion of the figures
represent the case without a segmented barrier (barrier influence is disabled), while
on the right side situation with a barrier is shown (barrier is enabled). Simulation
length is 120 ms, with four steps 30 ms each. In Fig. 4, the first row is a situation
after the first step, where each subsequent row represents another step. As it can
be observed, placement of the segmented barrier (Fig. 3—right) truly redirects the
sound to a longer path. In combination with the absorption in the metal perforated
panels, this has been proved to be a good course of action.
M. Liˇ canin et al.
turned off, the residual noise level at positions 4, 5, and 6 were in the range between
54.6 dB and 55.3 dB. After the analysis of the measurements, a decision has been
made that noise control should provide at least 8 dB of noise attenuation and as a
result, match the residual noise level. Another reason is the acoustical zoning of the
Belgrade, which is an ongoing process. By reducing more than 8 dB of noise, this
will satisfy the day noise limits of the most strict acoustical zones [5].
After the noise level evaluation, using the construction blueprint of the technical
room, the entire object has been made in 3D in a 1:1 ratio so different engineering
solutions can be visually exploited.
3 Simulation of the Acoustic Barrier
Traditional one segment barrier would not satisfy the need of HVAC air supply, and
can potentially create the overheating of the units. To solve this problem an investigation of the multi-segment barrier has been considered. During in situ measurements,
it has been observed that there is a possibility to redirect some of the noise energy
to a longer path. This will naturally attenuate the sound energy without a negative
influence on the nearby buildings. Area where noise could be redirected is highly
influenced by traffic noise from the nearby busy street. This has been tested in the
simulation.
Segmented noise barrier has been analyses in COMSOL Multi-physics. It is
composed of absorption metal perforated panels angled at the 25°. Figure 3 shows
the simulation results without barrier, and with barrier included.
Results are presented at frequencies of 100 Hz (Fig. 3—top), 500 Hz (Fig. 3—
middle), and 1 kHz (Fig. 3—bottom). As can be seen, when the barrier is placed,
more noise energy is contained inside the technical room where chillers are placed.
This is especially visible at the middle to high frequency.
Besides observation of the sound propagation, another simulation has been
performed using the Raytrace method (Fig. 3).
As mention before, some of the noise has to redirect to the longer path and
simulation has been used for evaluation of the geometry of the segmented barrier.
In Fig. 4, results have been presented in a way that the left portion of the figures
represent the case without a segmented barrier (barrier influence is disabled), while
on the right side situation with a barrier is shown (barrier is enabled). Simulation
length is 120 ms, with four steps 30 ms each. In Fig. 4, the first row is a situation
after the first step, where each subsequent row represents another step. As it can
be observed, placement of the segmented barrier (Fig. 3—right) truly redirects the
sound to a longer path. In combination with the absorption in the metal perforated
panels, this has been proved to be a good course of action.