Part of the following text is taken from the book “Difetti nella progettazione acustica in edilizia” (Defects in acoustic design in buildings) published by Maggioli. All rights reserved. They may not be copied, reproduced, published or redistributed without the permission of the author and Maggioli S.p.A.
The presence of access doors facing common areas can be a possible (and not negligible) acoustic bridge if they do not have adequate sound insulation performance and/ or are not properly laid.
The choice of doors not sufficiently performing from the point of view of sound insulation and/or the presence of defects in the installation of the same may lead to disturbing situations (caused for example by the noise coming from the common environments and penetrating in the living environments) up to the point of undermining the respect of the sound-insulating power of the partitions between real estate units.
To avoid such an acoustic bridge, the entrance doors to the accommodation facing the atria or landings of the stairwells must have a airborne sound insulation Rw certified in the laboratory at least 41 dB and must be equipped with seals around the perimeter and a guillotine working at the base.
The laying must be perfectly cured avoiding leaving holes, gaps or cracks that, if present, would affect the result.
The plane supporting the guillotine must be perfectly planar and there must be no joints between the tiles along the closing line of the guillotine through which noise passage would occur (in particular at medium-high frequencies).
In case the door is not already equipped with a guillotine, there are solutions on the market to be able to apply it at a later time.
In the following figure we report an example of correct laying, on the left (the door is open 90 degrees, while when closed the guillotine laying on a single tile, not interspersed with joints), and an example of not optimal laying, on the right, (joints between tiles perpendicular to the guillotine and loops under it).
In addition to the characteristics of the entrance door and the laying of the flooring, due attention must also be paid to the installation of the frame fixed to the wall compartment.
The following figure shows the incorrect laying method and the correct laying method:
The lack of sealing between fixed frame and masonry (or false frame) and the lack of adherence of the seal generate an important acoustic bridge, especially at “medium-high” frequencies.
This entails the intelligibility of speech between accommodation and stairwell and affects the sound insulation of the partition between the two units.
Conversely, the correct sealing between fixed frame and masonry (or false frame) and the correct adherence of the seal limit the acoustic bridge, especially at “medium-high” frequencies.
This reduces the intelligibility of speech between the accommodation and the stairwell and improves the comfort and sound insulation of the partition.
In addition to the abovementioned provisions concerning the entrance doors to the accommodation, in order to increase acoustic comfort by reducing the resonant effects of any noise coming from the entrance, it is advisable to install a sound-absorbing ceiling even in enclosed common areas, such as e.g. in stairwells and passageways.
Below we also report the sound insulation measures D (difference between sound pressure level accommodation 1 and accommodation 2, in which the passage of noise occurred mainly from the stairwell through the passage of the doors.
The door was certified with Rw at 41 dB and The guillotine at the base was properly laid and working.
The door was laid without due acoustic attention.
The incorrect installation generates an important acoustic bridge, which allows a greater passage of noise and reduces the sound insulation of the partitions.
P.A. Acoustic bridge.
The results show that incorrect installation of the doors leaving important cracks and without adjustment of the gaskets greatly reduced the sound insulation (continuous line).
The only sealing of the perimeter with silicone allows an increase in sound insulation especially at the frequencies of speech (dotted line).
The additional adjustment of the door gaskets allows to reach the maximum value of sound insulation.