Simply put, people greatly value the benefits of quiet environments, where good acoustic enhances the quality of life, improves mental health, provides better working and sleeping conditions – in general adding to the wellbeing of an individual.
A person’s reaction to noise differs from day-to-day depending on our mood, state of mind, stress levels, health conditions, and time of day.
Studies have shown that intermittent, irregular, impulsive or impact noises translate to be more annoying, as compared to a steady-state noise, with stress levels on the rise the more people are exposed to it. It has also shown that people are generally more tolerable to external noise sources (i.e., noise sources outside the building) as compared to noise from their neighbours.
With the COVID-19 pandemic, more people are now working from home, children with their online lectures, and the family tightly-knitted under one roof – indicating that any noise be it from external sources or internal sources, are placed to become more evident, disturbing, and disruptive.
Building regulations in different countries have specific acoustic requirements for different types of buildings. However, these regulations don’t always guarantee that occupants are satisfied with the acoustic conditions.
For this reason, ISO/TS 19488:2021 Acoustics – Acoustic classification of dwellings which was published in April 2021 has classification for six different classes A, B, C, D, E and F for dwellings, with Class A being the highest class and Class F the lowest class. The purpose of ISO/TS 19488:2021 is to make it easier for developers to specify a classified level of acoustic quality of a dwelling and help users and builders to be informed about the acoustic conditions and define increased acoustic quality.
The classification of ISO/TS 19488:2021 includes criteria for 5 acoustic aspects:
- Airborne sound insulation;
- Impact sound insulation;
- Airborne sound insulation of building envelopes against outdoor noise from traffic, industry or other sources;
- Sound pressure levels in the dwellings from service equipment; and
- Reverberation time.
In Dubai, all new buildings shall be designed in accordance with Al Sa’fat Dubai Green Building System Version 2.0-2020. Section 403 of this regulation, Chapter 3: Acoustic Comfort, states that all new Villas / Residential Buildings are to be designed in accordance with Building Regulations Approved Document E (latest version) (UK).
Approved Document E covers 4 parts:
- E1 Protection against sound from other parts of the building and adjoining buildings;
- E2 Protection against sound within a dwelling-house;
- E3 Reverberation in the common internal parts of buildings containing flats or rooms for residential purposes; and
- E4 Acoustic conditions in schools.
When it comes to controlling noise from adjacent dwelling units, Approved Document E has requirements for airborne and impact sound insulation which are summarized in the table below
|Purpose Built Dwelling-Houses And Apartments|
|Airborne Sound Insulation (Walls & Floors),
DnT,w + Ctr (dB)
|45 (minimum value)|
|Impact Sound Insulation (Floors),
|62 (minimum value)|
This article will focus on impact sound insulation only.
The table below is an extract from ISO/TS 19488:2021 regarding the maximum impact sound pressure level between habitable rooms in dwellings from other dwellings in all directions for the six different classes.
|Class A||Class B
||Class D||Class E
L’nT,w ≤54 dB
Differences in Design Requirements: Airborne vs Impact Sound Insulation
It is important to understand the difference between airborne and impact sound insulation, as the method of control differs.
In short, airborne sound refers to noise produced by sources that directly set the air around them into vibration. Impact noise refers to noise caused by sources which produce impulsive mechanical excitation of a part of a building (example footsteps, electric light switches, slamming doors)
A misconception by architects, developers and contractors is that having a thick concrete floor will reduce impact noise. Generally speaking, for any given type of construction, the heavier the wall/floor construction, the better its airborne sound insulation (mass law formula). It should be noted however, heavy slabs do little or none to impact noise.
Unlike airborne sound transmission where the sound insulation is related to the mass of the specimen (in case of single leaf elements e.g., concrete slab, masonry partition), the control of footfall noise from upper floors is dependent on the appropriate design and specification of structural slabs and suitable floor and ceiling constructions.
To control impact noise, soft floor covering can be used, or acoustic underlay can be specified above the structural floor which can be installed either under the screed or under the floor tile to create a structural decoupling between the spaces.
Based on Approved Document E, the soft floor covering should meet the following specification:
- Any resilient material, or material with a resilient base, with an overall uncompressed thickness of at least 4.5 mm; or
- Any floor covering with a weighted reduction in impact sound pressure level (∆Lw) of not less than 17 dB.
Based on the above, where there is no suspended ceiling on the level below and where there is hard floor finish on the level above, an acoustic underlay is required to meet the impact sound insulation criteria.
Thin layers of acoustic underlays are generally stiffer than thicker ones and thus there is a risk of acoustic bridging (i.e., between the floating screed and the structural slab) because in such cases due to unevenness or general building debris, the acoustic underlay might be punched through which eventually reduces the effectiveness of the impact sound insulation.
Attention shall also be paid by the contractor to ensure that there are continuous strips of acoustic underlay alongside the walls, pipe penetrations and door frames. The acoustic underlay shall also not be continuous between adjacent apartments and each apartment shall have its own acoustic underlay. This is shown in the figure below.