Demystifying Building Acoustics: A Guide for Builders and Renovators

Thursday, 06 June 2024

Building acoustics, often overlooked in the early design stages, is becoming increasingly crucial. With the rise in occupant complaints about noise disturbances and growing expectations for acoustic comfort, it is imperative to understand and master the fundamental principles of acoustics in multi-family buildings. This article is intended for builders and property managers who wish to design or transform buildings where tranquility prevails.

General Principles of Acoustics

Architectural acoustics aim to control sound quality in various types of buildings, from concert halls to multi-family dwellings. Sound is a mechanical wave that propagates through air or materials, and its perception varies depending on frequency and intensity:

• Sound Waves: Sounds are vibrations that propagate through a medium (air, water, solid materials) and are perceived by the human ear. Sound quality depends on frequency (low or high) and intensity (volume).

• Noise versus Sound: Pleasant and harmonious sound is perceived as music, while noise is often unpleasant and disruptive, such as the sound of heels on a floor or loud music.

Types of Noises and Their Impacts

There are primarily two types of noises to consider in buildings: impact noises and airborne noises.

• Impact Noises: Caused by shocks or vibrations like footsteps or moved furniture. These noises transmit through the building’s structures.

• Airborne Noises: Caused by sound sources like voice, music, or television. These noises propagate through the air and openings in the structures.

Acoustic Measurements: IIC and STC

To assess the acoustic performance of buildings, two main indices are used:

• IIC (Impact Insulation Class): Measures the ability of a floor-ceiling assembly to attenuate impact noises. A high IIC indicates better insulation against footsteps and other impacts.

• STC (Sound Transmission Class): Measures the ability of a floor-ceiling or wall-wall assembly to attenuate airborne noises. A high STC means better insulation against external noises.

Acoustic tests are conducted either in the laboratory (IIC/STC) or on-site (AIIC/ASTC). Laboratory results tend to be higher due to controlled conditions.

Building Structure and Noise Propagation

The design and materials used in a building greatly influence its acoustic performance:

• Material Density: Dense materials like steel or concrete carry high-frequency sounds better. Therefore, it is very important to decouple components to avoid flanking noises and thus improve comfort.

• Mass: Massive structures like concrete block sounds better than lightweight structures, especially for airborne noises. For impact noises, using acoustic membranes can improve this performance by acting as springs between two masses (concrete/floor).

• Cavities and Hard Surfaces: Uninsulated cavities amplify sound transmission, while hard surfaces reflect it. Again, decoupling construction materials is crucial to reducing noise transfer.

Acoustic Standards and Requirements

In Canada, the National Building Code (NBC) stipulates minimum standards for acoustic performance. For multi-family buildings, it requires an STC of 50, and there are no requirements for IIC. However, the building code recommends an STC and IIC of 55 for optimal acoustic comfort.

Choosing Acoustic Materials

Choosing acoustic materials is essential to achieve the desired performance. It is important to compare published values of materials considering test conditions (laboratory vs. field) and types of structures:

• Acoustic Membranes: Membranes should be chosen for their ability to meet or exceed minimum standards and maintain their acoustic and mechanical properties over time.

• Durability: Materials must resist wear and maintain their acoustic properties in the long term.

• Weight: Lightweight acoustic solutions can reduce loads on the structure and facilitate their installation.

• Ease of Use: Easy-to-install materials can reduce construction time and associated costs.

• No Emission of Toxic Products: Ensure that materials do not release harmful substances, guaranteeing a healthy indoor environment.

Case Studies

Examples of successful projects highlight the importance of acoustics in modern construction:

• University of Toronto, Ontario: A mass timber building with an exposed ceiling achieved an STC of 50 through innovative solutions.

• 283 Greene Avenue, Brooklyn: Use of AcoustiTECH systems to exceed acoustic standards with an AIIC of 54 and an ASTC of 57.

• 330 Goldstream, Victoria: Dry screed solutions meeting and exceeding acoustic comfort standards.

• QB District, Quebec: A concrete slab without a ceiling was treated with an AcoustiTECH membrane, achieving an AIIC of 65 and an ASTC of 62.

Conclusion

Building acoustics play a crucial role in occupant comfort and satisfaction. A thorough understanding of acoustic principles, coupled with careful material selection and thoughtful design, allows for the creation of quiet and pleasant living spaces. Collaborating with acoustic experts and following best construction practices is essential to avoid complaints and offer superior quality buildings. For any assistance or advice, feel free to contact us and request a free consultation with one of our acoustic experts at AcoustiTECH.

Vincent Moreau
Co-owner
Executive Vice President of Sales
Innovation & Strategic Development
Sustainability Ambassador
AcoustiTECH