To understand acoustics, its best to grasp how sound is perceived and understanding the dB measurement.
STC and IIC explained
In New Zealand, the primary measurements used to evaluate sound transmission between floors are the Sound Transmission Class (STC) and the Impact Insulation Class (IIC). These measurements address different types of sound:
Sound Transmission Class (STC): This measures the sound insulation of a floor/ceiling assembly against airborne sounds, such as talking or music playing. STC is measured in decibels (dB), with higher STC values indicating better sound insulation.
Impact Insulation Class (IIC): This measures the sound insulation of a floor/ceiling assembly against impact sounds, such as footsteps. IIC is also measured in decibels, using a calibrated tapping machine that generates impact sounds at different frequencies. Like STC, higher IIC values indicate better performance.
Understanding Delta IIC (△IIC) Values
Delta IIC (△IIC) values represent the improvement in impact sound isolation that a specific product brings to a construction. It is calculated by taking the difference between the overall IIC value and the initial IIC value before the product was added. These values are typically measured using ASTM E2179, which requires the measurement to be taken using a concrete floor.
This means that △IIC values are particularly relevant when considering flooring products for builds that include a concrete floor.
Key Considerations
For those involved in the design and specification of buildings, especially timber structures, it's crucial to look beyond just △IIC values. Instead, focus on fully tested assemblies to ensure the acoustic performance meets the desired standards. This approach will help you achieve the best sound insulation and comfort in your interior spaces.
By understanding these basic principles of acoustics and sound measurement, you can make informed decisions that enhance the acoustic environment of your spaces, providing greater comfort and functionality for occupants.
For more information on acoustics terminology, please refer to our acoustic terminology guide.