Testing IIC (Impact Insulation Class) involves a specific procedure using a tapping machine to measure the sound insulation of a floor-ceiling assembly against impact noise.
What is IIC?
IIC, or Impact Insulation Class, is a single-number rating that quantifies a floor-ceiling assembly's ability to block impact sounds, such as footsteps, dropped objects, or furniture scraping. A higher IIC rating indicates better performance in reducing these sounds transmitted to the room below.
The Standard IIC Test Procedure
An IIC sound rating test follows a standardized method to ensure consistent and comparable results. The core of the test involves generating a controlled impact noise on the floor and measuring the sound pressure level in the room directly below.
Here are the key steps involved, based on the standard test procedure:
- Placement of the Tapping Machine: The test begins by placing a tapping machine on the test floor. This machine is designed to simulate impact sounds consistently.
- Generating Impact Sounds: The tapping machine is equipped with steel faced hammers hitting the test floor. These hammers strike the floor at a controlled rate.
- Sound Frequency Range: The impact sounds generated by the machine fall within a specific frequency range, typically between 125 Hz to 4,000 Hz. This range covers the most common frequencies associated with impact noise.
- Sound Transmission: The vibrations created by the machine travel through the floor assembly to the room located directly underneath the test area.
- Sound Measurement: A sound engineer is present in the room below to measure the sound levels. Specialized equipment is used to capture the sound pressure levels at various frequencies resulting from the hammer taps above.
- Data Analysis: The measured sound data, representing "the tap" sound transmission, is then analyzed. The sound engineer plots the tap on a graph to compare the results across different frequencies. This data is used to calculate the single-number IIC rating according to standardized procedures (like ASTM E492).
This controlled environment and specific equipment ensure that the test accurately reflects the impact sound transmission performance of the floor-ceiling structure itself.
Why Test IIC?
Testing IIC is crucial for:
- Building Code Compliance: Many building codes specify minimum IIC requirements, particularly in multi-family dwellings like apartments and condominiums, to ensure occupant comfort.
- Material Performance: Evaluating the effectiveness of different floor coverings, underlayments, or ceiling treatments in reducing impact noise.
- Quality Assurance: Verifying that construction meets specified acoustic performance targets.
By following this standardized procedure, engineers and builders can accurately assess and improve the impact sound insulation of buildings.
