Transmission loss is a measurement of a partition’s ability to block sound at a given frequency, or the number of decibels that sound of a given frequency is reduced in passing through a partition. Measuring the sound transmission loss over a range of 16 different frequencies between 125 – 4,000 Hz is the basis for determining a partitions sound transmission class (STC) rating. The frequency range of 125 – 4,000 Hz is the frequency range of the human voice.
The STC is a single-number rating given to a particular material or assembly. The STC rating measures the ability of a material or an assembly to resist airborne sound transfer over the specified frequencies (see ASTM International Classification E413 and E90). In general, a higher STC rating corresponds with a reduced level of noise transmitting through a partition.
The Impact Insulation Class (IIC) tests measures a floor/ceiling assembly’s ability to attenuate impact sound (i.e. foot steps). Similar to STC, IIC tests also measure sound transmission loss over a range of 16 different frequencies between 125 – 4,000 Hz; however, it focuses on impact sound. The IIC is derived from ASTM method E989, which in turn uses a tapping machine specified in ASTM method E492.
Our experience and services include:
– Review of existing or proposed partition design
– Investigate and assess the theoretical acoustical performance for partitions
– Conduct STC and IIC field test performance
– Provide recommendations and upgrade mitigation requirements
