Sound Transmission Class (STC) – Definition & Detailed Explanation – Audio Terms Glossary

What is Sound Transmission Class (STC)?

Sound Transmission Class (STC) is a numerical rating used to measure how well a building material or assembly can reduce the transmission of airborne sound from one side of a partition to the other. In simpler terms, STC is a way to quantify how effective a material is at blocking sound from passing through it. The higher the STC rating, the better the material is at reducing sound transmission.

How is STC measured?

STC is measured in a laboratory setting using standardized testing procedures outlined in ASTM E413. During testing, a sound source is placed on one side of a partition, and a microphone is placed on the other side to measure the sound level. The difference in sound levels between the two sides is then used to calculate the STC rating of the partition.

What is the significance of STC ratings?

STC ratings are important because they provide a standardized way to compare the sound-blocking capabilities of different materials and assemblies. Higher STC ratings indicate better sound insulation, which can be crucial in environments where noise control is important, such as offices, schools, hospitals, and residential buildings.

How can STC ratings impact building design?

STC ratings can have a significant impact on building design, especially in spaces where noise control is a priority. For example, in residential buildings, higher STC ratings can help reduce noise from neighboring units, improving overall comfort and privacy for residents. In commercial buildings, STC ratings can impact the acoustics of a space, making it more conducive to productivity and concentration.

What are some common STC ratings for different materials?

Different building materials have different STC ratings based on their thickness, density, and composition. Here are some common STC ratings for various materials:
– Single-pane glass: STC 26
– Double-pane glass: STC 28-32
– Wood stud wall with drywall on both sides: STC 33-45
– Concrete block wall: STC 45-50
– Metal stud wall with insulation and drywall on both sides: STC 50-60

How can STC ratings be improved in a building?

There are several ways to improve the STC ratings of a building and reduce sound transmission. Some common strategies include:
– Adding mass: Increasing the density of a partition by adding additional layers of drywall, insulation, or other sound-absorbing materials can improve its STC rating.
– Sealing air leaks: Ensuring that all gaps and cracks in a partition are properly sealed can help prevent sound from leaking through.
– Using soundproofing materials: Installing soundproofing materials such as acoustic panels, soundproof windows, and soundproof doors can help reduce sound transmission and improve STC ratings.
– Designing for sound isolation: Incorporating sound-isolating design elements such as staggered stud walls, resilient channels, and double walls can help minimize sound transmission and improve STC ratings in a building.