Build your wall assembly layer by layer and watch the estimated STC rating update instantly — then get the lab-tested number for your exact design.
Sound Transmission Class (STC) is a standardized rating that quantifies how effectively a material or assembly reduces airborne sound. Commonly used in architectural acoustics, STC is essential for designing walls, ceilings, and glazing systems that provide privacy and comfort. It is calculated using ASTM E90 test data and ASTM E413 rating methods, offering a single-number benchmark for comparing assemblies.
Choosing the right wall assembly upfront avoids costly retrofits when noise complaints surface after occupancy. Higher-rated assemblies like staggered studs or CMU also align with code requirements in schools, multifamily, and healthcare.
Hitting the right target creates spaces that perform as intended — quieter classrooms, offices that keep conversations confidential, and multifamily projects that avoid tenant turnover from noise complaints.
STC ratings are calculated by measuring how sound moves through a partition at 16 standardized frequencies, then comparing that curve to a reference contour. Real-world conditions typically reduce performance by 3–7 points, reported as Apparent STC (ASTC) under ASTM E336.
Boosting STC isn’t just about thicker walls — it’s about smarter construction. Addressing these three areas can easily improve performance by 5 to 10 STC points.
When YKHC expanded its healthcare facilities, sound isolation was critical to patient privacy. High-STC wall assemblies and acoustic membranes kept confidential conversations protected in exam and consultation rooms.
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Medical offices face strict HIPAA regulations, making STC performance non-negotiable. We paired sound masking with high-STC wall assemblies to eliminate sound bleed between rooms.
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Noise bleed between auditoriums threatened the guest experience. Mass loaded vinyl achieved STC 65+, delivering low-frequency control while cutting three weeks from the schedule.
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Law enforcement facilities demand maximum confidentiality. Interrogation rooms were upgraded with enhanced STC-rated assemblies to stop speech from leaking between rooms.
Read the case study →An STC of 50 is the minimum required by the International Building Code for walls between dwelling units. However, STC 55 or higher is typically preferred in healthcare, education, hospitality, and corporate environments where privacy is critical.
Our calculator provides realistic estimates based on common wall types and configurations. It’s ideal for early-stage design and value engineering. For final specs or sensitive projects, lab-tested assemblies or consultation with an acoustic expert is recommended.
Lab tests (ASTM E90) are conducted in ideal conditions. Field ratings (ASTM E336) account for real-world factors like construction quality, air gaps, and flanking paths. Expect field results — also called Apparent STC (ASTC) — to be 3 to 7 points lower.
Yes. Adding fiberglass or mineral wool insulation into stud cavities can raise STC by 5–10 points, depending on wall configuration. Insulation works best when combined with added mass and structural decoupling.
Use IIC (Impact Insulation Class) when designing floor-ceiling systems to reduce impact noise like footsteps or dropped items. STC is for airborne noise, such as voices or TV. In multi-story buildings, both ratings are typically required.
ASTM introduced E90 and E413 in the 1960s, giving designers a uniform way to compare assemblies and defend acoustical decisions to clients and inspectors. Adoption into building codes in the 1970s cemented STC as the common language between architects, contractors, and code officials — which is why it remains the baseline requirement today.