Year
2026
STC Objective
STC 50 to 55
Measured, As Built
ASTC 30 to 32
Partitions Tested
3
A general contractor completed an office and warehouse build-out in Michigan, and the project set a sound isolation objective of STC 50 to 55 for its walls. The contractor brought in Memtech Acoustics to measure how three of the finished walls actually performed against it: two between conference rooms and the adjacent open office, and one between the work floor and the warehouse.
In June 2026, Memtech tested each partition following ASTM E336. A loudspeaker produced broadband pink noise in the source room, microphones on both sides of the wall recorded the sound levels, and an analyzer calculated the transmission loss from 125 to 4,000 Hz. Background noise was measured separately.
STC is a laboratory rating, so field results are reported as apparent STC (ASTC), which reflects the finished building, including flanking paths and room conditions. The project's STC 50 to 55 objective corresponds to roughly ASTC 45 to 50. For the large warehouse partition, Memtech also reported the Noise Isolation Class (NIC), which better represents what occupants experience across a very large wall.
None of the three partitions met the objective. The conference room walls measured ASTC 30 and ASTC 32, and the warehouse wall measured ASTC 32 (NIC 35). The results were consistent with laboratory data for similar construction: single-layer 1/2 inch gypsum board on a shared stud wall. In the office areas, the walls did not extend to the metal deck, leaving roughly 20 feet of shared plenum above the ceiling tile, and sound also passed through the door perimeters, hollow-core doors, and single-pane windows. The warehouse wall was further affected by its roll-up door and man-door seals.
Memtech's report recommended a structurally independent wall layer: an added layer of 5/8 inch gypsum board on one side, and another layer on hat channel with resilient isolation clips on the other. It also called for replacing the conference room drop ceilings with two layers of 5/8 inch gypsum board, adding door perimeter seals with automatic drop bottoms, replacing the hollow-core doors with solid-core or metal doors, and adding acoustical window inserts or laminated double-pane windows. The recommendations are interdependent, so the improvement depends on all of them being implemented and maintained.
The field test gave the contractor a measured rating for each partition and a specific list of the assembly and flanking changes needed to reach the objective. No results after these upgrades are available yet, so none are reported here.
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