Absorption tests specify how the sample was mounted. Type A is flat against a hard surface (typical for wall panels). Type E-400 has a 400 mm (16 in) air space behind it, simulating a suspended ceiling, and gives higher values at low frequencies. Compare products tested in the same mounting.
Learning center / Acoustics fundamentals
Mounting types and lab ratings (ASTM E795)
What Type A and Type E-400 mounting mean on a spec sheet.
2 minute read · Updated Nov 2026