Sabine defined absorption in units of equivalent open window area.

Evidence

In the Sabine equation, this is easily done by multiplying the absorption coefficient of the material by its total area and then adding up the contributions from all the surfaces in the room. These resulted in a figure that Sabine called the “equivalent open window area,” as he assumed, and experimentally verified, that the absorption coefficient of an open window was equal to 1. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1890

Categorization

• DEFINE: Clarifies the conceptual anchor of the Sabine equation: an open window as the unit of absorption.
• XREF: Connects to listener’s earlier work on soundscape and acoustic measurement; the open-window unit is a vivid physical anchor for ‘absorption’.

Related

• Sabine measured sound absorption by comparing a material to a fully open window. (similarity 0.96)
• The Sabine equation works well when absorption coefficients stay under 0.3 (similarity 0.82)
• An open window is the acoustic reference standard with absorption coefficient 1 (similarity 0.82)
• Room acoustics are tuned by budgeting equivalent open window absorption area (similarity 0.82)
• Sabine’s formula launched the science of architectural acoustics (similarity 0.79)
• The absorption coefficient measures the fraction of incident sound energy absorbed. (similarity 0.79)
• The Sabine formula assumes diffuse sound that real rectangular rooms rarely produce (similarity 0.78)