Rationale

Item #1: (5. Significance and Use) The task group decided that additional emphasis was needed to prevent the use of E2235 methods for determining the absorption of materials in a room. Item #2: (1. Scope & 17. Report) This standard is designed for use with other standards in which levels are corrected by a 10 log(A) term. There is a need for a standardized method for measuring the reverberation time in rooms in situations unrelated to determining the absorption of materials in the room. Item #3: (16. Determination of Decay Rate) Most laboratory methods in which E2235 could be referenced include rooms that are non-absorptive and relatively diffuse, resulting in reasonably linear decays. There are methods; however, such as E1414, where a room may have a significant amount of absorptive surface area, providing a less diffuse sound field and curved decays. In a small room with curved decays, it is better to use the slope from the initial portion of the decay curve. In these cases, the benefit of using a 25 dB range to get the best estimate of the slope is outweighed by the error introduced by the curvature. Therefore, a 15 dB range is preferable to a 25 dB range when decays consist of significant curvature.