The real world transmission loss chamber: A work in progress

Abstract

A “real world” transmission loss (RWTL) chamber was recently added to the undergraduate acoustics program at Columbia College Chicago. It aims to demonstrate concepts of transmission loss to students and to provide a “less-than-ideal” environment for construction evaluation prior to certified tests with full-size samples. Each side of the chamber can be used as either “send” or “receive,” and both speaker and microphone placements are infinitely variable. The noise floor can also be adjusted to illustrate potential issues in field tests. Measurements are taken simultaneously from multiple positions, then averaged to yield TL values and an overall isolation rating. Given its construction, the chamber is not expected to produce results as per existing standards as its small size results in modal effects and non-diffuse conditions on both sides of the tested partition. This study’s first goal was to better understand the performance limitations of the RWTL chamber by conducting a thorough evaluation of its maximum TL and modal properties. The second goal was to optimize the chamber’s testing methodology in order to more closely reflect certified laboratory results; this was done by utilizing recently obtained certified data from a door manufacturer who tested reduced-sized samples in the RWTL chamber.