Sound insulation performance of the compact audiometric test room P/No. 2 05 41000 The SN-4A is compact and lightweight, and features outstanding ease of use. It is widely employed by otolaryngologists as a tool for outpatient examinations. Normally, a room for performing hearing tests must have a noise level of below 40 phons. With ordinary rooms, however, it is not easy to find a place for conducting measurements that fulfills this criterion. The SN-4A is a compact audiometric test room that solves this problem. It provides the necessary sound insulation effects down to low-frequency sound, in particular, which causes problems with hearing tests, thus creating an ideal environment.