Is This Room Anechoic? A New Anechoic Room Qualification Standard May Be Needed for Impulsive Sound Quality Tests 2007-01-2217

This paper discusses a project that was begun shortly before an unexpected retirement opportunity appeared that limits the possibilities for follow-up work. Some simple measurements of impulsive sounds were made in an anechoic room to investigate concerns that room alterations for sound transmission loss testing had introduced what appeared to be some reflecting surfaces in the room. The impulsive sound tests confirmed that the alterations had indeed introduced reflections into the room. Ways to reduce those reflections were developed and confirmed. However, the test results also raise concerns about reflections from the perforated metal wedges used in the original room design. An important first question is how do these reflections affect the results of sound quality work performed in this type of room? If the reflections do significantly affect sound quality analysis, the second question is do we need a new standard for qualifying anechoic rooms to be used for measuring the sound quality of impulsive sounds? This paper only presents a brief look at some work to answer the first question. For those interested in the sound quality of impulsive sounds the next suggested tasks are to finish answering the first question and begin working on developing a new standard if one is needed.