Assessment of Absorbers in Normal-Incidence Four- Microphone Transmission-Loss Systems to Measure Effectiveness of Materials in Lateral-Flow Configurations of Filled or Partially Filled Cavities

The four-microphone standing wave tube system has proven useful for measuring the absorption and transmission loss of various fibrous and non-fibrous absorbers. The system is fast, repeatable, accurate and compact.

This paper discusses the advantages of the four-microphone system for measuring the transmission loss in lateral-flow absorber systems. The original four-microphone round impedance tube system and the migration to a four-microphone square tube system are discussed. The four-microphone square tube system allows effective study of filled and partially filled cavities.