Development of an Aircraft Intercom Replication System for Assessment of In-Flight Intercom Acoustic Sound Pressure Levels

Flight measurements were conducted on the National Research Council's (NRC) Dassault Falcon 20 jet to assess cabin and cockpit environment sound pressure levels (SPL) for determining the aircrew noise exposure. Furthermore, the NRC has developed a methodology to quantify the contribution of aircrew speech to personnel noise exposure. Preliminary onboard investigation suggested that aircraft intercom communications potentially increased aircrew at-ear noise exposure by 5-10 dB(A). The objective of this paper is to present the NRC's development of an in-laboratory intercom replication system for investigating the significance of aircraft intercom acoustic SPLs relative to the overall aircrew at-ear SPLs. The aircraft intercom system output to headset system voltage was measured and recorded onboard the NRC Falcon aircraft, and subsequently replicated through a headset fitted on an acoustic test fixture (ATF) in the NRC Flight Research Laboratory Hearing Protection Evaluation facility. Laboratory replicated SPLs exhibited a deviation of less than 3dB from operational Falcon 20 measurements between the 200 and 2500Hz 1/3rd octave frequency bands. Further investigation is underway to reduce the replicated intercom SPL discrepancies found in frequency ranges below 200Hz and above 3000Hz and to replicate combined intercom and cabin SPLs in laboratory.