The SAE Recommended Practice for measuring impulse noise from airbags, SAE J247, “Instrumentation for Measuring Acoustic Impulses within Vehicles”, was first published in 1971 and last affirmed in 1987. Many advances have occurred in understanding and technology since that time. Work in the automotive industry to investigate the characteristics of noise from airbag deployments has shown that large components of low frequency noise can be present when an airbag deploys in a closed vehicle. Others have shown that this low frequency noise can have a protective effect on the ear. Likewise, work for many years at the US Army Research Lab has investigated the risk of hearing loss for a human subjected to an acoustic impulse. That research led to the creation and validation of a mathematical model of the human ear, called Auditory Hazard Assessment Algorithm - Human (AHAAH).
In 1998, the SAE Impulse Noise Task Force (INTF) of the Inflatable Restraint Standards Committee performed a series of experiments to help understand the predictions of the AHAAH model. This work compared in-vehicle test results with those obtained from an acoustic reverberation chamber. These tests used a method published by a German Airbag Consortium called the AK-ZV Working Committee and documented in report AK-ZV01. Much of this work was summarized in SAE J2531, an Information Report developed by the SAE Impulse Noise Task Force, documenting the state-of-knowledge in 2003.
Also in 2003, Banglmaier and Rouhana reported on the results of over 100 tests performed to help clarify test conditions for the assessment of noise-induced hearing loss (NIHL). Based on all of this information, a new revision of SAE J247 has been drafted and is in the process of committee editing. This paper describes the changes made to SAE J247 and the rationale for those changes.