Head-related transfer function measurements in a compartment fire

TL;DR

This study measures how a fire affects the acoustic properties of a room, impacting firefighter alarm signals' detection and localization, with implications for safety in fire rescue scenarios.

Contribution

It provides the first experimental measurements of head-related transfer functions in a fire-affected environment, revealing how fire alters acoustic cues.

Findings

Low frequency modes increase in frequency

Higher frequency modal structure weakens and becomes unstable

Received level of tones varies by over 10 dB

Abstract

The Personal Alert Safety System (PASS) is an alarm signal device carried by firefighters to help rescuers locate and extricate downed firefighters. A fire creates temperature gradients and inhomogeneous time-varying temperature, density, and flow fields that modify the acoustic properties of a room. To understand the effect of the fire on an alarm signal, experimental measurements of head-related transfer functions (HRTF) in a room with fire are presented in time and frequency domains. The results show that low frequency (<1000 Hz) modes in the HRTF increase in frequency and higher frequency modal structure weakens and becomes unstable in time. In the time domain, the time difference of arrival between the ears changes and becomes unstable over time. Both these effects could impact alarm signal detection and localization. Received level of narrowband tones is presented that shows the fire makes the received level of a source vary by >10 dB. All these effects could impact the detection and localization of the PASS alarm, and life safety consequences.