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Slide 2 PASS Audibility Project Mustafa Z. Abbasi, Preston S. Wilson Applied Research Laboratories Department of Mechanical Engineering The University of Texas at Austin Joelle I. Suits, Ofodike A. Ezekoye Department of Mechanical Engineering The University of Texas at Austin Craig A. Champlin Department of Communication Sciences and Disorders The University of Texas at Austin Casey Grant Fire Protection Research Foundation Slide 3 Mustafa Abbasi (UTexas Austin); Bob Athanas (FDNY); Chris Barron (SFFMA of Texas); Rob Bredahl (Austin FD); Keith Bryant (OK City FD); Mark Burdick (Glendale FD); DK Ezekoye (UTexas Austin); Casey Grant (FPRF); Zach Haase (NFPA ESE TC Task Group); Todd Keathley (Portland Fire & Rescue); Steve Lumry (OK City FD); Dennis McFadden (UTexas Austin); Bob Nicks (IAFF Local); Kris Overholt (UTexas Austin); Dan Rossos (Portland Fire & Rescue); Joelle Suits (UTexas Austin); Bruce Varner (NFPA ESE TC); and Preston Wilson (UTexas Austin) Fire Protection Research Foundation University of Texas New York FD Austin FD Oklahoma City FD Glendale FD Portland Fire & Rescue NFPA ESE TC Task Group IAFF Local State Firemen's & Fire Marshals' Association of Texas Panel Slide 4 Outline History and Motivation Fireground sounds library Effect of gear on hearing Sound in compartment fires Future work Slide 5 Brief History Firefighter disorientation is major problem From 1994 to 1998, an average of 725 fire fighters per year were caught or trapped in structure fires that resulted in injury or death of fire fighters* Firefighters can be overcome by heat or smoke of a fire and may be unable to alert other fire ground personnel to their need for assistance PASS device was standardized in NFPA 1982 Significant improvements in testing and performance since New features include automatic activation, integration in the radio and SCBA, etc. *According to an analysis of National Fire Incident Reporting System (NFIRS) data by the National Fire Protection Association (NFPA) Slide 6 Shortfalls in PASS ? NIOSH reported that during the investigation of four fire fighter fatalities that occurred from 2001 to 2004, the PASS alarm signals were not heard or were barely audible. Slide 7 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. target radiating acoustic waves (sound) Slide 8 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. multiple propagation paths Slide 9 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. interaction with boundaries Slide 10 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. potentially inhomogeneous medium (sound speed gradients) sound speed depth Slide 11 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. potentially inhomogeneous medium (flow) Slide 12 Introduction Sonar Approach Passive sonar is used to detect, localize and classify underwater targets, in complicated environments, where optical means fail, by listening to the sounds they emit. potentially inhomogeneous medium (scattering objects) Slide 13 Introduction Sonar Approach Temperature gradient Fire Searching Firefighter Multiple Paths Interaction with Boundaries Inhomogeneous Medium (Smoke) Slide 14 source level transmission loss noise level directivity index detection threshold: signal-to-noise ratio required for operator to detect signal source-related environment related receiver-related The Sonar Equation Slide 15 detecability threshold PASS at 95 dB Effect of 3 dB increase in PASS Signal Slide 16 detecability threshold PASS at 95 dB Effect of 3 dB increase in PASS Signal FF inside the contour cannot hear PASS Slide 17 detecability threshold PASS at 98 dB area reduced by a factor of 2 Effect of 3 dB increase in PASS Signal Slide 18 detecability threshold PASS at 105 dB area reduced by a factor of 10 Effect of 10 dB increase in PASS Signal Slide 19 Fireground noise The fireground can be very noisy Chainsaws, smoke alarms, fans, trucks, etc. Previous studies have focused on absolute sound pressure levels. No previous has measured the spectral content of fireground noise Our current understanding of hearing shows that the level is the proper frequency is pertinent in regards to detection Slide 20 Octave Band Analysis Slide 21 Directionality Slide 22 Effect of Gear Humans have learned to localize sound without wearing protective gear Gear could reduce sound level heard Hypotheses : Protective equipment is reducing the level firefighters hear Gear could make it difficult to localize PASS location Slide 23 Procedure Purely physical measurement Helmets and other gear Acoustic Manikin (KEMAR) Anechoic chamber Head related transfer function Human subject testing Standard hearing threshold measurement With gear, without gear Discrete frequencies, and one sample PASS Slide 24 Example Results With Helmet Without Helmet *Note the change in patterns Slide 25 Overall Results : Helmets Slide 26 Helmet, Hood, Coat Vs. = 3 dB Lower Vs. = 1 dB Lower Bare Helmet, hood and coat Helmet only Slide 27 Manikin Testing Conclusions Significant difference amongst helmets The helmets change the physical patterns heard by the firefighters. The could affect localizing the PASS Average 3 dB level SPL drop with gear Maybe increase PASS levels to compensate Slide 28 Human Testing Manikin tests showed 3 dB lower level caused by helmet and gear Human subject testing was conducted to test this observation Standard method of limits with adaptive one up one down rules. Test were performed with subject wearing : No PPV Helmet Helmet, NOMEX hood, coat 6 subjects tested so far Slide 29 Procedure Playback signal Subject indicates if they heard the signal Operator turns the level down or up in correlation with the subjects response Slide 30 Subject Test Results + + Slide 31 Human Testing Conclusions Strongest effect shown by the helmet Increased auditory threshold Lower SNR, lower possibility of detection Slide 32 PASS Audibility Project Future Slide 33 Field Testing with Fire Service Partners Simulate real fire noise using recordings, and have firefighters locate the PASS. Need help from partners to identify structures that can be used for tests. Slide 34 Effect of Fire on PASS Experimental Measurement Computer modeling Ignitio n Extinctio n Free Field PASS Signal10 second into the fire Slide 35 QUESTIONS Slide 36 Humans dont hear all frequencies equally Most sensitive between 1-3 kHz with normal hearing Standard weighting curves mimic how we hear A weighting most commonly used Aside on Hearing (Loudness) http://en.wikipedia.org/wiki/Loudness