PASS Audibility Project

1. 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

2. Panel 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 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)

3. Outline • History and Motivation • Fireground sounds library • Effect of gear on hearing • Sound in compartment fires • Future work

4. 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)

5. 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.

6. 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)

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. multiple propagation paths

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. interaction with boundaries

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. sound speed potentially inhomogeneous medium (sound speed gradients) depth

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 (flow) ≈≈≈≈≈≈≈≈ ≈≈≈≈≈ ≈≈≈

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 (scattering objects)

12. Temperature gradient Introduction Sonar Approach Interaction with Boundaries Searching Firefighter Inhomogeneous Medium (Smoke) Fire Multiple Paths

13. The Sonar Equation noise level transmission loss directivity index source level detection threshold: signal-to-noise ratiorequired for operator to detect signal environment related source-related receiver-related

14. Effect of 3 dB increase in PASS Signal detecability threshold PASS at 95 dB

15. Effect of 3 dB increase in PASS Signal detecability threshold PASS at 95 dB FF inside the contour cannot hear PASS

16. Effect of 3 dB increase in PASS Signal detecability threshold PASS at 98 dB area reduced by a factor of 2

17. Effect of 10 dB increase in PASS Signal detecability threshold PASS at 105 dB area reduced by a factor of 10

18. 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

19. Octave Band Analysis

20. Directionality

21. 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

22. 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

23. *Note the change in patterns Example Results Without Helmet With Helmet

24. Overall Results : Helmets

25. Helmet, Hood, Coat 1 dB Lower Vs. = Bare Helmet only 3 dB Lower Vs. = Bare Helmet, hood and coat

26. 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

27. 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

28. Procedure • Playback signal • Subject indicates if they heard the signal • Operator turns the level down or up in correlation with the subjects response

29. Subject Test Results + +

30. Human Testing Conclusions • Strongest effect shown by the helmet • Increased auditory threshold • Lower SNR, lower possibility of detection

31. PASS Audibility Project Future

32. 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.

33. Effect of Fire on PASS • Experimental Measurement • Computer modeling Ignition Free Field PASS Signal 10 second into the fire Extinction

34. Questions

35. Aside on Hearing (Loudness) • Humans don’t 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 http://en.wikipedia.org/wiki/Loudness