Air Force Presentations
A Comparison of HPD Attenuation Measurements Obtained with Subject and Experimenter Fittings
Carolyn S. Bennett, Lt Col, USAF, BSC
Air Force Research Laboratory
Wright- Patterson, AFB, OH
The American National Standards, ANSI S12.6 - 1997, Methods for Measuring the Real-Ear Attenuation of Hearing Protectors, paragraph 0.2 states: “The need for a better human-factors model… experimenter-supervised fitting of HPDs…is intended to describe the upper limits of hearing protector performance…provide inadequate insight into the performance of HPDs when real-world human-factor considerations must be taken into account.” In an attempt to provide more valid estimates of field performance, the working group responsible for the revision of the ANSI 1984 standard for measurement of real-ear attenuation developed the subject-fit method of ANSI S12.6 - 1997. Under the subject-fit method, subjects must be naive hearing protector users.
The Department of Defense (DoD) Hearing Conservation Working Group (HCWG) Memorandum For The Record, 31 March 97, paragraph 14 states: “Consensus was reached that DoD should use subject fit methods to determine NRR…consensus that subject fit data were most appropriate for both the purchasing process and for field evaluation.”
Empirical data has not yet been presented, however, that validates a single HPD attenuation measurement method. The Air Force Research Laboratory, Wright-Patterson AFB has undertaken a group of experiments to determine empirically which method of hearing protector attenuation measurement will provide the most valid measurement of field performance. The present study, “A Comparison of HPD Attenuation Measurements Obtained with Subject and Experimenter Fittings” is a preliminary study in the investigation of the most valid method to predict hearing protector attenuation. Air Force Research Laboratory, measured attenuation values using ANSI S12.6 - 1997, Method B. Procedures followed were those specified in ANSI S12.6 - 1997, 9 Method B: subject-fit.
The study to be presented compared the attenuation values obtain using subject fit method with attenuation values obtained using the experimenter fit method previously employed by the Air Force Research Laboratory.
Deployment of an Auditory Readiness Information Center (ARIC) at International Military Air Show in England
Capt John Hall, USAF
48 MDOS/RAF Lakenheath
Air Fete, held each year at RAF Mildenhall in England, is one of the largest military airshows in the word. The event attracts nearly 200,000 visitors from around the globe and is joint sponsored by the American and British air forces.
Last year, at Air Fete ‘98, a new display was introduced in the exhibition hanger to promote awareness of hazardous noise in aviation and the need for hearing protection and hearing conservation. To appeal to an even larger area of interest, the Auditory Readiness Information Center was combined with other displays of aviation human systems technology under the title of Aerospace Medicine.
Flight medicine topics from hypoxia to G-suite development were presented in conjunction with auditory readiness and hearing conservation. Hands-on items such as the Combat Edge Pressure Suite, an ejection seat, a centrifuge ride video, and personal protective gear attracted much attention. Over 200 pairs of foam insert noise plugs were dispensed to the public and The Radio Suffolk BBC commentary reported this display to be the “most interesting” in the Air Fete exhibition hanger. The Aerospace Medicine Squadron Commander was even on hand for an interview.
A complete description of the planning and implementation will be offered. Ideas and talents from base graphics to the base arts & crafts shop were utilized to put together this museum quality professional display.
The Impact of Accent, Noise, and Linguistic Predictability on the Intelligibility of Non-native Speakers of English
Maj. Kimberly R. Scott, CCC-SLP
Department of Communication Sciences and Disorders
Alice M. Dyson, Ph.D., Committee Chair
In noisy, fast-paced situations, listeners have difficulty understanding speakers with foreign accents, especially when listeners cannot predict the meaning from other words in the sentence. This study examined the effects of noise levels and degrees of foreign accents on 50 listeners understanding of words in predictable and unpredictable sentences. Although noise and sentence predictability did affect understanding, the degree of foreign accent further compromised listener accuracy. As listening conditions became degraded by noise or unpredictability, listeners were less able to accommodate for the degree of accent.
In international airspace, communication breakdowns often occur because of accented speech and poor radio systems. The findings of this study have an implication for those who speak English as an international language in such situations or when English is the common language of two non-native speakers. These findings are also applicable to settings such as emergency rooms, telephone or radio communications, and classrooms.
Acoustic Remote Threat Detection (ARTD)
Dr. Daryl Hammond, AFRL/HECB
Lt Col Carolyn S. Bennett, AFRL/HEC
Defense and protection of USAF personnel and resources is a high Air Force priority and a prerequisite for air power operations (MNS CAF 314-92). The most obvious example: the Khobar Towers bombing demonstrates the need capability to detect, identify, warn, report, and protect against enemy attack
The Acoustic Remote Threat Detection will realize improved force protection through increased speed of location and classification of threats via integrated acoustic sensor arrays, signal processing, and human centered distributed interfaces. This expanded research program builds upon the 1992 & 1996 successful field demonstrations of 3-D auditory displays and the 1995 field application of the remote sonic boom monitoring and recording system.
Ears and eyes for security forces/sentries, Acoustic Remote Threat Detection, utilizes a series of affordable, expendable, small, low power, easily deployable multi-sensor research to process sensor information to identify and locate potential and/or active threats. High fidelity two-way communication links the sensors to a central command post and/or distributed users. The resulting product will provide a dramatically improved threat response for the Air Expeditionary Forces.
The Acoustic Remote Threat Detection package will employ at least 6 microphones at each location, a differential GPS for automatic sensor location, remotely generated acoustic impulse for microphone array calibration, local processing of sensor information to reduce communications and spectrum communications links for low probability of intercept, low power, secure, and jam resistant communication. The Acoustic Remote Threat Detection package will be able to screen against a library of sounds by determining what is different from background normal sounds. It will have the capability for remote updates of sound libraries and models in its motion analysis for velocity and direction and change in sound over time (loaded truck?).
The payoff for the remote user will be information to the scout/shooter, intuitive sensing of friendly vs. foe, enhanced signaling for target, locality information for potential threat (acoustic pointing), hands free/eyes free interface to the deployed troop and directional Information. Khobar Towers bombing demonstrates the need capability to detect, identify, warn, report, and protect against enemy attack.
New European Design: Venturi HPDs
Capt John Hall, USAF
48 MDOS/RAF, Lakenheath
A new custom Hearing Protection Device (HPD) ear plug has recently been tested at RAF Lakenheath and RAF Mildenhall which utilizes a venturi to limit sound pressure reaching the eardrum. Preliminary real world tests of this technology with 48th Fighter Wing F-15 pilots and 352nd Special Operations Combat Controllers have demonstrated significant benefits which will be studied further at the Air Force Research Laboratory at Wright-Patterson AFB.
The venturi principle has been used in gasoline engine carburetors for over 50 years, but a designer in Holland has creatively applied the principle to hearing protection. A venturi is a narrow opening designed to create aerodynamic turbulence as air pressure increases. Since sound is oscillating air pressure, it makes since that this technology can be used to restrict hazardous noise.
The venturi on board the “Sound Censors” custom earplug restricts sound pressures progressively more in the high frequencies where noise is most harmful. The attenuation characteristics pass enough low and mid frequency information (at safe levels) to enable the wearer to understand speech (as well as environmental auditory cues) in noise significantly better than other HPDs currently on the market. The plugs meet all International Standards Organization (ISO) requirements for hearing protection in hazardous noise and are low profile enough to fit comfortably under all DoD headgear, helmets, and communication headsets.
Several pairs of Sound Censors were tested this year. An 493rd Fighter Squadron F-15E pilot who recently mission tested a pair reports “marked improvement of radio and intercockpit voice communications.” Likewise, Combat Controllers at the 352nd Special Operations Group (SOG) report the devices “greatly enhance mission effectiveness” aboard SOG airframes and during tactical operations on the ground.
A complete summary of the venturi HPD principle, real world performance in the USAF, effective Noise Reduction Rating (NRR), and directions for further study at the Air Force Research Lab for possible Air Force wide approval will be discussed.