Carryl L. Baldwin
Western Iowa Tech Community College
Angela M. Galinsky
University of South Dakota
In today's complex systems, heavy demands may be placed on the operator both in terms of mental workload and human perceptual abilities. Automation may decrease operator demands in some instances; however, as pointed out by Parasuraman and Mouloua ( 1996) automation may also merely redistribute demands without reducing mental workload.
Because automated systems are not limited in terms of the amount of information which can be processed at any given time, designers have tended to make automated systems increasingly complex, thus shifting the operator's role to one of supervisory control or monitoring ( Wickens, 1992). The more complex the system, the greater the likelihood that some part of the system will fail. Wickens points out that failures can occur in teems of: a) failures of the initial system (like the aircraft engine); b) failure of the automation (like the auto pilot); or, c) failure of the monitoring system either in terms of failing to indicate system failure or indicating system failure when in fact there is none. Auditory displays can be used to enhance the human performance capabilities of operators in complex environments and are therefore frequently used to convey essential information to the operator both supplementing visual information and providing early warning of system failure.
Due to the essential nature of auditory displays in many complex environments, operators are frequently required to demonstrate minimum auditory capabilities as measured by audiometric testing. However, in light of recent research demonstrating performance changes across decibel (dB) levels under conditions of moderate mental workload, which are not found in low mental workload conditions, the validity of standard audiometric tests for predicting actual performance in complex environments is called into question ( Baldwin, 1996; 1997).
Older individuals experiencing decrements in auditory abilities may be particularly affected by the intensity of auditory displays. As our workforce ages, and the human role shifts increasingly to one of supervisory control in automated environments, strategies aimed at optimizing the performance capabilities of older workers become essential. Further investigation of the role of signal intensity and its relation to perceptual and cognitive processing of auditory displays has tremendous potential toward this end.
In the present investigation, the nature of the relationship between sensory abilities and the cognitive environment in which sensory abilities are examined was explored. It was hypothesized that pure-tone auditory thresholds would increase when participants were tested under moderate mental workload conditions (when participants had to perform a secondary task). Specifically, it was predicted that participants would require higher decibel levels to detect pure-tone frequencies when performing the detection test simultaneously with a cognitively challenging task as compared to detection thresholds obtained under standard assessment methods.
Forty volunteers from a Midwestern college, with a mean age of 22.2 years, participated in the experiment. Each participant completed two audiometric exams testing pure-tone threshold levels at 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz for both the left and right ears. In one of the audiometric exams,