A Meta-Analysis of Periodic Noise Stress on Human Performance J.M. Ross, G.E. Conway, J.L. Szalma, B.M. Saxton, A. Braczyk, & P.A. Hancock University of Central Florida Orlando, Florida, USA

Overview Problem Space and Background Research Questions Methodology and Procedure Results Discussion Conclusion

Problem Space and Background: Noise Stress Noise Stress in general is defined as unwanted sound. –Physiological Effects –Affective Effects –Performance Effects Periodic noise – Continuous –Machinery –Helicopter Engines Aperiodic noise – Intermittent –Speech –Gunfire

Problem Space and Background: Noise Stress and Task Type Noise Effects of Not Consistent –Noise Improves Performance –Noise Hinders Performance –Noise Does Not Effect Performance Moderator Variables –Task Type (Backer & Holding, 1983) –Dependent Measure (Staal, 2004).

Meta-Analysis A quantitative literature review. –Accumulates experimental results across independent studies that address a related set of research questions through effect-size estimates. Benefits –Provides a summary estimate. –Allows hierarchical analysis by moderator variables. Detriment –Limited by available literature.

Research Questions Will task-type (e.g., cognitive, psychomotor, perceptual) moderate the noise stress relationship? Will the dependent measure (i.e., speed vs. accuracy) moderate the noise stress relationship? Will there be a task type by dependent measure affect on the noise stress relationship? 1 2 3

Task Types

Methodology and Procedure Literature Accumulation –Examined 423 noise stress articles –k = 73 Criteria for Inclusion –Original empirical periodic noise stress study reported in paper. –A lower dB control condition was required for comparison with a higher dB noise condition. –The dependent variable must measure performance of a healthy adult human participant. –Each study had to present enough information to obtain effect size statistics

Effect Sizes and Variance Estimates Effect Size (ES) –Hedges g –Standardized mean difference between the experimental and control conditions (Hedges & Olkin, 1985). Direction of the Effect –Positive ES noise > control. –Negative ES noise < control. Cohen’s Guidelines to Effect-Sizes –Small g ≤ 0.20 –Medium g ≈ 0.50 –Large g ≥ 0.80 Variability –Sampling Error –Effect Size Error

Hierarchical Analysis Division of Studies Avoid violating assumption of independence Limitation of division of results Overall Periodic Noise k = 73 Perceptual Tasks k = 20 Cognitive Tasks k = 49 Psychomotor Tasks k = 6 Communication k = 8

Results Periodic Noise Stress –Overall there is a decrement in performance for periodic noise stress.

Results Task Type and Periodic Noise –Perception and Psychomotor contain zero within the CI. –Cognitive has a small negative overall effect. –Communication has a moderate negative effect.

Results Dependent Measure and Periodic Noise –True negative effect for both speed and accuracy.

Results Task Type by Dependent Measure –Three true effects:

Discussion Noise Effects –Periodic noise expected general negative effect –Task Types Higher order tasks break down (i.e., cognitive and communication tasks). Lower order tasks not impacted (i.e., perception and psychomotor). –Dependent Measure equal decrement –Gap in communication speed studies. Future Research –Add additional moderating variables to analysis. Intensity of Noise Duration of Noise –Compare with Intermittent Noise Effect by Task and Dependent Measure

Acknowledgements The views expressed here are those of the authors and do not necessarily reflect the official policy or position of the Department of the Army, the Department of Defense, or any official agency of the United States government. This work was supported by a sub- contract through Micro-Analysis and Design (MAAD) from the Human Research Engineering Directorate, Army Research Laboratory (HRED-ARL), P.A. Hancock, Principal Investigator (Grant # ). We wish to thank John Lockett, Laurel Allender, Celine Richer and Sue Archer, for providing their administrative and technical direction for this Grant.

Questions?