title: Cognitive performance and subjective experience during combined exposures to whole-body vibration and noise.
abstract: OBJECTIVE
  The goal of this study was to examine the effects of noise and whole-body vibration, individually and combined, and at various stimulus intensity levels, on cognitive performance and subjective experience.
  
  
  METHODS
  Fifty-four participants (27 men and 27 women) with a mean age of 25 years, ranging from 19 to 30, were exposed for 20 min each to a 16-Hz sinusoidal whole-body vibration, a helicopter sound at 21 Hz, both stimuli combined, and a control condition. Participants were randomly assigned to one of three groups: low intensity [77 dB(A) noise and 1.0 m/s2 vibration], medium intensity [81 dB(A)/1.6 m/s2] or high intensity [86 dB(A)/2.5 m/s2. During each environmental exposure, short-term memory performance was tested with a visual Sternberg paradigm. Reaction time was measured as a dependent variable. Directly following each environmental exposure, participants rated the difficulty of the task and the annoyance level of the exposure stimulus.
  
  
  RESULTS
  Results revealed no significant changes in reaction times due to environmental exposure or intensity level. However, participants significantly rated the combined exposure as both more annoying and more difficult than the other conditions. Further, the high-intensity group rated subjective annoyance significantly higher than the other groups for all conditions.
  
  
  CONCLUSIONS
  The results from this study indicate that performance alone is not a sufficient measure for the study of the effects of combined stimuli on a human operator.
authors.affiliation: National Institute for Working Life, P.O. Box 7654, 907 13, Umeå, Sweden. Jessica.Ljungberg@arbetslivsinstitutet.se
authors.forename: Jessica
authors.initials: J
authors.lastname: Ljungberg
authors.forename: Gregory
authors.initials: G
authors.lastname: Neely
authors.forename: Ronnie
authors.initials: R
authors.lastname: Lundström
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D003071:Cognition; D005260:Female; D006801:Humans; D008297:Male; D009622:Noise; D013548:Sweden; D014732:Vibration