Occupational Ergonomics

The purpose of the present paper was to review the literature to develop an understanding of the effects of noise and music on human performance. The second purpose was to study the effects of music on a commonly performed task that is frequently accompanied by background music: driving. Background noise not only affects public health, but it also negatively affects human performance in such tasks as comprehension, attention, and vigilance. However, some studies have indicated that noise exposure may not affect simple vigilance. Despite music's distinct difference from noise it too affects human performance negatively and positively. The results are inconclusive on the effects of music and task performance. More specifically, the effects of music on driving performance are quite similar to that of noise on task performance. Music seems to alleviate driver stress and mild aggression while at times facilitating performance. However, during other conditions of music, driving performance is impaired. Different aspects of sound (i.e. volume, type, tempo) impact human performance differently. It is still unknown which aspect (music or noise) affects task performance to a greater degree.

The objective was to determine whether specific types and volumes of sounds affect driving-related tasks. Participants completed six trials while exposed to different sound types (hard rock, classical music and industrial noise) and volumes (53 versus 95 db (A)). Participants executed a randomized order of tasks, involving: movement (MT), reaction time (RT), simulated driving (SimD), and non-conscious perception of masking stimuli. The results suggest high volumes impaired SimD, RT and MT. During hard rock music, accommodation HR was significantly higher whereas male RT was slower than female RT. However, RT was enhanced when subjects were exposed to hard rock music during a non-conscious task of longer duration. SimD crashes increased during quiet hard rock music in comparison to quiet industrial noise. Experimental HR was lower during quiet sound volumes for both genders. In summary, loud volumes affect simple vigilance whereas hard rock music may affect tasks involving concentration and attention especially with males.

Twenty right-handed male university students performed a full factorial experiment, consisting of three forearm rotation angles (60% prone and supine, and neutral), two elbow angles (45° and 90°), three humeral rotation angles (45°, 90° and 135°), and two upper arm angles (45° flexion and neutral). The task was a one-second pronation torque of 20% Maximum Voluntary Contraction (MVC) relative to MVC at the standard position of the arm, 15 times per minute for 5 minutes, at each postural combination. Discomfort rating after the end of each five minute exertion was recorded on a visual analogue scale. A repeated measures ANCOVA on discomfort score indicated that endurance time was a significant covariate. Other significant factors were upper arm flexion angle, forearm rotation angle, and the interactions of upper arm*elbow and humeral rotation*forearm*endurance time. A supplementary experiment showed that in some of the deviated posture combinations the subjects required additional muscle force to achieve the 20% MVC from the original testing posture. Such data can be helpful for designing workplaces and developing biomechanical models, especially for assessment of designs in virtual environments.

The most severe direct motion induced effect on the ability of an individual to work in a moving environment probably occurs in gross body tasks requiring balance and co-ordination, be it the crew trying to undertake their task effectively or the passenger trying to walk around the vessel. During rough weather working in the ship becomes more difficult and even the most experienced sailor will experience events where they must stop their activity, be it a specific task or merely standing, and hold on to some suitable point to minimise the risk of injury; these events are called Motion-induced interruptions (MIIs). MIIs were recorded during the performance of a series of tasks on board a ship at sea in rough weather. The tasks were: standing facing aft, walking athwartships, a simulated weapon loading task, standing facing athwartships and a simulated fire-fighting task.

Complex mathematical models of postural stability exist but currently lack the fidelity to accurately predict MIIs. This paper presents data from an empirical study in which MIIs experienced by subjects on a ship at sea were logged by an observer. Measurements of lateral and vertical acceleration of the deck immediately prior to the MII were made and thresholds of acceleration for undertaking task were determined. These so called tipping coefficients are presented for use with predictive tools in ship design.

The purpose of this work was to quantify upper limb and joystick kinematics, muscle activation of the prime movers and stabilizers of the shoulder (anterior deltoid, posterior deltoid and upper trapezius) as well as torque exerted by operators of hydraulic-actuation joystick controllers. Dynamic and impact torques were captured through the use of an instrumented joystick. Results indicate that the impact torque (5.36 ± 1.75 N·m for forward motion) sustained as the joystick reaches the end range of motion is substantial and is more than twice that of the operator exerted torque prior to reaching the hard endpoint. EMG data confirm that the upper trapezius is in a state of constant but low level activation, which may be largely attributable to postural demands forced upon the operator by the armrest.