Effects of noise on mental performance and annoyance considering task difficulty level and tone components of noise

Analysis of Factors Affecting Human Reliability in the Mining Process Design Using Fuzzy Delphi and DEMATEL Methods

Design errors have always been recognized as one of the main factors affecting safety and health management and sustainable development in surface mines. Unfortunately, scant attention is paid to design errors and the factors causing them. Therefore, based on expert opinions, this study aimed to identify, rank, and investigate cause-and-effect relationships among variables influencing human error in surface mine design in Iran. The study variables were identified by reviewing previous literature on “latent human errors” and “design errors.” After specifying effective variables, two rounds of the Fuzzy Delphi study were carried out to reach a consensus among experts. Nineteen variables with an influencing score of 0.7 and higher were screened and given to the experts to be analyzed for cause-and-effect relationships by the fuzzy DEMATEL method. The results of the study revealed that the following variables were the major factors affecting human error as root causes: poor organizational management (0.62), resource allocation (0.30), training level (0.27), and experience (0.25). Moreover, self-confidence (−0.29), fatigue (−0.28), depression (−0.25), and motive (−0.23) were found to be effect (dependent) variables. Our findings can help organizations, particularly surface mines, to opt for effective strategies to control factors affecting design errors and consequently reduce workers’ errors, providing a good basis for achieving sustainable development.

Redox Implications of Extreme Task Performance: The Case in Driver Athletes

Redox homeostasis and redox-mediated signaling mechanisms are fundamental elements of human biology. Physiological levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS) modulate a range of functional processes at the cellular, tissue, and systemic levels in healthy humans. Conversely, excess ROS or RNS activity can disrupt function, impairing the performance of daily activities. This article analyzes the impact of redox mechanisms on extreme task performance. Such activities (a) require complex motor skills, (b) are physically demanding, (c) are performed in an extreme environment, (d) require high-level executive function, and (e) pose an imminent risk of injury or death. The current analysis utilizes race car driving as a representative example. The physiological challenges of this extreme task include physical exertion, g loading, vibration, heat exposure, dehydration, noise, mental demands, and emotional factors. Each of these challenges stimulates ROS signaling, RNS signaling, or both, alters redox homeostasis, and exerts pro-oxidant effects at either the tissue or systemic levels. These redox mechanisms appear to promote physiological stress during race car driving and impair the performance of driver athletes.

Improving the performance of double-expansion chamber muffler using dielectric beads; optimization using factorial design

PURPOSE

Noise pollution is a common health hazard worldwide which is emitted along with chemical air pollutants, simultaneously from many sources. Some studies have been conducted to control these pollutants, simultaneously with promising results being achieved. Dielectric beads have been used in air pollution control technologies, successfully and probable effectiveness of them in noise reduction can be promising in dual use of them in the exhausts emitting noise and air pollution, simultaneously.

METHODS

In order to investigate the effectiveness of dielectric beads in noise reduction, two types of them; namely glass and ceramic beads, were placed separately inside the connecting tube of a double-expansion chamber muffler. Then the transmission loss (TL) of muffler was examined using impedance tube. A factorial design was used to evaluate and optimize the effect of noise related parameters on TL of such a system.

RESULTS

Results show that the presence of dielectric beads has significant effect on TL of muffler. The maximum TL was obtained as 74.76 dB for muffler with ceramic beads, under the optimal condition of 5250 Hz and 120 dB. Measurement of TL and sound absorption coefficient (SAC) of glass and ceramic beads showed that the noise reduction in muffler with ceramic and glass beads is probably due to SAC in ceramic beads and noise reflections in glass beads, respectively.

CONCLUSION

These results promise the dual use of dielectric beads in the exhausts emitting noise and air pollution simultaneously.

Innovative solution to enhance the Helmholtz resonator sound absorber in low-frequency noise by nature inspiration

Sound absorbing elements commonly used to make quieter spaces are very desirable for high-frequency noise control. It is more attractive if it is possible to produce sound absorbing structures that perform well for a wide frequency range, especially in low-frequencies. In this regard, Helmholtz resonator array is a well-known structure but the maximum performance of each resonator unit in an array panel can only be achieved at resonance frequency that is dependent on its size. Therefore, a resonator array panel with equal size units has insufficient performance in a wide frequency range. Hence, the consideration of suitable sizes for each resonator in an array panel consisting of unequal size units is a key point to widen the frequency range of sound absorption. On the other hand, it seems that engineering science can be developed by nature inspiration. In addition, Fibonacci sequence is a famous mathematical model which describes the shape/ratio of different phenomena which exist in nature. In this paper, Fibonacci sequence is utilized to investigate Helmholtz resonator arrangement to increase both the amount of sound absorption coefficient and frequency bandwidth of absorption without changing the total volume of resonator array with equal size units. Analytical solutions based on the modified equivalent electrical circuit theory is used to calculate the sound absorption coefficient of the proposed panel with numerical experiments in MAPLE and COMSOL Multiphysics softwares to validate the proposed overall approach. Results show that the Fibonacci sequence is an optimum candidate to design a resonator-based sound absorber in low-frequency noise.