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With the growing increase in the use of lawn mowers, it is necessary to control the vibration and sound pressure levels to which operators are exposed during their workday. Noise hearing loss can affect individuals exposed to high Sound Pressure Levels (SPL). Workers using lawn mowers are part of this population. With regard to this equipment, another factor that must be considered is the occupational exposure of the vibration imposed on the operator. Occupational exposure to vibration in the hands and arms is associated with a variety of adverse effects on the health of the individual, being collectively known as the vibration syndrome in the hands and arms. Exposure to full body vibration for seated people is associated with an increased risk of degenerative injuries lumbar spine, disorders in the central nervous system, and possible damage to the digestive and genital / urinary systems.

Despite its advantages for sustainable development, railways have great potential of noise generation. This is the main source of annoyance for railroads’ neighboring communities. Among the many types of noise that exist on a railway system, the impact noise generated at rail joints is one that stands out. To propose mitigation measures in order to solve this problem, it is necessary to understand how this noise is generated and by which parameters it is influenced. To that end, analytical models have been developed over the years. They are useful tools to verify which factors are more important to noise emission, and also can be used to predict the sound pressure level (SPL) generated and test possible solutions. This paper aims to validate an analytical model for impact noise which was originally designed for urban railways, used for passenger transportation. In this work, the validation is made using SPL measurements made at a Brazilian freight railway.

Noise pollution resulting from technological development, urbanization and economic growth is one of the major sources of complaints in urban areas. The sound generated by transportation systems, is one of the most important causes of noise-induced annoyance, since the exposure to high levels for long periods of time can be detrimental to health. Freight railway systems have great potential of noise emission, since they are designed to meet safety requirements, rather than comfort, and are subject to more severe operations and cruder maintenance procedures than passenger cars. Among the different types of noise that originate from a railroad, the squealing generated in curves is one that stands out since it can exceed regular rolling noise in 30 dB and often occurs in frequencies where the human hearing is more sensitive. Analytical models have been developed over the years to help understanding and predicting squeal.

Due to the great use of airplanes for transportation, it was necessary some studies to improve it, one of the most difficult problems to solve, is the noise generated by the systems. In-flight sound pressure levels can sometimes be intense and cause fatigue to the cabin crew, communication failures and discomfort to the passengers. This is often caused by the turbulent boundary layer over the aircraft body, engine noise and vibration and internal aircraft systems. The aircraft hydraulic system is responsible for moving the rudder, aileron, brakes, main door, and other components, and consequently, the noise of this system became more noticeable. This system comprises a pump, generally, located at the back of the aircraft and pipes, which are fixed along the fuselage. The pipes are connected to the fuselage using rubber mounts. Analyzing experimental measurements is possible to identify that hydraulic system contribute to the in-flight sound pressure level in the aircraft cabin.

One of the most important complaints about noise in small vehicles is related to the hydraulic steering pump, which is used strongly during parking maneuvers, and produces a noise that overcomes the one coming from the engine, due to its low speed. This noise can be eliminated by the introduction of two resonators inside the high-pressure tube designed to coincide with the tube's resonance frequency. However, in some cases, as in tubes with short rubber pieces, these resonators may be not sufficient to reduce the noise to non-audible levels, due to its low ability to absorb the pressure peaks coming from the pump. In these cases it is possible to introduce orifices at each resonator to maximize its effect. Here we present the theory related to the use of these orifices and the results obtained in tests on bench.

In recent years, SEA has been recognized as an important tool to model the vibro-acoustic behavior of vehicles in mid and high frequencies. Through SEA it is possible to develop vehicle models early in the design stage, reducing the risk of future noise problems and allowing the optimization of noise control treatments. Moreover, at the final design stages, a SEA model can be use to evaluate changes at the project, reducing costs with experiments. In a SEA model, the structure under study is divided in subsystems. The capacity of each subsystem of storekeeping, dissipating and transmitting energy is described by three parameters: modal density, loss factor and coupling loss factor. The noise and vibration sources are include in the model as power inputs to subsystem and, based on an equilibrium power balance, it is possible to calculate the energy of each subsystem.

Brake squeal noise has been under investigation by the automotive manufacturers for decades due to consistent customer complaints and high warranty costs. In most cases, the customer perceives the noise as a vehicle problem and demand having it fix by their dealer. J. D. Power surveys consistently show brake noise as one of the most critical vehicle quality measurements. Furthermore, the development of methods to predict the noise occurrence during the design of a brake system has been the target of many researchers in the last years. The complex eigenvalue analysis has been widely used to detect unstable frequencies in brake systems models. The method is fast and useful to provide design guidance, since operating parameters and control methods can be evaluated by a simulation procedure. This paper summarizes the application of the complex eigenvalue analysis in a finite element model of a commercial brake system.

In this study an objective metric is presented to evaluate the hiss noise of hydraulice power steering. The correlation between subjective tests and psychoacoustics metrics is investigated. The objective metric is obtained using multilinear regression where the psychoacoustics metric and the results of the subjective tests are the dependent and independent variables of the linear regression, respectively.

The application of sound quality tools in the design process of electro-hydraulic power steering (EHPS) is investigated in this paper. The EHPS acoustics performance is investigated by studying the correlation between objective measurements and subjective evaluation of the noise from the EHPS.

During the last years, the automotive industry dedicated great efforts to understand and solve the noise problem from disc brake systems. There are several types of brake noise problems, each one related with a frequency range of occurrence. In most cases, the customer perceives the noise as a vehicle problem and demand having it fix by their dealer. As a consequence, disc brake noise is one of the major contributors to the automotive manufactures warranty costs, leading the automotive industry to look for ways to control it. A large class of disc brake noise problems is associated with the resonant behavior of an operating brake system. However, the detection of these brake system modes during the operating condition can be very expensive, demanding the use of inertial dynamometers and laser vibrometer measurements.

The acoustic development of vehicles is a very important step during its design to ensure its success in a competitive marketplace. In recent years, the advances on the noise and vibration control engineering in vehicles provided the production of quite and comfortable cars. The main noise and vibration sources in vehicles, i.e., engine, gearbox and exhaust systems, had its noise levels considered reduced, and, as a consequence, other noise sources became more easily observed. The noise generated by pumps of power steering systems is an example of this kind of problem. For the majority of automotive applications are used vane pumps. These pumps generate noise due the vane passing frequency. Basically, the hydraulic pump noise can be classified as Moan or Whine, regarding the operating condition. This work presents a methodology to approach the noise and vibration problem from hydraulic pumps of power steering systems.