Cabin noise

Trends in the aerospace industry parallel those in the overall transportation-related market segments. Lighter weight for decreased fuel consumption and enhanced safety are trends that immediately come to mind. In addition to these, reduced cabin noise, and reduction of maintenance/extension of lifetime are important as well. 

In The Brave New World of Huxley [102], the helicopter represents the dominant means of personal transportation. Huxley s shining but essentially dark vision of the future is still in the future for the most part. No one today would seriously dare to compare the noise of helicopters with the buzzing of bees. Noise and vibrations limit the use of helicopters they are too noisy in towns, too easily detected in warfare. Cabin noise stresses both pilots and passengers. Vibrations can fatigue components and imply frequent and expensive inspections. Adaptive structural systems can mitigate these effects and improve flight performance. Vibration induced problems had to be addressed since the early days of rotorcraft development noise related problems become more and more critical with today s versatile deployment. Figure 2.1 shows how these problems are interrelated and points at their economic impact. 

Wind power has been slowed by public opposition. In 2002, a citizen s group in Prince Edward County, Ontario, vetoed a small windfarm project on the coast of Lake Ontario near Hillier. They proposed that the 22 proposed wind turbines would be noisy, kill birds and harm the neighborhood by being too visible. These are common complaints about wind-farms, but at a distance of about 200 meters, the sound of a windfarm is faint. At closer distances the noise is similar to the sound of an airplane s engine from inside the cabin. Even under the spinning blades it is possible to converse in a normal voice. One Dutch study showed that a small wind-farm is less harmful to birds than 1-kilometer of road or powerlines. 

DaimlerChrysler s newest fuel cell is in the Mercedes-Benz b-class car. The fuel cell is a sandwich design with the polymer PEM cell between two gas permeable electrodes of graphite paper. Hydrogen is introduced to one side of the fuel cell while the other side is exposed to the air. Like the GM Hy-Wire platform, the fuel cells, fuel tank and fuel systems are under the floor. The compressor is in the front of the car to reduce the noise. There are four hydrogen sensors on the fuel cell stack, on each of the hydrogen tanks, another at the electric motor and another inside the cabin. 

The best way of achieving good emission levels with relatively small ventilation rates is when shake-out is performed in enclosed units. Roof openings, possibly with a moving screen, doors and entry/exit chutes make it possible to use a crane or other means of transport. In addition, the closed cabins reduce the noise level. 

Trains Lighting and other cabin Reduce emissions and noise... 

Nondisturbing noise, pleasant environment (acoustic signals well absorbed, cabin air conditioned)... 

Other obstacles Cabin oscillations (vibrations), noise Uc 0.3 0.2-0.4... 

Noise reduction may be realized by means of a variety of technical measures. The measures include source noise reduction (e.g. noise generated by machines, woiking processes and procedures), noise reduction by noise absorption (e.g. by nsing shields, screens, absorbing panelling), noise reduction on designated locations (e.g. soundproof cabins, personal ear-protective equipment). 

Cameras, on the other hand, can overcome this limitation by being placed in other locations (e.g. hiding the camera modules in the cabin roof design). Even though some FO V can only be covered if the camera is placed at the same location as the traditional mirrors, noise creation will be reduced due to the smaller size of the cameras [9]. 

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