An active sound control system has been developed for automobiles which uses interior loudspeakers to counteract the low-frequency rumble of road noise when driving on typical road surfaces. Reductions of around 7 dB of A-weighted sound pressure level in the range 100-200 Hz were measured using the system. Six accelerometers were attached to the vehicle structure to detect road-induced vibration and to provide reference signals for a feedforward control strategy. In this paper the design basis of the control system is set out and the theoretical and practical limitations inherent in this approach are examined. It is seen that key issues are "1… the placement of reference accelerometers for maximum multiple coherence with respect to the interior noise to be attenuated, and "2… adequate time advance of the reference signals to allow the controller to act in real time.

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Axle whine is a continuous, steady state tonal sound, emitted from the differential unit’s hypoid gears. It is essentially induced by torque variations. This can be as a result of resonant conditions or torque fluctuations caused by engine order vibrations, compounded by gear transmission error. The principal mechanism of gear whine noise generation is, therefore, through transmission of vibration from the gear shafts and bearings to the differential housing, which is radiated as noise. Furthermore, interactions between the differential unit, axles and driveshafts often generate excessive tonal noises, which are the result of coupled bending and torsional resonances of assembled components. These resonances induce a magnification effect upon the noise source itself through exciting the gear shafts and distorting the alignment of the gear sets. Axle whine noise has become an important noise, vibration and harshness (NVH) concern, because of the nature of the noise; further compounded by the human aural system, which is highly sensitive in tonal memory. The result is continuously increasing warranty costs or use of expensive palliatives to mitigate the phenomenon. In this paper, a combined experimental and numerical investigation of axle whine in a rear-wheel-drive light truck is presented. The aim is to reveal some root causes of the drivetrain’s NVH behaviour, which can be related to the amplification/reduction of axle whine vibration and noise. Correlation of the experimental results with the vibration modes of the drivetrain has shown that for vehicle coasting conditions a number of modes are excited, which can interact with the vibrations of the hypoid gear pair. Finally, some light is shed on the role that differential bulk oil temperature plays in the severity of the ensuing vibration.

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Monitoring cues, such as an image of a face or pair of eyes, have been found to increase prosocial behaviour in several studies. However, other studies have found little or no support for this effect. Here, we examined whether monitoring cues affect online donations to charity while manipulating the emotion displayed, the number of watchers and the cue type. We also include as statistical controls a range of likely covariates of prosocial behaviour. Using the crowdsourcing Internet marketplace, Amazon Mechanical Turk (MTurk), 1535 participants completed our survey and were given the opportunity to donate to charity while being shown an image prime. None of the monitoring primes we tested had a significant effect on charitable giving. By contrast, the control variables of culture, age, sex and previous charity giving frequency did predict donations. This work supports the importance of cultural differences and enduring individual differences in prosocial behaviour and shows that a range of artificial monitoring cues do not reliably boost online charity donation on MTurk.