Showing papers in "The Open Acoustics Journal in 2011"
TL;DR: In this article, the authors used a Neumann KU-100 dummy head with embedded binaural microphones to measure noise levels in a motorcycle helmet as a function of velocity.
Abstract: The incidence of collisions between motorcyclists and other vehicles may be significantly reduced by research that improves the acoustic awareness of cyclists, and thus heightens the ability of cyclists to respond to unexpected incursions from the surrounding traffic. We use our hearing as an early warning system, and hearing swiftly redirects our vision and attention. This shift in gaze is critical to our capacity to assess the location, direction of travel, and velocity of approaching vehicles. The present study was composed of two experiments. In the first experiment a Neumann KU-100 dummy head with embedded binaural microphones was used to measure noise levels in a motorcycle helmet as a function of velocity. Noise levels were measured in two helmets, one with active noise reduction technology, and one without. The results showed that noise levels exceeded 100 dB (A) at highway speeds in the absence of noise reduction technology. The helmet with active noise control ear muffs was able to attenuate helmet noise by up to 26 dB. Active noise control technology shows great promise for noise reduction for the motorcycle helmet industry, and the development of "quiet" helmets is important for both hearing conservation and highway safety. The second experiment surveyed subjective perceptions of helmet noise by motorcyclists. The results from the present sample showed that 92.1% of the respondents objected to the high noise levels associated with cycling, 63.5 % wore earplugs, 46.8% reported tinnitus, and 95.2% wanted a quieter helmet.
16 citations
TL;DR: In this article, a ray-trace model has been used as forward model for inversion of bottom parameters with a genetic algorithm, and the inversion results were subsequently verified with a parabolic-equation model, and they were used to assess the level of reverberation.
Abstract: Abstract: The experiment BAROC (Baltic Acoustics on Rocky Outcrops) was performed in May 2002. Analysis and modelling of part of the received data are reported here, concerning transmission loss and reverberation in a shallow-water area south of Stockholm. LFM pulses were transmitted in two directions with frequency content between 500 and 5500 Hz. In both directions a clear sound channel was observed, for which the optimum propagation frequency was about 4 kHz. Strong bottom reverberation was measured. A ray-trace model has been used as forward model for inversion of bottom parameters with a genetic algorithm. The inversion results were subsequently verified with a parabolic-equation model, and they were used to assess the level of reverberation.
4 citations