Hz In Steps Research Articles

Effects of hearing protectors on head diffraction

The diffraction by the head and pinna of sound incident upon the ear has been well documented. However, the modification of head diffraction patterns by the placement of hearing protectors in, or over, the ears has not been investigated. Polar sensitivity plots were obtained in an anechoic sound field from the right ear of the Knowles Electronics Mannequin for Acoustic Research (KEMAR). Test frequencies ranged from 100–10 000 Hz in steps of 1/3 octave. Plots were obtained in the horizontal plane for three conditions: (1) ear open; (2) ear occluded with a malleable foam‐type ear plug; and (3) ear covered by a conventional ear muff. Polar data were converted to field‐to‐drum transfer functions for every 45° change in angle of signal incidence for each condition. The diffuse‐field ear‐open transfer functions will be compared to previously published functions for KEMAR. The effects of ear occlusion with muffs, caps, and plugs as seen by attenuation and canal resonance shift will be discussed.

Effect of Turret Location on the Dynamic Behaviour of an Internal Turret Moored FPSO System

An experimental investigation on the motions and mooring forces of a typical internal turret moored Floating Production Storage and Offloading (FPSO) system under regular sea waves for different loading conditions i.e., 40%DWT, 70%DWT and 100%DWT with different turret locations viz forward, midships and semi- aft positions is reported in this paper. A 1:100 scale model of 140000 DWT turret moored FPSO system was tested in a 2m wide wave flume at a water depth of 1m for the wave frequencies from 0.55Hz to 1.25Hz in steps of 0.04Hz. The motions were measured by rotary type potentiometers and proving ring type load cells were used to measure the mooring forces. From the analysis of the experimental results, it is found that among the three turret locations, the forward turret position is the best suited position for the internal turret moored FPSO system, so as to have favourable and safe working environment. In this turret location, the surge, heave and pitch motions are about 20% to 30% less in comparison with mid ship and semi-aft positions for all loading conditions. Keywords: FPSO system, internal turret, CALM, motions, mooring forces DOI: 10.3329/jname.v3i1.926Journal of Naval Architecture and Marine Engineering 3(2006) 23-37