This research has been carried out to determine the marine propeller hydro-acoustic characteristics by Reynolds-Averaged Navier-Stokes (RANS) solver in both uniform and non-uniform wake flow at different operating conditions Wake flow can cause changes in pressure fluctuation and gas effect on propeller noise spectrum. Noise is generated by the induced trailing vortex wake and induced pressure ...

To address the problem that acoustic transfer functions with underwater platforms cannot be measured accurately, this paper presents a method based on phase compensation to improve accuracy of function measurements platforms. The time-domain impulse response signals multiple cycles are first collected and intercepted, then their differences estimated using least-squares method, is used align ph...

this paper presents a new control structure to reduce torque ripple in switched reluctance motor. although srm possesses many advantages in motor structure, it suers from large torque ripple that causes some problems such as vibration and acoustic noise. in this paper another control loop is added and torque ripple is de ned as an objective function. by using fuzzy sliding mode strategy, the dc...

A LL jets have noise generation due to turbulent mixing; such mixing leads to the production of Reynolds stresses, the source term within the Lighthill acoustic analogy [1]. In addition to this source, a jet that possesses coherent, large-scale structures that travel with velocities exceeding the local speed of sound will emit Mach wave radiation, a highly efficient noise production mechanism. ...

background: in dental practical classes, the acoustic environment is characterized by high noise levels in relation to other teaching areas. the aims of this study were to measure noise levels produced during the different dental learning clinics, by equipments used in dental learning areas under different working conditions and by used and brand new handpieces under different working condition...

background; noise mapping in industry can be useful to assess the risks of harmful noise, or to monitor noise in machine rooms. using gis -based software for plot of noise maps in an indoor noisy work environment can be helpful for occupational hygienists to monitor noise pollution. methods; this study was carried out in noisy packaging unit of a food industry in ghazvin industrial zone, to eva...

BACKGROUND Noise pollution is currently a major health risk factor for workers in industries. The aim of this study was to investigate noise pollution and implement a control intervention plan for blast furnace in a steel industry. METHODS The measurement of sound pressure level (SPL) along with frequency analysis was done with the sound-level-meter Cell-450. Personal noise exposure was perfo...

A new method has been developed to perform a fantastic diagnosis monitoring for different kinds of machines, including small as computer, shaver, hand phone, or large as 4000hp engine, slow as a walking, or fast as flying in sky, based on acoustic imaging technology with a microphone array measurement system. With it noise field of machine can be analyzed from its sound image coupled in video i...