Phillip Joseph

Learn More
This paper investigates the noise radiated by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. An analytic formulation for the spectrum of acoustic power of a two-dimensional flat-plate is derived. The main finding of this paper is that the acoustic power spectrum from the cascade of flat airfoils may be split into two(More)
The presence of a "ladder" structure in the airfoil tonal noise was discovered in the 1970s, but its mechanism hitherto remains a subject of continual investigation in the research community. Based on the measured noise results and some numerical analysis presented in this letter, the variations of four types of airfoil tonal noise frequencies with the flow(More)
BACKGROUND The renin-angiotensin-aldosterone system is suggested to play a key role in the development of atrial fibrillation through structural and electrical remodeling. This review aims to assess the effectiveness of blockade of the renin-angiotensin-aldosterone system in the prevention of new onset atrial fibrillation. METHODS Electronic databases(More)
Knowledge of the modal content of the sound field radiated from a turbofan inlet is important for source characterization and for helping to determine noise generation mechanisms in the engine. An inverse technique for determining the mode amplitudes at the duct outlet is proposed using pressure measurements made in the near field. The radiated sound(More)
This paper is an experimental investigation of an inverse technique for deducing the amplitudes of the modes radiated from a turbofan engine, including schemes for stablizing the solution. The detection of broadband modes generated by a laboratory-scaled fan inlet is performed using a near-field array of microphones arranged in a geodesic geometry. This(More)
An analytical model of the sound power radiated from a flat plate airfoil of infinite span in a 2D turbulent flow is presented. The effects of stagger angle on the radiated sound power are included so that the sound power radiated upstream and downstream relative to the fan axis can be predicted. Closed-form asymptotic expressions, valid at low and high(More)
The spatial correlation has previously been investigated for tonal and narrow-band sound fields. This letter presents an experimental investigation of the spatial correlation coefficients in a reverberation chamber driven by broadband signals. The main objective is to verify recent theoretical results for broadband spatial correlation in diffuse sound(More)
The invasive nature of electrodes placed into sound fields is examined. In particular, perturbations of the sound field due to the presence of the electrode support are explored. The effect of an electrode on the drive sound field (at approximately 23 kHz) is shown to be negligible under the conditions investigated in this paper. However, scattering of(More)
Acoustic techniques have been used for many years to find and locate leaks in buried water distribution systems. Hydrophones and accelerometers are typically used as sensors. Although geophones could be used as well, they are not generally used for leak detection. A simple acoustic model of the pipe and the sensors has been proposed previously by some of(More)
Multimode sound radiation from an unflanged, semi-infinite, rigid-walled circular duct with uniform subsonic mean flow everywhere is investigated theoretically. The multimode directivity depends on the amplitude and directivity function of each individual cut-on mode. The amplitude of each mode is expressed as a function of cut-on ratio for a uniform(More)