Identification of partially coherent sound sources for centrifugal fan

The signal model with multiple inputs and single output (MISO) is often used for investigating sound sources of vehicles and mechanical equipment, in which transfer path analysis (TPA) and operational transfer path analysis (OTPA) procedure are well known in industry. Sources are completely coherent, as well as completely incoherent in TPA and OTPA models. However, some mechanical devices like centrifugal fans contain not only structure-borne and air-borne sound but also vibrational source and acoustical source. The sources may be partially coherent and cannot be calculated using traditional method. In order to understand the origination of sound from the partially coherent sources of the fan, a MISO model with partially coherent inputs was developed, in which the partially coherent sources were identified by partial singular value decomposition (PSVD) method. Vibration, pressure pulsation and sound signals were measured, and partially coherent sources contribution analysis were used to calculate the contribution of sources quantitatively. A test model was built, and an experiment was conducted to verify that this method is feasible. This method is also suitable for the identification and contribution analysis of sources with partially coherent characteristics, such as automobile exhaust system. This method can calculate the contribution of partially coherent sources, which is not available in other noise source identification methods.

Besinc Pseudo-Schell Model Sources with Circular Coherence

Partially coherent sources with non-conventional coherence properties present unusual behaviors during propagation, which have potential application in fields like optical trapping and microscopy. Recently, partially coherent sources exhibiting circular coherence have been introduced and experimentally realized. Among them, the so-called pseudo Schell-model sources present coherence properties that depend only on the difference between the radial coordinates of two points. Here, the intensity and coherence properties of the fields radiated from pseudo Schell-model sources with a degree of coherence of the besinc type are analyzed in detail. A sharpening of the intensity profile is found for the propagated beam by appropriately selecting the coherence parameters. As a possible application, the trapping of different types of dielectric nanoparticles with this kind of beam is described.