Evaluation of modal density, radiation efficiency and acoustic response of longitudinally stiffened cylindrical shell

Ramachandran, P.; Narayanan, S.

doi:10.1016/j.jsv.2007.02.020

Cited by 22 publications

(10 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…by measuring the diffuse field in a reverberant chamber [50,51,52]. At a certain distance from the sound source where the direct field is negligible compared with the reverberant field, the sound pressure is approximately uniform across the room.…”

Section: Experimental Work and Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Sound radiation from perforated plates

Putra

Thompson

2010

Journal of Sound and Vibration

View full text Add to dashboard Cite

FACULTY OF ENGINEERING, SCIENCE AND MATHEMATICS INSTITUTE OF SOUND AND VIBRATION RESEARCH Doctor of Philosophy SOUND RADIATION FROM PERFORATED PLATES by Azma PutraPerforated plates are quite often used as a means of engineering noise control to reduce the sound radiated by structures. However, there appears to be a lack of representative models to determine the sound radiation from a perforated plate. The aim of this thesis is to develop such a model that can be used to give quantitative guidance corresponding to the design and effectiveness of this noise control measure.Following an assessment of various models for the radiation efficiency of an unbaffled plate, Laulagnet's model is implemented. Results are calculated and compared with those for baffled plates. From this, simple empirical formulae are developed and give a very good agreement with the analytical result. Laulagnet's model is then modified to include the effect of perforation in terms of a continuously distributed surface impedance to represent the holes. This produces a model for the sound radiation from a perforated unbaffled plate. It is found that the radiation efficiency reduces as the perforation ratio increases or as the hole size reduces. An approximate formula for the effect of perforation is proposed which shows a good agreement with the analytical calculation up to half the critical frequency. This could be used for an engineering application to predict the noise reduction due to perforation.The calculation for guided-guided boundary conditions shows that the radiation efficiency of an unbaffled plate is not sensitive to the edge conditions. It is also shown that perforation changes the plate bending stiffness and mass and hence increases the plate vibration.The situation is also considered in which a perforated unbaffled plate is located close to a reflecting rigid surface. This is established by modifying the Green's function in the perforated unbaffled model to include an imaginary source to represent the reflected sound. The result shows that the presence of the rigid surface reduces the radiation efficiency at low frequencies.The limitation of the assumption of a continuous acoustic impedance is investigated using a model of discrete sources. The perforated plate is discretised into elementary sources representing the plate and also the holes. It is found that the uniform surface impedance is only valid if the hole distance is less than an acoustic wavelength for a vibrating rectangular piston and less than half an acoustic wavelength for a rectangular plate in bending vibration. Otherwise, the array of holes is no longer effective to reduce the sound radiation.Experimental validation is conducted using a reciprocity technique. A good agreement is achieved between the measured results and the theoretical calculation for both the unbaffled perforated plate and the perforated plate near a rigid surface.

show abstract

Section: Experimental Work and Methodsmentioning

confidence: 99%

“…Ramachandran and Narayanan [52] implemented experimental statistical energy analysis (SEA) to determine the radiation efficiency of a stiffened cylindrical shell. The estimated modal density was obtained from the measured point mobility of the cylinder.…”

Section: Experimental Work and Methodsmentioning

confidence: 99%

Sound radiation from perforated plates

Putra

Thompson

2010

Journal of Sound and Vibration

View full text Add to dashboard Cite

show abstract

“…Equations (9), (10), and (11) do not change whether the transverse shear deformation is considered or not. Also, the normal strains acting on the plane parallel to the middle surface are negligible compared to the other strain components.…”

Section: Strain Displacement Relationsmentioning

confidence: 99%

Modal Density of Honeycomb Sandwich Composite Cylindrical Shells Considering Transverse Shear Deformation

Florence¹,

Renji²,

Subramanian³

2018

IJAV

View full text Add to dashboard Cite

Honeycomb sandwich shells with composite face sheets are of extensive use in the spacecraft industry. Information on the number of resonant modes present in a frequency band is required to study their response behaviour under acoustic excitation. Modal densities of thin composite cylindrical shells have been reported while transverse shear deformations have not been considered. But in honeycomb sandwich panels, transverse shear deformations are significant, especially at higher order modes of vibration. In this work expressions for natural frequency and modal density of composite cylinders incorporating transverse shear deformation are derived. The modal densities of a typical cylinder that are obtained using the derived expression are compared with the results obtained using the finite element method and they are similar. Effects of transverse shear and orthotropic nature of the face sheets on the modal densities are investigated. It is shown that computing the modal density of honeycomb sandwich cylinders without considering the transverse shear deformation can lead to significant errors at high frequencies. Expressions of modal densities for special cases are also derived from the general expression.

show abstract

“…The use of microphones for vibration and modal purposes has been conducted in multi-physics structures [13][14][15]. An array of MEMS microphones permits the measurement of structural vibration and investigation of both the translational and rotational dynamics.…”

Section: Introductionmentioning

confidence: 99%