Sound radiation prediction by scale models

<p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The majority of acoustic modelling has been concerned with sound quality inside rooms and auditoria. Little attempt has been made to model the structural stiffness of the walls. These "rigid" walled models have given good results for auditoria but cannot be used for vehicles etc. On the other hand the structural dynamics work has been concerned almost exclusively with the vibration of structures in vacuo. The coupling of the wall vibration with the enclosed space has not been investigated thoroughly. Analytical solutions are available for a few special cases and the finite element method is being developed for use in such coupled problems.</p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">It is considered that there is a need for a technique which is able to take account of the details of the construction of a real structure. Dynamic models could play an important part in the advance checking of the details of new designs and may have important practical application in developing structural modifications to produce the desired acoustical environment.</p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The aim of this thesis is to verify the possibility of predicting, by scale models, the sound pressure levels inside enclosed structures which are mechanically excited. </p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The thesis is divided into two main parts: in the first part theoretical considerations have been developed with the aim of deriving similarity conditions between the prototype and the model. For this purpose the wave equation in an acoustic medium and the equations of motion of simple structures have been non-dimensionalized.</p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The second part is concerned with experimental work on two models: a 1/5 scale plastic model of a safety cab of a tractor and a simple apparatus which consists of a rigid cylindrical cavity that is closed at one end by a flexible panel.</p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The first model is intended to verify the possibility of having a prediction of the dynamic and acoustic behaviour of the real structure comparable to that obtainable by measurements performed directly on it.</p> <p class="MsoNormal" style="margin-bottom:0cm;text-align:justify;line-height: normal;mso-layout-grid-align:none;text-autospace:none">The second apparatus has the aim of verifying the actual possibility of using an acoustic medium different from air but compatible with the plastic models.</p>

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

1983

Author dc:creator

• Pompoli, Roberto

Advisor dc:contributor.advisor

• Clarkson, B.L.