Acoustoelasticity - General theory, acoustic natural modes and forced response to sinusoidal excitation, including comparisons with experiment

Sound absorption of a finite flexible micro-perforated panel backed by an air cavity

The transmission of sound through a cavity-backed finite plate

Sound transmission loss through double panels is studied with a patch-mobility approach. An overview of the method is given with details on acoustic and structural patch mobilities. Plate excitation is characterized by blocked patch pressures that take into account room geometry and source location. Hence, panel patch velocities before coupling can be determined and used as excitation in the mobility model. Then a convergence criterion of the model is given. Finally, transmission loss predicted with a patch-mobility method is compared with measurements.

/pdf/prediction-of-transmission-loss-of-double-panels-with-a-5dfwq3kxxn.pdf

Prediction of transmission loss of double panels with a patch-mobility method

Low-frequency duct noise is difficult to deal with by passive methods such as porous duct lining. Reactive methods like expansion chamber are rather bulky, while compact resonators are too narrow banded. This study shows that a suitably stretched thin membrane backed by a slender cavity can achieve a satisfactory performance from low to medium frequencies over an octave band. The present paper focuses on the details of the modal behavior of the fully coupled membrane-cavity system, and examples are given with parameters set in a practical range. Typically, the membrane has a structure to air mass ratio of unity, and is stretched towards the elastic stress limit for a material like aluminum. The backing cavity has a depth equal to the duct height and a length five times the duct height. Three resonant peaks are found in the low to medium frequency range while the transmission loss between adjacent peaks remain above 10 dB. For the first peak, almost complete sound reflection occurs as a result of an out-of-phase combination of the first and second in vacuo modes of simply supported membranes. The second peak is solely contributed to by the first mode, while the third peak features mainly the second mode vibration.

Modal analysis of a drumlike silencer

A multimodal analysis is made of the response of a cavity‐backed panel to an arbitrarily defined external forcing function. A general solution is developed which details the systems ’’characteristic functions.’’ These functions are examined and their properties detailed, in particular, the evaluation of poles and their representation in partial fraction form is achieved. Any external forcing function, provided that it is susceptible to finite Fourier cosine transformation with respect to spatial dependence and Laplace transformation with respect to temporal history, may be applied to the ’’characteristic functions’’ to determine the panel response. The general analysis is applied to the specific case of constant external pressure loading and the derived expressions are favorably compared with, and represent a further development of an accepted contemporary work.

The response of a cavity backed panel to external airborne excitation: A general analysis

Numerous subjective attributes of the listening experience in auditoria, particularly concert halls, can be described by the many available contemporary room‐acoustic indicators. Subjective response is also known to be influenced by the spatial distribution of sound energy. The spatial distribution is not only desirable to diagnose acoustical defects, but also to visualize and quantitatively appreciate the extent to which the various interior design features influence acoustic quality. The objective of the present work is to demonstrate the usefulness of spatial acoustic information for quality assessment and defect diagnosis within enclosures. A new measurement method based on transient sound intensity is employed for obtaining the spatial information and examples of applications are presented together with a discussion of the method’s potential.

R.W. Guy

Papers

The transmission of sound through a cavity-backed finite plate

The response of a cavity backed panel to external airborne excitation: A general analysis

Spatial information of sound fields for room‐acoustics evaluation and diagnosis

Coincidence effect with sound waves in a finite plate

The effect of some physical parameters upon the laboratory measurements of sound transmission loss