The vibrational energy flows occurring between a pair of unequal recta
ngular membranes coupled along a mutual edge are investigated. Since t
he membranes studied have different properties and form an L shape whe
n coupled this calculation may not be carried out directly, instead re
quiring some form of approximation. Here, the line coupling is modelle
d by a series of point couplings with sufficient points to ensure conv
ergence for the frequencies of interest. This L shaped composite membr
ane model is then perturbed by the addition of a number of random poin
t masses. The effects caused by varying the number and degree of rando
mness of the attached masses on the ensemble statistics of the combine
d system are subsequently investigated. The statistics of this ensembl
e are considered for weak and strong coupling between the membranes an
d for point and ''rain-on-the-roof'' type forcing. The existence of en
ergy flow vortices in some ensemble members at some frequencies is not
ed. Conclusions are drawn for the application of Statistical Energy An
alysis (S.E.A.) to coupled two-dimensional subsystems. (C) 1996 Academ
ic Press Limited