CLD stands for "constrained layer damping", doesn't it? So even IF there's some resonance in the audio range, that should serve to reduce the decay time of the resonance, if / when it gets excited. It does nothing regarding actually shifting the resonance frequency - that's a slightly different issue there.
PS: Aluminium is arguably one of the softer and less dense metals, so i'd expect that to have a lower resonance and shorter decay than the same volume (or thickness) of brass or steel.
PS: Aluminium is arguably one of the softer and less dense metals, so i'd expect that to have a lower resonance and shorter decay than the same volume (or thickness) of brass or steel.