An acoustic structure includes a first, rigid panel (7), a second, rigid
panel (11) aligned in spaced, substantially parallel, relationship with
the first panel (7), a multiplicity of partition walls (15) running
transverse to the panels of the panels (7, 11) and dividing the interior
space of the enclosures into a single layer of cells (17) bounded at one
face by the inside of the first panel (7) and bounded at the opposite face
by the inside of the second panel (11), the partition walls (15)
being bonded at the one face to the inside of the first panel (7) and at
the opposite face to the inside of the second panel (11), and a multiplicity
of apertures (19) in the partition walls (15) providing communication
between adjacent cells of the single layer of cells (17).
