acoustic volume acoustically coupled to the acoustic waveguide for increasing the amplitude of the sound waves radiated from the acoustic waveguide application_number US 201213630319 A description fig1 a and 1b show some geometric objects useful in understanding some of the figures that follow fig1 a is an isometric view of two waveguides 6 and 7 waveguides 6 and 7 are depicted as structures having rectangular cross sections in the y z plane and an x dimension longer than both the y and z dimensions the area dimension in the y z plane hereinafter the u201c area dimension u201d of waveguide 6 is a and the linear dimension along the y axis is h in the specification there are references to changes in the area dimension in the corresponding figures changes to the area are depicted by changes in dimension in the y direction holding the dimension in the z direction uniform so for example a waveguide 7 with an area dimension of 2 a would be depicted in the corresponding figure by a doubling of the linear dimension h along the y axis to 2 h fig1 b shows the waveguides of fig1 a as cross sections in the x y plane and includes some additional elements except where otherwise specified the waveguides in the following figures are shown as cross sections in the x y plane with the longest dimension.