An apparatus includes a housing. A waveguide is located within the housing. The waveguide includes a first subsection that bends around a first axis and has a first cross-sectional area with an aspect ratio that is substantially different from unity. A second subsection bends around a second axis that is non-parallel to the first axis and includes a second cross-sectional area with an aspect ratio that is substantially different from unity. A third subsection acoustically couples the first subsection to the second subsection. The third subsection includes a third cross-sectional area with an aspect ratio that varies between the first aspect ratio and the second aspect ratio.