An apparatus including a sound transducer; and a housing having the sound transducer connected thereto. The housing forms a substantially sealed air space back cavity acoustically coupled to the sound transducer. The housing includes a housing member having a first dividing structure located in the back cavity to connect two adjacent air mass sections of the back cavity, where the dividing structure includes at least one aperture to permit travel of sound waves through the at lease one aperture between the air mass sections.