A sensor assembly includes a housing having an external-device interface and a sound port to an interior to the housing. A transducer and an electrical circuit are disposed within the housing. The transducer is acoustically coupled to the sound port while the electrical circuit is electrically coupled to the transducer and the external-device interface. A cavity is formed in a portion of the sensor assembly. In some embodiments, the portion is a base of the housing of the sensor assembly. In other embodiments, the portion is a sound port adapter coupled to the sensor assembly. In any case, the cavity is acoustically coupled to the interior of the housing via the sound port and includes a wall portion structured to modify an acoustic property of the sensor assembly.