Provided herein are composite passive layers for ultrasound transducers having acoustic properties that can be easily tailored to the needs of the transducer application using current microfabrication techniques. In an embodiment, a passive layer comprises metal posts embedded in a polymer matrix or other material. The acoustic properties of the passive layer depend on the metal/polymer volume fraction of the passive layer, which can be easily controlled using current microfabrication techniques, e.g., integrated circuit (IC) fabrication techniques. Further, the embedded metal posts provide electrical conduction through the passive layer allowing electrical connections to be made to an active element, e.g., piezoelectric element, of the transducer through the passive layer. Because the embedded metal posts conduct along one line of direction, they can be used to provide separate electrical connections to different active elements in a transducer array through the passive layer.