This course presents the rich interplay between sensing, signal processing, and communications in energy-constrained sensor networks. The communications load in the network is highly dependent on the distributed signal processing strategy that is used for detection and estimation tasks. Decoupled design of the signal processing algorithms and communication network protocols may be drastically inefficient from the perspectives of minimizing communications bandwidth and node energy consumption. A cross-layer design approach that spans sensing, signal processing, and communications is the key to energy-constrained network design. The first half of the course presents a broad view of many aspects of communications and network topology, including a DoD perspective on current and future applications. Topics include duty cycling for energy savings, network architecture and capacity, network synchronization, node geolocation, and the interaction of the physical, MAC, and higher layers for energy saving communications. The second half of the course is focused on the specific application of an aeroacoustic sensor network used for detection, localization, classification, and tracking of acoustic sources such as vehicles. Topics include the basics of acoustic propagation, source detection, angle-of-arrival estimation, Doppler processing, and source localization. The theory is illustrated with many experimental examples. The network performance is strongly impacted by aeroacoustic propagation, and we present distributed signal processing schemes that maintain nearly globally optimal performance with significantly reduced communications load.