Autonomous sound recorders anchored to the seabed are often used to provide data over a given area for extended periods (from several months at a time, or up to years with regular service visits). They enable long-term studies to quantify the variation in marine mammal occurrence, measurement of sounds generated by both natural and anthropogenic sources, and trends in ambient or background sound levels. In addition, availability of these data throughout the lifetime of a development activity offshore can help to improve understanding of potential changes in the distribution and size of marine mammal populations within the monitored area over time. The use of fixed acoustic monitoring for estimating cetacean density has been an area of increasing research. For this method of density estimation to become a practical, and therefore a more commonly used methodology, data collection programs must balance effective equipment design, deployment and data collection, alongside safe and efficient offshore operations. Examples of survey design considerations for species of interest in different areas are presented and discussed in terms of technical specifications, data quality, and numbers of recorders and physical spatial layout of equipment, balanced with safe and efficient field operations.