Field recording often involves the capture of ambient noises that are low level and complex, and, in response, the requirements from the field recordist have often pushed the technical limits of recording equipment, that is, demanding low noise and extended frequency response in a portable, battery-powered unit. For this reason, field recordists have favoured high-quality (usually professional) recorders, microphones, and microphone pre-amplifiers. The history of the equipment used in this area closely tracks the development of professional portable audio recording technology.