Echolocating bats use sounds for both perceiving their surroundings and social communication, which makes bats vulnerable to environmental and anthropogenic noise. Whether a particular noise source affects bats depends upon the acoustic properties of the noise and those of the bat’s pulses as well as whether the bat is roosting, commuting or foraging. This chapter reviews some of the key discoveries on this topic that have emerged since the first North American Society of Bat Research (NASBR) meeting 50 years ago. A variety of different experimental approaches focused on noise have synergistically advanced the study of bat biosonar and acoustic communication. Psychoacoustic studies used noise stimuli to probe mechanistic questions about how the bat’s brain processes and interprets echoes. Behavioral studies examined the long-term effects of intense noise on bat hearing, revealing that bats were surprisingly resistant to noise-induced hearing deficits at noise levels that cause hearing loss in other mammals. Lab and field studies have explored how bats respond to noise, focusing especially on behaviors that appear to successfully mitigate its negative effects. Field research has investigated the ecological consequences of both natural and anthropogenic noise, identifying the significant threats of noise pollution for bat populations. Collectively, these studies provide a cohesive framework for understanding the evolution of bat biosonar while also identifying key issues for ensuring their conservation.