Audio sensors detect noises generated by an intrusion attempt into a protected area. This type of sensor is typically used to monitor indoor facilities such as critical storage areas, entrance foyers, and so forth.
Audio sensors must be mounted in areas where the noise generated by an intrusion attempt is expected to exceed normal environmental noise. Since loud background noise is common in outdoor applications (e.g. passing vehicles, thunderstorms, aircraft over flights, etc.) audio sensors are typically not recommended for perimeter monitoring purposes.