Described herein are systems, methods, and non-transitory computer readable media for determining a direction of movement of an authority vehicle in relation to another vehicle such as an autonomous vehicle and initiating or ceasing a vehicle response measure that may have previously been initiated based on the determined direction of movement. A signal source associated with the authority vehicle emits a periodic acoustic signal that is received at one or more audio capture devices, which may be provided at various locations on an exterior of a vehicle. One or more signal characteristics of the acoustic signal can be determined such as frequency, sound intensity, and/or phase. Detected signal characteristic(s) of the acoustic signal can be analyzed, and in some cases, compared against known information such as an expected frequency of the acoustic signal to determine the direction of movement of the authority vehicle in relation to the vehicle.