1. A method implemented on portable device for determining a detectability at a target site of a noise level emitted by a fleet of vehicles including at least one vehicle at a given location, the method comprising: receiving a noise signature for each vehicle in the fleet; receiving a user input indicating an estimated distance to the target site; estimating noise pressure level for the fleet along the estimated distance from the given location to the target site based on the noise signature associated with each vehicle; calculating a background noise level at the target site; subtracting the background noise level at the target site from the noise pressure level of the fleet at the target site to determine an expected noise level above background noise at the target site thereby providing an estimate of the detectability of the fleet at the target site; displaying the expected noise level above background noise at the target site.