A system for use in installation of blown fiber for detecting a signal indicative of presence of at least one of a gas flow or an optical fiber at a remote location, comprising a gas vibration detector configured to acoustically couple with an installation duct through which the signal can travel after its generation at the remote location, and a processor arranged to receive an input from the vibration detector and to process the input to identify the signal present within the input; and a sensor for generating the signal upon sensing the presence of at least one of the gas flow or the optical fiber at the remote location. The signal can be provided by a whistle mounted on the remote end of the installation duct. The vibration sensor is typically a microphone.