Results: “The goats reacted alert to the visual and/or acoustic stimuli that were presented in their room. They raised their heads and turned their ears forward in the direction of the stimuli.” None* of the goats, however, displayed any appreciable stress responses, or increased emotional reactivity – even with the Chinook flyover.
Conclusions : “In line with studies performed with other ruminants, goats may be quite resistant to the effects of intense, adverse visual and acoustic stimuli such as the sight and noise of overflying helicopters.”
‘Physiological and behavioral reactions elicited by simulated and real-life visual and acoustic helicopter stimuli in dairy goats’ is published in BMC Veterinary Research 2011, 7:16
 *Though apparently unstressed, one goat did make an attempt to escape.
 The research was commissioned and sponsored by the Royal Netherlands Air Force (RNLAF).
(Thanks to investigator Philip Dröge for drawing out attention to the research)