Jaycar had a couple of options when I looked and I went with the 92 db plastic one. We took the Mt Lindsay hwy back from Qld recently and the vibration caused the plastic foot to break at the mount point. Nicely gaffer tapped up now. Seems to work tho , no issues with Roos up to or back from Cooktown but it did spook the cattle. Haven't tried it on the dog.
Fatman useful info. Thank you for that. Not proper scientific based research here but two more things. It seems to me bright moonshine as in clear skies near full moon have an effect too, less trouble. The 'Animal Alert' whistles, sound experience of it showed it working fairly well on the african continent making animals and especially birds heads-up to look up and then move away. In Australia it really frightened me when I saw how roos react to them. The roos seemed to panick, become disorientated and hop at high speed in totally random directions often towards the bike. Birds in Australia seemed to react in similar manner to it as on the african continent.