Dog whistles

Last week, I noticed dolphins sending each other call signs in the form of whistles, with each whistle being of the order of a second in duration.

This morning I hear of some cats and dogs who, when they are being minded by a neighbour or some such, seem to know when their owner is coming back. More particularly, when their owner's car pulls up outside.

Maybe it would be an interesting six form project to make recordings of car (engines) and to investigate the extent to which individual cars could be identified from those recordings. It seems entirely plausible that make of engine should be identifiable in this way, but what about a particular engine? What about the degradation of the signal as it passed from the outside world into the interior of a house?

But then I thought to ask Bing, and there is already plenty of activity out there. Reference 2 talks of identifying type of boat from the engine noise - with type being nothing more complicated than private, taxi and cargo. Reference 3 does something similar with military aircraft. While Google turns up reference 4 which does cars.

Nothing yet to suggest that one can identify a particular car. But maybe for the purposes of cats and dogs, getting the model and perhaps the age (mileage) of a car right would be enough. The right sort of car would, nearly always, be the right car.

PS: it also seems entirely plausible that some engines will make some peculiar noise, that their sound signatures will include some unusual features, which mean that those individual engines can be identified. Perhaps the result of damage during birth or during life. Such things have featured on ITV3 murder dramas before now. But not necessarily something that you could rely on. Perhaps just a minority of engines have such peculiarities.

Reference 1: http://psmv4.blogspot.com/2021/05/the-call-signs-of-certain-dolphins.html.

Reference 2: Engine Noise Signature for Boat Identification - James Curry, Jonathan Ross - 2007.

Reference 3: Military aircrafts’ classification based on their sound signature - Maria Barbarosou, Ioannis Paraskevas, Amr Ahmed - 2016.

Reference 4: Engine Speed–Independent Acoustic Signature for Vehicles - Hüseyin Göksu - 2016.