Sound

Gravity yesterday and sound today.

I woke up to the faint sound of a sort of rustling or fluttering outside, something which has happened at least once before. Not the sort of rustling or fluttering that you would get from a single individual, rather that you would get from a lot of somethings. I had the thought that whatever it was was high in pitch, perhaps because it was rather faint and I had been told by a free lady at Boots that my hearing of high pitches was better than my hearing of low pitches, although on reflection now the sound was too faint to have pitch in the ordinary, musical sense at all. I then had the thought that it was bats flying around early morning and that what I was hearing was their navigational squeaks, perhaps because I recently heard about a gadget which is tuned for such squeaks, to the point of telling you which sort of bat is doing the squeaking.

BH tells me that the hot water pipes driving the radiators during the day are apt to make odd noises during the night when the hot water gets cold, but I don't think that is it. Maybe I was not really awake at all and the whole thing was a dream. Certainly can't hear whatever it was any more.

For those interested in bats, there is a good range of detectors out there and you can spend more than a thousand pounds on one. I have yet to find one that one that can put them on a screen, as an air traffic controller might put aeroplanes on a screen, but I dare say they will come if they are not out there already. I would want an advanced model on which I could chose the colours used to colour the bat icons on the screen to show variety of bat. See http://www.batbox.com. For those interested in other nocturnal animals, it seems that the same technology can be used, at least to some effect. Rats, for example, make characteristic ultrasonic transmissions.