Can anyone identify this sound please?

Hi Alison

It could be the  "wow-wow-wow" contact call of a fox. Foxes are particularly vocal at this time of year coming up to the breeding season.

Have a listen to the sounds in this video. The prominent one is the vixen calling out for a male. Somewhat quieter is the barking call which sounds similar to your clip. It may be the male responding.

What do you think - no guarantee I'm right.

Hi Alison
TeeJay's instincts are spot on; the dominant monotone shriek is a vixen calling for a male and the wow, wow, wow, call is a dog fox responding. We live right on the urban edge of York, with houses to one side of us and heathland on the other. We've been hearing the vixen for a few weeks now and about a fortnight ago the dog fox started calling as well. If they wake me up, which they often do, I always get up to watch them cavorting around the neighbours' gardens.