This product does not work.
I live in the countryside and I was able to test it against a large number of birds (large and small) that are populating my garden.
The sound is loud and clear. It does sound like real hunting calls of sparrow hawks, falcons and owls. That is the only good thing about it.
Unfortunately, it did not scare any type of birds (at least 8 types of birds, small and large, were in my garden who did not show any fear and ignored it).
Some birds actually appear to be attracted by the noises and come closer (pigeons) and some smaller birds completely ignore it by sitting next to it (within 1 metre) undisturbed by the noises it produces. There were other birds sitting much further away (about 50 metres, who also ignored it). Therefore, no matter the distance, all birds ignored it. So much for the manufacturer's claim of 1-acre coverage.
I also noticed that the PIR is not triggered by the birds (not even by large birds such as pigeons that were within 2 metres of it flapping their feathers). It also did not detect the smaller birds that were close to it (within 1 metre). The PIR is only triggered by a human. Therefore, I had to put it on a timer. When it did come on, the birds were ignoring it.
I returned it for a refund, as it does not work as advertised. Amazon's service was excellent (as usual) as they offered refund without problems.
CONCLUSION: this product did not scare any bird (small or large) in my garden. Also the PIR is not detecting the birds., which means it only works on a timer basis.