House was noisy last night.

The house was noisy last night. Some of the sounds were really frustrating. Just before dark I was tending some plants on the rear porch. A loud tapping sound occurred. It really sounded like someone hitting the concrete with a steel hammer. The sound was not cons istant, it came in bunches with a lull between. My back porch (on the eastward side of the house is block and concrete. There are shrubs (I'd like to eradicate) planted around the base of it. As a result of these shrubs, I cannot see the base of the porch. The hammering was relatively loud. I quit what I was doing and walked the length of the porch trying to locate the source of the noise. I finally narrowed it down to an area near the center. But as soon as I was kneeling to part the shrubs the tapping moved away from that area and started again several feet further on. I never saw the source of the noise as it appeared to be leading me on. I finally gave up when it got too dark to see much (I have no light on that porch). So what the heck could be tapping steel on concrete (or sound like it?) I haven't been back there again yet to see if the noise continues. I know of no animal or bird that would likely be hammering on concrete with what sounds like a steel hammer. When Shadow and I turned in last night , I heard what sounded like a drop of water hitting a tin plate. The sound occurred several times with various periods of silence between. I also heard sounds like a twanging of metal at odd times. Like I said, the house was simply noisy. No point in asking my wife if she heard anything because once she removes her hearing aids she hears very little. It will be interesting to see if the odd noises continue tonight. The weather here last night and today was very unsettled. Temperatures in the upper 80"s daytime and mid 60's at night. We have had a good bit of rain but none yesterday or today.