Often I will hear an intermittent, low frequency, powerful, booming sound that resolves into that of an airliner flying enroute high (FL 300+) overhead. So the first sounds that an airliner flying overhead to be heard are those. Why? I assume it has to do with the atmospheric conditions and how sound waves of different frequencies propagate forward..
The air attenuates high frequencies more than it does low. Thus, lower frequency sounds travel farther, so you hear them first. Also, longer wavelengths will appear to "bend" around obstacles more than ones with shorter wavelengths, so buildings around you will in many cases develop acoustic "shadow" zones for higher frequencies as those buildings' dimensions are significantly larger than their wavelengths.
Low frequencies are attenuated less over distance and by obstacles. The lower frequencies, even from the music from a dance hall or band, or that car near you playing loud music will be heard first. It may be all you hear! It is also common that as we get older, and especially those in aviation, we become high tone deaf!!
If you live in the approach path to a big airport, then there will be thumps and muffled booms as the landing gear is extended. It could be this that you are hearing.