Could that have been what we were hearing last night? My son was outside looking for his cat and he came in and asked what kind of gun would sound like a heartbeat. We all went outside, and whatever it was sounded kind of far off, but the "explosions" were literally like a heartbeat rhythm. Never heard that before. There were also three closer things that sounded like transformers blowing, but none of the lights or neighbors lights went out. My son saw a flash in the sky (like a shooting star or something), but I didn't realize there was a meteor shower....