one speaker sounds like a helicopter...no music though

2018 SR5 Premium...
weird problem started tonight. driving home, no music playing and suddenly from the back I hear this sound...at first I thought a rear tire was flat but the 'rhythm" was constant regardless of speed. got home and found it's definitely from the drivers side back door speaker. sounds like the 'thump thump" of a helicopter while the engine is on. if I turn engine off but leave the key on, it's a much slower thump. stays on about 5 seconds after key off. also noted that I can't play music through bluetooth or radio.
edit....went back out, turned the truck on. very slight 'pop" from rear speaker but this time the music played but only through the front door and dash speakers. after maybe 2 minutes, the music stopped and the helicopter sound came back