I also have my Echo near the entertainment center. While I have not yet had it activate from any TV show, I usually forget to turn her off when I watch a YouTube video of some Echo demo...it is really confusing for a few seconds until I realize my Echo is responding to the video commands, LoL.
Other than that, the other problem is when I am streaming music and the volume is up in the 5-7 range; Alexa can't hear normal voice command to pause/stop, etc. I either have to significantly raise my voice or wait until the song has a break or ends.
They need to do some work on the audio normalization; my news flash audio is all over the map in volume level and i have to either adjust it manually or verbally command it vol up or dn.
The Echo does pretty good in my setup with a fair amount of background noise, but with the TV/Soundbar/Subwoofer going strong, I have to mute it momentarily to use Alexa. I keep experimenting with moving it around, as the omnidirectional mics do really well throughout the living room area, so am trying to find a sweetspot where Alexa can hear me with normal voice level but still have the TV going.
Monty