Quiet Exhaust linked to CEL?

[ProjectM96]

As soon as I started my car today, I noticed the exhaust was a slightly deeper and quieter tone. It did not sound like it used to.

I drove about 10 miles then the CEL turned on:
PO134 and PO154.
O2 sensor circuit no activity detected bank 1 sensor 1
O2 sensor circuit no activity detected bank 2 sensor 1

Both O2 sensors went bad at the same time. Could that happen? Could they cause the exhaust tone and sound to change like that? Now @90,000 miles.

A little history. Bought the car 2 years ago with PO134 code at 77,000 miles. Reset it and it never came back on. I never replaced the O2 sensors.
2 months ago, CEL light turns on for PO134 while it was raining, then later turns off by itself in the same day.
1 month ago, CEL turns on again for PO134. I turn off the car and come back 30 minutes later and the CEL is gone.
In the past, the exhaust sound did not get quieter or deeper when this CEL code turned on.