That's not the bluetooth latency you're hearing, that's just how active noise cancellation works. QC35s buffer about 75ms worth of ambient noise and then phase

That's not the bluetooth latency you're hearing, that's just how active noise cancellation works. QC35s buffer about 75ms worth of ambient noise and then phase-invert it and play it back. This destructively interferes with the outside noise, and cancels it. But you have to sample your environment on some time window to get it to work, so when ANC is on, there's lag. This is also why ANC only works well for slowly-varying noise like airplane drone, but can't handle impulsive sounds like gunshots. https://en.wikipedia.org/wiki/Active_noise_control https://en.wikipedia.org/wiki/Active_noise_control