Update 08/22/2019: We've re-tested the noise isolation of the Bose QC35 II and the Bose Noise Cancelling Headphones 700 after noticing a flaw in our testing methodology for both headsets.

The Bose 700 Headphones have great noise isolation performance. They have good isolation in the bass range, isolating bass-heavy sounds like the deep rumbles of airplane and bus engines by about 17dB. They’re great at blocking out speech since they isolate by about 24dB in the mid-range, and are also very good at blocking out sharp sounds, like sibilants such as S and T sounds as well as noises produced by A/C units, since they reduce noise by 41dB in the treble range.

It's worth noting that these headphones have better passive isolation when the headphones are completely off than when the ANC is set to "0". It appears that the lowest levels of ANC control seem to feed some mic input to the headphones, providing a bit of talkthrough. You can consult our more detailed noise isolation graph here .