The isolation performance of the Etymotic ER4XR is great. These in-ears don't have an active noise cancelling (ANC) system, and achieve this level of isolation passively. In the bass range, where rumble of airplane and bus engines sits, they achieve about 22dB of isolation, which is very good. In the mid-range, important for blocking out speech, the isolate by about 29dB, which is excellent. In the treble range, occupied by sharp sounds like S and Ts, they achieve more than 48dB of isolation, which is outstanding.

It should also be noted that these headphones were measured with their silicone tips. Their comply foam tips provide significantly better isolation.