Compression brake noise (also known as “Jake Brake” noise) has been a significant issue for heavy duty trucks for several decades. As a result of compression brake noise, there are many local ordinances in North America banning the use of engine brakes, and some countries such as Australia and South Africa have in the past considered total bans on compression brakes. Previous research showed that the primary problem is caused by operators who remove the OEM muffler system and replace it with a “straight stack” exhaust pipe with no sound reducing properties. On the other hand, even with the OEM exhaust system in place, compression brake noise is sometimes significant.The introduction of exhaust aftertreatment to meet stringent 2010 EPA emissions requirements (diesel particulate filters and selective catalytic reduction systems, DPF + SCR) provides two potential benefits for compression brake noise. The first benefit is that these aftertreatment devices are very good at attenuating noise in the exhaust stream. The second benefit is that aftertreatment systems make tampering with the exhaust system a very complex engineering undertaking which few truck operators are likely to undertake. With older trucks, removing the muffler was both technically simple and only a violation of noise control regulations.Data presented in this paper shows that at least for the truck and engine models evaluated, compression brake noise is no longer an issue. In fact, most people would be unable to detect compression brake operation, even if they are close to the truck when it is operating the brakes. As the population of older trucks without exhaust aftertreatment declines, the issue of compression brake noise should fade away, at least in markets where aftertreatment is used.