Quoting from the Federal Highway Administration:
Noise barriers are solid obstructions built between the highway and the homes along a highway. They do not completely block all noise they only reduce overall noise levels. Effective noise barriers typically reduce noise levels by 5 to 10 decibels (dB), cutting the loudness of traffic noise by as much as one half. For example, a barrier which achieves a 10-dB reduction can reduce the sound level of a typical tractor trailer pass-by to that of an automobile.
No matter what measure is used for estimating the cost of constructing noise barrier walls for highways, it's damned expensive – exceedingly so! Depending on what Internet search result one references, these noise barrier walls cost from $2 million per linear mile and upwards to as much as $20 million per mile (reportedly) for an installation in Los Angeles. When installing these sound walls on both sides of the highway; multiply by 2. Using a different measure, funding the construction of noise barriers can cost taxpayers as much as $92,000 per impacted home.
Highway noise is a real problem for many residences. However, if we believe even government is subject to the law of finite resources, there's likely three choices: