What Causes the Increase in Car Exhaust Noise?
2 Answers
If the noise suddenly becomes louder, it can be confirmed that there is a perforation in the exhaust pipe muffler, resulting in a broken sound. Below are the relevant explanations: 1. Muffler structure: The structure of a car muffler is such that after the engine completes its power stroke, the exhaust stroke follows. Exhaust is the process of expelling the waste gas from the cylinder. Since the waste gas at this time is high-temperature and high-pressure, directly discharging it through the exhaust pipe would create significant noise. The muffler is a multi-stage diversion and pressure reduction combination. 2. Muffler noise reduction principle: (1) By utilizing reflections from several interfaces, the originally forward-propagating sound wave returns to its origin and is redirected forward again. This wave meets the second forward-propagating sound wave that has not yet been reflected, and the two waves are equal in amplitude but differ by an odd multiple of 180 degrees in phase, thus canceling each other out through interference. (2) By utilizing sudden changes in the pipe cross-section (i.e., changes in acoustic impedance), the sound waves propagating along the pipe are reflected back toward the sound source, thereby reflecting the sound energy back to its origin.
I remember driving for over thirty years, and the issue of exhaust noise getting louder is quite common, mostly due to leaks in the exhaust pipe or muffler. Back in the winter, my car would make a loud noise on the highway, and upon inspection, it turned out the exhaust pipe had corroded and developed small holes, allowing cold air to rush in and amplify the vibrations. Another possibility is engine misfiring causing poor exhaust flow, which makes the sound louder and rougher. In severe cases, black smoke may appear or fuel consumption may increase, so it's crucial to stop and check immediately—otherwise, the excessive noise on the road can also affect others' driving safety. I recommend regularly cleaning corroded parts of the undercarriage and avoiding rough roads to prevent damage from bumps. If the noise persists, head straight to an auto repair shop to replace the faulty parts. Nowadays, I maintain my car by using more anti-rust coatings to extend the exhaust pipe's lifespan, saving a lot on repair costs.
