This discussion topic concerns potential for improvements to sound-related regulations: UN Regulation No. 9 | Three-Wheeled Cycle Noise, UN Regulation No. 28 | Audible Warning Devices and Signals, UN Regulation No. 41 | Motorcycle Noise, UN Regulation No. 51 | Vehicle Noise Emissions, UN Regulation No. 59 | Replacement Silencing Systems, UN Regulation No. 63 | Two-wheeled Moped Noise, UN Regulation No. 92 | Replacement Exhaust Silencing Systems for Motorcycles, UN Regulation No. 117 | Tire Rolling Sound Emissions, Adhesion on Wet Surfaces, and Rolling Resistance,UN Regulation No. 138 | Quiet Road Transport Vehicles, and WP.29 Regulatory Project | Audible Reversing Warning Systems.