Noise monitoring of loud vehicles in four Dutch cities

Excessive noise from loud cars, motorcycles, mopeds, trikes and quads is commonplace in Dutch cities and is a major source of annoyance. In order to assess the sources, causes and potential solutions, TNO has performed a series of noise monitoring campaigns in four major cities including vehicle identification. Sound and vehicle data was acquired at 3 locations in each city for a period of five days. Several steps were applied to separate vehicle noise from other noises, and to attribute the noise to the correct vehicles. The resulting analysis provided insight into the types of vehicles and driving conditions causing most noise. A set of characteristic driving conditions were derived from the measurement data, including high acceleration, engine revving, engine backfire, high engine speed and others. Besides driving behaviour, vehicle modifications such as louder exhausts, removed dB-killers and mechanical or electronic engine modifications are common causes of high noise levels. Also an overview of suggested mitigation options and future outlook is given, based on the findings of the analysis.