Prediction of noise from small to medium sized crowds

The prediction of crowd noise is a problem faced by acoustical consultants. Although consultants are frequently required to predict noise emissions from activities involving crowds of people, there are no reliable prediction methodologies available. In the past, reliance has been made upon the adoption of results measured at similar venues or by extrapolating the vocal effort from an individual to derive the overall level for a defined crowd size. Applying these methodologies can result in prediction errors are largs as 15dB(A), indicating that they do not correctly characterise this type of noise. To derive an appropriate prediction methodology, the authors have investigated the factors that influence the generation of crowd noise such as Lombard effect, crowd size, orientation of individuals within the crowd and whether individuals act together as a synchronised source or behave randomly. Using these factors as a basis, a series of controlled and uncontrolled experiments have been conducted in order to derieve a set of equations that are suitable for use by consultants to predict the noise emissions from small to medium sized crowds (up to 100 people) located in outdoor spaces