Noise Levels in Cinemas

Over the last couple of years there have been numerous media reports about the potential risk posed to personal hearing from watching movies in cinemas. The reports often describe noise levels that patrons are exposed to as “ear shattering” and in excess of the recommended levels for the workplace resulting in potentially serious damage to hearing. The aim of this project was to measure sound levels of a number of movies in order to determine what level of noise an ordinary cinema goer may be exposed to during the course of a movie. Noise levels of movie trailers have not been measured or considered and are outside the scope of this project. A Brief History Of Cinema Sound The acoustic requirements of a cinema are intended to maximise the quality of the reproduction and movie%going experience. George Lucas has been quoted as saying “sound is 50% of the motion picture experience” [1]. Special effects are used to improve the movie going experience both visually and aurally, as well as lend authenticity and “realism” to the story line. The use of surround sound speaker systems and the ability to reproduce sound at higher levels without distortion, has meant that the aural special effects are being used increasingly to “enhance” movies, particularly those which utilise action packed scenes for example James Bond, Star Wars etc. Criticism in the media about excessive noise levels occurs from time to time. However, the noise levels quoted are vague at best, and the use of acoustic terms often misleading. Standards And Guidelines There are no existing standards relating to the level of sound an audience can be exposed to from the replay of movie soundtracks in cinemas. As an aside, the competitive nature of commercials and trailers means there has been a trend to record the sound level as high as possible [8]. Thus, when the advertisement is replayed to an audience before the main feature it is subjectively considered as “too loud” and “earshattering”. When the main feature is played it can seem quieter than it is, due to the audiences’ previous exposure to noise. When a cinema manager receives a complaint from patrons about an excessive or uncomfortable level of sound from trailers and advertisements, there is a temptation to lower the replay level by using the fader control in the projection room. If the fader control is not reset to the “calibrated” position after the trailers and advertisements have concluded then when the main feature is played, some of the quieter sections containing speech for example, may be lost, as they were originally mixed assuming the “calibrated” replay level within the cinema. A considerable amount of research has been done and is currently in progress into environmental noise and its impact upon communities. None, however, has been carried out in terms of damage caused, or annoyance as a result of watching movies at cinemas. This may be because people can choose whether or not to attend a movie. Of course this argument applies to any leisure activity where the individual has the control in terms of exposure level and duration. It is widely accepted that a daily exposure of 80%85 dBA (Leq) for an 8%hour day over an individual’s working life is the upper limit before permanent damage will occur and hearing protection is required. For instantaneous noise, up to 200 Pascal (140 dB Linear) is acceptable. The World Health Organisation (WHO) [11] recommends a 24 hour LAeq of 70 dB or lower to avoid hearing impairment from “industrial, commercial shopping and traffic areas, indoors and outdoors”. Impulse noises for adults should not exceed 140 dB (Linear) and 120 dB for children. Clearly it would be difficult to measure a person for 24 hours and Non refereed Damian Ellerton Marshall Day Acoustics, Christchurch An abbreviated version of a paper submitted as part fulfillment of a MSc degree in Environmental Acoustics at South Bank University, London, Nov 2000.