Noise measurements were made in cinemas during the showing of four films, to establish whether the noise levels from films might pose a risk of damage to hearing. The L Aeq levels for the full playing time of each film were all below 80 dB(A). Noise levels did sometimes exceed 90 dB(A) but this was never for more than a total of two minutes, and was usually for only a few seconds. Repeat L Aeq levels for the same films were shown to vary by 3-4 dB across different cinemas. Based on this limited sample of films and cinemas, there is no evidence that sound levels in cinemas cause permanent damage to hearing.
Keywords: Social noise, cinemas, noise exposure, L Aeq
|How to cite this article:|
Ferguson MA, Davis AC, Lovell EA. Cinemas - do they pose a risk to hearing?. Noise Health 2000;2:55-8
| Introduction|| |
Over the last year there have been a number of reports appearing in the media about excessive noise levels in cinemas (e.g. Guardian, 1998). These reports suggest that the levels of noise are loud enough to cause damage to hearing, although a study of 24 films in the USA has suggested that cinema noise does not present a risk of permanent hearing loss (Ihne et al, 1999). Films such as Saving Private Ryan, Lethal Weapon 4 and Armageddon have been highlighted as being particularly loud, with reported noise levels in the media as loud as 110 dB in the climax to Armageddon (Guardian, 1998). These reports were very vague and it was unclear how the measurements had been made, what type of measuring equipment was used and what the reported decibel values represented. Following on from our research investigating the effects of social noise on young peoples' hearing (Smith et al, 1999; Smith et al, 2000), noise measurements were made during four films. The noise levels were measured for seven film showings in total, across four cinemas. The aim was to obtain measurements with a clearly described method and well-defined parameters.
| Methods|| |
Noise measurements were made using two different types of equipment (i) a precision sound level meter (Bruel and Kjaer, type 2260) and (ii) a noise dosimeter (Quest, Q-400), both of which were calibrated to standards traceable to the National Physical Laboratory and met the specifications according to BS6698 (1986). Noise levels were recorded continuously throughout the films and the following
parameters recorded: L Aeq , equivalent continuous A-weighted sound pressure level (SPL) for the measurement period; L Amax , the highest A-weighted SPL occurring during the measurement period; LAx, the exceedance level, the A-weighted SPL that was exceeded x% of the measurement period, where x was 0.01, 1, 5 and 50; L Aeq8h , L Aeq for an 8-hour period. For both the noise dosimeter and the sound level meter, a 'fast' time constant of 125 ms was used. Measurements were made in the central area of the auditorium.
Measurements were made on seven occasions during four films - Saving Private Ryan, Lethal Weapon 4, Armageddon and The Siege. Most of the films had a digital soundtrack see [Table - 1]. National and independent cinemas were randomly selected; three in Nottingham and one in London.
| Results|| |
A summary of the results is shown in [Table - 1]. For the duration of the film the L Aeq range was 73 to 79 dB(A), which dropped to 67 to 74 dB(A) for an equivalent 8-hour daily exposure. The maximum SPL (L Amax ) recorded for each film exceeded 90 dB(A) in every case. However, this is put into context when looking at the exceedance levels. No film exceeded 90 dB(A) for more than 5% of the time, which varied between 6 and 8 minutes. With the exception of The Siege, no film exceeded 90 dB(A) for more than 1% of the time, which was approximately 1 to 1.5 minutes. Furthermore, for all films except The Siege, sound levels exceeded 90 to 95 dB(A) for only 0.01% of the time i.e. less than 10 seconds. The Siege exceeded 90 dB(A) for about 90 seconds. All the films had a number of scenes with explosions and gunfire, however for a large proportion of the time the noise levels (L Aeq ) were below 75 dB(A). This is illustrated in [Figure - 1].
For one set of measurements made during Lethal Weapon 4 (not shown in [Table - 1] as the noise levels were only recorded for part of the film) the L Aeq was 75 dB(A). However, the unweighted frequency measurements were much higher; the unweighted equivalent continuous level (L Leq ) was 82 dB and the unweighted maximum (L Lmax ) was 101 dB. The latter value is much closer to the decibel levels reported in the media.
| Discussion|| |
None of the soundtracks for any of the films had a continuous, equivalent A-weighted noise level (L Aeq ) greater than the upper safety limit of 85 dB(A) set by the Health and Safety Executive (HSE, 1989). This is broadly consistent with Ihne et al (1999) in the USA, who reported a mean L Aeq of 75.5 dB(A) across 9 films with traditional sound systems and a mean L Aeq of 84.5 dB(A) across 15 films with digital surround sound systems. In the present study the L Aeq levels measured were all below 80 dB(A) regardless of the type of sound system. When the noise levels did exceed 85 dB(A) this was for short periods of time only, usually a total of less than two or three minutes for the whole film. All the films exceeded 90 dB(A) for less than 10 seconds, with the exception of The Siege.
Noise-induced damage to hearing is dependent not only on noise levels but also on duration of exposure. The upper safety limit of 85 dB(A) set by the HSE is not a health based value but necessarily takes into account economical and practical aspects. ISO 1999 (1990) on the other hand also takes duration into account and gives a lower threshold value for daily noise exposure over an 8 hour period (LAeq8h) of 75 dB(A). Because of the relatively short duration of films compared to the average working day, there were no occasions when a film exceeded an L Aeq8h level of 75 dB(A), although at times they came close. It could be argued that the cumulative effect of cinema noise in addition to other types of noise during the day might cause hearing damage. However, as the frequency of cinema attendance is relatively low, it is unlikely that cinema noise contributes to noise-induced damage to hearing.
Comparison of the L Aeq levels measured in the cinemas in this study with those reported in nightclubs by Smith et al (2000), show that the L Aeq levels in cinemas were well below the levels measured in the quieter areas in nightclubs. Noise levels in the quieter areas of nightclubs, usually the bar, averaged about 84 dB(A) at the beginning of the evening, rising to about 90 dB(A). L Aeq levels on the dancefloor were higher still, on average between 94 and 98 dB(A).
The data in the present study show some variation in L Aeq levels for the same film across different cinemas of about 3-4 dB and so the possibility that films in cinemas elsewhere in the UK might exceed an L Aeq of 80 dB cannot be excluded. A larger scale study that would allow multi-level analysis would be required to investigate this. However, based on this sample of just seven recordings, there is no evidence that cinemagoers are exposed to enough noise to damage hearing. It is possible that the decibel levels reported in the media, which were highly discrepant with those reported here, were the maximum unweighted levels recorded without A-weighted filtering.
| Conclusions|| |
1. The noise levels in this limited sample of seven cinemas were not loud enough to damage hearing and cause hearing loss or tinnitus.
2. The L Aeq levels in cinemas were well below the upper safety limit recommended by the Health and Safety Executive.
3. The L Aeq8h levels in all cinemas were below the threshold value for occupational noise exposure recommended by ISO 1999 (1990).
4. Although noise exposure from cinemas will have cumulative effect on daily exposure, cinema attendance is relatively infrequent.
5. The LAeq levels in cinemas were much quieter than the levels measured in nightclubs.
| References|| |
|1.||BS 6698. (1986) Specification for integrating-averaging sound level meters. London: British Standards Institution. |
|2.||Guardian. (1998) Have you heard the one about Lethal Weapon 4? The Guardian Review, 8-9 (October 2). Manchester. |
|3.||Health and Safety Executive. (1989) Noise at Work Guide No.1: Legal duties of employers to prevent damage to hearing. London, HMSO. |
|4.||Ihne, M. Lankford, JE. Lee, LW. DeLorier, J. (1999) Sound measurements of movies. National Hearing Conservation Association Annual Conference, Atlanta, USA. |
|5.||ISO 1999. (1990) Acoustics - Determination of occupational noise exposure and estimation of noiseinduced hearing impairment. Geneva, Switzerland: International Organization for Standardization. |
|6.||Smith, P. Davis, A. Ferguson, M. Lutman, M. (1999) Hearing in young adults. Report to ISO/TC43/WG1. Noise and Health; 4: 1-10. |
|7.||Smith, P. Davis, A. Ferguson, M. Lutman, M. (2000) The prevalence and type of social noise exposure in young adults. Noise and Health: 6; 41-56. |
Melanie A Ferguson
MRC Institute of Hearing Research, Clinical Section, Ropewalk House, 113 The Ropewalk, Nottingham NG1 6HA
Source of Support: None, Conflict of Interest: None
[Figure - 1]
[Table - 1]