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Location: Ministry of Labour > Health and Safety > Publications > Safety Guidelines for the Live Performance Industry in Ontario

6. Sound Levels

It is a unique characteristic of the live performance industry that performers and support staff are critically dependent on their hearing.

Acceptable sound levels have recently been the subject of re-assessment in Canada and the United States. The Occupational Safety and Health Administration in the U.S. recommends lowering the present limits. The Advisory Committee agrees that the present regulations for noise exposure limits and hearing protection (Regulations for Industrial Establishments, section 139) are not adequate for workers in live performance, and is recommending that the Ministry of Labour develop a new regulation to address this concern.

The following recommendations are intended to help prevent short-and long-term auditory damage to workers without affecting artistic integrity.

Definitions

dB (Decibel)

A measure of sound pressure level.

Exchange rate

The increase in dB that doubles the damage done by sound exposure.

Hearing conservation program

Any action that will result in lowering the potential for hearing damage. It may involve the reduction of sound levels or the use of personal hearing protection.

Impulse sound

Percussive sound such as gunshots or cymbal crashes. The sound is often very loud and may have peak dB levels over 115 dB.

Leq

Equivalent levels over a specified period of time.

Steady state sound

Sound that does not involve the rapid rise and fall of levels as in impulse sound. The sound can be loud but has a more consistent level than impulse sound.

Sound pressure level

The correct term for “sound level”. The intensity of sound measured in decibels.

General Guidelines

1. Sound pressure level issues should be identified, addressed and resolved during the rehearsal period and before the first performance.
2. The exchange rate should be 3 dB.
3. Workers should not be exposed to impulse sound pressure levels in excess of 100 dB. Where sound levels above 100 dB cannot be avoided, a hearing conservation program shall be established to reduce the exposure to 100 dB or less.
4. Workers should not be exposed to steady state sound pressure levels in excess of 85 dB. Above this threshold, a hearing conservation program should be implemented to reduce the exposure to less than 85 dB.
5. Sound pressure level readings should be taken with a Type 2 sound meter that meets the CSA Standard Z107.2 rating. The meter should be set for the “A weighted network” with a slow meter response when measuring. Steady state sound pressure levels should be measured for a period of one minute to establish an leq.
6. Sound pressure levels should be measured at the ear of the worker most exposed to the sound source. All measurements should be taken at performance levels.
7. Hearing conservation programs are the mutual responsibility of workers and management and shall have the agreement of all parties involved. Both workers and management should understand the importance of annual hearing assessments.
8. Where a hearing conservation program is in place, an assessment log should be kept as proof of maintenance and “signed off” by both management and workers.
9. In hearing conservation programs for long-running productions (in excess of six months), all workers in the program should have periodic hearing assessments.

Sound Level Reduction Guidelines

The best way to reduce sound impact is to put a distance between source and worker. Even in a limited space, repositioning or re-angling the sound source can make a useful difference.

1. Hearing protection: Uniform attenuator ear plugs are available in custom and non-custom forms. Other types of hearing protection are available for specific situations. An audiologist or other hearing health care professional should be consulted before choosing.
2. Speakers: Speakers and monitors should have minimal floor contact since low frequencies tend to travel through solid surfaces rather than through air. Reducing the surface contact of speakers and monitors will increase the low end frequencies received by audience and performers, so the overall sound level need not be as high. Workers should not be exposed to the backs of open speaker enclosures. Baffles between the worker and the speakers should also be used.
3. Risers: Raising the sound source 30-60 cm (1-2 ft.) above the ear of the affected worker greatly reduces high frequency sound exposure. Because high frequency sounds, typically those produced by a speaker horn or a belled musical instrument, are directional, sound pressure levels above, below or to the side of the source are significantly lower than those in front of it.
4. Spacing: Wherever possible, 2-3 m (6-8 ft.) of reflective floor surface should be left unoccupied in front of a performance group. This generates additional reflections, which raise the sound level in the audience but not on stage, so the overall level need not be as high.
5. Isolation of impulse sound: Workers should not be within 2 m (6 ft.) of an impulse sound. Wherever possible, shields and baffles should be used and reflective surfaces around the sound source should be acoustically treated to reduce the impulse effect. Where it is not possible to isolate the worker, additional hearing conservation should be used.
6. Sound baffles and acoustical shields: Baffles and plexiglass shields may give protection if used with other strategies to reduce the overall sound exposure. However, acoustical baffles afford minimal effect unless they are within 18 cm (7 in.) of the worker’s head. In addition, the maximum high frequency attenuation is only about 15-17 dB.