Sound Advice Note 13

Orchestra pits
Orchestra pits in theatres and opera houses

This is the full text of the Sound Advice Working Group specific recommendations covering orchestra pits

Background

13.1 This advice note covers indoor orchestra pits. See also Sound Advice Note 12 'Orchestras'and Sound Advice Note 14 'Stage bands'.

13.2 Musicians may experience two main problems when playing in orchestra pits:

  • Orchestra pits are often cramped and can be almost totally enclosed spaces. A space of 1.7 m2 per musician in an orchestra pit is regarded as good; if this is reduced to 1.2 m2 per musician the conditions are confined and the musicians can feel claustrophobic and hemmed in, with difficult resonances. Height also has an effect. Wherever possible there should be between 2.5 m and 3.5 m between the floor of the orchestra pit and the underside of any overhang.
  • Pit-orchestra musicians and conductors may have to play the same show several times a week, often for months on end. In this case scheduling would not be an effective control measure.

13.3 These two factors make it all the more critical that noise-control measures are effective and observed. For representative noise levels in orchestra pits see the table below

Representative noise levels in orchestra pits

Noise source dB
Opera orchestra pit
Violin 84 - 90
Viola 87
Cello 86
Double bass 86
Trumpet 93
Trombone 90
Horn 91
Piccolo/flute 90
Clarinet/bassclarinet 88
Oboe/bassoon 87
Percussion 85
Conductor 82
All instruments 88

13.4 Touring companies should carry out a separate noise risk assessment for each pit-venue on the tour. Different sizes and shapes of pits may require alternative control measures. Ensure that any changes do not cause additional/secondary safety problems.

Control Measures

13.5 Possible control measures include:

  • using sound-absorbent materials;
  • position of performers;
  • amplification;
  • using shakers, acoustic screens or risers.

Use sound-absorbent materials

13.6 Reduce sound hazards by installing acoustic panelling and other sound-absorbent materials. This treatment can be highly cost effective.

Use of sound-absorbent materials in a small music theatre pit

Use of sound-absorbent materials in a small music theatre pit

Position performers strategically

13.7 Positioning is especially crucial in orchestra pits because they are often very confined spaces with low ceilings. The musicians are often playing directly into each other's and the conductor's ears. The low, overhanging ceilings prevent sufficient sound escaping to the audience, resulting in louder playing levels, or even amplification. Consider the following:

  • Maximise the space between the performers (in particular between the loudest instruments, for example percussion) and other performers where the size of the pit and the relationship between the performers (as required for artistic purposes) permit. This will help lessen the effect on other performers of sound levels produced by the noisiest sections.
  • Position loud instruments or sections in open ceiling areas of the pit so their sound can escape out of the pit.
  • Consider seating brass players near the front of the pit around the conductor/musical director so the other musicians will not be exposed to loud, highly directional sound coming from the brass.
  • Stand the conductor/musical director on a riser above the brass section to limit the exposure of the conductor/musical director to excessive noise.
  • Encourage conductors/musical directors to work with players to reduce sound levels. They play an essential role in co-operating to reduce noise exposure including looking at repertoire and performance noise levels.
  • Consider seating rotation and/or adjusting the schedules of the performers to reduce their individual levels of exposure. The ears should be allowed time to recover from noise exposure (See Recovery periods in Sound Advice Note 3 'Noise risk assessment and planning).
  • Where the performance is to be amplified, consider the orchestra layout with a view to minimising the effects on performers of sound levels produced by other performers. One possible measure might be to place the percussion section in a segregated area. This would enable the sound levels produced by the percussion section to be controlled through the amplification system.

13.8 Allow time within the scheduling for any necessary adjustments, such as moving seats, musician stands and acoustic screens, or minor variations in layout.

Amplification

13.9 Sound equipment should be selected by a sound designer or other suitably qualified person who should ensure that it meets the requirements of the production in the venue concerned and is used within the manufacturer's specification while bearing in mind the need to manage sound levels. Consider the following:

  • Position loudspeakers strategically. The volume of amplifiers, on-stage monitors and front-end speakers can be turned down while still achieving the same acoustic effect if careful thought is given to positioning.
  • Raise monitor speakers and fold-back speakers off the floor. This puts them closer to ear level, which means the overall output level can be reduced with the benefits of minimised spill, less reverberant noise and increased clarity. Advice on good working practice for monitor headphones and in-ear monitors is provided in Sound Advice Note 4 'Rock and Pop' and Sound Advice Note 15 'Studios'.

Use shakers

13.10 Shakers can allow performers to monitor and maintain contact with their instruments. They can easily be attached underneath drummers' seats or to small plywood boards placed on the floor.

Use acoustic screens

13.11 Moveable screens may be needed as well as sound-absorbent panels (also see Acoustics screens in Sound Advice Note 12 'Orchestras').

Use risers

13.12 If the pit overhang allows it, using risers to elevate brass sections may help to project their sound, which is highly directional, over the heads of the performers in front of them (see Risers in Sound Advice Note 4 'Noise control measures and training').

Case Study

Musical theatre pit orchestra

The following case study highlights the problems facing musicians when working in the confined space of a theatre orchestra pit.

The musicians performed six evening shows each week with two matinee performances, each lasting about three hours. The assessments were all made under the Noise at Work Regulations 1989.

Initial noise assessment July 2002

Noise measurements were taken with four sets of static noise monitoring equipment to establish range of noise levels in the pit.

Measurement position Show LAeq dB Daily noise exposure with one show per day LEP,d dB Weekly average of daily noise exposuresLEP,w dB
Drum booth 92 88 89
Timpani 87 83 85
Conductor 87 83 84
Flautist 92 88 89

Conclusions

  • Replace the previously installed perspex screens with absorbent screens between sections (particularly between brass and woodwind).
  • Place absorbent material on the net at the stage edge to reduce spill from the stage-edge fill speakers into the pit and to make the edge of the pit by the flautist absorbent.
  • Investigate the contribution to the noise exposure of the musicians from the front-of-house stage-edge show sound system.
  • Provide hearing protection.
  • Carry out a further noise assessment to quantify improvement.
  • There would be little benefit in introducing more absorption within the drum booth as this was already 'dead'. The drummer was provided with closed-back headphones with a small mixer and a direct feed from the sound desk which enabled him to control the mix he heard and so reduce the intrusive airborne noise from the drums.
  • Initial assessment should have been carried out on all the musicians to obtain a clearer picture of individual noise exposure. This would have saved costs and time and would have resulted in achieving the reduction in exposure levels sooner.
  • Other recognised noise sources: the sound of a musician's own instrument; the sound of other instruments, especially nearby; the sound of a house sound system, particularly from speakers set into the stage edge over the pit; noise from the auditorium (such as applause)

Second noise assessment August 2002

Noise measurements were taken on the right side of the flautist and the left side of the flautist - to establish any variation from side to side; between the horns and the bass trombone (level with the horn players' left ears); and above the head of the trumpet player.

Measurement position Show LAeq dB Daily noise exposure with one show per day Lep,d dB Weekly average of daily noise exposuresLep,w dB
Flautist right 89 85 86
Flautist left 89 85 86
Horn player/bass trombone 94 90 92
Trumpet 96 92 93

Conclusions

  • Improvements resulting from remedial works in the pit caused a reduction in the LEP,w at the flautist's position of 3 dB. As this position was still above the first action level, hearing protection needed to be made available.
  • After the first assessment it was recommended that the entire perspex screen between the brass and woodwind should have absorbent material fixed to both sides. The first trial would be to have 30 mm dense mineral fibre applied on each side and black wood serge used as a decorative cover stretched over the fibre. The perspex should be left alone for the top section of the screen to allow the brass section to see through it. The mineral fibre should have a minimum density of 60 Kg/m3. If, after these controls have been carried out and reduction is still insufficient, hearing protection should be provided and used.

Third noise assessment September 2002

Noise measurements were taken between violas; between saxophone/clarinet and cello; between French horn and trombone (by horn players' left ears); by trumpeter's left ear; by flautist's left ear.

Measurement position Show LAeq dB Daily noise exposure with one show per day LEP,d dB Weekly average of daily noise exposures LEP,w dB
Violas 85 81 82
Sax/85 85 82 83
French horn (left ear) 91 87 88
Trumpet (left ear) 94 89 91
Flute (left ear) 89 85 86

Conclusions

  • Flautist: further remedial works resulted in a negligible reduction, so hearing protection should be made available.
  • Brass: the additional absorptive material on the perspex screen in front of the brass position resulted in a significant reduction in exposure levels. Hearing protection should be made available for the French horn but provided to and used by the trumpet.

Glossary

For a more detailed explanation of terms see Useful information and glossary.

Foldback Loudspeakers sited near performers to allow them to hear specific sounds which would otherwise be too quiet, for example for a singer on stage to hear a pit orchestra. Includes onstage monitors and side fills.

Noise exposure 'The noise dose', which can be calculated, takes account of the actual volume of sound and how long it continues. Noise exposure is not the same as sound level, which is the level of noise measured at a particular moment.

Noise measurements Decibels (dB) are used for measuring noise. A-weighting is used to approximate to the frequency responses of the human ear. C-weighting is used to measure peak, impact or explosive noise.

Orchestra pit In a theatre, an area in which the orchestra performs at a lower level in front of, and usually partially under, the stage.

Risers rostra or platforms - see 'Risers' in Sound Advice Note 4 'Noise control measures and training'

Seating rotation The amount of exposure to noise depends on where the musician sits and plays within the orchestra/band. The noise exposure of musicians may be varied by moving them.

Shakers (or thumpers) an attachment that fits directly to the drum stool and transmits low frequency vibration - giving the player the right 'feel' without the need for high volume bass speakers, effectively a loudspeaker without a cone. They allow performers to use hearing protection and monitor their performance while still maintaining contact with their instruments.

Bibliography

  • Control of noise in the music entertainment industry. Code of practice Worksafe Western Australia Commission 2003 www.docep.wa.gov.au/worksafe
  • Controlling noise at work. The Control of Noise at Work Regulations 2005. Guidance on Regulations L108 (Second edition) HSE Books 2005 ISBN 978 0 7176 6164 0
  • Listen while you work: Hearing conservation for the arts for performers and other workers in art and entertainment Safety & Health in Arts Production & Entertainment (SHAPE), Canada 2001 ISBN 978 0 7726 4643 9 www.shape.bc.ca/resources/pdf/listen.pdf
  • Noise at work: Guidance for employers on the Control of Noise at Work Regulations 2005 Leaflet INDG362(rev1) HSE Books 2005 (single copy free or priced packs of 10 ISBN 978 0 7176 6165 7)
  • Protect your hearing or lose it! Pocket card INDG363(rev1) HSE Books 2005 (single copy free or priced packs of 25 ISBN 978 0 7176 6166 4) www.hse.gov.uk/pubns/indg363.pdf

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