Sound Advice Note 15

Background

15.1 This advice deals with recording live music, primarily in purpose-built facilities: studios. It may also be relevant to broadcasting music. It should be read in conjunction with Sound Advice Note 10 'Rock and pop' and Sound Advice Note 12 'Orchestras'.

15.2 What makes this advice different is that typically there is no paying audience involved. This to some extent reduces the usual burden which typically gives priority to appearance over audibility. Layout can therefore be optimised for sound without such severe space restrictions. Microphones and their leads and stands need not be obscured, distant parts of the studio and other remote areas are equally useable and when recordings are being made there is usually the ability to 'retake' when desired. Where multi-mic methods are used, it may also be possible to keep performance noise down irrespective of whatever balance is achieved at the mixing desk. These features can provide the opportunity for a degree of experimentation, which will help comply with the Noise Regulations.

15.3 A noise risk assessment flow chart for studios is at the end of this advice note.

Control measures

15.4 Where a noise risk assessment has indicated there is a risk, possible control measures may include the following

• planning;
• positioning performers;
• reducing exposure for everyone;
• adjustment to speakers.

Planning

15.5 The room size, shape, design and acoustic all have a direct bearing on the sounds being generated. At the event-planning stage, consider noise-exposure levels for performers, engineers, crew, and ancillary activities such as hospitality. Allow enough time to comfortably complete the project - an extra day or half day could reduce the overall intensity for everyone.

15.6 When new-build or structural modifications are planned, try to envisage how all those involved with the end product are likely to interact with the environment created. Consider how noise risks can be eliminated or reduced by thoughtful design, for example, will the Green Room enable its occupants to be part of an event without the risk of noise hazard?

15.7 Try to reduce noise 'hot spots' in performance areas by installing sound-absorbent materials, screened areas and acoustic refuges.

Positioning performers

15.8 The positioning of performers is important:

• When calculating how many musicians/performers can be accommodated in a studio, aim for 2.0 m2 of floor space per person together with a surrounding perimeter area.
• Separate the performers from each other as far as practicable which may help to reduce exposure levels. Provide risers - see Sound Advice Note 4 'Noise control measures and training'.
• Take into account the sources of sound and visualise the noise footprint that each will have. It may be helpful to carry out noise measurements before and after layout adjustments to help gauge the effect.

Reducing exposure

15.9 Minimise the duration of noise exposure for everyone:

• Make sure staff who are not needed for a particular piece leave the studio or use 'acoustic refuges' where provided.
• Control rooms should only contain essential staff, and not be treated as Green Rooms.
• Make good use of acoustic screens to isolate loud instruments or shield individuals/groups from prevailing sounds.
• Drum kits can be positioned and shielded to minimise noise spill.
• Particularly noisy instruments could be positioned and mic'd in a separate area from the main performance.
• Any shielding materials should be acoustically absorbent rather than reflective.
• Play more quietly, especially if instruments are individually mic'd.

15.10 Disposable hearing protection, for example earmuffs or disposable earplugs, should be kept available in case they are needed.

Performers' monitor speakers

15.11 Remember that any reduction in sound levels from the loudest instruments will result in less need for high fold-back levels.

• Try replacing floor wedges with smaller stand-mounted speakers at ear level.
• Use headphones or in-ear monitors rather than fold-back speakers, so reducing unwanted sound in the performance area. All headphones and in-ear monitors should be fitted with noise limiters - see 'Click tracks and headphones' and Sound Advice Note 10 'Rock and pop'.
• Try using single-earpiece headphones and swapping ears between takes to reduce overall exposure.
• Consider using click tracks in place of monitors - see 'Click tracks and headphones'.

Control room monitor speakers

15.12 Reduce monitor levels in the control rooms to the lowest feasible listening levels when recording, overdubbing and mixing. There are often other workers, for example producers, performers and engineers, who need to be present, and who may be there for many hours.

15.13 It is often necessary for the sound engineer to raise the volume of quiet pieces of music for analytical purposes. If these listening levels were to be maintained during loud passages, even the peak action level would probably be exceeded. It can therefore be appreciated why control room speaker levels need to be frequently adjusted, but there should be some safeguard to avoid inadvertently leaving speaker volumes at high levels. The use of electronic limiting in loudspeaker feeds is not favoured by sound engineers.

15.14 An alternative approach is to lock off the system to achieve a maximum level (say 80 dB for an 8-hour session or 87 dB for a 3-hour session) but then provide a method of fleeting gain increase. This could be achieved with a simple push button on the mixing desk that provides full gain while pressed. A more sophisticated electronic version might calculate the duration of the full-volume mode, so that a cap could be applied to its use.

Classical concert recording

Novel layout for pop concert recording

 

A noise risk assessment method for a studio session

15A1 Click tracks and headphones

Click tracks

1 Avoid overusing click tracks. They should be electronically limited. Keep the number of users to a minimum as not everyone in a section may need to hear the track. When using single monaural headphones, consider alternating the earpiece from one ear to the other occasionally, dividing exposure between both ears. Individual user-volume controls for each set of headphones should be provided.

2 It may be possible to avoid the use of click tracks, for example by providing pulse mats. Experimentation with pulsed cue lights proved unsuccessful and this system is not advised.

Headphones

3 This advice mainly relates to the general use of headphones. For the use of headphones as hearing protection see paragraphs 7-9 below.

4 If headphones are used, the tendency is to generate in-ear noise levels louder than those in the venue. To counteract this it is sensible only to use headphones provided with limiters. In particular in-ear headphones (buds) such as provided with MP3 players should be used with extreme care and only if equipped with limiters. Most commercially available headphones with limiters are currently set at 93 dB. Other limits are possible. Advice should be sought on how long they can be used for. It is good practice to check all types of limited headphones annually to make sure the limiter is working properly.

5 The advantages and disadvantages of headphones are:

Advantages

• Allow a very quiet stage environment.
• Easier to slip on and off than in-ear monitors.
• Do not require custom-fitting.
• Noise-cancellation models help block out background sound.

Disadvantages

• Heavier and more obtrusive than in-ear monitors.
• Many noise-cancellation models create a feeling of 'fullness' in the ears.
• Expensive.
• Dangerous unless limited.

Useful for

• Studio applications (musicians, vocalists, and sound engineers).
• Live applications (DJs and sound engineers).
• Live-performance communication purposes.
• Low-ambient-noise environments (areas where the daily noise exposure is below 85 dB).

6 Most headphones offer no or little protection from ambient noise.

7 The only type of headphone that can be defined as a hearing protector is one incorporated into an earmuff.

8 Headphones that comply with BS EN 352-1 provide hearing protection from ambient sources but do not provide limitation of the signal received from the communication system unless noise limiters are fitted. Headphones that also comply with BS EN 352-6 provide noise limitation of the signal received from the communication system. It is strongly recommended that headphones be fitted with noise limiters to reduce the risk of damaging sound levels being delivered direct to the wearer's ears.

9 Headphones can incorporate a combination of active and passive protection as well as signal-limiting capabilities (sound conveyed electronically) to afford optimum protection with ease of operation. Both active and passive protection is highly desirable as otherwise there is a risk that the in-ear noise levels may be louder than those in the venue because the wearer will receive both the ambient noise and the electronically communicated noise.

Good working practice

10 A list of suggestions for good working practice for headphone users in the music and entertainment industry is given below:

• Headphones should not be shared. Where this cannot be avoided, users should be given their own ear pads and voice tubes.
• Headphones should be fully adjustable and well-maintained.
• Headphones or associated equipment should incorporate an adjustable volume control that enables the user to listen to incoming signals at a comfortable level.
• Headphones should be cleaned regularly. Foam pads can be washed, wiping cables prevents them from becoming brittle, and cleaning voice tubes (which can become blocked with food, dust and make-up) ensures the level of transmitted signals remains audible.
• Users should be allowed time to make adjustments to their equipment, and to clean and maintain it.
• Users should receive regular training that includes how to use the headphones and associated equipment, any volume-control features and why adjustment of the listening level through the headphones is important, and the importance of regular cleaning and maintenance.
• Reducing ambient noise levels will enable headphone users to keep listening levels as low as possible.

Glossary

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

Click track Backing or metronome track that is played back to musicians (normally through headphones) to enable them to keep accurate time. It is common for situations where drummers have to keep time with a pre-recorded or sequenced track.

Cue lights A means of indicating to performers when to start and stop, using a (typically green) lamp.

Fold-back monitors 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.

In-ear monitors Essentially earplugs with built-in miniature monitors (loudspeakers). It is essential that they are fitted with noise limiters.

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 limiters Sometimes known as volume regulatory device (VRD), controls noise exposure from amplified music. Modern noise limiters can be fitted with anti-tamper relays connected to external switches to improve system security.

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.

Pulse Mat An electro-mechanical mat that pulses in time with an applied signal, typically a click track.

Risers Rostra or platforms

VRD Volume regulatory device (see noise limiter).

Bibliography

• BS EN 352-1:2002 Hearing protectors. Safety requirements and testing. Ear-muffs British Standards Institution
• BS EN 352-6: 2002 Hearing protectors. Safety requirements and testing. Ear-muffs with electrical audio input British Standards Institution
• 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. INDG362(rev1) HSE Books 2005 (single copy free or priced packs of 10 ISBN 0 7176 6166 2)
• 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