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This is the full text of the Sound Advice Working Group specific recommendations covering studios.
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.
15.4 Where a noise risk assessment has indicated there is a risk, possible control measures may include the following
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.
15.8 The positioning of performers is important:
15.9 Minimise the duration of noise exposure for everyone:
15.10 Disposable hearing protection, for example earmuffs or disposable earplugs, should be kept available in case they are needed.
15.11 Remember that any reduction in sound levels from the loudest instruments will result in less need for high fold-back levels.
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.
There were two performances before an invited audience. Both performances had the same orchestra and pop group. At the first concert light music was played and the performance was arranged in a traditional 'classical' layout. At the second concert pop music was played and a 'novel' layout was tried.
Noise levels within the brass and percussion sections of an orchestra can exceed 95 dB. In the traditional layout of the orchestra, players of quieter instruments seated in front of these sections can receive a significant noise exposure from these louder instruments. During the pop concert recording the orchestra experimented with placing the brass and percussion sections to the front of the orchestra. The woodwind and strings were on raised staging behind. Individual microphones were used for each player and the sound heard by the audience was amplified and balanced electronically. Players used headsets to hear backing tracks and clicks.
Clear, head-height screens, separating the pop musicians from the orchestra, provided some additional protection where pop and orchestra musicians were in close proximity.
To maintain the benefit of the physical noise controls the pop musicians and sound technicians were reminded of the need to moderate amplified sound levels on the stage. As a consequence the monitor speakers for the pop musicians gave a lower level than the pop musicians were accustomed to.
The table below compares the daily noise exposure of the orchestra during the 'classical' concert recording with a traditional layout of the players, and the noise exposure during the pop concert with the novel arrangement.
Both events were at the same venue. The exposure in both cases arises from a full-length rehearsal and performance within the same day.
Comparison of daily noise exposure
|Player||Traditional layout for 'classical' concertLEP,d dB||Novel layout for pop concert LEP,d dB|
|Clarinet||91||80 (on back row of orchestra)|
|Cello||83 (at far edge of orchestra)||86 (in front of woodwind)|
The orchestra musicians had said that previous recordings of pop concerts had given much higher sound levels than classical recordings. Compared to a classical recording this experimental arrangement of the orchestra gave a reduced exposure for most string and woodwind players, and no increase in exposure for the brass players.
The rearrangement of the orchestra was viable because musicians were playing with backing tracks and clicks heard through headsets with electronic balancing of the sound from each instrument for the recording and audience. The additional microphones and sound equipment significantly increased production costs. The orchestra layout described here is unsuitable for a classical concert where players need to hear other orchestra sections or where the audience need to hear the quieter instruments acoustically (not amplified).
Illustrations of the two layouts are in the figures below.'Classical' concert recording shows a traditional orchestra layout, which places the quieter section, the strings and woodwind, between the pop group and the orchestra's brass and percussion sections. Transparent acoustic screens were placed between the strings and the pop group's equipment but these did not provide enough protection from their loud amplifiers and monitors.
Pop concert recording shows how the layout was changed to provide more noise protection for the orchestra. The strings and woodwind sections were tiered which moved them away from the noisiest area of the stage. The brass and percussion sections were situated down-stage and separated from the pop group's band by acoustic screens. These screens were placed far enough away from the brass so as not to cause any noise reflection but also to protect them from the loudness of the group's amplifiers.
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.
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:
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.
10 A list of suggestions for good working practice for headphone users in the music and entertainment industry is given below:
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).