Useful information and glossary

This is a list of terms used on the Sound Advice website and in Sound Advice notes containing recommendations by the Sound Advice Working Group

ABO: Association of British Orchestras

Action values: see ‘Exposure action values’.

Backline: Collection of musical instruments and their direct amplification on stage.

Bone conduction: Transmission of sound signals through the bones of the skull. The signal is directed straight into the inner part of the ear, bypassing the middle and outer parts of the ear.
BS: British Standard.

BS EN: European Standard adopted as a British Standard.

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.

Competent: People having such practical and theoretical knowledge and such experience as is necessary to carry out the work. Need to be aware of the limits of their expertise and knowledge and sufficiently independent and impartial to allow them to make objective decisions. Do not necessarily need to be employed by an independent company, but in-house personnel must have enough authority and independence to be able to make necessary decisions and recommendations.

Cue lights: A means of indicating to performers when to start and stop, using a (typically green) lamp.
Diplacusis: Condition where the two ears hear a given pitch as two distinct tones.

Distributed sound system: Technical term for a sound reproduction/reinforcement system that uses a number of smaller loudspeaker enclosures placed around the venue rather than one or two large stacks at the side of the stage. This reduces the sound level from individual speakers while achieving an even overall spread of sound at an acceptable level for listeners.

Engager/Contractor: In the entertainment industry employers are often known as engagers or contractors. Other terms used, which may or may not imply employment, include producers, promoters, managers and fixers.

Exposure action values (EAV): Levels of exposure to noise at which certain actions need to be taken. The values are:

  • lowerexposure action values (LEAV):
    • daily or weekly exposure of 80 dB:
    • peak sound pressure of 135 dB;
  • upper exposure action values (UEAV):
    • daily or weekly exposure of 85 dB;
    • peak sound pressure of 137 dB.

Exposure action values and exposure limit values


Daily or weekly personal average noise exposure

Peak sound level


Below lower exposure action values

Less than 80 dB

Less than 135 dB

Reduce noise levels as far as reasonably practicable.

Lower exposure action values

80 dB
or above

Cannot take the effect of hearing protection into account

135 dB
or above

Cannot take the effect of hearing protection into account

Undertake risk assessment. If any employees are identified as being particularly susceptible to noise, health surveillance should be implemented.

Make suitable hearing protection available.

Establish a maintenance programme for equipment supplied to reduce noise risk such as noise limiters and hearing protection.

Provide training.

Upper exposure action values

85 dB
or above

Cannot take the effect of hearing protection into account

137 dB
or above

Cannot take the effect of hearing protection into account

Implement the actions required by lower exposure action values (above).

Establish and implement a programme of control measures.

If these measures are not sufficient to reduce exposure below 85 dB then:

  • suitable hearing protection must be worn; and
  • a health surveillance programme implemented.

Exposure limit values

87 dB
Allowed to take hearing protection into account

140 dB
Allowed to take hearing protection into account

Must reduce to below limit values.

Exposure limit values (ELV): These relate to personal exposure to noise and must not be exceeded:

  • daily or weekly exposure of 87 dB;
  • peak sound pressure of 140 dB.

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.

Freelancer: Someone who is not permanently employed full-time by any one employer. A freelancer may go through periods of self-employment or be employed by more than one employer.

Frequency analysis: The breakdown of sound into discrete component frequencies, measured in Hertz and usually grouped in bands or octaves. Appropriate for selecting suitable hearing protection and designing acoustic control measures.

Health record: Record of the person’s details, work assignments and exposures, dates of any health surveillance procedures and information on the person’s fitness to work in noisy environments. The record does not contain clinical details and must be kept by the employer. It is not a confidential document.

Health surveillance: For the purposes of this guidance, ongoing assessment of the state of aural health of an employee as related to exposure to noise.

Hearing Passport: Includes details of training and health surveillance undertaken (for more information see Musicians Hearing Services)

Hearing protection zones (sometimes referred to as HPZ): Areas where the wearing of hearing protection is compulsory. Wherever practicable all such zones should be signed using the sign shown. Signs introduced under the Noise at Work Regulations 1989 which refer to ear protection zones are also acceptable.

ear protection zone sign

Hyperacusis: Increased sensitivity to sound which may cause discomfort or physical pain.
Hz: Hertz, SI unit of frequency. The human ear can detect frequencies between 10 and 20000 Hz.
In-ear monitors: Essentially earplugs with built-in miniature monitors (loudspeakers). It is essential that they are fitted with noise limiters.

LAeq: The ‘equivalent’ continuous noise level that would deliver the same noise dose as a varying level over a given period, and is a good way of describing the average level of noise.

LEP,d: Daily personal noise exposure level. It is averaged over an 8-hour period rather than the actual time in the work environment.

LEP,w: Weekly personal noise exposure level. It is averaged over a period of 5 days (40 hours) by measuring the noise exposure on each of 7 days, then dividing the result by 5.
Limit values: See ‘Exposure limit values’.

Line array systems: Sometimes known as phase array design. A vertical hang of loudspeakers which generates a cylindrical wave front with a better throw and accurate control of off-axis sound. This can mean that levels at the front of a venue do not need to be so loud to reach the back.

Medical Record: Account of a person’s examination and treatment including their medical history, any medication, therapies and referrals. An individual may have more than one medical record. The medical record for hearing health surveillance will contain the hearing health questionnaire, the ear examination, the audiogram and any referral correspondence. It is kept by the doctor or occupational health professional in charge of the health surveillance programme. Medical records are confidential and may not be shown to the employer without the written consent of the individual.

Monitors: See ‘Fold-back monitors’. Musicians’ Union: 60-62 Clapham Road, London SW9 0JJ. 020 7582 5566

Musicians Hearing Services (MHS): An organisation set up to look after musicians’ hearing. They  will assess hearing, give advice on hearing conservation and supply custom-moulded musicians’ hearing protection. They have a long-standing relationship with the music industry and offer a service not only to musicians but to all performers. Tel: 020 7323 2076 or

Noise dose: See ‘Noise exposure’.

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 response of the human ear. C-weighting is used to measure peak, impact or explosive noise.

Occlusion effect: Occurs when an object (like an unvented earplug) completely fills the outer portion of the ear canal. This changes the way sounds are produced in the ear canal, especially noises produced by the body (for example breathing, swallowing and noise travelling through bone and tissue.) The result is these noises appear louder.

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.

PA: Public address system. Sometimes called a ‘Tannoy’. Often used to refer to any loudspeaker transmitting messages rather than music.

Peak values: See ‘Exposure action values’ and ‘Exposure limit values’.
Pulse mat: An electro-mechanical mat that pulses in time with an applied signal, typically a click track.
Reference position: Standard location, usually static, selected to enable monitoring of noise levels to be conducted by measurements.

Risers: Rostra or platforms.

RNID: Royal National Institute for Deaf and Hard of Hearing People, 19-23 Featherstone Street, London EC1 8SL Tel: 0808 808 0123 Information: 0870 6050 123 They also offer a telephone hearing test on 0845 600 5555.

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.

Simple listening checks: An easy way of establishing whether there might be a noise problem. Where it is difficult to hold a normal conversation without shouting or where there is live amplified music (as in a pub, club or pop concert) it is probable that the noise is above the lower exposure action value.

Single number rating (SNR) value: Method of indicating the degree of protection offered by a hearing protector.

Sound restoration: Device in earmuffs that reduces ambient noise levels to allow relayed communication or other signals at a reduced level.

Stage pit:In large pop concert stages and outdoor events, an area in front of the stage formed by the edge of the stage and a barrier a few metres away, which restrains the crowd.

Three-decibel rule: The sound intensity doubles with every three dB increase. Thus sounds at 88 dB are actually twice as intense as they are at 85 dB and 115 dB is 1000 times as intense as 85 dB.

Tinnitus: Buzzing, ringing or tone in the ear. Temporary tinnitus is a warning; a sign that ‘you got away with it that time.’

VRD: Volume regulatory device (see noise limiter).