In response to the The Royal National Institute for Deaf People (RNID) and TUC study, the HSE commissioned HSL to conduct a study to establish whether there is a noise hazard associated with the call centre industry. The noise exposure of 150 call handlers was assessed at 15 call centres from a range of different sectors within the industry.  Background noise levels were measured using dosimeters.  Noise levels generated by headsets were measured at the eardrum position of a KEMAR manikin and appropriate corrections made.  The results indicate that the risk of hearing damage from using a headset is extremely low.  Although call handlers may occasionally experience high noise levels, these are usually of very short duration.  Consequently, even taking these events into consideration, call handlers' overall daily personal noise exposure is unlikely to exceed the 85dB(A) action level defined in the Noise at Work Regulations 1989.

Noise-cancelling Microphones: Headset manufacturers recommend noise-cancelling microphones for use in environments in which background noise levels are high.  The HSL study recorded a mean background noise level of 62dB(A).  Unless background noise levels increase to 65-70dB(A), noise-cancelling microphones are of little benefit to the majority of call centres and conventional voice tubes or boom microphones are adequate.

Microphone Positioning: There is an optimal position for a microphone in front of a call handler's mouth to avoid excessive vocal feedback for both the caller and the call handler.  It is, therefore, essential for call handlers to be trained to position microphones correctly and avoid compromising the microphone's effectiveness.  Callers may become frustrated if they cannot hear call handlers clearly, and there is a risk that call handlers may start to strain their voices in order to be heard.

Noise Absorbers: Special material, often in ceilings, can help to reduce reverberation in the call centre.  Carpet, chairs with soft seats and padded screens between call handlers can also be effective noise absorbers if designed and fitted appropriately.

Volume Control: To limit call handlers' daily personal noise exposure, headsets, amplifiers and/or turrets should be fitted with volume control, and call handlers should be trained how to use the volume controls.   There is a risk that call handlers will turn the volume up in order to hear a quiet caller but forget to turn it down for the next caller even if that caller speaks at a higher level.  Call handlers may then get used to listening to callers at higher levels than is really necessary.  Some systems return the call handler's listening level to a default setting after each call.  An on-screen reminder at the start of a new call could also prompt call handlers to assess the level and adjust the volume if necessary.   At one of the call centres visited in the HSL study, one of the keys on the call handlers' keyboards - designated in blue - reduced headset noise immediately to minimum when pressed.  It was a very quick method for call handlers to reduce sudden high headset noise levels.

Acoustic Shock:  An acoustic shock incident is defined as a sudden increase in high frequency noise transmitted through a headset.  It is usually caused by interference on the telephone line.  Although call handlers may be shocked or startled by the noise, exposure to these unexpected acoustic events should not cause hearing damage as assessed by conventional methods.  However, emerging evidence suggests that exposure to these acoustic incidents, at levels much lower than is traditionally associated with hearing damage, is giving rise to other symptoms.  Further work on acoustic shock is ongoing.  Call handlers should be encouraged to report to management exposure to all acoustic shock incidents or any other abnormally loud noises.  Management should make a record of these reported events.

Headset Limiters: One practical way of limiting exposure to unexpected high noises from headsets is through headset design.  Since 1991, major manufacturers have incorporated an acoustic (shock) limiter in the electronics of their headsets to meet the requirements of the Department of Trade and Industry (DTI) specification 85/013.  In the UK, this limiter ensures that any type of noise (eg conversation, short duration impulses) above 118dB is not transmitted through the headset.

Headset Type: There is no difference in the impact on hearing depending on whether the headset has two ear-pieces or only one.   Some people feel it is easier to concentrate wearing binaural headsets, but others feel isolated and prefer monaural models.  It is good practice to give call handlers the choice of either.

Headset Hygiene: Call handlers wear a headset throughout their shift every shift so it is important that it is fully adjustable to ensure a comfortable fit.  This is particularly important if the ear pieces sit at the entrance to the ear canal rather than resting on the outside.  Prompts about adjusting display screen equipment when call handlers log on at the start of their shift should include a reminder to adjust headsets to make them comfortable.  Headsets should be checked regularly and repaired or replaced immediately if necessary.  There may be an increased risk of ear irritation and infection because headsets are worn so intensively.  To reduce this risk, staff should be trained in headset hygiene and given the time and the materials to complete a hygiene programme.  The issue of headsets to individuals is strongly recommended.  If the sharing from a pool of headsets is unavoidable, then each call handler should be issued with their own personal foam ear pads and voice tubes.  These should always be available so call handlers who have forgotten or lost theirs, or worn them out, do not endure a shift with hard ear pieces and an incomplete headset.

Voice tubes can become blocked with food, make-up and dust, and this compromises the effectiveness of microphones.  Call handlers must be trained how to clean the voice tubes in order to optimise the volume of the transmitted signals and avoid the risk of frustrated callers and strained voices.

Hearing Tests: Guidance on when it is appropriate to introduce hearing checks is given in the HSE document 'Health surveillance in noisy industries - Advice for employers'.  It is considered good practice for employers to carry out regular hearing checks on all employees whose daily personal noise exposures equal or exceed 90dB(A).

Employees should be encouraged to report immediately exposure to any acoustic incident that results in physical damage.  Management should implement a policy so that the details of these incidents are recorded, and employees are examined by an appropriate expert to investigate the extent of any physical damage (this may include a hearing check).

Information and Consultation: Call handlers should be provided with information about the potential risks to hearing and the measures being taken by their employer to control these risks.  Call handlers or their representatives should be consulted before working practices that may substantially affect their hearing are introduced.

User Comments: The main sources of background noise, within the call centres, were reported as other call handlers speaking to customers, staff talking to each other, particularly at shift changes, meetings being held and telephones ringing in other parts of the open-plan office.  At the caller's end, the television, radio, dogs barking and babies crying were cited.

Good practice:

• Prompt call handlers to adjust the listening level (both up and down) through their headsets at the beginning of each call.
• Ensure a sufficient stock of new or sterile headset pads and voice tubes is maintained. (HSE)