The risk assessment noise in call centers

Consequences and limits of the new Uni technical report on the evaluation of noise exposure in the workplace for workers using sound sources placed close to the ear. The methods of assessment.

There are about 200,000 workers in Italy who work in call centers and are exposed to a risk often overlooked in these work environments: the noise hazard.

In a recent article published on the portal Inail remember that it was developed a new technical report Uni (National Italian unification), the 'UNI / TR 11450: 2012 "Assessment of noise exposure in the workplace for workers who use sound sources placed close to the ear. "A document that completes the previous technical standards (UNI EN ISO 9612: 2011 and UNI 9432: 2011) for the assessment of exposure to noise of those operators, such as telephone operators who work in call centers, which use active devices and headsets for not covered by the usual photometric methods.

In the current technical standards (UNI 9432, which has undergone various revisions, and the UNI EN 9612: 2010) "the situation of workers exposed to noise introduced directly into the ear canal is not considered. This explains why it was decided to adopt a technical standard ad hoc. "

The rapporteur also dwells on the difficulties of assessing the noise.

The problems are mainly two:

- "That the input sound occurs in a small space (the ear canal) closed";

- "That the sound level in the ear canal is significantly different from what we measure outside of it when the noise propagation occurs through the environment. The difference between the sound pressure levels inside and outside is the transfer function. "

For example, "if an environment is measured in a sound pressure level of 82 dB at 1000 Hz, with diffuse field, inside the ear the sound level increases by about 4 dB, resulting in a value of 86 dB." Do not forget that "the comparison with the limit values ​​laid down by Legislative Decree no. 81/2008, however, happens on the level of external sound." So "if the measurement is carried out inside the ear canal (as in the case of telephone operators) must calculate what is the external sound level that would result in the same measured noise."

We come then to the UNI technical report TR 11450: 2012.

In particular, the methodology of assessment of noise for the telephone operators "must take into account several aspects:

-the device type (monaural or binauricolare);

-l'accoppiamento the device to the ear;

-la possibility for the operator to adjust the volume of the conversation;

-i normal communication signals emitted by devices such as voice, music, telephone signals, but also the abnormal signals such as pulses, discharge and electrical noise, vibrations or resonances, which can also generate high peak levels. "

And to assess the 'noise exposure of workers using sources of noise next to your ear, the "standard provides for three methods:

-technical MIRE, described in the UNI EN ISO 11904-1: use of miniature microphones placed in the ear canal;

-technical the manikin equipped with artificial ears with microphone (UNI EN ISO 11904-2);

Method, electro, encoded in the standard ETSI EG 202 518 V1.1.1: it is based on the measurement of the electrical signal at the entrance of the acoustic device worn and converting the sound level through the transfer functions of the device and the human ear. "

some problems and open questions. For example in relation to:

- "Uncertainty evaluation of workers exposed to noise generated in the ear";

- "Calculation of environmental noise which adds to the noise injected into the ear."

After showing the value of this uncertainty, the report focuses on the assessment of environmental noise that, in the case of telephone operators, "is placed in the ear of the worker filtered through the headset (or other device)."

If the MIRE method and the method of "dummy already take account of this fact, as they measure the entire sound signal that comes into the ear canal (both the voice is transmitted electrically to environmental airborne)", with the electroacoustic method "instead you measure only the signal transmitted electrically; environmental noise should be assessed separately instead. "

Ilcriterio more correct - continuing the relationship - "is added the noise level of the signal transmitted electrically (reported in free field) with the environmental level are corrected with the attenuation of the headset (or the device used). When UNI is, however, a problem arose: the headset (or other device) is not only the means by which the signal is transmitted voice, also a means of hearing protection in noisy environment. "

And this would explain the problem point UNI TR 11450:

a) For the purpose of verifying compliance with the lower and upper values ​​of actions envisaged by the legislation in force, the sound levels measured with the acoustic chain must be added to the sound levels obtained with the electrical chain ignoring the attenuation provided by the headset device.

b) For the purpose of verification of compliance with the exposure limit value stipulated by the legislation in force, the sound levels measured with the acoustic chain must be added to the sound levels obtained with the electrical chain, taking into account, if available, the attenuation provided by the headset device .


A setting which I consider a precaution, but that "opens the way to a remark founded and very probably the standard itself must be re-examined."

In particular, the headset device "has the function of transmitting the voice signal, not the personal protective equipment (which would justify the policy expressed in the standard)":

- "If the headphones are not worn by the worker, the speech signal is not output and the worker suffers the only ambient noise;

-if the headphones are worn, the voice signal is transmitted, but the ambient noise is attenuated by the headphones. "

And therefore "does not occur then ever the condition of simultaneous exposure to environmental noise and speech signal is not attenuated by the headset device."

After referring instead to the case, "not explicitly covered by the rule," monaural devices used in call centers, the report concludes by stating that "in any case, is not correct in the case of these workers use different criteria to evaluate the compliance with the limits of action and the limits of attention "risk-related noise.

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