This procedure allows to assess the effectiveness of widespread hearing protectors such as:
Ear-muffs
Formable ear-plugs
Preshaped ear-plugs.
The manufacturer must supply, along with the protector, the attenuation values that it provides by declaring, in particular, the Simplified Noise Reduction (SNR) index and the attenuation in octave bands.
The procedure allows to choose the hearing protector from a database of Personal Hearing Protectors (PHPs) or to enter its attenuation values manually, if the device is absent from the database.
The procedure uses both the SNR method and the Octave Band Method (OBM).
Much evidence suggests that the laboratory-measured attenuation is strongly overestimated compared to that achieved in a real working environment for the following reasons:
To account for the loss of attenuation due to the elements set forth above, the nominal attenuation values provided by the manufacturer under the CE marking of the PPE are multiplied, within the scope of the effectiveness assessment of the hearing protector worn in real conditions, by the β factors reported in Table C.4. of the UNI 9432.
Table C.4 – Values of the multiplying β factor to be applied to the nominal SNR
Hearing protector | β |
Ear-muffs | 0.75 |
Formable ear-plugs | 0.5 |
Preshaped ear-plugs | 0.3 |
Values of β greater than those specified in the table (but obviously always lower than 1) are possible if the employer ensures the compliance with the following rules:
The procedure carries out the assessment of the appropriateness of the hearing protector (with respect to the equivalent sound levels) by using the following criterion.
The level of protection of a hearing protector is determined based on Table 1. This table has been extracted from the standard EN 458.
Table 1. – Assessment of the protection provided by the PPE as a function of the achieved sound level
Equivalent sound level calculated by taking into account the hearing protector
L’Aeq,Te (dB)
|
Protection rating |
greater than 80 | Insufficient |
from 75 to 80 | Acceptable |
from 70 to 75 | Good |
from 65 to 70 | Acceptable |
less than 65 | Too high (Overprotection) |
A hearing protector is considered to be effective if it allows a "good" or "acceptable" protection i.e. an equivalent continuous sound level equal to L’Aeq,Te when it is worn, as specified in Table 1. It must also be considered that, in any case, the use of a hearing protector must ensure that the level of daily exposure of a worker does not exceed the exposure limit, set to 87 dB(A) by the binding standards.
The values L’Aeq,T < 65 dB (A) can still be considered acceptable provided that there are no contraindications related to the capability of hearing danger signals or alarms or to particular feelings of isolation expressed by the worker.
Since hearing protectors should be made available when the lowest action values are exceeded (LAV: 80 dB (A) for LEX, 8h and / or 135 dB(C) for Lpeak,C), the assessment of effectiveness should be performed when such values are exceeded and in any case where the hearing protectors are provided.
HEARING PROTECTOR EFFECTIVENESS
For the purposes of the effectiveness assessment it is necessary to confirm that:
Go to the details of the calculation algorythm