Hearing Protection Calculator

Check if a hearing protector provides adequate attenuation for your workplace noise using the SNR, HML or octave-band methods per BS EN 458. All formulas from HSE hearingcalc.xlsx V1.01.

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SNR — Single Number Rating method

Simplest method. Use when only the C-weighted noise level (LC) is available. Formula: L'A = LC − SNR.

SNR (dB)from CE marking

LC dB(C)workplace noise level

L'A = LC − SNR

100 − 25 = 75.0 dB(A)

L'A + 4 (HSE recommended) = 79.0 dB(A)

LC is the C-weighted noise level at the workplace. SNR is from the CE marking on the protector. This method is least accurate of the three — use HML or octave-band where possible.

SNR method — Protection assessment

75.0dB(A) L'A

79.0dB(A) L'A + 4

Good. L'A at ear is between 70 and 80 dB(A). Protection is adequate and the worker can still hear speech and warnings. This is the target range per BS EN 458.

L'A at ear	Rating
< 70 dB(A)	Over-protection
70–80 dB(A)	Good ✓
80–85 dB(A)	Acceptable
> 85 dB(A)	Under-protection

Rating based on L'A before the +4dB real-world correction. L'A + 4 is the HSE recommended “likely level” at the ear. Source: hearingcalc.xlsx ProtectionRatingHelp sheet.

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HML — High / Mid / Low frequency method

Requires both A and C-weighted levels. More accurate than SNR. Formula: f = LC − LA; PNR from H, M, L values; L'A = LA − PNR.

Hearing protector values (from CE marking)

h (dB)

m (dB)

l (dB)

Workplace noise levels

LA dB(A)

LC dB(C)

f = LC − LA = 97 − 95 = 2.0

f ≥ 2: PNR = M − ((H−M)/4) × (f−2)

PNR = 22.0 dB

L'A = LA − PNR = 95 − 22.0 = 73.0 dB(A)

L'A + 4 (HSE recommended) = 77.0 dB(A)

LC is the C-weighted average level — not LCpeak. LCpeak is typically 20+ dB higher. If only LA is available (no LC measurement), use the SNR method.

HML method — Protection assessment

73.0dB(A) L'A

77.0dB(A) L'A + 4

Good. L'A at ear is between 70 and 80 dB(A). Protection is adequate and the worker can still hear speech and warnings. This is the target range per BS EN 458.

L'A at ear	Rating
< 70 dB(A)	Over-protection
70–80 dB(A)	Good ✓
80–85 dB(A)	Acceptable
> 85 dB(A)	Under-protection

Rating based on L'A before the +4dB real-world correction. L'A + 4 is the HSE recommended “likely level” at the ear. Source: hearingcalc.xlsx ProtectionRatingHelp sheet.

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Octave-band method

Most accurate method. Requires octave-band noise data and manufacturer attenuation data. APV = mean − (1.00 × SD). The 63 Hz band is optional.

Band (Hz)	Mean atten. (dB)	Std dev (dB)	Unprotected (dB)	APV (dB)	Protected+A (dB)
63opt.	63 Hz mean attenuation	63 Hz standard deviation	63 Hz unprotected noise level	21.0	37.8
125	125 Hz mean attenuation	125 Hz standard deviation	125 Hz unprotected noise level	20.0	51.9
250	250 Hz mean attenuation	250 Hz standard deviation	250 Hz unprotected noise level	19.0	62.4
500	500 Hz mean attenuation	500 Hz standard deviation	500 Hz unprotected noise level	20.0	67.8
1,000	1000 Hz mean attenuation	1000 Hz standard deviation	1000 Hz unprotected noise level	22.0	66.0
2k	2000 Hz mean attenuation	2000 Hz standard deviation	2000 Hz unprotected noise level	22.0	62.2
4k	4000 Hz mean attenuation	4000 Hz standard deviation	4000 Hz unprotected noise level	27.0	54.0
8k	8000 Hz mean attenuation	8000 Hz standard deviation	8000 Hz unprotected noise level	34.0	39.9

L'A = 10 × log₁₀(Σ 10^((Protected+A)/10))

L'A = 71.4 dB(A)

L'A + 4 (HSE recommended) = 75.4 dB(A)

Mean attenuation and SD from manufacturer data sheet (BS EN 13819). Unprotected levels from octave-band noise measurement. APV = mean − (1.00 × SD). α = 1.00 fixed (84.1% protection performance). Source: hearingcalc.xlsx.

Octave-band method — Protection assessment

71.4dB(A) L'A

75.4dB(A) L'A + 4

Good. L'A at ear is between 70 and 80 dB(A). Protection is adequate and the worker can still hear speech and warnings. This is the target range per BS EN 458.

L'A at ear	Rating
< 70 dB(A)	Over-protection
70–80 dB(A)	Good ✓
80–85 dB(A)	Acceptable
> 85 dB(A)	Under-protection

Rating based on L'A before the +4dB real-world correction. L'A + 4 is the HSE recommended “likely level” at the ear. Source: hearingcalc.xlsx ProtectionRatingHelp sheet.

Include these calculations in your RAMS documents automatically.

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Need to calculate daily exposure first? Use the Noise Exposure Calculator to find LAeq and LCeq values, then return here to check protector adequacy.

This calculator is provided for guidance only. Results are based on formulas from HSE hearingcalc.xlsx V1.01 (December 2020). The calculator is not a substitute for a formal noise assessment or hearing protection programme carried out by a competent person. Employers must ensure suitable hearing protection is provided under SI 2005/1643.