Noise Dose
Calculate the occupational noise dose, D = (C ÷ T) × 100%, dividing the effective exposure time C by the maximum allowed time T for the measured noise level and multiplying by 100. The result, in %, shows how much of the maximum daily exposure the worker accumulated: 100% is the tolerance limit (85 dB(A) for 8 hours, with a 5 dB exchange rate in Brazil). Doses above 100% require controls and indicate risk of noise-induced hearing loss. For several levels, the C/T terms are summed. Enter the exposure time and the maximum allowed time.
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Dose de ruído (NR-15)
A dose de ruído é a forma de medir exposição que reconhece que o dano auditivo depende tanto da intensidade do ruído quanto do tempo de exposição. Para um nível de ruído constante, ela é D = (C ÷ T) × 100%, onde C é o tempo de exposição real ao nível e T é o tempo máximo permitido para aquele nível (obtido da tabela ou fórmula da NR-15). O resultado, em %, diz quanto da 'cota diária' de ruído o trabalhador consumiu: 100% equivale exatamente ao limite de tolerância (no Brasil, 85 dB(A) por 8 horas, com fator de duplicação de dose q=5 dB). Acima de 100%, a exposição é insalubre e exige medidas de controle (engenharia, organização do trabalho ou EPI). Quando o trabalhador passa por vários níveis de ruído ao longo do dia, a dose total é a soma das parcelas C/T de cada nível — e se essa soma passar de 1 (100%), o limite foi excedido. A dose é a base da avaliação de risco de perda auditiva induzida por ruído (PAIR), a doença ocupacional mais comum na indústria. Informe o tempo de exposição e o tempo máximo permitido.
Related Tools
Maximum Noise Exposure Time
Calculate the maximum daily allowed noise exposure time, T = 8 ÷ 2^((SPL − 85) ÷ 5), from the sound pressure level SPL (dB(A)). The result, in hours, is the maximum exposure duration before reaching a 100% dose under the Brazilian NR-15 (85 dB(A) limit for 8 h, with a 5 dB dose-doubling rate). Every 5 dB above 85 halves the allowed time: 90 dB(A) allows 4 h, 95 dB(A) only 2 h. It is the basis for dose calculation and the planning of rotation and breaks. Enter the sound pressure level.
Normalized Exposure Level (NEN)
Calculate the 8-hour normalized exposure level (NEN), NEN = NE + 10·log₁₀(t ÷ 480), from the measured exposure level NE (dB(A)) and the actual exposure time t (minutes). The result, in dB(A), converts an exposure of any duration into the equivalent level that would produce the same dose over a standard 8-hour (480 min) shift, allowing direct comparison with the tolerance limit and action level. It is the quantity used by occupational hygiene standards to assess continuous or intermittent noise. Enter the measured level and the exposure time.
Dilution Ventilation Flow
Calculate the airflow needed to dilute a contaminant, Q = (G × K) ÷ C, from the contaminant generation rate G, a safety/mixing factor K and the allowable limit concentration C. The result, in the consistent flow unit, is the volume of clean air that must be supplied/exhausted to keep the contaminant concentration below the tolerance limit in the breathing zone. General dilution ventilation suits low-toxicity, diffusely generated contaminants; the K factor corrects for imperfect air mixing. Enter the generation rate, the safety factor and the limit concentration.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.