Acoustic performance of the Hellberg NN4 hearing protector comparison of foam seals with fluid seals (IM-SAV-058)

Hellberg, the manufacturers of the BS standard ear muff, NN4, have requested that future supplies be fitted with foam seals rather than fluid seals. A comparison of the acoustic performance of the NN4 with foam seals with that of the NN4 fluid seals was therefore required. A new sample...