The sh 230 is an entry level over the head monaural headset that offers premium quality safety and comfort featuresthe sh 230 incorporates sennheisers unique patented activegard sound compression technology to guard against acoustic shock and maintain distortion free reception the sophisticated activegard circuitry protects the users hearing from sudden and unexpected noise levels over the telephone system limiting the maximum spl to 104dbuser comfort is assured through ball mounted spea