Jackhammer chisel noise control design optimization

A robust chisel damper for quieting a jackhammer has been developed. The noise produced from a jackhammer chisel is dominated by the ringing of the chisel moil resulting from impacts of the internal hammer against the end of the chisel producing airborne radiation of the transverse bending and longitudinal modes. A model steel chisel moil point was constructed and the design optimized for maximum damping. Anechoic tests showed 70.3 dB linear (re. to 20 micro Pa) at one meter from a standardized longitudinal impact; this is compared to 86.8 dB linear for the maximum overall unweighted sound pressure level for the undamped chisel; and represents a 16.5 dB reduction with a 40 dB drop of the dominant chisel ring tone of 1.37 kHz and its harmonics. This paper discusses the optimization of the design to maximize the rigidized Coulomb friction damping.