Arc welding noise assessment from the measured ultrasound pressure levels. Part III: Modern welding techniques

The new method of the assessment of total sound pressure levels and their A-weighting-filtered counterparts from the sound pressure levels in a selected high-frequency band, reported in previous papers from this series, was tested for four modern techniques of welding: RapidArc, CMT, AC Pulse, and Cold Arc. The measurement results for 113 welding runs were divided into two groups. These in the first group served as data for calculations of the correlation equations for the sound pressure levels, while the others were applied as control ones. The 1/3 octave bands from these with center frequencies of 20 to 80 kHz were selected and used in the calculations. The selection was based on the values of the correlation coefficients and standard deviations of the fit. The assessed sound pressure levels averaged for ca. 17 s long welding times showed ±1 dB uncertainty, which was equal to that attainable in the direct measurements with class 1 m in the field. For the averaging time of 0.5 s, the uncertainty was higher but still acceptable. Moreover, the time series of the assessed sound pressure levels closely resembled those measured directly. Minor discrepancies observed at the very beginning of the welding runs were explained by unstable acoustic emission during the electric arc strike between the base material and the electrode rod.