A contribution to the research of circular saw lateral stability II - Research of some influencing factors on circular saw idling noise levels and noise frequency spectrum

In this study the measurement results of the noise level and noise frequency analyses of differently designed circular saw blades in variable conditions are presented. The measurement was carried out at idling. The influences of the following parameters were investigated: 1. tooth type, 2. rotational frequency, 3. clamping ratio, 4. damping layer in the contact area between saw and clamp, 5. dampening. The standard measuring equipment was used. The highest level of noise was measured in the medium range of frequency (1 - 5 kHz) for all the samples with teeth. The comparison of the noise level for specific frequency ranges between samples with teeth and those without teeth shows that the noise of lower frequencies (at the idling of the saw) was the result of the saw blade vibration, and the noise of the medium and especially higher frequencies was the result of the aerodynamic occurrences connected to the teeth of the blade. The biggest changes in the spectrum of emitted noise with placing a damping layer between sawblade and clamp were recorded with fhe blade that has four radial slots and without any special realisations of damping. With that sample the use of a rubber damping layer completely removes the resonant (screaming) noise. The noise spectrum of the damped samples does not change with additional damping. The dependency of the noise level on the rotational frequency can be described with the equation y = A • ln(x) - B with a high correlation coefficient. For a complete comparison of the tested saws this research should be supplemented by measurements when sawing.