On the noisiness of steady state and intermittent noises

An experiment was designed to investigate the effects of sound level (L_A), number of single noises (N), level of total energy (L_T) and mean energy level ($\text{dB(A)}$) on the noisiness of steady state and intermittent noises. With the level and duration of pink noise controlled with a sound system called “Programmable Sound Control System”, 16 kinds of intermittent noises and 22 kinds of steady state noises were prepared. Seven subjects judged the noisiness of these stimuli by magnitude estimation. Their judgments were converted into the corresponding sound level (point of subjective equality, abbreviated PSE) by using the power function obtained between sound level and magnitude estimation for the seven kinds of steady state noises. As a result, the level of total energy and mean energy level were found inappropriate to evaluate the noisiness of intermittent noises though they showed high correlation with the noisiness of steady state noises. PSE's of the intermittent noises showed good correspondence with L_N, which is expressed by the equation $\text{L}{}_{\mathrm{N}}\text{=}\text{dB(A)}\text{+ 10}\text{log}\text{N}$. L_N could also be applied to steady state noises if it was assumed that a steady state noise with a duration of D_T is equal to a 2000 ms noise presented $\text{N (}\text{D}{}_{\mathrm{T}}\text{2000}\text{)}$ times. This result suggests that L_N is a good measure of the noisiness of both steady state and intermittent noises.