Loudness of traffic noises using the method of continuous judgment by line length

The present study was conducted in order to compare the loudness of aircraft noise, road traffic noise and train noise in the same context. Also the time constant in the evaluation of the loudness and the relation between instantaneous judgment based on perception and overall judgment based on memory were examined. Four kinds of sound level were selected for each sound source. The stimulus used for the continuous judgment consisted of the 12 sounds connected in random order with 1 s silent interval. The participants were asked to judge the loudness at each moment using the method of continuous judgment by line length. After three trials they were asked to judge the overall loudness of each sound. A-weighed sound pressure level was sampled every 2ms and LAeq,100ms was calculated on the basis of these values. Following results were found. (1) There was a high correlation between LAeq,100ms and instantaneous judgment sampled every 100 ms. (2) Also a high correlation was found between LAeq and the average of instantaneous judgment of each sound and between LAeq and the overall judgment. (3) The overall loudness was judged louder than the average of instantaneous judgments. (4) There was no systematic difference among the three traffic noises in the relation between LAeq and loudness judgments. (5) The fact that LAeq calculated on the basis of A-weighted sound pressure level sampled every 2 ms showed good correlation with loudness judgments suggests that it is not necessary to consider the time constant. Simple average on energy basis is sufficient for the prediction and estimation of physical values for environmental noises.