The Loudness of Non-steady State Sounds: Is a Ratio Scale Applicable?
Seiichiro Namba Sonoko Kuwano Osaka University
In daily life there are various kinds of non-steady state sounds, such as road traffic noise, aircraft noise, train noise, construction noise, music, and speech. It is important for us to decide on a representative value of the perceived intensity of the overall level fluctuations.
Because there are so many kinds of noise sources in our surroundings, a useful objective measure of environmental noise should correspond to people's subjective impressions of various noises that may differ widely in their temporal structure and frequency characteristics. In other words, a value indicated by the objective measure should always correspond to the value indicated by the subjective impression, whatever the noise source. This study assumes that loudness is representative of the subjective impression because loudness is regarded as a basic subjective impression in noise evaluation.
In a series of experiments conducted by Namba, Kuwano, and their colleagues, the effect of temporal structure on loudness was examined using a variety of non-steady-state sounds produced in the laboratory ( Kuwano, Namba, & Kato, 1978; Kuwano, Namba, & Nakajima, 1980; Namba, Kuwano, & Kato, 1974, 1976; Namba, Nakamura, & Yasuda, 1972; Namba, Yoshikawa, & Kuwano, 1968). From their experiments it was found that loudness and LAeq,T (equivalent continuous A-weighted sound pressure level; mean energy level) are highly correlated. LAeq,T is defined as