The Use of Kurtosis Measurement in the Assessment of Potential Noise Trauma
The current noise standards for the United States were originally formulated in 1968/1969 as part of the Walsh–Healy Act for Federal Contractors (U.S. Department of Labor 1969). The standards for a permissible noise exposure are based on data from a number of large-scale demographic studies of hearing loss in industrial settings in the United States and Europe (Burns and Robinson 1970; Baughn 1973; Passchier-Vermeer 1974).
Non-Gaussian noise composed of background lower level noise and intermittent higher level impacts or impulses or short bursts of higher level noise.
A unit is composed of 10 × sound (x)/reference sound. Note dB is an undefined term unless it has a suffix stating the reference, i.e.,
dB SPL: dB sound pressure level and the reference is 20 μbar pressure
dB SL: dB sensation level and the reference is the listener’s threshold for that specific sound.
Sound measurements made with an A-scale weighting on the sound level meter. Low-frequency sounds (less than 500 Hz) are negatively weighted with the A scale because low-frequency sound energy is not as damaging to the ear as sounds above 500 Hz.
(HTL) Hearing threshold levels are expressed in decibels relative to appropriate clinical norms.
A statistical parameter used in describing a distribution of a variable. It is this 4th moment of a distribution (see Fig. 4.1) and as kurtosis increases, more of the variance is due to infrequent extreme deviations (i.e., the impact and noise bursts in Fig. 4.2). Kurtosis is used in finance to describe the pattern of variation associated with a given stock or hedge fund.
Refers to the average sound level over an 8-h period. The L eq 8 h is the basic unit for noise assessment. A 4-h exposure of x dBA would be averaged over 8 h to determine the equivalent L eq 8 h.
Noise exposures are defined by both the intensity of noise (I) and the duration of the exposure (T) because hearing loss is related to both I and T. The trading relation refers to how I and T are combined. In the current U.S. standards (Table 4.1), for each 5-dB increase in exposure level there is a 50% decrease in time; therefore the trading relation is 5 dB. It should be noted that European noise standards have a 3-dB trading relation.
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