Characteristics spectral distribution

The extent to which a ventilation noise is perceived as disturbing depends not only on its dB(A) level, but also on the spectral distribution and the presence of tones or intermittent components in the noise. From an experiment carried out on respondents exposed to ventilation noises with different characteristics in a simulated office room, it emerged that the highest acceptable level was about 7 dB higher for ventilation noise with a superimposed tone at 30 Fiz than for other types of noise. In another experiment, it was found that the tolerance level was much higher for a tone than for a noise at 100 Hz, whereas the opposite tendency applied at 1000 Hz. ... 

Searle NZ, Giesecke P, Kinmonth R, Hirt RC. Ultraviolet spectral distributions and aging characteristics of xenon arcs and filters. Appl Opt 1964 3(8) 923-927. 

Many variables influence the intensity and spectral distribution of radiation that reaches the lower atmosphere Leighton (37) thoroughly discusses these factors. It is not yet possible to incorporate quantitatively into an airshed model the effects of many of these variables on radiation characteristics. In a simple treatment, Seinfeld et al. 49) have considered the variations in radiation intensity with latitude (for Los Angeles) with time of year and time of day. Wayne et al. 22) have adopted portions of the model suggested by Leighton. Much more work is needed, however, before the influence of incoming radiation can be properly included in airshed models. 

Understanding the formation of the ions requires knowledge of the spectral distribution of solar radiation at short wavelengths, the structure of solar and galactic cosmic rays, as well as the chemical composition of the atmosphere and its physical characteristics such as pressure, temperature, and transport. The variations of solar activity must also be considered. 

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