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We have used a sensory comparison technique to evaluate the effectiveness of different automotive glazings in reducing the heat experienced from direct irradiation of the skin by sunlight. Three categories of single sheet glass have been evaluated: clear, standard, and solar absorbing. The data are consistent with laboratory measurements on the solar transmittance of the glasses and with Weber's Law for human sensitivity to differences in radiant heat. People cannot distinguish between two glasses unless the relative difference in total solar transmittance is at least 10%.

We have compared the capabilities of two optical instruments -- a conventional opacity meter and a photoacoustic device developed in our laboratory -- as tools for measurement of diesel particulate emissions. The devices were tested using emissions from several 5.7 ℓ engines operated at various steady-state conditions of speed and load and also over the Federal Test Procedure driving cycle. The photoacoustic instrument is about 10 times more sensitive than the opacity meter. Further, unlike the opacity meter, its calibration to give mass concentration is independent of particle size variations.