ARCHITECTURAL ACOUSTICS 120 rear seat forward one centimeter. This distance is so slight that without moving in his seat, in fact, without moving his shoulders, a slight inclination of the head would accomplish an equivalent gain. Thus, while the effect is in the right direction, it is of entirely imperceptible magnitude. If we take into account the sound re¬ flected from walls and ceiling, the gain is even less. But the suggestion which is the text of the present paper was not made by one, but by several gentlemen, and is based on the well-recognized fact that one can hear better, often very much better, with the wind than against it, and better than in still air. Therefore, the suggestion is not groundless and cannot be disposed of thus summarily, certainly not without submitting to the same calculation the out-of-door experience that gave rise to the thought. In the nomenclature of the United States Weather Bureau a wind of from “1 to 5 miles an hour is called light, 6 to 14 miles fresh, 15 to 24 miles brisk, 25 to 37 miles high, and a wind of from 40 to 59 miles is called a gale.” Taking the case of a “high wind” as a liberal example, its average velocity is about 14 meters per second, or about one twenty-fifth the velocity of sound. In such a wind the sound 1000 meters to leeward would be louder than in still air only by an amount which would be equivalent to an ap¬ proach of 40 meters, or 8 per cent. Similarly, to windward the sound would be less loud by an amount equivalent to increasing the dis¬ tance from 1000 to 1040 meters. This is not at all commensurate with general experience. The difference in audibility, everyone will agree, is generally greater and very much greater than this. The discrepancy, however, can be explained. The discrepancy is not between observation and theory, but between observation and a very incomplete analysis of the conditions in the out-of-door ex¬ perience. Thus, the ordinary view is that one is merely hearing with or against the wind and this wind is thought of as steady and uniform. As a matter of fact, the wind is rarely steady, and partic¬ ularly is it of different intensity at different altitudes. Fortunately, the out-of-door phenomenon, which in reality is very complex, has been carefully studied in connection with fog signals. The first adequate explanation of the variation in loudness of a sound with and against the wind was by the late Sir George G.