ARCHITECTURAL ACOUSTICS
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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.