Table II - STATE OF SEA - WIND WAVES 
(WMO Code 75) 
Code Description Height(feet) 
~0 Calm - glassy On 
1 Calm - ripples 0-1/3 
2 Smooth - wavelets 1/3 - 12/3 
3 Slight 12/3 - 4 
4 Moderate 4-8 
5 Rough 8-13 
6 Very rough 13 - 20 
7 High 20 - 30 
8 Very high 30 - 45 
9 Phenomenal over 45 
NOTE: The exact bounding height is to be assigned 
to the lower code figure, that is, a height of 
4 feet is coded as 3. 
Table II - SWELL CONDITION CODE 
—$—$—— 
Approximate 
length in feet 
Code Height in feet 
eS af all 
ORS nO Swell ere. vrei ele utel lel ten et eer ce 
lto-6 = low swell... . 3.06%. 
6 to 12 =moderate {a seo. ss 
Greater than 12 =high. «. . « 
ANRMMHhWNrO 
SS ee 
Confused .7. «3 
: 
There was a time when a general know- 
ledge of the height of the higher waves was 
sufficient for all practical purposes. This is 
no longer the case. Acoustical research has 
indicated that it is desirable to know the sig- 
nificant wave_ height to within plus or minus 
10 percent, Even if the wave height is 
measured to this accuracy its value is lost 
234 
0 
0 to 600 
Above 600 
.| 0 to 300 
300 to 600 
Above 600 
0 to 300 
300 to 600 
Above 600 
sa 6 Oe Ce 
if it is coded as, say, sea state 6 which 
covers a 7 foot range of height. It also 
is becoming increasingly obvious that 
the high frequency waves in the spectrum 
may be as important in the generation 
and reflection of sound as the lower fre- 
quency waves with their greater height. 
Because of this, some idea of the shape 
