MARINE SCIENCE 119 
needs for such knowledge, the laboratory established an oceano- 
aphic and acoustics study group which has grown to be about one- 
ourth of our scientific staff. This group not only supplies the studies 
and surveys required by our development programs, but also, in keep- 
ing with university tradition, conducts basic research. There is bene- 
ficial cross-fertilization here between practical and basic research. 
Two examples may be of interest. The underwater tracking range, 
mentioned above, which itself arose from basic research, is also uti- 
lized to make detailed studies of water current velocities throughout 
the depth of water by tracking the movements of a slowly sinking 
free body. Thus, this practical development—that is, the range— 
has supplied the instrumentation required for more basic investiga- 
tions. A second example will illustrate the converse. One long-term 
study has involved the theoretical and experimental relationships be- 
tween water circulation patterns at depth and the existence of regions 
of poor acoustic transmission. After the study was completed, it was 
found that these results allowed us to understand and predict the oc- 
casional poor performance of a particular weapon. 
The CHarmrman. Would those acoustical studies that you people 
are doing out there have some benefit to pure communication under- 
water between, say, submarines or other underwater vehicles? 
Dr. Henverson. I will have to answer that in a somewhat general- 
ized way, because any study that you make of acoustic transmission, 
which is really the problem involved here, has the bearing of trans- 
mission of information from one body to another. Actually what 
we do is transmit information from the bottom of the submarine back 
to the bottom, and that is how we know where the object is located. 
The CuHarrman. It is my understanding that one of our real No. 1 
problems—some of it is classified of course—is the problem of com- 
munication between two underwater bodies. 
Dr. Henverson. That is correct. However, to transmit a lot of 
information becomes difficult in the sea-water medium because of 
the low velocity of propagation of sound in the sea-water medium. 
You understand this when you realize that transmission by radio fre- 
quency proceeds at about 186,000 miles per second, whereas sound in 
water you have about 145 feet per second. So that the amount of 
information you can transmit is very small in sound compared by 
what you can do with radio-type transmission. 
The CHarrman. This isa real problem. 
Dr. Henverson. This is a real serious problem for all underwater 
work. 
The Cuarrman. And I suppose the degree of its effectiveness is 
determined by how much we know about the currents, about ma- 
rine growth, all these things that would clog up those windows as we 
call them, of the sea? 
Dr. Henperson. Particularly and perhaps the most important is 
the actual absorption or attenuation of sound of different frequencies 
in sea water. This is probably the dominant thing which determines 
what you can do in terms of communication. With long wave lengths 
of course, lower frequencies travel greater distances and are less 
absorbed than the higher frequencies. 
The Cuarrman. I don’t think it is particularly a classified matter, 
but this is a problem every place. 
