are intended to be somewhat descriptive of the sound and do not infer 

 the source. To date, 26 categories have been noted. New sounds are 

 being heard each week, while concurrently some of the earlier ones are 

 no longer heard. For example 5 the "Grunts" were heard in December 1960 

 and January 1961, but have not been heard since that time. "Bursts" 

 were common until the last of December, but have been steadily diminishing. 

 The "Moo", first heard on 21 February 1961 is now an extremely frequent 

 sound as is the "Tuba" which was first recorded on 1 March 1961. 



To date no concerted effort has been made to identify the sound 

 producers; however, plans are underway for several methods to do this. 



Preliminary data concerning the frequency of occurrence of 

 the sound categories are shown in Figures 16, 17, and 18. It appears 

 (Figure 16) that some of the sounds show a diurnal pattern. The "A" 

 Pop, for example, consistently shows a somewhat greater night than day- 

 time activity but the "B" Honk shows a tendency toward greater daytime 

 activity. The "A" Honk fails to show a diurnal pattern. 



Considering the occurrence of a single sound category in 

 four hour intervals, it can be seen (Figures 17 and 18) that there is 

 some tendency toward a pattern of soniferous activity for the 24 hour 

 periods. Both the "A" Honk and the "B" Roar exhibit reduced activity 

 about 4:00 a.m. 



Because of the short time period which has elapsed since 

 the first sustained recording, it is not possible to generalize on 

 seasonal variation. However, a continued increase of the overall 

 sonic activity has been noted in the area of the two hydrophones. For 

 one or two sounds, it is possible that this is due to an accompanying 

 increase in aural acuity of those doing the monitoring. 



(b) Ambient Noise 



Preliminary results of the measurement of broad band ambient 

 noise levels on a diurnal basis, are shown in Figures 19 and 20. The 

 averages of the observations for the seven days, are shown on the bottom 

 chart of Figure 20. There appears to be a slight diurnal pattern exhibited 

 by a small increase in the average level at 0200 hours and a slight decrease 

 at 1500 hours. It is planned to investigate this further employing sel- 

 ected frequency bands and continuously observing wind speed and direction 

 and tide heights. The noise levels at the shallow and deep hydrophones, 

 averaged over 24 hours , are respectively, 1.7 and=0.5 dbyib. 



The above level measurements were obtained with the aid of 

 Esterline Angus milliameter chart recorders. Short sections of the 

 noise level charts are shown in Figures 21 and 22. Levels were read at 

 hourly intervals from the lower edge of the traces. The irregularly 

 occurring level increases having durations of several minutes to several 

 hours are caused by passing boats and ships. Such increases were 

 excluded from the above noted preliminary results by using the mean of 

 the levels before and after the increase. 



=.10= 



