Provision for different width filters would be advisable. 
3) The band pass filter should not tune through the record too 
rapidly; that is, the entire record should pass through the filter 
before it has been tuned through, say, one tenth of its band width. 
4) The rectification time constants which provide the output 
voltage to portray the spectrum should be long enough to average 
effectively over the entire record. 
5) A square law detector would be best so that the graph of 
the spectrum would be that of a power spectrun. 
6) Variable controls should be eliminated, and a choice of four 
or five calibrated set switch positions provided. 
Present results of wave record analyzers 
Figure 44 is a collection of examples of electronic analyses 
as taken from the literature. Various spectra are shown as analyzed 
by the machines described by Klebba [1946, 1949] and Barber and Ur- 
sell [1948]. An autocorrelation as performed by Rudnick's device 
[1951] is also shown. Some of the spectra have been modified by add- 
ing some dashed and dash-dot curves in order to illustrate some 
points in the forthcoming discussion. & 
Spectrum number one as shown on the upper left of figure 44 is 
taken from a paper by Seiwell [1949a]. It is an analysis on Klebba's 
machine of a pressure record taken in 120 feet of water off Bermuda 
on 25 Uctober 1946 at 1405 for 350 seconds. Fér periods less than 
about 7 seconds the amplitudes are negligible due to the filtering 
effect of depth. 
The dashed curve drawn by eye through the ‘irregular curve of the 
figure is a smoothed interpretation of what the spectrum might just 
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