112 Lecture 6 
dencm 
i TTT 
2 Tee a OO 2 > « se 7eo7 2 > - Se7e0F 2 aaa 
1 10 100 
Fig. 6.9. Minimum separation distance as a function of frequency, and transducer size. 
Ti 
$41 LLL Ut 
Be 7 eer 
1000 
fen kHz 
Denm 
10 
out in our tank. This value permits adequate signal integration on a B.K. Level 
Recorder for a convenient speed of directivity recording. 
6.2.2.4. Size of the Anechoic Tank 
It appears from the diagrams that the tank we now have in use is adequate 
for transducer measurement at frequencies above 10 kcps, provided that its 
largest dimension is less than 1 m. 
In our opinion, the best proportions for measuring tanks are: length equal to 
1.5 times the width, and a width equal to the depth. 
When d is the largest dimension of a transducer to be calibrated and A is the 
wavelength of the lowest frequency wanted, we choose the maximum separation 
distance between transducers equal to the width of the tank and to d’/,. If, for 
example, a transducer with a maximum dimension of 1.5 m has to be measured 
at 5 kcps, we have d7/A= 7.5 m, and the tank size would have to be 11.25 by 7.5 
