The Equivalent two-way beam angle (TWBA) \(\Psi\) is frequency and transducer-specific, and the value can be calculated (in Steradians) for the circular transducer through the following equation (for \(ka\)>10):
| \( \Psi = \frac {5.78}{(k a)^2} \) | (1) | |||
| or in dB format: | ||||
| \( EBA = 10 log (\Psi) \) | (2) | |||
| \(k\) | - | wave number \( k= \frac{2 \pi}{\lambda}\) | ||
| \( \lambda\) | - | wavelength \( [m]\) | ||
| \(a\) | - | active radius of the transducer \( [m]\) | ||
The calculated Equivalent two-way beam angle for each instrument with monochromatic setup is given in the table below:
| Instrument/Frequency | a [mm] | Ψ [sr] | Ψ [dB] |
| Signature 1000 | 15 | 0.0015 | -28.3443 |
| Signature 500 | 30 | 0.0015 | -28.3443 |
| Signature 250/500kHz | 40 | 8.23e-04 | -30.8431 |
| Signature 100/70kHz | 43.5 | 0.0355 | -14.4942 |
| Signature 100/90kHz | 43.5 | 0.0215 | -16.6771 |
| Signature 100/120kHz | 43.5 | 0.0121 | -19.1759 |
Updated