What is the dB loss associated with dipolar spreading?

Dipolar spreading refers to the way sound propagates in a medium, particularly in underwater environments. When sound emanates from a point source and spreads out, it does so in a manner dependent on its geometrical configuration.

In the case of dipolar sources, the sound pressure level decreases with distance at a rate of 12 dB per doubling of distance. This occurs because the sound waves spread out in three dimensions, and since dipolar sources radiate in two opposing lobes, their effective range diminishes more rapidly. To understand this, it's crucial to recognize that the power level is proportional to the area over which the sound energy is distributed. For a dipole, the effective radiation pattern leads to greater attenuation than merely spherical or cylindrical spreading.

With the doubling of distance from the source, the intensity of the wave decreases significantly, resulting in a measured loss of 12 dB. This is a fundamental concept in underwater acoustics and helps in predicting how sound behaves in aquatic environments, impacting both military and environmental acoustic studies.