Originally Posted by
jugofpropwash
Wouldn't it helpful to have the pinger at a frequency where it could be easily heard? (Or quite possibly at both a high and low frequency.) Wouldn't an audible ping help divers/searchers to quickly locate the box under certain conditions?
Nope.
...
low frequencies will travel further, however they take more energy to develop than the higher frequencies. Low frequencies are also in the main background frequencies of the ocean, below the snapping shrimp and whale song freqs. Shipping noise has primary frequencies in the very low levels, with blade rates and shaft rates that are down in the bottom of the spectrum, (still audible to human ears though), but they have harmonics above that which can be strong, particularly when a multiple of the number of blades.Higher frequencies will attenuate faster than the lower frequencies, but they are also usually easier to analyse with fewer artifacts from the sampling rate that is used for the transform.