In addition, all feature a specially designed Acoustic Optimizer that ensures dynamic sound and deep rich bass response, with optimum acoustical characteristics achieved by adjusting the sound pressure balance in front of and behind the diaphragm.
Those characteristics can include a brief dip in air pressure, a change in wind direction, a change in wind speed, a rise in air temperature or a dip in ultraviolet light reaching the rover.
Because it's so hard in water and to maintain voice features, one of the other aspects of this is that when you dive down the pressure increases, the water pressure increases and actually changes these air filled cavities and you have that influence voice characteristics quite a lot.