What is the difference between noise in air or underwater?

Definition

The following differences can be observed between acoustics in air or under water:

  • structure / fluid interactions are stronger in water, whereas it can be neglected in air for electric motors
  • acoustic waves propagation is different (and therefore radiation efficiency)
  • fluid density is different, resulting in higher sound pressure levels in water

Besides, applicable acoustic standards may differ.

Application to e-NVH

It is therefore important to know if an electric motor will be used in air or under water to calculate and minimize its vibroacoustic signature. As an example, marine applications include underwater propellers where electric motors may disturb marine environment.

Application to MANATEE

MANATEE software dedicated to e-motor noise calculation includes in its fast vibroacoustic analytic model underwater propagation assuming weak fluid/structure interactions. To account for strong interaction, MANATEE can be coupled to ACTRAN.

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