Acoustics/formulas/Max efficiency

This formula is a template, for inclusion into pages about Acoustics. Use the following syntax to include it:

{{:Acoustics/formulas/Max efficiency}}

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$\eta _{\max }=1-{\frac {2}{k_{\mathrm {eff} }{\sqrt {Q_{E}Q_{m0}}}}}\qquad \left(k_{\mathrm {eff} }{\sqrt {Q_{E}Q_{m0}}}\ll 1\right)$