Question

In vibration isolation, which one of the following statements is NOT correct regarding Transmissibility (T)?

• A. T is nearly unity at small excitation frequencies
• B. T can be always reduced by using higher damping at any excitation frequency
• C. T is unity at the frequency ratio of $\sqrt{2}$
• D. T is infinity at resonance for undamped systems

Answer 1

The correct option is B T can be always reduced by using higher damping at any excitation frequency

Transmissibility,

$T=\frac{\sqrt{1+{\left(\frac{2\xi \omega }{{\omega }_n}\right)}^2}}{\sqrt{{(1-\frac{{\omega }^2}{{\omega }_n^2})}^2+{\left(\frac{2\xi {\omega }_n}{{\omega }_n}\right)}^2}}$

$\text{If}\frac{\omega }{{\omega }_n}<\sqrt{2}$
"T" reduces as damping increases.

$\text{If}\frac{\omega }{{\omega }_n}=\sqrt{2}\text{then T=1}$

$\text{If}\frac{\omega }{{\omega }_n}<\sqrt{2}$
"T" increases with increasing damping but remains less than 1.