calculus - How to evaluate the integral $int_0^{+infty} frac{sin^4{x}}{x^4}dx$?

As we know that $\int_0^{+\infty} \frac{\sin{x}}{x}dx=\pi/2$,but how to evaluate the integral $\int_0^{+\infty} \frac{\sin^4{x}}{x^4}dx$?