What is normalized angular frequency?
HINT:


Determine the argument of a continuous-time sinusoid with frequency $f=440$ Hz.
Sample that continuous-time sinusoid by replacing $t$ by $nT$, $n\in\mathbb{Z}$, with $T=1/f_s$ being the interval between samples.


This gives you an expression $\sin(n\omega_0)$, where $\omega_0$ depends on $f$ and $f_s$. $\omega_0$ is the normalized angular frequency.