  Let $H(2r, q^2)$ be a non-degenerate Hermitian variety of $PG(2r, q^2)$, $r
\ge 1$. Let NU$(2r + 1, q^2)$ be the graph whose vertices are the points of
$PG(2r, q^2) \setminus H(2r, q^2)$ and two vertices $P_1$, $P_2$ are adjacent
if the line joining $P_1$ and $P_2$ is tangent to $H(2r, q^2)$. Then NU$(2r +
1, q^2)$ is a strongly regular graph. In this paper we show that NU$(2r + 1,
q^2)$, $r = 1, 2$, is not determined by its spectrum.
