oh; ho; exclamation of surprise, admiration, etc.
hoo (owl call); toot (sound of a flute)
ほう、それは面白いね。
Oh, that's interesting.
ほう、こんなことがあるとは。
Oh, I didn't expect this.
ほう、なかなかやるじゃないか。
Ho, not bad at all.