No, in the book we only get an explosion, fair and square. There's no scene of Saruman preparing any device, no description of in what form it took, how it was its transported nor even any description of how its positioned in the culvert.
Everything we know about it from the book is found in this quote:
The film thus take liberties, which is not a complaint, merely a conclusion, though a specific topic that is not of concern for this mod so refer to the TGD-thread if of interest to discuss further by folks.Originally Posted by The Two Towers; Helm's Deep
As for the voices, I do not recall ATM. They'll be checked when I'm at it, whether the case. From my vague memory I don't recall the Dunedain impressed me, so think your bias is correct