Well, let's look at the facts, shall we:
The Hebrews had an army of about what -- 6,000, give or take? (My memory's a little rusty on this, so bear with me) While archaeologists have estimated that the city of Jericho had a total population of about 2500. Assuming about 500 of those were actual soldiers, we're looking at a rather one-sided battle without the walls.
However. the Hebrew army was almost entirely light infantry -- they were built for speed ("blitzkrieg" tactics, if you don't mind the irony) not for siege warfare.
Knocking down the walls (conventionally) is not an option; climbing over them will get them picked off by the guards, and starving them out won't do -- the longer the Hebrews stay in one location, the more likely that their enemies will find them and send out a force they can't fight off. (When your strategy is based on mobility, standing still is suicide)
So... before we jump straight to divine intervention, how could such an army bypass the walls?
Here's a hint: How did the Greeks do it at Troy?
If you can follow where I'm going with this, I'll tell you one way they could've done it -- no divine sonic weaponry required.