I see a sentence in this site:
But both can be quite strong depending on how they are spoken.
Is depending on […] an adverbial clause?
"How they are spoken" is a clause of manner or an interrogative clause, subordinate to the preposition "on".
"On how they are spoken" is then a prepositional phrase. As an alternative, you could say that "how they are spoken" is a noun clause that is the object of "depending on".
Now to "depending on how they are spoken". It is not a clause: it merely contains a clause. If you take "depending on" as a preposition, it is a prepositional phrase expressing a condition or something like that. Or could it be regarded as a participial phrase? Consider this sentence:
Suppose "depending" were a participle. Then it could be rephrased thus:
This does not make much sense. A better rephrasing would be this:
It seems clear that "depending" is not a participle, or it would have belonged to the subject "she". Therefore it must be a preposition here.
Your example would give this, if it were taken as a participle:
Or it could be a preposition:
The first interpretation is not entirely impossible, but I'd call it weak at best; the second one sounds much better. Therefore it is best considered a preposition here, which makes the whole phrase an adverbial adjunct of condition.
First let's define Adverbial Clause:
Hence in case it's an adverbial clause.