"they awoke on hearing a strange noise"
Any answer to this question about the usage of
"They awoke on hearing a strange noise"
in its conversion to passive voice will be tricky.
As has been pointed out, passive transform lends itself best to transitive verbs. However, these different forms of the same verb have a history.
BrE. a past tense or (now rare or dialectal) past participle of awake
AmE. verb transitive, verb intransitive pt. of awake
There is a lot of confusion about these verbs.
At this point in time, our evidence shows that the most common inflections of awake are awoke in the simple past ("he awoke") and awoken as the past participle ("she was awoken"). The most common inflections of awaken continue to be awakened in the past ("he awakened") and awakened as the past participle ("she was awakened").
It helps if you remember that awaken and awake are different verbs, and that awakened is regular. Maybe just don't think about it too hard when you first wake up.
In summary: Awake and awaken are two distinct verbs that mean the same thing. The verb forms for awake are irregular, but the most common choices are awake, awoke, and was awoken. The verb forms for awaken are regular: awakens, awakened, was awakened.
: to arouse from sleep or a sleeplike state
He was awoken by the storm.
As John Lawler said in a comment:
In a word, Don't. There are four verbs: wake, the adjective awake, which can be used as a verb, the causative waken meaning 'cause to wake', and the causative awaken meaning 'become (or cause to become) awake'. The first two verbs are deponent; there is disagreement on the form of the past participle of wake -- woke, woken, waked, waken, and what have you. So mostly people avoid the perfect and passive with these verbs because nothing sounds right.
"en" with a verb indicates "cause, or make so"
"a" is more or less "to become" .
Since both verbs are accepted, I agree with John, except I would also accept "awoken" as the PP.
In other words...
"They were awoken upon hearing strange noises."
But the verb does not actually lend itself well to passive transform.
To have some fun with the exercise of converting an active verb to passive, it's best to start with a transitive verb. A transitive verb takes a direct object. Examples of sentences with verb-object: She saw the crime. I will ask a question. She's making a cake. We can now do the fun conversion to passive, where we flip our point of view and focus on the object: The crime was seen (by her). A question will be asked (by me). A cake is being made (by her).
Examples of sentences that don't have a direct object: I like to read. I'm cooking. She can't see. These don't work for conversion to passive. There's nothing to grab hold of to do the flip with.
"They awoke" has exactly that problem. The only way to make a passive version is to use a slightly different formulation, as suggested by Will.