Heaven observed: head turns when this happens, by the sound of it? (4,5)

'heaven' is the definition.
(thesaurus)

'observed head turns when this happens by the sound of it?' is the wordplay.
I cannot really see how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'by' could be 'x' (as in 'multiplied by') and 'x' is found within the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'of' could be 'o' and 'o' is located in the answer.
This explanation may well be incorrect...

Can you help me to learn more?