From Longman Dictionary of Contemporary Englishtrail away/off phrasal verbSTOP DOING somethingif someone’s voice trails away or trails off, it becomes gradually quieter and then stops She trailed off, silenced by the look Kris gave her. → trail→ See Verb table
Examples from the Corpus
trail away/off• His sentence edged around a raspy cough, then audibly trailed off.• Philip stood on Lee's foot and Lee's voice trailed away.• From time to time her voice trailed off and she became her grief, heavy as a stone.• The sentences are less likely to run out of puff in mid-stream and trail off into inaudibility.• Timber wolf is what they sounded like, their deep and resonating power now trailing off into musical tremolos.• However, this began to trail off towards the end of June due to outside distractions - Wimbledon tennis and International cricket. 