Tail away
Definition 1 of 1
Pro Tip 1/3Sensory Descriptions
Use 'tail away' to describe senses fading, like sounds or sights becoming less intense. 
As I walked away, the party noise tailed away until silence.
Pro Tip 2/3Emotional Intensity
'Tail away' can also reflect a reduction in emotional strength or interest in something. 
Her enthusiasm for the project tailed away after several setbacks.
Pro Tip 3/3Non-physical Contexts
Apply 'tail away' to non-physical things, like a conversation or a line of thought diminishing. 
The debate was intense but tailed away as the topic changed.