Possible Answer:
The auditory sense is based on the stimulus of timeline sensory registration and the ambiance. The noise detection level of the individual can register noises of lower decibels thresholds in a quiet ambiance as opposed to an ambiance with noise levels.
Example:
This would be similar to a person being able to hear the drop of a penny in a quiet room as opposed to a concert. Their hearing capabilities get adjusted to the quiet noises levels so they are able to detect any changes in low noise room. Meanwhile being in a high noise room (concert) means that they are adapting to the high noise surroundings, unable to detect lower noise level sources.