loudness       
noun [ U ] uk/ˈlaʊd.nəs/ us/ˈlaʊd.nəs/
 大声,响亮
the fact of making a lot of noise, or the amount of noise something or someone makes
  The loudness of their arguing worried me, but then I realized that they were just excited. 他们大声的争辩让我很担心,但后来我意识到他们只是很兴奋。 
 Differences in loudness are measured in decibels. 不同的响度以分贝计量。 
 See: loud
 - More examples
 - She was a refreshing blend of confidence, loudness, and charm.
 - His increasing deafness is not due to the loudness of the crowd at concerts, but to studio headphones.
 - The increase in loudness was gradual.