Isopleths

http://www.mdpi.com/1660-4601/5/3/165/htm

The image above is an example of a isopleths map.  It shows the amount of noise decibels (dB) during the day across a study hall in Asansol, India.  Throughout the day an average decibels of sound were recorded at specific locations.  The isopleths group the regions with the similar amount of decibels similar to isobars.  The map shows areas with the greatest amount of noise and areas with the least amount of noise that one should most likely chose to study at.