Blue Cat's FreqAnalyst Pro is a real-time spectrum analyzer. It allows you to fine-tune the frequency analysis of your audio such as managing the precision and rate, applying offset/slope to the measured spectrum, etc. Two thresholding systems are available, and the time response can be changed thanks to the attack and release parameters. Three modes are offered for each channel: instant, peak or average response can be displayed on the same graph.
This RTAS version of FreqAnalyst Pro can be installed on supported audio editing software such as Avid Pro Tools.