An acoustic unit is a combination of several components that work together to measure sound levels. The decibel (7 letters) is the most common unit of measurement for sound intensity, and is used to measure the loudness of a sound. A sone (4 letters) is a unit of loudness, and is equal to the loudness of a 1 kHz tone at 40 dB. A STOOL (5 letters) is a type of chair or seat that is often used in recording studios to reduce sound reflections. ARIE (4 letters) is a type of soundproofing material that is used to absorb sound waves and reduce reverberation. Finally, Sabin (5 letters) is a unit of sound absorption, and is used to measure the amount of sound energy that is absorbed by a material.