What is the sound absorbing characteristic of a material called?

I understand that lead is one of the best acoustic barriers because it absorbs sound very well; in other words, it converts sound to heat. By comparison, other materials tend to either transmit the sound or reflect it.

This property of sound absorption, what is it called? Is there some physical quantity that measures how well a material absorbs sound?

There are a number of terms used to describe this, with varying definitions. The sound attenuation coefficient measures how much sound energy is lost in passing through a given sample of material. It is also called transmission loss or sometimes insertion loss and is usually quoted in terms of decibels of reduction at a specific frequency.

Sometimes the reduction is quoted in terms of decibels lost in bouncing off a sample of the material. In this case it is called an absorption coefficient.

The property of converting sound to heat is characterized by a material's acoustic attenuation coefficient. A high attenuation coefficient means the material is good at converting sound waves to heat.

The amount of attenuation in viscoelastic materials is called acoustic attenuation coefficient. viscoelastic materials stretch and bounce back like rubber and have viscosity

the equation is P(x+Δx)=P(x)*e^(-a(w)Δx) and a(w)=a(0)(w^n) where w is angular frequency P is pressure Δx is wave propagation distance, a(w) is acoustic attenuation coefficient.

a(0) and frequency dependent exponent n are determined experimentally

n in viscoelastic materials is between 0 and 2 n in crystalline materials , water and many metals is 2 n in soil, sediment and rocks is 1