Acoustic Foam

[utopianemo]

What exactly is the difference in absorption quality between acoustic foam and other foams? For example, many boxes come with black foam for packing and one can cheaply purchase large slabs of foam for camping mattresses. How do these foams differ in sound absorption from acoustic foam? I'm frankly astounded at the cost of acoustical treatments. Are they really that different?

 

[highfigh]

What exactly is the difference in absorption quality between acoustic foam and other foams? For example, many boxes come with black foam for packing and one can cheaply purchase large slabs of foam for camping mattresses. How do these foams differ in sound absorption from acoustic foam? I'm frankly astounded at the cost of acoustical treatments. Are they really that different?

Look at the NRC (Noise Reduction Coefficient) ofr the different materials. The density and cellular arrangement work to reduce the reflections and materials like this need to have flame retardant, too. Packing foam doesn't and if it ignites, toxic fumes are given off.

You don't need to use foam- other materials do the job as well and don't use as much space. All of the materials will do a better job of reducing mid-range frequencies than low frequencies, but additional layers help.

 

[HDPCsound]

Regarding the acoustic foams, the higher density on foams improves the sound absorption efficiency at lower frequencies, and helps to maintain a low flammability performance. The foam on boxes is usually low quality.