Is cork underlayment effective for sound proofing?

While true "sound proofing" is nearly impossible, 6mm thick cork is widely used in the construction industry for sound reduction and curtailing noise transmission.

Cork underlayment is the most effective and economical product for meeting building codes aimed at sound control.

Cork underlayment is used under hardwood, ceramic tile, carpet and laminate flooring. It is available in 4' x 50' rolls in thicknesses of 5/64", 1/8", and 1/4". It is also available in 2' x 3' sheets in thicknesses of 1/4" and 1/2".