Patent ID: 7566475

Claim:
A method of making an acoustic insulator, the method comprising: depositing a composition consisting of thermoplastic particulates on a first surface of a base layer; and heating the particulate such that the particulate at least partially melts and penetrates the first surface of the base layer, thereby increasing density and airflow resistance of the base layer proximate the first surface such that the base layer, proximate the first surface, has an areal mass in the range of 0.1 to 1.0 kg/m 2 and an airflow resistance in the range of 300 to 5,000 Nsm −3 after the depositing and heating steps to form the acoustic insulator; wherein, after the depositing and heating steps: 1) a majority of the particulate is disposed within a first portion of the base layer adjacent the first surface, the first surface being an outer surface of the base layer; 2) the first portion has an areal mass in the range of 0.1 to 1.0 kg/m 2 and an airflow resistance in the range of 300 to 5,000 Nsm −3 ; and 3) the base layer has a second portion disposed away from the first surface and having a different density compared to the first portion.