A thermally expandable material is provided that, once expanded, has a Young's storage modulus E' between 0.1 MPa and 1000 MPa, a loss factor of at least 0.3 (preferably, at least 1) and preferably a shear storage modulus G' between 0.1 MPa and 500 MPa at a temperature between -10 and +40 degrees C. in the frequency range 0 to 500 Hz. Such materials are useful in combination with a carrier to form a dissipative vibratory wave barrier that effectively reduces the transfer of vibrations from a vibration generator, as may be present in a vehicle.