A dash insulator is constructed by layering a front layer, a sound absorption layer of a membrane-vibration type and a perforated sound insulation layer. A layered body of the sound absorption layer and the perforated sound insulation layer is constructed such that the inner diameter and the opening ratio of opening portions of the perforated sound insulation layer are set to enable suppression of a resonance phenomenon between vibrations of the sound absorption layer and the perforated sound insulation layer in relation to low frequency range noise components of noise.