A pneumatic tyre comprising: a toroidal carcass consisting of at least one body ply ; two annular beads , which are arranged on both edges of the carcass and preferably are at least partially surrounded by the body ply ; an annular tread , which is supported by the carcass ; at least one insert , which is arranged on the inside of the body ply and in correspondence with a central area of the tread and is made of a sound-absorbing material, preferably a polymer matrix foam; and a spacer layer interposed between the insert and an inner most layer (3; 11) of the tyre and arranged in correspondence with a central area of the tread ; wherein the spacer layer comprising a three-dimensional fabric with fibres and is provided with a first wall , which is fixed to the inner most layer (3; 11) of the tyre ; with a second wall , which is radially arranged more on the inside of the tyre than the first wall , is fixed to the insert and is at a given distance - other than zero - from the first wall ; and with an intermediate layer , which connects said two walls to one another and comprises a plurality of connection elements , each extending between said two walls and being transverse to the said two walls ; the tyre is characterized in that: each connection element consists of monofilament fibres; the stiffness of said three-dimensional fabric is greater than or equal to 15 kPa; the intermediate layer has a density ranging from 10% to 45% of a density of said walls and ranging from 40 kg/m 3 to 65 kg/m 3 ; and each wall has a thickness ranging from 5% to 20% of a total thickness of the spacer layer and the intermediate layer has a thickness ranging from 60% to 90% of the total thickness of the spacer layer . a toroidal carcass consisting of at least one body ply ; two annular beads , which are arranged on both edges of the carcass and preferably are at least partially surrounded by the body ply ; an annular tread , which is supported by the carcass ; at least one insert , which is arranged on the inside of the body ply and in correspondence with a central area of the tread and is made of a sound-absorbing material, preferably a polymer matrix foam; and a spacer layer interposed between the insert and an inner most layer (3; 11) of the tyre and arranged in correspondence with a central area of the tread ; wherein the spacer layer comprising a three-dimensional fabric with fibres and is provided with a first wall , which is fixed to the inner most layer (3; 11) of the tyre ; with a second wall , which is radially arranged more on the inside of the tyre than the first wall , is fixed to the insert and is at a given distance - other than zero - from the first wall ; and with an intermediate layer , which connects said two walls to one another and comprises a plurality of connection elements , each extending between said two walls and being transverse to the said two walls ; the tyre is characterized in that: each connection element consists of monofilament fibres; the stiffness of said three-dimensional fabric is greater than or equal to 15 kPa; the intermediate layer has a density ranging from 10% to 45% of a density of said walls and ranging from 40 kg/m 3 to 65 kg/m 3 ; and each wall has a thickness ranging from 5% to 20% of a total thickness of the spacer layer and the intermediate layer has a thickness ranging from 60% to 90% of the total thickness of the spacer layer . each connection element consists of monofilament fibres; the stiffness of said three-dimensional fabric is greater than or equal to 15 kPa; the intermediate layer has a density ranging from 10% to 45% of a density of said walls and ranging from 40 kg/m 3 to 65 kg/m 3 ; and each wall has a thickness ranging from 5% to 20% of a total thickness of the spacer layer and the intermediate layer has a thickness ranging from 60% to 90% of the total thickness of the spacer layer . <EOS>