A sound absorber is configured as a rectangular hexahedral box and forms a porous double-layer Helmholtz resonance sound absorbing structure, at the same time, the sound absorber in the form of a box forms a structural resonance sound absorbing device itself, and the first-order natural mode frequency of the device is identical to that of a wheel air chamber. When the box-type sound absorbing structure is assembled in a wheel, double functions of absorbing acoustic resonance of the wheel air chamber under the organic combination of Helmholtz resonance sound absorption and structural resonance sound absorption can be realized.