Abstract: In view of the problems of low frequency noises in substation, the polyester fiber impedance tube is chosen to study the low frequency sound absorption properties of polyester fiber. The influences of bulk density, material thickness, air cavity on the low frequency sound absorption properties are discussed with composite structure of polyester fiber and Helmholtz resonator. The results show that the bulk density of polyester fiber has an optimum range for sound absorption performance. The low frequency sound absorption coefficient of polyester can be improved by increasing the thickness of both the polyester fiber and air cavity while it is still low at 100 Hz; The sound absorption coefficient of composite structure of polyester fiber and Helmholtz resonator can reach up to 0.9 at 100 Hz while their average sound absorption coefficient is also high.

Key words: substation, low frequency noise, polyester fiber, sound absorption property, composite structure