Abstract: The self-tuning Helmholtz resonator is studied in order to control the noise in the enclosure.According to modal superposition theory,the frequency-domain model and time-domain control model of enclosure-Helmholtz resonators (H.R.) are established.Three frequency tuning algorithms are adopted,that is,minimization of the sound pressures outside the H.R.throat,maximization of the sound pressure inside the H.R.cavity,and judgement of the dot-product of the sound pressures outside the H.R.throat and inside the H.R cavity called as dot-product method. Theoretical analysis and numerical results show that the dot-product method is superior to the others.A Helmholtz resonator whose neck is tunable is designed.The numerical simulations and experiments of noise control using the designed Helmholtz resonator and dot-product tuning method are conducted.The results demonstrate good noise control effect and frequency tuning accuracy.