An Investigation of Helicopter Transmission Noise Reduction by Vibration Absorbers and Damping

Abstract : A test program was conducted to evaluate the effect of dynamic absorbers and damping on the noise generated by a CH-47 rotor transmission. Comparison was made between predicted and measured results, and a method for comparing the efficiency of various methods of transmission noise reduction was developed. Gear damping was achieved by filling the gear shafts with Viton, and by a ring of Viton on the spiral bevel ring gear. Constrained layer damping was also used on the outside of the planetary ring gear.