Solidborne noise and vibration is decoupled in a rotary wing aircraft by a laminated ball joint (15) for a suspension bar (13) of a transmission gearbox, the ball joint including at least two damper layers (19) dedicated to a frequency band for decoupling in the range 0 to 7000 Hz. For this purpose, the damper layers (19) and possibly also likewise dedicated interleaved layers (20) are given shape and/or dimension and/or physical-property parameters as a function of the frequency for decoupling in the determined frequency band.