Silencer elbows are elbows lined with absorbent material, which significantly attenuate sound waves. The sound attenuation consists of three parts: absorption and reflection of the near-axial waves on the elbow wall, as well as the conversion of the energy of the near-axial waves into oblique wave energy during the bend, which is then effectively absorbed by the absorbent material.

Principle of silencing elbow

When sound waves propagate into the bend pipe, some are reflected, while the rest propagate around the bend in the form of non-planar waves. When the frequency of the sound waves is higher than the cutoff frequency of the pipe, some non-planar waves can propagate along the pipe. In this case, the transmitted sound through the bend is accelerated in absorption, and the sharp attenuation of sound energy occurs behind the bend because the absorbent material backing the bend is more effective at absorbing non-planar waves than planar waves. In other words, the bend pipe sections lined with absorbent material absorb more sound energy than the front sections. Research results show that when those planar waves with frequencies higher than the cutoff frequency of the pipe pass through a lined bend, they can convert planar waves into non-planar waves, exclude sound, and then effectively absorb sound, converting sound energy into heat energy, thereby achieving the purpose of improving the noise reduction effect.