Effective elevator sound control often requires a multi-point treatment to achieve the desired levels of sound reductions. All elevator types will generate both airborne and structure-borne sound migration, the sounds are the same with the only difference being the medium they’re traveling through. Each sound source and migration point must be identified in order to develop an effective elevator sound reduction treatment.
Hydraulic elevator modernizations from a dry to a submersible type often lead to equipment sound disturbance complaints. One of the reason is the differences in motor speed and pump type between these elevator power units.
While the old system used the same pipe, submersible hydraulic power units generate a different range of frequencies have a different influence on the piping and building structure. There are numerous pro-active steps that can be taken during the modernization to minimize sound migration; however, there isn’t anyway to predict the influence the new system will have on existing piping.
There are multiple points of sound generation and migration that may impact hydraulic elevator sound disturbance complaints, in this post though we will provide insight on the sound generation and migration points from the hydraulic piping.
Acoustic resonance in a piping system occurs when reflecting pressure pulses from a piping discontinuity (closed valve, tee, and elbow) and reflect back to and arrive at their source in time to join in phase with the next pulse. The resultant larger pressure pulse travels down the pipe, is reflected back again, amplifying in intensity (loudness) again, and so on.
Here are a couple of our recent favorite (shake my head) pipe configurations:
Tip #1 Minimize pipe length and direction changes (elbows)
The other area having significant influence on pipe resonance and sound migration are the pipe supports. Commonly used pipe supports are of a metal-on-metal clamp or hanger type design. These type supports create direct mechanical shorts allowing the sound to migrate into the building structure. For sound control reason it is recommended that the pipe is never supported on a wall.
Pipe supports; regardless if its ceiling suspension or floor support, it is recommended that a support type with isolation be used to minimize structure-borne sound migration into surrounding occupied spaces. Regardless if it is BTN isolation (Better Than Nothing) or a high vibration signal damping dual isolation product as in the picture below, the metal-on-metal contact points must be broken.
ASME A17.1 – 2010 spells out the specific support locations and support spacing limits to minimize pipe vibrations. These specifications are based on the natural frequency limits of the piping to minimize undue stresses and control of pipe resonance to proper support of the pipes to minimize vibration (sound).
Tip # 2 Following the established pipe support standards and include isolated pipe supports is an essential step for a quiet installation.
Author: Captain C. Quiet
CQuiet |ˈsē ˈkwī-ət | verb: to have the ability to see quiet