Reduce Fluid Flow Noise Without Pressure Drop

In an earlier post, Reduce Process Noise Without Pressure Drop, I shared a brief video about how the Fisher WhisperTube Modal Attenuator offers full-bore aerodynamic noise reduction for all sources upstream, with no impact on process flow.

In this 9:51 video, Fisher WhisperTube Product Demo, Emerson’s Shelby Daniels explains in detail how this technology is a passive reactive silencer that reduces system noise across a wide range of conditions without impacting the flow capacity or process.

Shelby notes that the WhisperTube is used in gas and vapor applications and can reliably provide 10 to 15 DBA noise reduction for all noise sources upstream—all with no pressure drop and no impact on process flow. She shows the screen, which serves as the primary flow path for the process, and the cavities where the noise reduction happens. As the process flows through the WhisperTube, acoustic waves propagate through the screen and into the cavities. Destructive interference occurs when the waves reflect back at each other off the cavity walls. This interference results in reduced noise propagation downstream. Each cavity is of a different depth, enabling targeting different frequency ranges of noise for broadband noise reduction.

The traditional noise reduction approach has been piping, insulation, silencers, specialty engineered control, valve trims, and diffusers. The WhisperTube can be used in place of or paired with some of these methods to reduce noise. While valves and diffusers can be great solutions, the WhisperTube avoids pressure drops to reduce noise across various conditions without affecting the flow capacity or the process.

The performance of the WhisperTube depends on the fluids’ flowing velocity and the frequency spectrum of the incoming noise. Flow testing in Emerson’s Marshalltown lab has determined no effect on noise reduction performance for velocities less than or equal to a 0.3 Mach velocity, which is typical pipeline velocity. The WhisperTube is not limited to applications by only valves but can be used to mitigate noise from any noise source in a compressible fluid service. Other applications include regulators, safety valves, or other manufacturers’ equipment. Since the WhisperTube fits in the process like a piece of pipe,  it can be easily retrofitted into any noisy spot.

See the difference for yourself in a live demo starting at 5:21 in the video and visit the WhisperTube section on for more information on reducing fluid flow noise in your process.

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