Emerson unveils its new modal noise attenuator

Emerson unveils its new modal noise attenuator

Emerson, the global technology and engineering giant, has unveiled its Fisher™ WhisperTube Modal Attenuator for noisy gas or vapor applications in a wide range of industries. The modal attenuator is a full-bore device which the company claims will offer 15 decibel sound suppression to reduce noise inside pipes produced by sources upstream, such as control valves or other devices. The attenuator is designed to be installed downstream of these types of devices in place of a pipe spool piece and, since it generates no additional pressure drop, has no impact on process flow.


Industrial users have long searched for a solution which enables them to reduce process piping noise without generating significant pressure drop, reduced flow, and/or introduced obstructions. The drive to reduce this piping noise has led some users to install acoustic insulation to pipe sections to reduce noise, but this can be very costly and cumbersome to install and also does nothing to reduce internal piping noise. Emerson claims that its modal attenuator addresses these and other issues with a drop-in solution, thereby improving worker safety and regulatory compliance, while also reducing the risk of damage to downstream equipment due to high noise levels internal to piping.

To give readers a clearer understanding of just how revolutionary a 15 decibel reduction in noise level is, it should be noted that the decibel is a unit of measurement for sound intensity and is measured on a logarithmic scale, meaning that the difference between 10 decibels and 20 decibels is not simply double the sound intensity, but 10 times the sound intensity. It goes without saying that in an industrial context, noises are typically louder than in other settings since they have more machinery and equipment running at once.

In an industrial setting, the decibel level of a gas or vapor application is generally somewhere in the range of 85 and 95 decibels, while simply raising your voice when speaking to someone within earshot can result in noise levels of over 85 decibels.

Under current guidelines laid out by the Occupational Safety and Health Administration (OSHA), employers are required to implement a hearing conservation program when noise exposure is at or above 85 decibels averaged over 8 working hours. These hearing conservation programs are designed to protect the hearing of employees through proper training and provision of hearing protection devices. Without the necessary protection and training, prolonged exposure to loud noise may result in the nerve endings in the inner ear being destroyed, leading to possible permanent hearing loss.


At the launch of the Fisher WhisperTube Modal Attenuator, Emerson claimed that leading applications for the modal attenuator would include those applications where upstream process flows are changed by control valves, pressure relief valves, pumps, compressors, and other devices that generate noise. Since many of these devices must be installed in lengths of piping with no flow restrictions downstream, the modal attenuator is particularly suitable for these applications as it introduces no such restrictions.


Emerson also boasted that, unlike other noise suppression solutions, its modal attenuator does not introduce an obstruction into the piping, so it can be used in applications where particulates are suspended in process flows, and/or where pigging is required for cleaning and maintenance.


WhisperTube devices are offered in sizes from 2” to 12”, with American Society of Mechanical Engineer (ASME) flange ratings of Class 150, 300, and 600. Pressure ratings match the flange rating sizes, and the maximum temperature is 700 degrees Fahrenheit.