Over the course of two years, the cause of excessive noise from two industrial chiller pumps could not be identified. The pump manufacturer brought in three consultants to take measurements of the pumps, which did not meet noise specifications, using standard sound level meters. A root cause, however, could not be determined.
Enter Acoustiblok. The NASA Spinoff listed company used its acoustical real-time video-imaging system (ARTVIS) to solve the problem. ARTVIS can measure the intensity and overall frequency content of noise as well as visually identify the direction, source and reflections of a noise. It also helps reveal modal transitions of resonance in structures and buildings that a standard spectrum analyzer does not reveal.
After two hours of testing, the Acoustiblok team discovered the cause was sound escaping through the bottom of the cabinet upon which the motor was mounted. In effect, the cabinet was acting like an acoustic guitar, amplifying the noise from the motor, which then leaked out of the numerous openings in the cabinet. The average overall sound levels within the cabinet reached 106.3 dBA compared to the average overall sound levels around the motor of 97.4 dBA — an increase of 9 dB.
As a result of the findings, Acoustiblok made several recommendations:
l Install sound-absorption material within the cabinet to eliminate sound reverberation.
l Implement heavy mineral-filled viscoelastic polymer sheet material by adhering it to all cabinet surfaces. The polymer sheet would to increase the cabinet mass, deaden resonance and block the sound escaping out of the cabinet openings.
l Install all-weather sound panels around the motor to directly attenuate the motor noise.
Tampa, Fla.-based Acoustiblok has successfully used its ARTVIS system on many projects involving industrial and power plant noise.
