A major Hawaiian asphalt company was having trouble with the community from noise  during night time operations.

AAI conducted testing with a local sound testing company to isolate the sound frequency causing the an disturbance in the vicinity of the plant. AAI's diagnostic testing at the invitation of the asphalt plant on the island of Oahu demonstrated  our role in developing technology for a custom application.

A small community in close proximity to the plant (about two blocks away) was affected by operations at this plant.

Specifically, a resident had been complaining about noise keeping her awake at night. Operations at this plant are unavoidably performed at night to provide asphalt product for doing road paving the following day.  The primary sources of noise were heavy equipment (loaders) and processing equipment on the site.

The analysis of the AAI diagnostics data revealed that the noise problem was caused by low frequency noise absent in other previously tested applications.  This prompted Argosy Acoustics to design a major variation of the  Highway Veil panel technology.

THE DIAGNOSTICS

For the test, a three-row configuration with standard Veil panels was used to mitigate the offending sound.  In response, additional diagnostic testing was performed in octave bands to determine the frequencies of the noise causing the problem.

The Highway Veil panels are tuned to a mid-band of 880 hertz. It soon became obvious that the offending noise was fairly low frequency, below 250 Hz. The readings taken at the community property line fence showed the Highway Veil panel system performed as predicted reducing sound at higher frequencies (above 250 Hertz), but not at frequencies below 250. Therefore, we designed two new panels to mitigate low frequency noise.

ARGOSY ACOUSTICS IS MEETING THE CHALLENGE !

The two primary noise sources, the first Loader 1, and some equipment at the Plant showed spikes at 31 HZ, a powerful low rumble. This same low-frequency sound was picked up at the complainant's open sided  roofed structure with open sides (called a lanai in Hawaii). Other spikes found were at 63 Hz. (Loader 2), and 125 Hz, so we designed the new panels to a resonant frequency of 100 Hz. It will also absorb at 30.5, 61 and up to about 190 Hz. 

Argosy Acoustics is addressing the challenges that low frequency noise provides.   

AAI's  first new product is the Low-Rez Panel, perforated on the front but not at the top and bottom, so it doesn't produce a Veil. It's specifically designed to take out high intensity, low frequency sound and will used in making acoustic barriers. It absorbs low frequency sound, blocks higher frequency sound and will be used combined with Acoustax® panels, as walls mounted close to high noise sources to lower sound levels locally.

As an illustration, at the Plant Burner sound levels are at about 110 dB. Walls at both sides of the Burner will bring sound levels behind the Walls down about 30 dB locally to the vicinity of 80 dB. Because much of this sound is absorbed not just blocked, this installation will have an impact on the general noise levels throughout the plant. The panel will be very broadband as it will absorb sound well below 250 Hz and by transmission loss, also block sound very well above 250 Hz. The sound absorbed, of course, is gone forever. The sound from solid barriers. The sister panel, the Low-Rez Veil system is designed specifically to mitigate lower frequency sound.

The Low-Rez will be tested very soon.  This new data will be posted on our site as soon as it is available, so stay tuned.   AAI is also addressing the environmental challenge of dust and maintenance within project areas.  Concurrently, AAI-Pacific will be  working with the local companies to set up distribution and installation.