Acoustic consulting engineering practice Mackenzie Hoy Consulting Acoustics Engineers (Machoy Consulting) completed the installation of biplate panel absorbers on a research ship laboratory last month, reducing noise levels by about 5 dBA, or about 45%.
Machoy Consulting owner Terry Mackenzie-Hoy explains that biplate panel absorbers are back-to-back perforated metal plates that contain a single absorption layer in the middle.
“These plates are tuned to specific ranges of frequencies to absorb sound over frequency bands in any given area,” he says, highlighting that these panels can simultaneously absorb low- and high-frequency noises.
Machoy Consulting installed the absorbers, collectively valued at about R200 000, in mid-June in one of the laboratories aboard the research ship to eliminate the high noise and acoustics levels.
The benefit of the biplate absorber is that customers get ‘more bang for their buck’ because the absorbers achieve twice the absorption in a given ceiling area, he emphasises.
The panel absorbers can be used in any environment, particularly in industrial plant environments and large entertainment areas, where reverberation time has to be reduced and low-frequency noise has to be absorbed.
Mackenzie-Hoy highlights the disinterest from the local engineering industry in investing in noise reduction technologies or solutions, as these require capital expenditure and do not generate any profit.
Although South African companies are required by the Occupational Health and Safety Act to barrier off noisy areas, create ways of reducing noise or, as a last resort, supply employees with ear defenders, Mackenzie-Hoy believes that several companies prefer only to supply staff with ear defenders and do not focus on noise-reduction engineer- ing solutions.
He further laments the lack of local international-standard testing facilities as a result of progressing dilapidation and a lack of funding to maintain acoustics testing facilities at several universities and laboratories across the country.
Progressing dilapidation affects anechoic chambers – rooms designed to completely absorb reflections of sound or electromagnetic waves, where noise levels of machinery are tested, and reverberation chambers, which are used for testing sound absorption of materials.
“While industry can still develop new acoustic, or noise-reduction products or technologies, these products cannot be tested to international standards,” Mackenzie-Hoy says.
Research is further affected and stunted, owing to a lack of research chambers. “This adversely affects South Africa’s product offering, as industry has to rely on international product offerings,” he says, stressing the need for the South African Bureau of Standards and universities, therefore, to invest in noise-testing facilities.
While Mackenzie-Hoy highlights the need for African countries to have noise-measurement training for local African people, he notes the success of the company in transferring noise-measurement skills to several African countries.
Mackenzie-Hoy suggested in 2013 that, as African people are most familiar with the challenges and conditions of their own surroundings, the “noise will be measured . . . to an insider’s perspective, which will guarantee the accuracy of the results”.
“However, in the past year, Machoy Consulting has finalised several environmental-impact assessments in different African countries, including Zambia, the Republic of Congo and Mali. In each of these countries, we have transferred skills to local staff to develop the African acoustics industry,” he says.
Machoy Consulting has been successful in training staff to use sound level meters and interpret the measurements, even though there are vast language and education barriers, Mackenzie-Hoy says, concluding that this educational drive is assisting African countries in becoming more self-sufficient in the acoustics industry and in measuring occupational noise.