A SUSTAINABLE ACOUSTIC DESIGN ALTERNATIVE TO GREEN WALLS
This project presents a sustainable acoustic product design solution as an alternative method to the use of green walls in architecture, in order to solve the construction problems and maintenance costs they present nowadays. Besides the additional benefits and cost savings that “acoustic pots” can provide compared to real vegetation, they also improve acoustic performance in some aspects.
The first part of the project examines the sustainable demands in architecture of urban and interiors spaces, the opportunity to integrate sustainability and art on walls as a need nowadays. The built environment is a semi-enclosed space in between the free field and lab conditions, where room acoustics should be also taken into account.
The second part of the project presents a definition and classification of green walls. Types, drawbacks and benefits, techniques of construction and their acoustic properties that can be extrapolated to a new acoustic design product.
The third part of the project describes a sustainable acoustic design proposal as a bespoke-standarised design solution, presented as an alternative to green walls. Some research is done on the concept design and about fabrication and material systems. Process of production of the prototype at 1:1 scale and assembly of different parts
“Acoustic pots” can have the same acoustic properties than vegetation within an interior space
Green “Acoustic pots” taking part of public space to absorb and diffuse reverberant sound within the square
DESIGN OF THE PROTOTYPES
“Acoustic pots” as part of decoration in a waiting area
PROTOTYPE A Outdoors (10.6 % open area)
Total area: 70.131 mm2
Holes (16mm): 201 mm2
Open area (36 holes) = 7437 mm2------->10.6%
Outdoors needs: semiwaterproof prototype, very diffusive and a bit absorbent.
PROTOTYPE B Indoors (27 % open area)
Total area: 57474 mm2
Holes (16mm): 201 mm2
Open area (77 holes) = 15477 mm2--------->26.92%
Indoors needs: very absorptive prototype, some diffusion
EXPERIMENTS IN THE ACOUSTICS LAB OF LONDON SOUTH BANK UNIVERISTY
Diffusion experiment for prototype A & B
Insertion Loss experiment for prototype A & B
Absorption experiment with impedance gun for prototype A & B
RESULTS
The main purpose on this work was to study the acoustic performance similiarities and improvements of the product compared with real vegetation. Besides the additional benefits and cost savings that “acoustic pots” can provide, they generally also improve acoustic performance depending on the product location (indoors/outdoors) and user needs (% coverage). The results showed that only shaped modules diffuse sound (outdoors) and module B performs better for absorption (indoors). The major area covered the better results would be achieved.
Polar scattering responses at different frequencies at Stage 2 of the experiment: Module B, shaped Binary Amplitude Difuser
The experiment was carried out with recyclable materials, jute and tetra packs,with an initial prototype of 300x300mm in two stages:
The first tests were done with a flat Binary Amplitude Diffuser (BAD) prototype in order to test the performance of the materials. Results showed that the panel was effective in a middle frequency range of 500-2500 Hz for absorption (α >0.8), and a narrow range of mid-high frequencies (1000-2000 Hz) for diffusion of sound.
The second stage tests were done with two prototypes of shaped Binary Amplitude Diffusers (BAD) in order to test the performance, which was better than stage1 for both absorptin and diffusion of sound. Results showed that the standalone panel were effective in a lower frequency range of 400-2500 Hz for absorption (α >0.8) compared with the flat panel. Module B had better performance at lower frequencies (315-3150 hz) due to the thickness (10cm) and greater open area (27%). It was also demonstrated the effectiveness of the panels as a system, in different area coverage, concluding that the system or “barrier” is more effective than vegetation only when covered 100%, with the three prototypes (A,B,flat). The panels perform less than vegetation for a minor percentage of coverage ( 44% and 66%). In terms of diffusion of sound, while the vegetation experiment concludes that generally the higher scattering pattern is obserbed for high frequencies above 1000 Hz, the polar responses are similiar between the two modules among the frequency bands and the diffusion is better achieved in a range of 500-2000Hz. It is noticeable that at 4000 Hz some scattering is produced in both modules, whereas above that frequency some level of diffusion is produced.
The insertion Loss was also tested in stage 2, it was demonstrated than the system performed in a similar way as green barriers. All configuration of the two shaped prototypes (A,B) with different coverage (100%,66%,44%) don’t provide significant noise reduction (5-10dB) if the modules are not placed against a wall. Both modules perform equally: when the coverage was 100% the greater noise reduction was achieved (5-8dB), whereas the insertion loss is only 0-5dB for 44% coverage. When the modules are placed against the board, similar results are obtained for different coverages (20-25dB), being an effective barrier above 1000 Hz.
“Acoustic pots” can improve speech and intelligibility in reception areas
The results of the product indicate that only shaped modules diffuse sound (outdoors), and module B performs better for absorption (indoors). The major area covered the better results would be achieved.
The conclusions indicate the selection of the most suitable combination of prototypes according to location, and applications for better acoustic performance. The presence of the product affects the behaviour of sound in a similar way than vegetation, absorbing, scattering and diffusing. However further research should be done with a bigger area sample of modules in order to compare test methodologies more accurately.
These results demonstrate that it is possible to use recyclable materials to imitate properties of existing architectural elements and hence acoustic sustainable design can be achieved and be more integrated in the project improving the perception of any space.
Colourful “Acoustic pots” form part of urban art to avoid facade reflections from road traffic noise