MOSS LAB 2.0

What is the effect of plant properties and plant arrangements on acoustics in a hybrid office space?

BACKGROUND

MOSS LAB 2.0 was established to tackle one of the many challenges confronting post Covid-19 offices: noise! Since the pandemic, companies have embraced hybrid working, giving employees the flexibility to work remotely, while also creating a more seamless online platform for communication.

Although hybrid working opens doors to many opportunities, but when paired together with the up and coming open office plan layout, it can hinder employees’ concentration, productivity, and well-being due to excessive noise present in the office.

For this challenge, we gathered a team with six Masters (MSc) students from the University of Wageningen, two technicians from Sorama, and a project developer from COD to dive into the topic of plants, sound, and buildings.

The University of Wageningen MSc students are specialized in plant science, biology, and plant biotechnology. Sorama is specialized in measuring and visualizing sound. COD is a real estate developer in Amsterdam.

As commissioner of the research question, MOSS guided the team in investigating the effects of plant properties and plant arrangements on acoustics in a hybrid office space.

LITERATURE REVIEW

The literature review carried out by the MSc students revealed that sound can be reduced by increasing sound absorption, which can be affected by the material thickness, porosity, density, position, airflow resistivity, and air gap thickness.

It is found that the plant properties that help absorb sound are in the leaf characteristics: higher leaf density, coarser texture, more dominant angle of the leaves, as well as larger leaves, are favored.

Moreover, it is apparent that as most sound is absorbed in the substrate, it is ideal to use large plant containers and highly porous soil, where a mixture of perlite and coconut fibers is proven to perform best in absorbing sound.

Perlite is a naturally occurring mineral that is added to garden soil to improve aeration, water retention, and drainage while coconut fibers can provide soil structure, drainage, and aeration.

WITH SO MANY VARIABLES, IT IS MOST BENEFICIAL TO MIX VARIOUS SPECIES OF PLANTS WITH THE HIGHLIGHTED LEAF CHARACTERISTICS IN ORDER TO ENSURE THE MOST OPTIMAL SOUND ABSORPTION.

PILOT EXPERIMENT

Five pilot experiments were conducted by the project team in order to find out how plant species, substrate, and arrangements influence acoustics. The five arrangements were four plant arrangements (perimeter, scattered, divider, and circular) and an empty room with no plants.

A combination of eight species of 40 potted plants including Kentia, Ficus lyrata, Caryota mitis, Raphis excelsa, Ficus bengamina, Schefflera amate, Schefflera arboricola were placed and rearranged in an office-emulated lab where the plants equated to 4.1% of the room’s total volume.

PROCEDURE

For each arrangement, three different parameters were tested: the reverberation time, the location of the reflections in the office space, and the level difference between the two sides of the office.

A DS-303 Omni-directional speaker emulated conversational office noises, while the Sorama CAM iV64, Sorama CAM1K acoustic camera, and NTI XL2 sound level meter measured sound.

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RESULTS

The results reveal that potted plants have the ability to improve spatial acoustic quality in regards to reverberation, reflection, and protection, in which the scattered arrangement performs best. It is worth noting that the acoustic baseline of the pilot lab is not average due to the lack of objects and equipment, high amount of concrete, and open ceiling design causing the reverberation time to be 2.07 as opposed to 0.4 – 0.6 as recommended for a general office environment.

The scattered arrangement improves the reverberation time by more than 25%. Therefore, improving the sound quality as reverberation time is a measure of the time required for reflecting sound to “fade away” in an enclosed area after the source of the sound has stopped.

The scattered arrangement is effective at shielding and isolating spatial acoustics as it increases the level difference of sound between two points by more than two times as compared to a room with no plants. Level difference is the difference in decibel, a unit of measurement for sound in relation to loudness, between point A which is located in close proximity to the sound source and point B which is located at a greater distance from sound source.