Many buildings serve purposes other than just giving us a roof over our head for shelter. Buildings such as hotels, offices, shops and medical facilities seek to offer inhabitants a sense of calmness, refuge and tranquillity from the hustle and bustle elsewhere. This encourages people to stay in the buildings longer, either to relax more, shop more, linger, have a bite to eat, concentrate more easily and improve productivity.
However, noise is a constant feature in most buildings usually generated by phone chatter, children shouting or crying, footsteps on hard floors, unwanted conversations in adjacent cubicles, printers, copiers, HVAC systems...the list goes on and on. This noise is distractive, interruptive, makes employees less productive, can taint the customer experience and reduce privacy. One way to create a welcoming, stress-free environment is through reducing this unwanted noise in buildings using plants.
Plants have many known benefits to their environments and the people in them, but noise reduction is one of the less-known advantages. Plants absorb, diffract and reflect sound. The balance varies with the frequency at which the sound is generated and the room's physical properties. The type of plant, its size, shape, the container, top dressings and the compost, all have an effect on the sound reduction capabilities of plant displays.
Sound absorption
Plant parts such as stems, leaves, branches and wood all absorb sound. Rough bark and thick, fleshy leaves are particularly effective at absorbing sound with their dynamic surface area. The greater number of plants, the size of the plant and its surface area will all affect its ability to absorb sound. Plants alter room acoustics by reducing the reverberation time. They tend to work better in acoustically live spaces, such as those that have hard surfaces like marble walls, exposed concrete and stone floors. The impact of plants is less likely to be noticeable in an acoustically quiet space, containing soft furnishings, carpets, heavy curtains or well upholstered chairs, which have a much greater capacity to absorb sound.
Sound deflection
When sound hits a masonry wall, the wall does not vibrate because it is rigid, so sound waves are reflected off the wall and back toward the source. When sound waves hit a flexible material, like plants, the material will vibrate and the waves are transformed into other forms of energy, as well as being deflected in other directions.
Sound refraction
A good example of a common material that helps refraction is carpeting in a home. If a room has all solid floors, sound waves bounce all over and can create echoes. When carpeting is added, the echoes disappear. Plantings that cover surface areas help accomplish the same feat. For example, vines on walls and the sides of buildings will help refract sound. Lawns, ground cover plantings and green walls are also excellent at refracting sound.
How to use plants to reduce noise
Large plant containers
Bigger plant containers contain more compost and have a greater area of top dressing. Both of these have a significant effect on noise reduction, so it follows that they make a larger impact on the room acoustics. Experiments have shown that arrangements of different plants in groups appear to work better than individual plants.
Several small arrangements are better than one big one
Positioning several arrangements around a space works better than concentrating the plants in one location. In this way the surface area of the plants exposed to noise may be maximised and individual work areas in an office space will all benefit from a localised effect.
Edges and corners are better than the centre
Plants placed near the edges and corners of a space are better than plants in the middle. This is because sound is reflected from the walls straight into the foliage.
Consider using screen plants instead of office partitions
Open-plan offices are often very noisy places. Often these spaces are divided up with partitions or ranks of filing cabinet but plant screens are an effective and usually a more attractive alternative. The tops of filing cabinets and other office surfaces can also be used to place plants, for example small bushy plants in narrow troughs which take up little space but still offer effective results.