Wellington commuters breathed a collective sigh of relief when the last of the city’s ‘red rattler’ and Ganz Mavag trains were retired over half a decade ago. No more lurching around in loud clattering carriages. Sleek new Matangi units glided in as long-awaited replacements. Much quieter on the inside, the change in comfort was immediate. It was little wonder - sound is a key sense through which we experience our world.
Some sounds are part of the everyday background hum that we soon forget. Some, like noisy old trains, penetrate our consciousness, distract and grab our attention. For this reason, there’s a broad range of effects and impacts that the design of acoustics in the human environment can have.
Soundscaping our public spaces
In engineering we often speak in terms of ‘noise’ not ‘sound’. Noise is ‘unwanted sound’, and as acoustic engineers, we’re often tasked with removing it.
With soundscaping, we aim to eliminate noise and enhance and manipulate pleasant, desired sounds. We can do this by introducing sound and music via artificial means (like loudspeakers) or with the careful placement of physical elements - water features, trees, bird feeders, musical instruments and so on.
The theory of manipulating the wanted sound in a public environment opens up a new facet of design for human spaces with wide ranging possibilities. For example, we can introduce calming sounds to high traffic spaces to reduce agitation and anxiety, by installing things like slow-flowing water features, trees or a bird feeder, or introducing musical soundscapes.
Introduction of ‘outdoor’ sounds near the exits of public spaces like bus and train stations can provide a sub-conscious auditory cue to help people locate building exits and escape routes.
Noise and accessibility
Because our public spaces are often designed for the majority, there’s often less consideration of how some people experience sound.
Take bus and train stations for example. They’re usually busy and loud. So are the machines that service them. In a large transport terminal, there are lots of conflicting sounds – passenger units arriving and departing, service announcements, and people talking.
The high noise environment and large size of these spaces can make it difficult for people with hearing impairments to understand announcements over PA systems, meaning they could miss their departure time or – more seriously – emergency evacuation instructions. Hearing impairments range widely between slight difficulties in noisy environments through to full hearing loss.
People with vision impairments often rely more on audio cues, and for those with heightened sensitivity to sound – such as neurodiverse people - the high noise environment and busy activity in a train station might cause an emotional response. This could make the station an uncomfortable and disagreeable place for that person, and prompt them to avoid going there, consciously or subconsciously. This would impact the mobility of that person.
Good vs. bad acoustic design
Places that feature good acoustic design can improve the intelligibility of speech. Positive impacts range from enhancing announcements in transport hubs to improving learning outcomes in education spaces. Good acoustic design also generally results in spaces where people enjoy spending time.
There’s a good reason why reducing noise is the acoustics priority for most urban design projects. The impacts of high noise environments are well understood and include disruption, sleep disturbance and, at the extreme end, hearing damage.
Good acoustic design will often not be noticed, but spaces with poor acoustics are quickly identified. They’re usually noisy, reverberant, or lack appropriate audio privacy. Spaces like these often get used less (or not to their full capacity) because they’re unpleasant places to be.
Acoustic engineers use the Speech Transmission Index to measure how likely syllables, words and sentences will be comprehended in noisy places. The index goes from 0 (unintelligible) to 1 (clear). Most of our public spaces register at 0.5.
Because people’s experience of sound is inherently subjective, we’ll never design an acoustically-perfect system that meets everybody’s needs. But taking a leaf from the soundscaping playbook there are some acoustic changes we could make to improve public sonics, including:
- Placing higher importance on acoustic design of PA systems and acoustically treat spaces in large transport hubs to improve the intelligibility of announcements.
- Electrifying public transport – the engine noise generated by acceleration or set off can be significant and is a primary contributor to unwanted noise within the urban environment.
- Introducing more trees and green space to our urban environments to enhance natural sounds like the wind rustling leaves, bird life, and water movement.
The benefits are worth it. When soundscaping techniques are incorporated into the design of public spaces, we can move beyond simply removing noise, to designing and shaping the sound of the built environment to improve everybody’s comfort, accessibility and experience of place.
Soundscaping - you’ll know it when you hear it
There aren’t too many examples of intentional soundscaping on a city-wide scale. But one example that New Zealanders may be familiar with is at Auckland Airport where a karanga welcomes you to the arrivals area. This instils a sense of place for those arriving and a sense of home for returning New Zealanders. At the same time, it provides an audio cue for finding the exit.
Click here to read more on creating a decarbonised and equitable transport system in Te Ara Matatika: the Fair Path