Characterising the walking environment – noise and greenery

Noise and greenery are parameters on which we decided to focus – they are key for defining the direct and tranquil and green routes and for objectively describing the environments participants walked in.

Our routes present a wide diversity – of course, they are in three cities, on three continents. But each also presents a range of lushness of green infrastructure and varying levels of noise as well.

For both metrics we used both quantitative and qualitative data.

Assessing the green environment

For the green environment, quantitative data is the Green score, calculated using the false colour vegetation satellite imagery from Sentinel Hub, indicating vegetation density. False colour images use a combination of wavelengths that are not necessarily in the visible spectrum. For assessing the density of green infrastructure, the score is calculated using near infrared and green (reflected by plants) and red (absorbed by plants).

The score is complemented by a qualitative assessment done by researchers walking the routes, and capturing:

• The presence of trees and other green features, using Healthy Streets indicators number 15 & 16
• The condition of trees and green features, examined examining for instance the presence of rubbish, on a 5-point Likert scale.

Assessing noise

Noise varies in space but also time, following some common patterns (typically, traffic), and sporadic or unpredictable events (e.g., building site operation, or ambulance).

Quantitative noise assessment are modelled levels of traffic-related noise data produced by Tranquil City and illustrated below. The measure is complemented by manual measures of noise (dB measure over a 30 second period, made at several points of the walk and at both peak and off-peak times) and qualitative soundscape assessments, aiming to characterise the soundscape, typically distinguishing between the predominance of mechanic or natural sounds.

In the next entry we will be examining how the associations between greenery, noise, and people’s experiences are examined.