Perception of aircraft height and noise

Gatwick commissioned an independent study to look at the perception of aircraft height and noise following a recommendation from the 2015 Independent Arrivals Review. The study was carried out by Gianluca Memoli from the University of Sussex. 

The report itself is a necessarily detailed independent academic study which explores new areas previously not captured in this way. We have summarised some of the main findings below.

Perception of height and noise study: main findings  

  • Participants living below arriving aircraft could correctly describe the “average plane” i.e. the most frequent aircraft in their area. This is true for its height, size and distance from where they live.
  • Participants were also very good at accurately perceiving how a passing aircraft was different from the “average plane”: in height, size and distance from where they live.
  • However, when asked a quantitative judgement about a specific aircraft – including the “average” one – most participants underestimated its height by between 1200ft and 1500ft and overestimated its size by as much as twice. This error was larger for louder planes and is probably due to the absence of objects in the sky to compare with.
  • While the height of “average plane” has not changed much over the last  five years – the report identified a small proportion of planes (between 2% – 5% in 2016) that have started flying much lower (more than 1000ft below) than the “average plane”. 
  • While these planes have always been there, their number has increased over the past five years. This finding may be sufficient to justify the comment, reported in the Arrivals Review, that “planes are flying lower”.
  • The study also found evidence that participants’ long term perceptions on the noise/ disturbance generated by arriving aircraft may be based on their experience of these lowest, nosiest planes – and not on the average planes.
  • In a context where perception seems to be set on the lowest planes – addressing the causes of these ‘outlying’ aircraft could potentially reap large benefits for local communities.

Perception of height and noise study: other findings

  • The study highlighted that annoyance indoors was reduced for the participants by the feeling of “being in control”, linked to the presence of sound insulation. The University did not find effects of sensitivity and demographics, present in other studies.
  • The study found that the impact of planes on their life outdoors was crucial for approximately one participant out of every 10.
  • Conversely, almost half of the interviewed (and a quarter of the postal respondents) reported not to be disturbed by plane sounds, highlighting a wide divergence of perceptions between individuals.
  • When asked “when you would consider a plane to be flying over you?”, most of the participants (either by mail or by interview)  agreed on a angle with the horizontal, in line with one of the definitions proposed by the CAA (CAP1498). For one participant out of every 10, however, hearing a plane was sufficient to judge it as “flying over”, whatever its distance.

Read the full IMM15 Perception of Aircraft Height and Noise study (This is a very large file and we recommend viewing from a desktop)

Perception of aircraft height and noise presentation - Gianluca Memoli, University of Sussex. 

Gatwick Airport will study these conclusions in detail over coming months and provide an update to the Noise Management Board (NMB) in due course. This report will be shared with key local stakeholders through the NMB, the Gatwick Airport Consultative Committee (GATCOM) and the Gatwick Airport Noise and Track Monitoring Advisory Group (NaTMAG)  but also more broadly with cross-industry stakeholder groups, for instance other airports, the academic community and Sustainable Aviation.