Noise – noise is often defined as "unwanted sound". The Civil Aviation Authority (CAA, 2018) suggests that laws around noise make it clear that the sound only becomes noise when it exists in the wrong place or at the wrong time. Then, it can cause annoyance, sleep disturbances or other effects. In the context of aviation, airports in more densely populated areas are, therefore, considered to have a greater noise impact, as greater number of people are likely to be affected.
Noise annoyance – it is regarded as a multifaceted psychological concept, covering:
- the experience of repeated disturbances due to noise and the behavioural response to cope with it;
- an emotional and attitudinal response to the sound and its disturbing effects; and
- the perceived loss of control of the noise situation, or in other words, the perceived lack of capacity to cope with noise.
In this way, noise annoyance is not just the response to sound but the judgement of one or more situations in which noise occurs. It means that both acoustic and non-acoustic factors affect annoyance.
Noise Abatement Departure Procedures (NADP's) – procedures for aircraft take-off, designed in a way to cause the least noise while also considering the appropriateness of any of other measures (physical layout of the airport, its surroundings and safety). ICAO doc 8168 contains guidance for the development of a maximum of two noise abatement departure procedures per aircraft, designed generally to mitigate noise either close in (NADP 1) to the airport or further out (NADP 2) along the departure path (source). Essentially, two noise abatement procedures are:
- NADP 1 – aircraft climb to 800 ft+ and then reduce thrust. Aircraft has to keep the flaps lowered in take-off mode and continue climbing as fast as possible to 3,000ft. Then, it has to retract flaps, increase thrust and go further;
- NADP 2 – aircraft climb to 800ft+ and then reduce thrust. At that point, it has to withdraw flaps and continue at a decreased rate of climb until 3,000ft. Then, it increases climb and thrust to go further.
Noise compensation – an action taken to compensate people in situations where noise management and mitigation have failed to alleviate the impact sufficiently.
Noise-induced awakening – sleep stage transition from higher sleep stages to stage awake or sleep stage 1 (i.e. shallow, non-restorative sleep) that was induced by a noise event.
Noise management – an action taken to reduce noise at source or to maximise the horizontal or vertical distance between the noise source and the receiver.
Noise mitigation – an action taken to minimise the transmission of noise from the source to the receiver (for example, sound insulation).
Noise Preferential Route – the departure route from an airport's runway that allows for the minimum noise impact to local communities on the ground.
Noise Preferential Routes or Noise Preferential Configuration –in common use, these routes exist at many airports for managing the noise impacts from aircraft departures.
Non-acoustic factors – situational circumstances or personal state that influence the annoyance judgment besides the mere noise exposure (e.g. an individual's attitude towards aviation, one's general sensitivity to noise). These factors of noise annoyance are regarded as those factors that are supposed to have an impact on noise annoyance but are not directly associated with the sound. In general, personal characteristics and traits, social factors, as well as environmental features, including situational factors, are counted among non-acoustical factors.