How loud is a plane flying over a house?

The most reliable answers come from noise monitors: microphones that airports place under their flight paths to log every plane that passes. The figures here come from monitors around Heathrow, analysed by the Civil Aviation Authority's noise specialists. They are peak levels (LAmax), measured outdoors on the A-weighted decibel scale used for all aircraft noise; dB vs dBA explains what that means.

How loud is a plane overhead?

Directly under the flight path, within a few kilometres of the runway, a landing or departing jet typically peaks between 75 and 90 dB. Further out, where planes are several thousand feet up, it is more like 60 to 70 dB. These are the averages from three recent monitors:

Two things stand out. Height matters: take-offs over Shepperton averaged about 12 dB less than those over Stanwell Moor, even though most of the Shepperton flights were large long-haul jets. And the aircraft matters almost as much: on the same take-off route at Stanwell Moor, an A380 averaged 15 dB more than an A220.

These are averages, and single flights vary by several decibels either way. The Shepperton and Kiln Green monitors only logged planes above 60 dB and 58 dB, so the quietest flights are missing and those averages lean slightly high.

Landing planes: how the level builds towards the runway

Landing planes descend on a straight, shallow slope, so the noise rises steadily the closer you are to the runway. Over three years, the CAA measured large twin-aisle jets (the Airbus A330, A340 and A350 and the Boeing 777) at monitors under Heathrow's approaches:

The heights are what a normal 3° approach gives at each distance, not measurements; the CAA puts 20 km at about 3,500 ft. How high planes fly when landing covers the heights in detail.

Smaller jets are a few decibels quieter. At Stanwell Moor, A320neo landings averaged about 3 dB below the average for all types. The Airbus A320, including the neo, is the most common type at Heathrow, with more than a third of its flights.

Take-offs

Take-offs generally make more noise than landings, but they climb much faster, so the loudest places are the first few kilometres beyond the end of the runway. In the same CAA study, the A330, A350 and 777 peaked at 74 to 84 dB 6 to 7 km from where they started their take-off run, and at 66 to 74 dB 15 to 16 km out, with the A350 the quietest at each point.

How a take-off is flown changes the noise too. A heavy long-haul flight, full of fuel, climbs more slowly than a short hop, and airlines use different climb procedures, which move the noise from one area to another rather than removing it. Take-off vs landing compares the two in more detail.

What makes one plane louder than another

• Height and distance. The figures above show it: the peak falls fastest close to the runway, and more slowly as the planes get higher.
• How far to the side you are. At Stanwell Moor, directly under the approach to Heathrow's southern runway, the monitor logged 1,464 landings above its 64 dB threshold. It caught only 111 on the northern runway 1.4 km away, although that runway takes most landings on easterly days. Sound that reaches you at a low angle also loses extra energy to the ground on the way.
• The aircraft. At Heathrow the A350 measured up to 6 dB quieter on take-off than the A330 and 777 it is replacing, and about 10 dB quieter than an MD-80 on the same route in 1998. The A320neo and A321neo were 3 to 4 dB quieter on take-off than the older A320 and A321.
• The time of day. At Shepperton the background noise fell to about 40 dB between midnight and 4 a.m., against 45 dB or more through the day. The same plane stands out far more against a quiet night.
• Being indoors. Australian government noise assessments assume a plane sounds about 10 dB quieter inside with the windows open and about 20 dB quieter with them closed.

How that compares with everyday sounds

Next to household sounds, a jet landing a few hundred feet overhead, at 85 to 92 dB, is as loud as a food blender at arm's length, about 90 dB. A take-off at 1,300 ft, around 83 dB, is like a hair dryer, about 80 dB. A plane 3,000 to 4,000 ft up, at 62 to 70 dB, sits between a normal conversation (about 60 dB) and a washing machine (about 70 dB).

The difference is repetition. A hair dryer goes off when you choose; under a busy approach, the next plane follows a couple of minutes later, for hours. What 65 dB sounds like sets out the everyday levels in full.

When does a plane count as loud?

We count a plane as loud when it passes 65 dB outdoors, loud enough to interrupt a conversation in the garden. In the approach figures above, the large jets were still over that level 15 km from the runway, and some of them at 20 km. Smaller jets drop below it sooner, and so does the noise a couple of kilometres to the side of the line.

What decides how noisy a house is, then, is not one plane but how many pass that line each day and night, and at what time.

Checking the planes over a particular street

Many airports publish readings from their own noise monitors, some through a flight tracker called WebTrak, and the CAA's monitor reports for Heathrow are public. For a particular address, start with the flight paths: the height of the planes and how far they pass to the side tell you most of what the figures above can. Our free flight map replays a whole day of landings and take-offs with their heights, so you can see how low and how often they pass.