There is no denying that aviation has come very far technology-wise. In its early infancy, commercial aviation was an expensive and rather uncomfortable endeavor, as the turboprops that powered aircraft were loud, produced a ton of vibration and were limited in power, making passengers travel onboard an aircraft for a very long time.

As jet engines gained traction commercially, passenger comfort and airline operations improved dramatically. The first turbojets were more efficient, faster and most importantly – less noisy, thus providing a much more comfortable journey on board. Yet, aviation authorities and governments worldwide now seek to reduce how much noise aircraft produce with manufacturing limits, operational restrictions and regulations.

To counter aircraft noise pollution, the International Civil Aviation Organization (ICAO) has issued the Annex 16, which includes several chapters with noise restrictions. ICAO measures sound levels in Effective Perceived Noise (EPNdB), which relies on human annoyance, rather than general loudness.

Why is reducing aircraft noise pollution important?

Noise pollution can significantly impact the experience onboard. Airlines today aim to deliver the best product possible, including top of the line in-flight entertainment (IFE), catering, cabin layout changes and even lightning inside the aircraft are crafted in a way to make passengers as comfortable as if they were in their own home.

But one aspect of comfort for airlines is hard to control – noise. It puts carriers in a difficult position, as configuring a cabin in various ways can help to reduce the noise inside, but at the same time increase the weight of the aircraft and subsequently, boost operational costs.

According to a report by the Federal Aviation Administration of the United States (FAA), exposing a person to loud noise (higher than 90dB) for a prolonged period of time (eight or more hours per day) for several years “may cause permanent hearing loss”. A 2006 study highlighted that even at 65 dB(A), “humans become irritated from noise”. The same study tested sound levels on two Airbus A321 flights and the average noise levels in-flight were between 80-85 dB(A), just below the 90dB threshold, but way above the human annoyance sound level of 65 dB(A).

Furthermore, studies like the one by The University of New South Wales (UNSW Sydney) have shown that continuous exposure to noise can reduce the recognition of memory and cause a person to be more fatigued. A recent example of how fatigue can cause issues inside the cockpit is Air Canada Flight 759. the National Trasnportation Safety Board (NTSB), which investigated the horrofing close-call, concluded that fatigue most likely contributed to the crews’ decision making.  

However, the A321 is a fairly new aircraft and is categorized under Chapter 4 in ICAO’s Annex 16, which allows for a maximum of 92.8 EPNdB for the aircraft. On average, it emits 88.3 EPNdB during a flyover. Newer aircraft are even under stricter noise restrictions and manufacturers have to comply with Chapter 14 regulations released in 2013. As a result, newer aircraft like the Airbus A321neo emits 83.7 EPNdB, while Boeing 737 MAX generates 82.6 EPNdB.