Aircraft Noise Measurement Method Evaluation and Measurement Methods -Aircraft Noise Measurement Method -

Aircraft noise is measured using specialized equipment to accurately assess the noise conditions.

Aircraft noise level

Instantaneous value

  • This is the measured instantaneous value at the noise measurement station installed by Kansai Airports.
  • Displays the measured value every 2 seconds at each measurement station.
  • Non-aircraft sounds are included.

A diagram showing the instantaneous value, which is the current measurement value. The y-axis represents decibels (dB) and the x-axis represents time. The curved graph shows measurements taken at measuring stations every two seconds.

Evaluation value (Lden)

  • This is an evaluation value over a certain period of time based on the noise value measured at the noise measurement station installed by Kansai Airports.
  • Since only aircraft noise is identified from the measured noise, no other sound is included.
  • Energy is calculated and evaluated for each aircraft when the difference between the maximum noise level and the background noise level is 10 dB or more.

A diagram illustrating a process of calculating the noise evaluation index Lden. The process uses noise occurring over a 24-hour period, and from that noise, only aircraft noise that exceeds background noise by 10 decibels or more is extracted. Then, the Lden value is calculated by time-weighting the energy of the aircraft noise, adding 5 decibels for the period from 7 pm to 10 pm, and adding 10 decibels for the period from 10 pm to midnight, followed by averaging the data for one day.

  • Calculate the energy of each noise level for the number of occurrences.
  • The same sound feels louder late at night and early in the morning, so weight it according to the time zone. (From 19:00 to 22:00: + 5 dB , From 22:00 to 7:00: + 10 dB)
  • Calculate an evaluation value (Lden) by summing all the energy in a time period (one day unit).

Review of Aircraft Noise Assessment

The evaluation index for aircraft noise has been revised from the previous “Weighted Equivalent Continuous Perceived Noise Level (WECPNL, commonly known as the ‘W value’)” to the “Day-Evening-Night Equivalent Sound Level (Lden).” Accordingly, the environmental standards related to aircraft noise are as shown in the table below.

Area Classification Standard Values
[After revision] Lden [Before revision] WECPNL (W value)
Ⅰ 57 dB or lower 70 or lower
II 62 dB or lower 75 or lower

Type I areas: Areas used exclusively for residential purposes
Type II areas: Areas other than Type I where it is necessary to maintain normal living conditions

Following the revision of the evaluation index for aircraft noise, Lden values have been published starting with the observation results in April 2013.
To facilitate comparison of aircraft noise observation data, the Lden values from the FY2012 observation and the WECPNL (W value) from the FY2013 observation were published as reference values.

Reference of noise level

Noise level varies depending on the measurement time and various conditions. Below is the reference of noise level.

A chart comparing various sound levels in approximate terms in decibels. Measured at 110 dB is a car horn, 100 dB, the sound level under an overpass when a train passes, 90 dB, a dog barking and karaoke, 80 dB, a piano, 70 dB to 60 dB, an alarm clock, telephone ringer, vacuum cleaner and television, 50 dB, talking (everyday) and a quiet office, 40 dB, a library, and 30 dB, a whisper. Aircraft noise falls into the 50 to 90 decibel range.

Partially quoted from “Current Status of Living Noise and Future Issues” (Ministry of the Environment)