Noise level

A sound level meter is used for acoustic measurements. It is a handheld measurement with microphone.

Sound Level Limits
There are certain limits to sound levels.

Nighttime flights coming to Singapore are subject to restrictions. Between 11.00pm and 4.00am, the noisiest aircraft between QC/8 and QC/16 cannot be scheduled for operation, whereas during the night quota period from 12.00am to 4.00am, there are also limits.
 * A limit on the number of flights allowed;
 * A Quota Count system which limits the total amount of noise permitted, but allows operators to choose to operate fewer noisy aircraft or a greater number of quieter planes;
 * QC/4 aircraft cannot be scheduled for operation.
 * A voluntary agreement with the airlines that no early morning arrivals will be scheduled to land before 04:30.

QC/2 has become the de-facto standard for midnight and late night operation.

A trial of noise relief zones ran from December 2012 to March 2013, which concentrated approach flight paths into defined areas compared with the existing paths spread out. The zones were alternated weekly, meaningly residents in the "no-fly" areas received respite from the aircraft, apart from noisy periods. However, it was concluded that some residents in other areas experienced a significant disbenefit as a result of the trial and that it should therefore not be taken forward in its current form.

No more than 67 decibels are allowed for the MRT, of which it is a rule since 1996. For the expressways, no more than 67 decibels are also allowed as well.