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Notes on Boundary noise limits for ACMV systems in non industrial buildings (Feb 2018)Date: October 04, 2019

To conduct noise assessments of ACMV (air conditioning and mechanical ventilation) systems under NEA's guideline for TOP submission, each test point is tested for a 15 minutes equipment "ON" and another 15 minutes "OFF" state. As it would take time to switch equipment on and off, each point usually take about 45 mins to test.

That is assuming a one-take measurement, and external factors such as a sudden event of airplanes, motorcycle, MRT, cars etc are not present to affect the measurement. If they are and it influenced the measurements, a re-measurement of would have to be performed. 

Hence, for a 10 measurement points project, with 1 sound level meter, it would take approximately 7.5hrs to complete for each session/day period.
With 2 sound level meters, it would take half that time, 3hrs 45mins for 10 points.

number of test points  1 slm 2 slm 3 slm 4 slm 5 slm
1 0.75 0.75 0.75 0.75 0.75
2 1.5 0.75 0.75 0.75 0.75
3 2.25 1.5 0.75 0.75 0.75
4 3 1.5 1.5 0.75 0.75
5 3.75 2.25 1.5 1.5 0.75
6 4.5 2.25 1.5 1.5 1.5
7 5.25 3 2.25 1.5 1.5
8 6 3 2.25 1.5 1.5
9 6.75 3.75 2.25 2.25 1.5
10 7.5 3.75 3 2.25 1.5

Table above: Estimated hours required for each test session, assuming 45 mins each test.

There are 3 time periods for each test point; Day (7am-7pm), Evening (7pm-11pm) and Night (11pm-7am).

ACMV guidelines feb 2018
(source: NEA website)

The purpose of this test is to ensure noise emitted from ACMV equipment of buildings met with NEA's requirements. Hence, designs and quality of works are important to ensure that time is not wasted during assessment.

Mitigating measures are required for equipment that fail to meet the requirements, and a re-test would have to be rescheduled. Incurring cost and time delays in the TOP application process.

Contractors and QPs should check to ensure designs and works of ACMV equipment comply with the noise limits before the assessment are conducted by NEA approved Noise Consultants.

Sound level meters used must have IEC61672 Class 1 type-approval certification from a third party certification bodies (please refer to NEA websites for more info.) NEA only accept test reports that are measured with calibrated and type-approved sound level meters.

Click here to find out more information about our class 1 type-approved sound level meters.

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