Indoor Noise

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Indoor Noise

Noise Criteria (NC), Transmission Loss (TL)

Evaluation of indoor noise was performed for office and control room in industrial building. The general application of building noise criteria (NC) was defined to reduce speech and work interference, which criteria definition is determined as per room purpose in the related building drawing provided from Customer. And, Noise levels inside buildings was calculated, taking into account the noise from outside. Calculation of transmission loss as per wall detail design was carried out with consideration of the noise attenuation from outside to within a building.

Contents

  1. Scope of this analysis
  2. Noise Criteria
  3. Transmission Loss
  4. Indoor Noise Assessment

1. Scope of this analysis  

This indoor noise assessment includes below activities.

  • Definition of Noise Criteria (NC)
  • Calculation of Transmission Loss (TL)
  • 1/1 Octave band frequency
  • Speech and Work Interference
  • Indoor Noise Assessment

2. Noise Criteria (NC)

Indoor noise assessment is one of major factor for this noise analysis to achieve the conservation of hearing of workers and to allow adequate speech, telephone and radio communication. In the initial design of building noise design, the related sound criteria are needed to determine the degree of noise impact. Noise Criteria (NC) has been used for more than 50 years, and this method consists of a family of criterion curves extending from 63 to 8000 Hz. The criterion curves define the limits of octave band spectra that must not be exceeded to meet occupant acceptance in certain spaces. See below Noise criteria (NC) curve.

Noise Criteria, NC
[Noise Criteria, NC]

The following noise level limits are generally applied in order to reduce speech and work interference from adjacent equipment to acceptable proportions. It is a single number rating that is somewhat sensitive to the relative loudness and speech interference properties of a given noise spectrum. The NC values are formally defined in 5 dB increments.

 Room Types

 Details

 NC

 dB(A)

 Residences

 Living Areas

 30

35 

 Hotels

 Individual Rooms

 30

35 

 Meeting Rooms

 30

35

 Office Buildings

 Office

 30

35 

 Conference Rooms

 30

35 

 Open Plan Offices

 40 

45

 Lobbies

 40

45 

 Laboratories

 Testing/Research

 50

55 

 Extensive Phone use

 45

50 

 Schools

 Classrooms

 30

35 

 Libraries

 

 30

35 

 Indoor Stadiums

 Gymnasiums

 45

50 

3. Transmission Loss

There were many kinds of buildings designed and located in this industrial plant area, and it was necessary to evaluate the noise transmission as Break-in from building outside to indoor room, which space was planned to be permanently manned and could be considered sensitive receptors (such as office, meeting room, etc.).

Wall Details - transmission loss
[Wall Details]

Based on building drawing provided by Customer, it was selected the major wall list around building room having sensitive receptors, and those major wall specification for building has been tabulated in below. Those walls will be constructed by reinforced concrete wall with insulation and gypsum board, and the transmission loss of wall was calculated with consideration of safety factor.

[Wall Transmission Loss]

 No

Wall Specification

Transmission Loss, dB

63

125

250

500

1k

2k

4k

1

Thk.250 Conc. Wall + Thk.10 Air space + Thk.135 Insulation + Thk.9.5(2ply) Gypsum board

25.6

38.2

44.2

37.6

37.6

38.2

37 

2

Thk.200 Conc. Wall + Thk.10 Air space + Thk.135 Insulation + Thk.9.5(2ply) Gypsum board 

24.4

35.8

42.4

37.6

37.6

38.2

37

3

Thk.75 Sandwich Panel + Thk.150 Conc. Block w/Thk.20 Cement M0tar + C-stud 90x45x0.8T @450 W/Thk.60 Insulation + Thk.9.5(2ply) Gypsum Board

21.4

30.4

41.2

37.6

37.6

38.2

36

4. Indoor Noise Assessment

Indoor noise criteria (NC) was defined as per room purpose of each building, and outside noise and wall transmission loss was also aligned in order to calculate the indoor noise assessment. As results of evaluation, indoor noise for all location is satisfied with NC criteria from building outside noise. Below figures show the results of indoor noise assessment, which indicate both the estimated noise curve and noise criteria (NC).  

Building Noise Assessment
[Building Noise Assessment]

5. Relates Services

INERTANCE has a full capability regarding related noise and vibration engineering as listed in below, and feel free contact us at (mountain@inertance.com).