Faculty of Civil Engineering Technology UNIMAP
PAP256 : Experiment Sound Level Meter
Sound level meter is used to measure the sound pressure from known source.
Identification of Noise
The important of identifying the noise is very crucial due to the personnel health and lives. Any
excessive sound more than normal person can hear will create harm especially to the hearing
capability.
The most common hearing risk will be in working places, gathering occasions and roads
(transportation) just to name a few. The need of noise controlled was created to quantify the
noise level risks. The quantifying level of noise will be the guidance practice for any reference of
risk and health conduct.
Noise Hazards in Working Place
Factory and manufacturing industry were known to have high level of noise during their daily
operation. The demand for noise guidelines is fulfilled by the Department of Occupational Safety
and Health (DOSH). The guidelines are created to be complying by all related industries. The
abnormal noise will create harm to the hearing. The guideline is to create a standard conduct and
measurement where it can identify the accuracy of human noise threshold.
The excessive noise means that any noise exposure of
I) More than 82 dB(A) exposure
II) Daily exposure of maximum 50% of personal noise dose
III) Any time of sound pressure exceeding 115 (dBA)
IV) Peak sound level exceeding 140 dBC
What daily personal noise dose means the cumulative noise exposure of eight hours of daily
work. When the noise exposure are exceeding the maximum allowance the employer are require
to find prevention measure such as reduce the noise level or providing personal hearing
protection to the employees.
Dose Noise, D= 100 (C1/T1 + C2/T2 +..… + Cn/Tn) ≤ 100
C = Time spent at specified noise level (hours)
T = Time permitted at specified noise level (hours)
Faculty of Civil Engineering Technology UNIMAP
The noise dose is converted to an 8-hour weighted average (TWA) sound level, where
TWA = 16.61 log (D/100) + 90
TWA is the sound level exposure for 8 hours daily working hours. The worker is assume safe
and allowed to given working environment. This experiment also will find the noise dose and
noise limit in several common work places.
Table 1 : Permissible noise exposure according to OSHA
Sound Level (dBA) Permissible Time (hour)
80 32
85 16
90 8
95 4
100 2
105 1
110 0.5
115 0.25
120 0.125
125 0.063
130 0.031
Table below show some sound intensity for comparison.
Table 2 : Common Sound Intensity in Places
Sound intensity (Db) Location / Point Source
160 Near jet engine
130 Threshold of painful sounds, limit of ear’s endurance
120 Threshold of feeling (varies with frequency)
105 Express train passing at high speed
100 Loud automobile horn, 23 feet away
80 A subway
70 A stenographic room
60 Average busy street
55 Noisy office or department store
50 Moderate restaurant clatter
45 Average office
35 Soft radio in apartment. The average residence
20 Average whisper four feet away
10 Rustle of leaves in gentle breeze
0 Threshold of audibility
Faculty of Civil Engineering Technology UNIMAP
Lab Sheets : Experiment Sound Level Meter
A. Objective :
1. To measure the level of noise in selected location for study
2. To analyze data and interpret the result
B. Apparatus : Sound level meter
C. Procedures
1. Identify several places to conduct the experiment accordingly.
2. Switch on the Sound Level Meter instrument and reset
3. Set the Time Response (fast and slow) and Frequency Time Weight (A and C) is selected.
4. The noise meter is held and pointing toward the subjected area.
5. Data are taken in 1-minute interval for 20-60 minutes continuously.
6. Once finish, move to the next selected location and repeat the same procedures.
7. Tabulated the result in graph paper to see the noise trend.
D. Result
Location : A/B/C
Time Noise Point A (dBA) Noise Point B (dBA) Noise Point C (dBA) Note
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E. Discussion :
1. Plot the result (Noise (dB) vs Time).
2. Explain the trend and sound spike if occurred.
3. Calculate the Noise Dose and TWA values
4.Compare with the OSHA Noise Standard and discussion
F. Conclusion
