fani's Site: 2012

BASIC THEORY of Noise

1.1. Term In Noise

Before you understand more deeply about the noise, the authors present some important terms in this Final Report, including:

1. Sound level meter or the SLM is a measuring instrument noise.

2. Weighting networks is electronic circuits that sensitivity is subject to change with the frequency of the human ear. There are three kinds of weighting that has been standardized internationally namely A, B and C. Weighting A close similarity to the low noise level, the noise level is B and C are at high noise levels. Now, only weighting A widely used, since B and C do not reflect the appropriate relationship with subjective tests.

3. Criterion Level: Load a maximum acceptable noise ear, a condition resulting in 100% dose. OSHA CL = 90 dB for 8 hours.

4. Threshold (threshold): All sound below the threshold are not considered as noise to the function of integration and averaging.

5. TWA: Average sound samples for 8 hours. TWA starts from zero and increasing.

6. Sound Pressure Level (SPL): The sound is detected by the microphone. Calculated in decibels (dB).

7. MAX Level: Example of sound level with the highest weighting for the tool mounted lights depending on response.

8. Response (Fast, Slow): response which determines the speed of the unit responded to the noise fluctuations. Fast: has a time constant 125 ms. Slow has a time constant 1 s. OSHA uses Slow response rate.

9. Background noise level : noise level around is the noise level of a zone that has not been affected by artificial noise, in other words is a natural sound level.

10. Noise mapping : noise mapping is a very thorough sketch depicting the relative position of all points of sampling noise. To this sketch was added a data of the noise level around the point of sampling noise.

11. Noise dose or doses of noise is the potential noise which damages hearing is not dependent on the level, but also to the duration of noise going on.

12. Decibel (dB) is a unit of noise level. dB is 10 times the amount of logarithma (base 10) of the comparison.

13. dBA is a unit of noise level; obtained when using the gauge on the filter SLM weighting A, with a response to the frequency response of the SLM near the ear.

14. Equivalent Level (LEQ) or the equivalent continuous noise level is the level of steady noise (steady noise) equal to the noise fluctuations in a period / time interval measurements.

In addition there are some terms that need to be known abbreviations, such as:

1. LASeq = Level Weighting Detector Equevalen, Equivalent sound level, A-weighted, slow detector

2. LAS = Sound level pressure, A-weighted, Slow detector

3. LCSmx = Maximum sound pressure level, C-weighted, slow detector

4. LCSeq = Equivalent sound level, C-weighting, Slow detector

5. LCSmm = Minimum sound pressure level, C-weighted, slow detector

1.2. Definition of Noise

Definition of noise according to some experts, that is :

· According Doelle (1993): "physically sound or sound is pressure irregularities, shifts of particles in an elastic medium such as air. Physiologically the sensations that arise as a result of the propagation of vibration energy from a vibrating source that reach the eardrum. "

· According to Patrick (1977): "noise can also be interpreted as a form of sound that does not fit with the place and time."

· According to Prabu, Putra (2009) noise is sound that interferes.

· According Ikron I Made Djaja, Ririn AW, (2005) noise is unwanted sound that can interfere with or endanger health.

· According to the Decree of the Minister of Environment No. KEP-48/MENLH/11/1996 definition of noise is "unwanted noise from the business or activities within a certain time level and that can cause health and environmental comfort."

· According Arifiani (2004) noise in occupational health can be defined as "hearing voices that can lower both quantitatively (increase in hearing thresholds) and qualitative (narrowing the spectrum of hearing), with regard to factor intensity, frequency, duration and time pattern".

· Noise is defined as "unwanted sound, for example, which hinders hearing voices, music etc, or causing pain or blocking the lifestyle. (JIS Z 8106 [IEC60050-801] electro-technical vocabulary section 801 International: Akustikal and elektroakustik) ".

Noise can be defined as the entry of unwanted sound energy in the environment in such a way as disrupt the function their hearing. From the standpoint of the environment, including categories of environmental noise pollution because it can cause disruption to human comfort and health. Therefore, this potential dangers of noise should be controlled.

1.3. Types of Noise

Noise has several types, namely:

1. Constant Steady Noise: noise which has SPL (sound pressure level) is relatively constant.

2. Continuous Noise: Noise that occurs in a sustainable manner within a specified time. (Prabu,Putra, 2009) : "Noise is a constant noise intensity where the fluctuations of no more than 6 dB and not dotted." Continuous noise is divided into 2 (two), that is :

· Wide Spectrum is noisy with a wide frequency spectrum, this noise is relatively fixed within less than 5 dB for a period of 0.5 seconds in a row, like the sound of the fan, the sound of looms.

· Norrow Spectrum is noise which also relatively fixed, but will only have a certain frequency (a frequency of 500, 1000, 4000 Hz) such as circular saws, gas valves.

3. Intermittent Noise: Noise that occurs intermittently in units of time.

4. Impulsive Noise: Noise that occurs suddenly marked by ups and downs in the SPL in less than 1 s. The effect initially causes a greater disruption, as a result of the explosion, for example from pemancang machine, punch, fire guns or cannons, explosions and the sound of gunfire (Goembira, Fadjar, Vera S Bachtiar, 2003). Noise of this type have a change in sound intensity exceeding 40 dB in a very fast and usually surprise the listener like a gunshot blast firecrackers, cannon (Prabu,Putra, 2009).

5. Background Noise: Noise coming from outside the work environment.

6. Annoyance: The noise that can interfere with communication, making it difficult to distinguish the sound with the noise.

7. Patterned noise (tones in noise): This is the noise caused by an imbalance or a repetition of the transmitted through the surface into the air. Such interference patterns caused by the spin machine parts such as motors, fans, and pumps. The pattern can be identified subjectively or objectively by listening to the frequency analysis (Goembira, Fadjar, Vera S Bachtiar, 2003).

8. Low frequency noise : noise has significant acoustic energy in the frequency range 8-100 Hz. Noise of this type are usually produced by large diesel engines in trains, ships and factories, where the noise of this type is covered and hard to spread easily in all directions and can be heard for miles (Goembira, Fadjar, Vera S Bachtiar, 2003).

9. Repetitive impulsive noise : Similar to impulsive noise, this noise only occurs repeatedly, for example forging machines (Prabu,Putra, 2009).

Based on effects on humans, noise can be divided into (Prabu,Putra, 2009) :

1. Noise that interferes (Irritating noise). Is the noise that has the intensity is not too hard, for example snoring.

2. Noisy covering (masking noise). Is a sound that covers clear hearing, indirectly, this sound would endanger the health and safety of workers, because the cries of danger signs or signals drowned in noise from other sources.

3. Damaging noise (Damaging / Injurious noise). Is a sound whose intensity exceeded the Threshold Limit Value. The sound of this type will damage or reduce the function of hearing.

Categories of environmental noise according to JIS is :

Table 2.1. Type of Noise Environment According to JIS

The amount of noise	All the noise in a given place and a particular time.
Specific noise	Noise in the amount of noise that can be clearly distinguished for acoustical reasons. Often the source of the noise can be identified.
Residual Noise	Noise that remains after the removal of all specific noise of the amount of noise in a given place and a particular time.
Background Noise	All of other noise when focusing on a particular noise. It is important to distinguish between the noise residual and background noise.

1.4. Noise Characters

Noise has several characters, that is :

1. Free Field : noise-influenced environment, where environmental conditions are isotopic (no echo effect and is not limited to walls/ floor).

2. Reverberation : the echoes that arise when the sound source has stopped.

3. Noise Propagation : propagation of sound energy through certain media in the neighborhood.

4. Noise Source In Reverberant Field : return reflection noise caused by the barrier/ wall/ equipment and material characteristics.

5. Resonance : resonance or sound changes frequency.

1.5. Impact Noise

Hearing loss is the change in level of hearing that resulted in difficulty in carrying out a normal life, usually in terms of understanding speech. Noise can cause various disorders such as disorders of physiological, psychological disorders, communication disorders and deafness. Auditory disorders, such as disruption to the hearing. Non Auditory, such as disruption to communication, safety hazard, decreased performance of work, stress and fatigue.

1. Physiological Disorders

High pitched noise is annoying, if intermittent, or which come suddenly. Disorders can include increased blood pressure (± 10 mmHg), increased pulse, and can cause pale.

2. Communication Disorders

Communication disorders are usually caused by the masking effect (hearing sounds that cover the less obvious) or impaired voice clarity, communication must be by way of shouting. This disorder causes disruption of the work, to the possibility of errors due to not hear the signal or alarm. This communication disorders are not directly endanger the safety of a person.

3. Balance Disorders

Disorders can lead to a very high impression of walking in space or drift, caused a physiological disorder in the form of dizziness (vertigo), or nausea.

Table 2.2. Types Of Due to Noise

Type		Description
Consequences of bodily	Hearing Loss	Changes in thresholds temporary and permanent changes in thresholds due to noise.
Consequences of bodily	Physiological Consequences	Discomfort or increased stress, increased blood pressure, headaches, ringing
Psychological Consequences	Emotional Distrubance	Aggravation, confusion
	Lifestyle Disorder	Sleep disturbance or break, loss of concentration at work, reading etc.
	Hearing Loss	Hinder the ability to hear TV, radio, conversations, phone etc

(Source : Buchari, Industrial Noise and Hearing Conservation Program, 2007)

Hearing loss caused by noise can be determined using the parameters of everyday conversation as follows :

Tabel 2.3. Gradation of Hearing Loss Due to Work

GRADING	PARAMETERS
Normal Moderate Intermediate Weight Very Heavy Deaf Total	No trouble in ordinary conversation distance of 6 m Difficulties in everyday conversation started distance> 1.5 m Difficulties in hard everyday conversation distance> 1.5 m Difficulties in the conversation loud / shouting distance of> 1.5 m Difficulties in the conversation loud / shouting distance of <1.5 m Loss of hearing ability in communicating.

(Source : Buchari, Industrial Noise and Hearing Conservation Program, 2007)

According to ISO (international Standars Organitation), degree of deafness due to noise are as follow :

Tabel 2.4. Degree of Deafness Due to Noise

Classification	Category
Increased hearing threshold between 0-25 dB Increased hearing thresholds between 26-40 dB Increased hearing thresholds between 41-60 dB Increased hearing thresholds between 61-90 dB Increasing the threshold of> 90 dB	Normal Mild deafness Moderate deafness Heavy deafness Very heavy Deafness

(Source : Buchari, Industrial Noise and Hearing Conservation Program, 2007)

According Suma'mur M. Sc, Viewed from the consequences or impacts arising, noise can provide the following effects:

Acoustic Trauma: Caused by a single exposure to very high noise intensity and occur suddenly, such as the explosion sound. Acoustic Trauma is a combination of Conductive deafness and perceptive deafness. Conductive deafness is due to the conduction of sound, this is caused by abnormalities - abnormalities in the outer and middle ear. While perceptive deafness due to abnormalities in the inner ear and retrocochlear (auditory nerve and brain).
Temporary Threshold Shift: Hearing loss is temporary time. Recovery takes time ranges from several minutes to several days (3-7 days) and a maximum of up to 10 days. Factors that determine the magnitude of TTS is the intensity, duration of exposure, frequency, type of noise, individual susceptibility.
Permanent Threshold Shift (PTS): This effect is often referred to NIHL (noise induced hearing loss), occurred after a long exposure of about 10 years or more and takes place slowly without realizing that he had suffered from deafness. The amount of PTS influenced factors as follows:

a) The high level of noise

b) Long exposure

c) Sound spectrum

d) Individual Sensitivity

e) The influence of drugs, some drugs may aggravate deafness when given in conjunction with voice contact, such as quinine, aspirin.

Tinnitus: Signs symptoms of the onset of hearing loss. The first symptom is ringing in the ears. People who can feel the tinnitus can experience these symptoms at the time of such a state of silence when sleeping at night or when in the room audiometric examination (ILO, 1998).

1.6. Noise Standars

To determine the noise criteria of an area, it is necessary to know the standards applicable to such noise. Berikut ini standar atau kriteria kebisingan yang ditetapkan oleh berbagai pihak. The following noise standards or criteria set by the various parties.

1. Decree of the Minister of Manpower No.KEP-51/MEN/1999 of noise threshold values. For more details look at Table 2.5.

Table 2.5. According to Threshold Values

Minister of Manpower No. Kep. KEP-51/MEN/1999

Exposure Time Per Day	Intensity Noise (dBA)
8 Hours	85
4 Hours	88
2 Hours	91
1 Hours	94
30 Minutes	97
15 Minutes	100
7,5 Minutes	103
3,75 Minutes	106
1.88 Minutes	109
0,94 Minutes	112
28,12 Seconds	115
14,06 Seconds	118
7,03 Seconds	121
3,52 Seconds	124
1,76 Seconds	127
0,88 Seconds	130
0,44 Seconds	133
0,22 Seconds	136
0,11 Seconds	139

Sources: Ministry of Manpower Decree No. KEP-51/MEN/1999 KEP-51/MEN/1999

2. Circular of the Minister of Manpower, Transmigration and Cooperatives No.SE 01/MEN/1978:

"Threshold Limit Values are abbreviated NAB to noise at work is the highest intensity and is the average value is still acceptable labor without causing a permanent loss of hearing power for the continuous working time not more than 8 hours a day and 40 hours per week ".

3. Noise Criteria According to the Department of Labor OSHA,

Table 2.6. According to OSHA Threshold Limit Value

Time (hours/day)	Noise Level (dBA)
8	90
6	92
4	95
3	97
2	100
1,5	102
1	105
0,5	110
<0,25	115

4. Noise Standard Under Regulation of the Minister of Health of the Republic of Indonesia No.718/Men/Kes/Per/XI/1987, about health-related noise.

Table 2.7. Distribution Zone Noise By Ministry of Health

Zone	Maximum recommended (dBA)	Maximum permitted (dBA)
A	35	45
B	45	55
C	50	60
D	60	70

Description :

· Zone A = study sites, hospitals, health care, etc.;

· Zone B = housing, education, recreation, and the like;

· Zone C = offices, shops, trade, markets, and the like;

· Zone D = industrial zones, factories, railway stations, bus terminals, and the like.

5. Noise zones according to IATA (International Air Transportation Association):

· ZONE A:
intensity of > 150 dB → dangerous area and should be avoided

· ZONE B:
intensity of 135-150 dB → individuals who are exposed to wear ear protectors (earmuff and earplug).

· ZONE C:
115-135 dB → need to wear earmuff

· ZONE D:
100-115 dB → need to wear earplug

6. Noise criteria according to Formula ACGIH and NIOSH. By using a specific formula, this formula, used to calculate the maximum time allowed for a worker to be in workplaces with unsafe levels of noise.

Table 2.8. Noise Criteria According to ACGIH and NIOSH

dB	Allowable Exposure Time (hours)	dB	Allowable Exposure Time (hours)
80	25,4	106	37,5
81	20,16	107	2,98
82	16	108	2,36
83	12,7	109	1,88
84	10,08	110	1,49
85	8	111	1,18
86	6,35	112	0,94
87	5,04	113	0,74
88	4	114	0,59
89	3,17	115	0,47
90	2,52	116	0,37
91	2	117	0,3
92	1,59	118	0,23
93	1,26	119	0,19
94	1	120	0,15
95	0,79	121	0,12
96	0,63	122	0,09
97	0,5	123	0,07
98	0,4	124	0,06
99	0,31	125	0,05
100	0,25	126	0,04
101	0,2	127	0,03
102	0,16	128	0,02
103	0,13	129	0,02
104	0,1	130	0,01
105	0,08

1.7. Noise Measurement

There are three ways or methods of measurement due to noise at work sites.

1. Measurements with sampling points

This measurement is done when the noise is thought to exceed the threshold at only one or a few locations only. These measurements can also be performed to evaluate the noise caused by a simple equipment such as compressors/ generators. Distance measurements of the source should be included, eg 3 meters from a height of 1 meter. It also must be considered directional microphone gauges are used.

2. Measurements with a contour map

Measurements by making a contour map is very useful in measuring noise, because the map can determine the image of the noise conditions in the coverage area. This measurement is done by making drawings on paper isoplet scale according to the measurements being made. Usually made coloring code to describe the state noise, the color green for intensity noise below 85 dBA with the color orange for high noise levels above 90 dBA, yellow for noise with an intensity of between 85-90 dBA.

3. Grid Measurement by Grid

To measure the Grid is to make an example of data noise on the desired location. These points must be made with a sampling interval of the same distance in all locations. Thus in the location measurement is divided into several boxes of the same size and distance, for example: 10 x 10 m. Box is marked with rows and columns for easy identification.

Noise measurement was carried out aiming to find out the data noise in the workplace, can then be carried out appropriate controls to reduce the noise level. In the implementation of the measurement noise given the appropriate equipment needed to measure the noise level, equipment used to support the process of noise measurement are as follows:

1. SLM (sound level meter): This tool is basic instruments used in the measurement noise. SLM consists of a microphone and an electronic circuit including an attenuator, 3 responders network frequency, scale indicators and amplifiers.

Figure 1.1. Sound Level Meter Larson Davis LXT 2

2. Noise Dose Meters: This tool is used to measure the dose of exposure of workers to noise, and the tool is calibrated by using the Noise Dose Calibrator Adaptor.

Figure 1.2. Noise Dose Meter 706-RC

3. Tripods: the tool is used to buffer the SLM are used to measure.

4. Noise Measurement Sheet: a sheet of data which is used as a form field for monitoring the data noise.

To measure the noise dose received is:

D = 85+10 log Exposure time/TLV............................................ equation 2.1

To measure the Intensity Level using the following equation :

L1 = 10 log intensity/ I₀.......................................................... equation 2.2

Description :

I₀ = 10^-12 Watt/m²

To measure Sound Pressure Levels using the following equation :

Lp = 20 log P/𝑝₀...................................................................... equation 2.3

Description :

𝑝₀ = 2 x 10^-5N/m²

𝑝 = Pressure

To measure the mean of the data presented are :

Lmean = 1/n x (L1+L2+....+Ln) ......................................... equation 2.4

ACGIH and NIOSH formula to calculate the maximum time allowed for a worker to be in workplaces with unsafe levels of noise are as follows :

T = 480/2^(L-85)/3............................................................................. equation 2.5

Description :

T = maximum time in which workers may be dealing with the noise level (in minutes)

L = noise level (dB) are considered dangerous

3 = exchange rate

18. Control of Noise Hazards

Noise can be controlled in several ways, including:

1. In Control Engineering ie for example by reducing noise at its source, it could by installing silencers or replacement of equipment, perform labor or machine isolation.

2. Administrative controls, such as organizing work time, monitoring the area, training, etc.

3. Protection of workers with PPE / APT, such as using Ear Plugs or Ear Muff.

Each tool has a protective ear noise reduction level (NRR), so the selection of PPE must be appropriate. To determine the value of NRR can use the following equation :

dBA’ = dBA – (NRR – 7)..................................................... equation 2.6

Description :

dBA’ = level of the desired noise level

dBA = The measurement results

NRR = Noise Reduction Rate

To determine the required protective equipment appropriate ear noise absorption and noise, can use the following equation :

AR = 2 x NRR....................................................................... equation 2.7

Description :

AR = Ability ear protective devices to absorb the noise source or can be called as the endurance of ear protective devices.

NRR = The ability to reduce the noise level of the ear protectors.

Source : Final Project of Fani Purnama Hasan

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