2Dr.Kadim Karim Mohsen Ali College of Engineering) byDr.Kadim Karim Mohsen AliThi-Qar UniversityCollege of Engineering)2012Analysis of Penetration of Noise Waves to the Human Body
3الضوضاءقال تعالى: (وعباد الرحمن الذين يمشون على الأرض هوناً . وإذا خاطبهم الجاهلون قالوا سلاماً)-الفرقان63قال تعالى: (واقصد في مشيك واغضض من صوتك) - لقمان19وعندما أراد رسول الله (ص) اختيار طريقة لتبليغ الناس دخول وقت الصلاة استشار أصحابه في ذلك ورفض اقتراحات بعضهم باستعمال الناقوس أو الطبول أو الأجراس، واختار الأذان بصوت الإنسان لأنه أدعى إلى الهدوء والسكينة والبعد عن الصخب، واختار بلالاً لأدائه لأنه أندى صوتاً وإذا كان الإسلام ينهى عن إحداث الضوضاء في عباداته، فما بالك بهؤلاء الذين يحدثون الضجة بغير هدف سوى التلذذ والتمتع بإيذاء الناس بصراخهم أو إطلاق زمور سياراتهم، أو رفع مكبرات الصوت لمذياعهم أو آلات التسجيل وسواها وإزعاج جيرانهم وإجبارهم على سماع ما لا يريدون، كل هذا تعدٍّ على الحرية الشخصية التي احترمها الإسلام وأقرتها الشرائع الدولية .ثم ألا يعلم هؤلاء الذين يحدثون الضجيج، كم من مريض في البيوت يحتاج إلى الراحة والنوم، أو شيخ مسن مضطرب في نومه، أو من طالب علم يحتاج إلى الدراسة والمذاكرة.
4Noise is any undesirable sound. Noise can increase stress. Objective of the WorkNoise is any undesirable sound.Noise can increase stress.Very loud noise can damage your hearing, or even make you completely deaf.
5What is Sound and what is Noise? The word noise is derived from the Latin word NAUSES which means "seasickness" the unpleasant sounds made by seasick passengers or sailorsBritannica encyclopedia defines Noise as Unwanted sound and U.S. Encyclopedia as Undesirable sound From the legal view point may be defined as wrong pollution is from the air, causing a material wounding of the right of individualsNoise is a form of energy which is emitted by a vibrating body and transmitted by pressure fluctuation which the human ear can detect and on reaching the ear causes the sensation of hearing through nerves.When one is speaking, the vibrating of vocal chords set air particles into vibration and generate pressure waves in the air, the person nearby may then hear the sound of the speech when the pressure waves are perceived by the ear.
6Sound can also travel through other acoustic media, such as water or steel or Gases Sounds produced by all vibrating bodies are not audible. The frequency limits of audibility are from 20 Hz to 20,000 Hz.<20Hz Hz to 20000Hz > 20,000HzInfrasonic - inaudible sonic-Audible Ultrasonic - inaudible
8Animals that can hear altrarasonic sound Fish Dogs WhalesSnakesapplication seismographs use for monitoring earthquakesAnimals that can hear infrasonic soundBatsElephantsapplicationSonarUltrasonic weldingUltrasonic disintegration bacteria
10Noise health effects consequences exposure to elevated sound levels. Temporary and sometimes permanent hearing lossPresbycusisHypertensionHeart diseaseTinnitusAnnoyance and sleep disturbanceChanges in the immune system Birth defects , exposure of the pregnant woman in trouble and become unstable neurological condition which affects the fetusIschemicVasoconstriction and other cardiovascular impacts Impairment
11Stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors. Human life decrease from 8 to 10 yearsMental AutismExcess secretion of certain glands cause high blood sugarThe headaches and fatigue and insomniaStomach ulcersBlood pressure in school children in the vicinity of the airport is higher than the school children away with him, and their speed in solving mathematical problems less, and at their failure to resolve the matter quickly throw aside what they are not trying to re-solve.Speech interference: if children who are learning to read cannot understand their teacherMental collapse
13The power of jet noiseA new study was published present a link, between jet noise and mental illness. The study find that the rate of mental illness hospital admission was 20 percent higher in Inglewood , where the los Angeles International Airport is located , than in El Segundo , about five miles away.The researchers chose El Segundo for comparison because census data showed its residents to be very much like those of Inglewood in age, race and Socio-economic background. The main difference was the jet noise level: above 90 decibels in Inglewood, 60 to 65 decibels in El Segundo.A study by British psychiatrists produced similar results .Mental hospital admission were 31 percent higher among people living close to London’s Heathrow Airport than among those who lived farther away.
14General statistics1- Hearing loss is the number one of disability of the world2- hearing loss is the most preventable disability in the world3- the number of people who need hearing aid 25 million4- 15 every 1000 people under 18 yrs have hearing loss5- 3 out of 100 school children are affected by hearing loss6- percentage of people loss their hearing before age of 3 is 5.4 %7- percentage of people who loss their hearing between 3 to18 yrs. is 14.2%8- percentage of people who loss their hearing at age of 19 yrs. is 76.3 %
15Sources of Noise Vehicles, trains, aircraft Radio and television Children playingHousehold gadgetsRoad trafficTransportation systemsConstruction work - construction of buildings, highways, and streets cause a lot of noise, due to the usage of air compressors, bulldozers, loaders, dump trucks, and pavement breakers.Industrial noiseBoilers, generators, air conditioners, fans, plumbing and vacuum cleanersProlonged exposure to loud music
16Sound can be produced by many other sources - man's vocal cord, a running engine, a vibrating loudspeaker diaphragm, an operating machine tool, and so on.
17Unpleasant, unwanted, disturbing sound is generally treated as Noise
18The nature of noiseNoise , phenomena of vibration, travels in wave patterns through solids, liquids and gases.The waves, caused by vibration of the molecules, follow sine functions, characterized by the amplitude and wavelength (or frequency)Noise waves of equal amplitude with increasing frequency from top to bottom
19When the medium is the air and pressure fluctuations falls on the air the hearing is produced Sound is form of energy and is transmitted by collisions of air molecules one against the next and so on.It may represented as a series of compressions and refractions in the density of air molecules which travel away from source
21Frequency: Number of pressure cycles / time Sound is a disturbance that propagates through a medium having properties of inertia ( mass ) and elasticity. The medium by which the audible waves are transmitted is air.Basically sound propagation is simply the molecular transfer of motional energy. Hence it cannot pass through vacuum.Frequency: Number of pressure cycles / timealso called pitch of sound (in Hz)Guess how much is particle displacement??8e-3nm to 0.1mm
22The disturbance gradually diminishes as it travels outwards since the initial amount of energy is gradually spreading over a wider area. If the disturbance is limited to one dimension ( tube / thin rod), it does not diminish as it travels ( except loses at the walls of the tube )
23Classification of noise #according to duration#according to frequencyContinuous noiseSpinning & weavingindustryHigh frequencySaw soundInterrupted noiseGrinders soundTraffic noiseLaw frequencyWhite noiseBoiler soundImpulse & impact noiseexplosions
24White noise Combines the noise pulse and random noise and has a spectral bandwidth over a flat area of influence White Noise is a set of noise or sounds that brings together all the frequencies that humans can hear, which is located in the area of the frequency spectrum between 20 to Hz
25Consists of three inter-related elements source receiver Noise problemConsists of three inter-related elementssourcereceivertransmission path.Transmission path is usuallythe atmosphere throughwhich the sound is propagated,but can include the structural materials of any building containing the receiver
28Characteristics C/CS of noise and the Decibel Scale 1- Frequency of noiseIs the number of pressure fluctuation per secondMeasured in (Hz)The higher the frequency, the more high-pitchedThe sounds produced by drums have much lower frequencies than those produced by a whistle
302- LoudnessA loud noise usually has a larger fluctuation and a weak one has smaller pressure fluctuation.Loudness of a sound is depends on the amplitude of the fluctuations above and below atmospheric pressure and frequencyAre expressed in Pascal (Pa)Amplitude is the magnitude of pressure fluctuations compared with atmospheric pressure (1000 millibars =1bar= 105 N/m2 (Pa))
31Range of PressureThreshold of Hearing (20x10-6 Pa=20µPa)Threshold of pain(sensation of pain) (2000 Pa = 2x109 µPa) times larger
32To express noise in terms of Pa is quite inconvenient because we have to deal with numbers from as small as 20 to as big as 2,000,000,000.
338 Sones is twice as loud as 4 Sones LOUDNESS INDEXLoudness Level (Phon) useful for comparing two different frequencies for equal loudnessThe phon is a unit of loudness level for pure tones 1 phon is equal to 1 dB of SPL at a frequency of 1 kHz0Phon: threshold of hearingSone A unit of perceived loudness equal to the loudness of a 1000-Hz tone at 40 dB above thresholdDirect relationship between Loudness Level ‘P’ (Phons) and Loudness Index ‘S’ (Sones)8 Sones is twice as loud as 4 Sones
34/.,m bnx hsaj ppqw [[we I ooosa p'qwd h = g + f jh k l s a k d g fq ew mcm zxc/.,m bnx hsaj ppqw [[we I ooosa p'qwdowqdjwq poqwdjqmlSound pressure levelBels and decibels
35Quantifying Sound Root Mean Square Value (RMS) of Sound Pressure The ‘rms’ pressure is the square root of this time-averaged value.In calculation of the ‘rms’, the values of sound pressure are squared to make them all positive and time-averaged to smooth out fluctuation.
36Sound Intensity : Average rate of energy transfer per unit area Sound Power levelSound Intensity : Average rate of energy transfer per unit areaSpeed of Light: 299,792,458 m/s Speed of sound 344 m/sFor air, 0c 415Ns/m3 so thatSound Power Level:dBReference Power Wref =10-12 Watt (0dB)A sound in free space radiating sound uniformly in all directions as a sphere of radius rSPL=SWL-10 log 4πr2
37Peak Power output:Female Voice – 0.002W, Male Voice – 0.004W,A Soft whisper – 10-9W, An average shout – 0.001WLarge Orchestra – 10-70W, Large Jet at Takeoff – 100,000W 15,000,000 speakers speaking simultaneously generate 1HP
38Situation and sound source sound power level SWL dB re 10−12 W sound power Pac wattssound power level SWL dB re 10−12 WRocket engine1,000,000 W180 dBTurbojet engine10,000 W160 dBSiren1,000 W150 dBHeavy truck engine or loudspeaker Rock concert100 W140 dBMachine gun10 W130 dBJackhammer1 W120 dBExcavator, trumpet0.3 W115 dBChain saw0.1 W110 dBHelicopter0.01 W100 dBLoud speech, vivid children0.001 W90 dBUsual talking, Typewriter10−5 W70 dBRefrigerator10−7 W50 dB
39SOUND BITSUnless there is a 3 dB difference in SPL, human beings can not distinguish the difference in the soundSound is perceived as doubled in its loudness when there is 10dB difference in the SPL.
42Levels in decibels calculation It is practical measure of the amplitude of pressure fluctuations.The human ear responds to a very wide range of intensities from the threshold of hearing TOH 20 µPa at 0 dB to the threshold of pain –feeling (loudest sound) TOP 20 X106 µPa is 120 dB.
46Addition of sound or Noises (decibels) levels Combination of sounds
47Addition of sound or Noises (decibels) levels Combination of soundsadding 60 decibels to 60 decibels gives 63 decibels. The following formula explains the general principle of adding sounds on the decibel scale.One can use the above formula to add three sounds together - 60 dB, 65 dB and 70 dB.
50Addition of sound levels can also be done simply using the following chart.
51Let us try adding the three sounds of 60 dB, 65 dB and 70 dB by using the chart. In using the Chart, two sounds are added together first. The resultant sound is then added to a third sound and so on. Please
53For e.g. The effective sound level from two air conditioners 60 dB (A) each, say is not = 120 dB (A) but = 63 dB(A).Similarly, the effective sound level of 57 dB, 63 dB, 63 dB, 66 dB and 69 dB is 72 dB. The computation is illustrated below.
55Noise Attenuation Process of removing noise from a signal. or is the reduction in amplitude and intensity of a signal.Attenuation is usually measured in units of decibels per unit length of medium (dB/cm, dB/m dB/km, etc) and is represented by the attenuation coefficient of the medium.
58Frequency analysis bands They are used to cover the audio frequency spectrumThey have lower frequency fL and upper frequency fUA normal human ear is able to hear sounds with frequencies from 20 Hz to 20,000 Hz. called the audible frequency range.The sounds we hear of various frequencies.The entire audible frequency range can be divided into 8 or 24 frequency bands known as octave bands or 1/3 octave bandsEvery 3 1/3 octave bands comprise one octaveA particular sound or noise can be seen to be having different strengths or sound pressure levels in the frequency bands
59Instruments for analysing Noise Constant Bandwidth DevicesProportional Bandwidth Devicesoctave bandy center frequencyAbsolute Bandwidth ∆f= fU - fLn=1 for octave band,n=3 for 1/3rd octaveFor 1/10th Octave filters,
64Frequency Weighting scales The responses of the sound level are modified with frequency-weighting networks that represent some responses of the human ear.A-weighting dB (A) : adjusts overall scale so it better matches what the human ear would hearC-weighting dB (C) : adjusts scale for loud or low frequency soundsB-weighting dB (B) : adjusts by factors that are “in between” the A-weighted factors and C-weighted factors (rarely used)D-weighting dB (D) : for Aircraft Noise
67Most sounds or noises we encountered in our daily life are from sources which can be characterized as plane or point or line sources.Plane source -Points of same sound pressure (for example, in the cross-section of the duct) form parallel planesIf a sound source produces spherical spreading of sound in all directions, it is a point sourceFor a point source, the noise level decreases by 6 dB per doubling of distance from it.If the sound source produces cylindrical spreading of sound For a line source, the noise level decreases by 3 dB per doubling of distance from it
71Radiation from Source Point Source (Monopole) Radiates sound waves equally in all directions (spherical radiation)W: is acoustic power output of the source;Constant termDepends on distance from source
72If the point source is placed on ground, it radiates over a hemisphere,the intensity is then doubled and
73Line Source(Long trains, steady stream of traffic, long straight run of pipeline, stream of motor vehicles on a busy road at a distance)
74DIRECTIVITY OF SOUND SOURCE Directivity of the source must be taken into account to calculate level from the source powerSound sources whose dimensions are small compared to the wavelength of the sound they are radiating are generally omni-directional;otherwise when dimensions are large in comparison, they are directional
77Environmental Effects Wind GradientHot Sunny DayVelocity Gradient (-)Temperature GradientCool NightWind & Temp effects tend to cancel outIncrease or decrease of 5-6dB
78Hearing Damage Potential to sound energy depends on its level & duration of exposureEquivalent Continuous Sound Level (Leq)tj : Fraction of total time duration for which SPL of Lj was measuredTotal time interval considered is divided in N partswith each part has constant SPL of Lj
79Basis of 90dB(A) for 8hr a day. Regulations:Basis of 90dB(A) for 8hr a day.ISO(1999): Increase in SPL from 90 to 93dB(A) must reduce time of exposure from 8 to 4 hoursOSHA: with every 5dB(A) increase, reduce exposure by halfOccupational Safety and Health Administration
80Errors of the order of 6dB around 400Hz due to reflections
81USEPA United States Environmental Protection Agency, is an agency of the federal government of the united charged with protecting human health and the environment,There are direct links between noise and health.Noise pollution harmfully affects the lives of millions of people.Noise pollution can damage physiological and psychological health.High blood pressure, stress related illness, sleep disruption, hearing loss, and productivity loss are the problems related to noise pollution.It can also cause memory loss, severe depression, and panic attacks.The World Health Organization (WHO) Organization stated that “Noise must be recognized as a major threat to human well-being”
91Response of the Human Ear to Noise Sound with a high frequency is said to be high-pitchedsoundwomen & children, scream, fire-alarm, siren, whistle, airplaneSound with a low frequency is low-pitched.grass, flowers, worm
96International conventions The Control of Noise at Work Regulations 2005 (Commencement date April 2006)The Health & Safety at Work etc. Act 1974C148 Working Environment (Air Pollution, Noise and Vibration), 1977ConferenceInternational Noise Conference Australia 2011International Noise Conference USA Tour 2010International Noise Conference Euro Tour 2009International Noise Conference SXSW Austin2009International Noise Conference Spokane WA 2008International Noise Conference Seoul South Korea 2008International Noise Conference Toronto 2008International Noise Conference USA Tour 2008
98Planting bushes and trees (e. g Planting bushes and trees (e.g. Tamarind , Banyan , Neem , Casoria ) in and around sound generating sourcesRegular servicing and tuning of automobiles , lubrication of the machinery and servicingBuildings can be designed with suitable noise absorbing material for the walls, windows, and ceilings.Workers should be provided with equipment such as ear plugs and earmuffs for hearing protection.Soundproof doors and windowsRegulations should be imposed to restrict the usage of play loudspeakers in crowded areas and public places.Factories and industries should be located far from the residential areas.keep schools and hospitals all sources of noise.Keep cities and populated areas airports a distance of not less than 30 km.railway lines and highways Must be away from residential areas as possible.Community development or urban management should be done with long-term planning, along with an aim to reduce noise pollution.Social awareness programs should be taken up to educate the public about the causes and effects of noise pollution.Acoustic insulation by good glazing can cut down noise
99Prevention of noise induced hearing loss Medical measuresEnvironmental measures* Pre employment audiogram# reduce exposure to noise* Periodic medical examination for hearing levels#substituation of noisy machines or noisy operation by less noisy one# segregation of noisy machines in remote places# isolation of noisy machines by using sound absorbing materials to reduce noise* Personal protective devices as ear plugs & ear muffs* Health education about hazardes of noise