Here is a compilation of term papers on ‘Noise’. Find paragraphs, long and short term papers on ‘Noise’ especially written for school and college students.
Term Paper on Noise
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Term Paper Contents:
- Term Paper on the Definition of Noise
- Term Paper on the Perceived Noisiness
- Term Paper on Nuisance
- Term Paper on the Kinds of Sound
- Term Paper on the Speed of Sound
- Term Paper on Noise Exposure Index (NEI)
- Term Paper on Sonic Booms
- Term Paper on Ultrasound and Infrasound
- Term Paper on Environmental Noise
- Term Paper on the Range of Human Ear
- Term Paper on Measurement of the Intensity of Sound
- Term Paper on the Pervasive Nature of Popular Music
Term Paper # 1. Definition of Noise:
Sounds is the form of energy giving sensation; of hearing and is produced by longitudinal mechanical waves in matter including solid, liquid, and gas and transmitted by oscillation of atoms and molecules of matter.
Although and soft rhythmic sound is the form of music and dance stimulates brain activities, removes boredom and fatigue, but its excessiveness may prove detrimental to living things. Noise is an unwanted sound without agreeable musical quality.
Thus, otherwise sound and; noise can be taken to mean the same thing but in considering our acoustic environment, we must differentiate between these two terms. It is only when the effects of a sound are undesirable that it may be termed as noise.
Encyclopaedia Britainica Defines:
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In acoustics noise is defined as any undesired sound. According to this definition, a sound of church bells may be music to others. Usually, noise is a mixture of many tones combined in a non-musical manner.
Encyclopedia Americana defines it as:
Noise by definitions is unwanted sound- What is pleasant to some ears may be extremely unpleasant to other, depending on a number of psychological factors. The sweetest music, if it disturbs a person who is trying to concentrate or to sleep, is a noise to him, just as the sound of a pneumatic riveting hammer is noise to nearly everyone. In other words, any sound may be noise if circumstances cause it to be disturbing.
The predictive ability of such noise measures can be estimated from the results of social survey data and from laboratory studies. It is obvious, however, that human responses to noise are complex and can take differing forms depending upon attitudinal and environmental factors. These latter factors are hard to quantity, but their relative importance is particularly interesting to note in the overall context of the formulation of criteria for the prediction of annoyance due to noise.
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Term Paper # 2. Perceived Noisiness:
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The subjective impression of the unwantedness of a not unexpected, non-pain of fear-producing sound as part of one’s environment is defined as the attribute of perceived noisiness. Kryter further states that the measurement of estimation of this subjective attribute or quality is of central importance to the evaluation of environmental sounds or noises with regard to their physical content.
Descriptor terms of such a disturbing, unwantedness, unacceptableness, objectionableness, or noisiness fit the total attribute of perceived noisiness and are fairly consistently used by subjects in psychological judgement tests.
The concept of perceived noisiness and its historical development into rating scale units such as PNdB for Perceived Noise Level and EPNdB for Effective Perceived Noise Level has depended upon a clear distinction between loudness and noisiness. In parallel to the use of the sone for loudness, the noy became the subjective unit of noisiness.
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A sound that is judged to be subjectively equal in noisiness to an octave band of random noise centered at 1000 Hz and of sound pressure level 40 dB re 2.10-5 Pa is designated a value of one noy; sounds judged to be twice or three times is noisy are 2 noys and 3 noys, respectively, etc.
Annoyance:
Noise can cause annoyance and frustration as a result of interference, interruption and distraction, when engaged in activities like thinking, conversing, relaxing listening to music, resting or sleep. This can produce stress.
Generally, louder the noise:
(a) Greater number of people likely to be annoyed.
(b) The more annoyed each person is likely to be.
Total, Impulsive or modulated characteristics can make a noise more annoying. A quite background can make it more intensive.
Term Paper # 3. Nuisance:
This term to have a legal connotation and means ‘injurious or obnoxious’ to the community. In the case of noise it implies ‘annoying’ or ‘disturbing’. There is no doubt that the annoyance caused by sound is most closely related to the loudness of that sound. Such effects as masking and other unusual stimuli tend to distract the attention from a particular sound but when that sound becomes so loud that it intrudes upon the sphere of activity of the noise exposed individual then he notices it.
Quite often he chooses to ignore it. This can be for many reasons; he knows what it is, it is something which he has control over, or it is something that he tolerates because he happens to be that sort of individual. In a minority (about 20%) of the population, high sensitivity to noise is shown. A larger group of the population (about 60%) will tolerate quite loud sounds and are not particularly disturbed and there is a small minority who even though they are not deaf, will hardly ever complain about noise.
Thus many standards of measuring noise and annoyance relate the annoyance basically to the loudness of the sound. Corrections are sometimes made for other factors such as pitch, duration, whether or not the sound is impulsive, and whether it goes on during the day or the night.
Term Paper # 4. Kinds of Sound
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The kind of sound—whether noisy musical, abrasive, soothing, displeasing, or pleasant on a combination of characteristics in addition to pitch, amplitude, and loudness. A vibrating object produces many frequencies even though, as with a musical instrument, one tone may predominate.
A blend of many frequencies produces a characteristic sound which in music is called quality. It distinguishes a guitar, for example, from a mandolin. The variations that occur in addition to the fundamental frequency are called overtones or harmonics.
If two objects vibrate at different frequencies, there will result pulsations of loudness called beats. Since the number of beats per second is equal to the difference in frequencies of the two objects, the closer the tones, the beats. When the number of beats reaches about 30 per second from tones that are very close but not quite the same, the sound is very unpleasant.
Musicians call this a form of dissonance. At beats above 30 per second, the frequencies are so close that the human ear cannot detect the beats. Since the ear cannot tell that anything is wrong, the disagreeable sensation disappears.
Whether sound has been pleasant or unpleasant is determined partly by resonance, produced when repeated vibrations of the same frequency create a strong response. A sound box of the right size and shape increases resonance. Sympathetic vibrations are a form of resonance produced in an unattached objects having the same natural resonance at the object that produces that sound.
For example, dishes in a cupboard or a picture on a wall may rattle when a certain note is sounded on the piano. A comparable situation is when a strong wind creates resonant vibrations in a suspension bridge. The bridge creates resonant vibration becomes intense. Soldiers are always ordered break step when crossing a bridge because when marching in unison, they can set up vibrations that may cause the bridge to break apart.
Term Paper # 5. Speed of Sound:
Sound travels at different speeds, depending on the density, elasticity of the medium through which it travels. The denser and less elastic the substance, the slower the speed of the sound waves. Sound travels at a velocity of 1.130 feet per second in air when at a temperature of 20°C (68°F).
This is equal to about 344 meters per second or about 770 miles per hour. When the temperature drops to 0°C (32°F), the air is denser and the sound waves travel at a slightly slower speed, about 1,090 feet per second. The velocity increases about 2 feet (0.6 meter) per second for each centigrade degree rise in temperature, equal to an increase of about 1 foot per second for each Fahrenheit degree.
Water is denser than air but also more elastic. Sound travels through water at a velocity of about 4,800 feet (1,440 meters) per second. Steel is 6,000 times denser than air and this quality retards the movement of sound waves, but steel is also much more elastic than air by a magnitude of 2 million times; therefore, sound travels more rapidly through steel, at a velocity of 16,400 feet (5,000 meters) per second, or about 11,000 miles per hour.
Thus, the speed of sound, regardless of the substance through which it travels, has been much slower than the speed of light, which is 186,282 miles per second. It is easy to estimate the distance from the source of a far-off sound if there is some other signal to identify it, such as a puff of smoke or a flash of light. Five seconds between a lightning flash and a clap of thunder equals a distance of about 1 mile.
Term Paper # 6. Noise Exposure Index (NEI):
Almost all standards quote a maximum peak noise level which should not be exceeded, but the recent concept is that of the maximum allowable noise dose which takes into account both the time varying noise level and its duration. This noise dose is A-weighted equivalent continuous noise level, LEQ which assumes a continuous level of noise over a given duration of 8 hr.
In any 24 hr. period. Actually the noise level fluctuates and LEQ exposure is measured on the principle that higher level of noise are tolerable for a shorter period of time.
The severity of noise exposure is indicated by the noise exposure index (NEI), which includes both the noise level and the exposure duration as follows:
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Where K1, K2, ……… are the actual times the worker is exposed to each noise level above 90 dB (A);
t1, t2,………. are the allowable exposure time (Table 1) for the noise levels to which the worker is exposed.
NEI values are often expressed as percentage of the allowable noise dose. When the NEI values exceed 1, the worker is assumed to be over-dosed.
Term Paper # 7. Sonic Booms:
The flow of air around an aircraft or other object whose speed exceeds the speed of sound (supersonic) has been characterized by the existence of discontinuities in the air known as shock waves. These discontinuities result from the sudden encounter of an impenetrable body with air.
At subsonic speeds, the air seems to be forewarned; thus, it begins its outward flow before the arrival of the leading edge. At supersonic speeds, however, the air in front of the aircraft has been undisturbed, and the sudden impulse at the leading edge creates a region of over-pressure where the pressure is higher than atmospheric pressure.
This overpressure region travels outward with the speed of sound, creating a conical-shaped shock wave called the bow wave that changes the direction of airflow. A second shock wave, the tail wave, has been produced by the tail of the aircraft and is associated with a region where the pressure is lower than normal. This under pressure discontinuity causes the air behind the aircraft to move sideways.
Major pressure changes have been experienced at the ear as the bow and tail shock waves reach an observer. Each of these pressure deviations produce the sensation of an explosive sound—the double crack of a sonic boom. Small objects moving at supersonic speeds also produce both bow and tail shock waves; however, they occur so close together in time that only one crack is heard.
A common misconception has been that a sonic boom is produced when the aircraft first accelerates past the speed of sound. Actually, the shock waves exist during the entire period the aircraft is travelling supersonically, and a sonic boom has been heard each time the shock waves sweep over an observer.
Term Paper # 8. Ultrasound and Infrasound
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Infrasonic:
Sounds which are at frequencies below the range of human hearing (i.e., less than 15 Hz.)
Audio-Sonic:
Sounds which are at frequencies above the range of human hearing (i.e., greater than 20,000 Hz.)
Ultrasonic:
Sounds which are at frequencies above the range of human hearing (i.e., greater than 20,000 Hz.)
A continuous spectrum in which sound pressure in bands of frequency of one cycle/sec. wide is substantially constant over a wide range of frequencies is called white noise. But in urban and industrial environment, the noise comprises of complex tones having different frequencies and amplitudes which are not harmonically related to each other.
The combined effect of these sounds may be called as noise. The characteristics of noise and the perception of hearer depend on the time rate at which sound pressure reaches the ear of the hearer.
Term Paper # 9. Environmental Noise
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Music and speech have been to of humanity’s contributions to the world of sound. Unfortunately, they have been not the only ones. Even from earliest days, our advancing technology has been accompanied by an increase in environmental noise. It is only within recent years, however, that the problem has been recognized as a serious danger to our well-being.
There are three ways to attacking the problem of noise:
(1) Reduce its production through design,
(2) Connect it to an area or exclude it from others, or
(3) Set a limit, by legislation, to the amount that will be tolerated.
Only through an increased understanding of the nature of sound and its interaction with our environment can the first two ways be fully employed to control the mushrooming problem of environmental noise.
Term Paper # 10. Range of Human Ear:
People can hear sound from 16 to 20,000 hz, but this range is reduced with age and other subjective factors. The range of vibration below 16 hz and infra-audible and those above 20,000 hz ultrasonic. Some persons can hear frequencies that others are not able to detect. Many animals (e.g., dogs) can hear sounds inaudible to the human ear, sometimes sound is exposed in psychoacoustic terms, the phon. It takes into consideration intensity and frequency. A sound level of 92 dB at 20 hz has a loudness of 40 phons.
Human ear is known to be sensitive to an extremely wide range intensity from 0 to 180 dB. Here 0 dB is the threshold of hearing while 140 dB is the threshold pain. By threshold, it implies the lowest intensity at which stimulus gets perceptible. Some people feel discomfort even with sound of 85 dB whereas most do not feel discomfort with sound of 115 dB. Pain is usually felt at 140 dB.
Ordinary talk or discussion is having the frequency range from 30-60 dB while noise produced by a jet plane at take-off may exceed 160 dB. The effect on man depends upon the frequency or pitch of the sound. The sound pressure level has been regarded to be of greater loudness for higher pitched than for the lower pitched sound.
Term Paper # 11. Measurement of the Intensity of Sound
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The ISO (International Organization for Standardization) defines noise intensity level as:
L = 20 log10 P/Po = 10 log10 I/Io
Where P equals the measured sonar pressure level given in N/m2;
I equals the measured intensity of sound given in W/m2;
Po equals the pressure level at the limit of audibility for the normal ear when the frequency of emission is 1000 cycles per second;
Io equals the intensity of sound at the limit of audibility for the normal ear when the frequency of emission is 1000 cycles per second.
Sound pressure and sound intensity at the limit of audibility naturally have been found to vary from person to person. For the sake of standardization they have been assigned the values of 2 x 10-5 N/m2 and 10-12 W/m2 respectively. Therefore, when the sound pressure equals 2 x 10-5 N/m2 and the intensity of sound equals 10-12 W/m2 the intensity level of the sound will be equal to 0 decibels.
The relationship between sound pressure, sound intensity and intensity level is given as follows:
The sound does not get perceived by the human ear in the same manner over the whole audible frequency range. Low pitched sounds of high intensity level (decibel count) could not be judged by the human ear to be particularly loud. Similarly, the human ear has been incapable of perceiving vibrations of a frequency much above 20,000 cycles per second, although many animals—such as dog— have been able to detect these sounds.
In order to allow for these facts loudness must either be given in decibels at a given frequency of vibration, or expressed by means of a different system for quantifying sound levels. A method for the latter has been the ISO/R 226 (1961) recommendation which is employing the units ‘phons’.
At a frequency level of 1000 cycles per second the number of phons of a given sound intensity will be equal to the number of decibels. As the frequency of the sound falls, the number of phons falls off, even though the ‘true’ sound level or decibel count remains the same.
There has been a third way of expressing the loudness level of noise. This has been related to the number of phons by the following formula:
log10 S = 0.03 (P – 40)
Where S denotes the loudness in ‘sones’
and P denotes the corrected sound level in phons.
The number of sones of sounds provides a true basis for comparison of the actual perceived noise levels, whereas the number of phons provides the sound level expressed in decibels corrected to a frequency of 1000 cycles per second. The following table compares the value in phons (decibels at 1000 c/s with the number of sones.
If sounds have been produced within a range of about 250 to 8000 cycles per second, little difference exists between the value decibels and the value in phons. It is only when sound frequencies have been very much higher or very much lower that the frequency of the sound must be taken into consideration.
The following table lists sound levels in decibels and their sone equivalents for a number of different environments:
These figures are naturally, somewhat approximate, as individual conditions have been found to vary considerably. By application of the inverse square law, doubling the distance between the observer and the noise source reduce the intensity of the noise to a quarter, and the number of decibels gets reduced by six.
Experience has revealed that the following environmental noise levels will be satisfactory for most people:
Maximum acceptable sound levels inside buildings have been lower than this:
Film, broadcasting and TV studios- 30 dB
Concert halls and theatres- 35 dB
Hospitals, hotels, etc. – 40 dB
Offices, libraries, etc. – 45 dB
Shops, banks, etc. – 50 dB
Restaurants, precision workshops, etc. – 55 dB
One of the recent methods of measuring noise involves tape recording the sound levels at a microphone for about 3 minutes every hour over a 24-hour period and subsequently analysing the sound. Noise is generally made up of components of different pitch mixed in various proportions.
Each component has its own potentiality for noisiness. Noise is very subjective, based on personal evaluation. It differs from man to man, place to place and time to time. It may be said that the degree of unwantedness is a measure of the noisiness of noise.
In India, we have to keep our doors and windows open most of the year, with the result that the level of noise inside the house is almost as high as it is outside. This is because sound behaves somewhat like gas in balloon—even the tiniest opening in the enclosure reduces the enclosure’s effectiveness as a barrier.
The Acoustics Division of National Physical Laboratory, New Delhi has found that an average noise level of cities are quite high. In Delhi, the average is 90 dB, and in Bombay 75 which compare very small with Rio de Janeiro where noise level often bits 130 dB.
Noise from vehicular traffic and rail roads is a major source of pollution in urban areas. Modern buildings using thin walls, coupled at the same time with compact and multistories construction contribute to high noise in cities. At an express way a single truck may generate sound levels exceeding 90 decibels; while truck traffic is generally heavy during the night when ambient background noise levels are low.
Dropping of a pin on the floor produces about two decibels of sound. A marriage procession on an average produces about 80 dB of noise. Diwali crackers are much louder, producing as much as 120 dB. A public meeting causes anywhere between 85 and 90 dB. Market noises range between 72 and 82 dB as shown by various studies.
Term Paper # 12. Pervasive Nature of Popular Music:
The pervasive nature of popular music makes it an easy target of concern about its potential effects on hearing. Whether music gives pleasure or not is a subjective question. Depending on one’s attitude, music can give pleasure, can be intensely stirring or extremely irritating. That it is a source of sound, and sometimes extremely high intensity sound is, however, beyond debate.
In music, one cannot talk of “noise” in the proper sense of the word, as noise has been defined as undesirable sound. However, musicians, conductors of orchestras and the audience are sometimes exposed to sounds upto 116 decibels.
If the sound of an orchestra is considered integrally, as a certain kind of noise, one can see that the sound spectra usually contain many transient, one or more peaks, and gradual dropping in the end. The highest intensity and the highest sound pressure level are produced by pop, jazz, disco and symphony orchestra while the sound level is slightly lower in folk orchestra.
The distribution on the constituents depends on the source of sound and the tonality of the orchestra’s playing, so that this too has to be taken into consideration in interpreting the spectrum obtained. In other words, when the same composition is played in another tonality, the spectrum shifts along the frequency axis, the ratio of constants remaining identical.
Analysis of the sound measurement from different groups of instrument in some orchestras indicates that the highest total sound level is produced by drums. Trumpets and trombones were also found to be quite close to drums, followed by saxophones. The string instrument recorded minimum sound levels, which compared closely to that generated by voice in orchestral accompaniment.
The addition of electronic amplifiers to music has led to much greater sound pressure levels than had previously been possible. Now the smallest group with its 200 watt amplifiers can make more intense sound than a 100 piece symphony orchestra.
It is indeed remarkable that listeners in a concert hall audience of 200 can hear the solo violinist without any form of amplification, whilst in a room one- tenth the size, a pop music group requires amplification of an intensity that may be painful.
Loudspeakers which may be as close as 1 metre to the listeners result in a sound pressure level in the listener’s ear of 120-130 dB. The purpose of high intensity sound in popular music is to produce vegetative effects of a general kind quite apart from imposing sound on the listeners. In order to have a musical ‘trip’ it seems necessary to be above ‘safe’ levels.
