SCIENCEI.C.T PRESENTATION

Sound is a sensation or feeling that we hear. We produce sounds by doing something. The motion of materials or objects causes vibrations. A sound originates in the vibration of an object, which makes the air or another substance around the object vibrate. The vibration of the air moves outward in all directions in the form of a wave

In a drum sound is produced when its membrane vibrates

SOUND

HOW THE SOUND IS PRODUCED ?

The human voice is produced in the larynx, which is a part of the throat. There are two small pieces of tissue that stretch across the larynx with a small opening between them, these tissues are our vocal cords. As we speak, muscles in our larynx tighten the vocal cords making this small opening become narrower. When air from our lungs passes through the tightened cords a vibration is produced. This vibration produces vocal sounds. The tighter the vocal cords, the more rapidly the vocal cords vibrate and the higher the sounds that are produced. This is what causes the human voices to have different pitches.6

HUMAN VOICE

Animals also produce sounds. Almost all mammals, birds, and frogs have vocal cords or similar structures, which allow them to produce sounds in a similar way to humans. However, many other animals produce distinctly different sounds. For example, bees buzz as they fly because of the rapid movement of their wings. Their wings make the air vibrate producing a buzzing sound. A cricket produces a singing type sound as it scrapes parts of its front wings together. Some types of shellfish produce clicks by tapping their claws together.7

ANIMAL VOICE

Musical instruments produce many different sounds in various ways. There are three categories of musical instruments, percussion, string, and wind

Some instruments need to be struck by an object in order to produce a sound, these are called percussion instruments. For example when the membrane of a drum is hit the membrane vibrates, producing a sound, or when a bar of a xylophone is struck, a sound is produced. Each bar of a xylophone produces a different note when struck.

MUSICAL INSTRUMENTS

String instruments, such as a harp or violin, produce sounds when one or more of their strings are plucked, causing them to vibrate. This vibration causes parts of the body of the instrument to vibrate, creating sound waves in the air. The pitch of a stringed instrument depends upon the string's thickness, its length, the distance stretched, and the number of times it vibrates.

Wind instruments, such as a flute or trumpet produce sound when a column of air inside the instrument vibrate. For example, with a trumpet it is the vibrating lips of the player which makes the air column vibrate

HOW THE SOUND IS PROPAGATED ?

A sound wave is a transfer of energy as it travels away from a vibrating source. Sound waves are formed when a vibrating object causes the surrounding medium to vibrate. A medium is a material (solid, liquid or gas) which a wave travels through. As sound waves move through a medium the particles vibrate forwards and backwards. A sound's volume, how loud or soft it is, depends on the sound wave. The more energy put into making a sound or a sound wave, the louder the volume will be. The father a sound wave travels, the more it spreads, this makes it more difficult for us to hear a sound. So the nearer you are to a sound the louder it sounds to us. A sound wave enters the ear and is changed into nerve signals, which are interpreted by the brain.12

Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Through solids, however, it can be transmitted as both longitudinal waves and transverse waves. Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and rarefaction, while transverse waves (in solids) are waves of alternating shear stress at right angle to the direction of propagation.

longitudinal waves

Transverse waves

The behavior of sound propagation is generally affected by three things:

A relationship between density and pressure. This relationship, affected by temperature, determines the speed of sound within the medium.

The propagation is also affected by the motion of the medium itself. For example, sound moving through wind. Independent of the motion of sound through the medium, if the medium is moving, the sound is further transported.

The viscosity of the medium also affects the motion of sound waves. It determines the rate at which sound is attenuated. For many media, such as air or water, attenuation due to viscosity is negligible.

Sound waves are often simplified to a description in terms of sinusoidal plane waves, which are characterized by these generic properties:

Frequency, or its inverse, the periodWavelengthWave numberAmplitudeSound pressureSound intensitySpeed of soundDirection

The perception of sound in any organism is limited to a certain range of frequencies. For humans, hearing is normally limited to frequencies between about 20 Hz and 20,000 Hz (20 kHz)although these limits are not definite. The upper limit Generally decreases with age Human hearing system

PERCEPTION OF SOUND

As a signal perceived by one of the major senses, sound is used by many species for detecting danger, navigation, predation, and communication. Earth's atmosphere, water, and virtually any physical phenomenon, such as fire, rain, wind, surf, or earthquake, produces (and is characterized by) its unique sounds. Many species, such as frogs, birds, marine and terrestrial mammals, have also developed special organs to produce sound. In some species, these produce song and speech. Furthermore, humans have developed culture and technology (such as music, telephone and radio) that allows them to generate, record, transmit, and broadcast sound. The scientific study of human sound perception is known as psychoacoustics.

Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation). During propagation, waves can be reflected, refracted, or attenuated by the medium.[2]

PROPERTIES OF SOUND

Wavelength: The distance between any point on a wave and the equivalent point on the next phase. Literally, the length of the wave.

Amplitude: The strength or power of a wave signal. The "height" of a wave when viewed as a graph.Higher amplitudes are interpreted as a higher volume, hence the name "amplifier" for a device which increases amplitude.

Frequency: The number of times the wavelength occurs in one second. Measured in kilohertz (Khz), or cycles per second. The faster the sound source vibrates, the higher the frequency.Higher frequencies are interpreted as a higher pitch. For example, when you sing in a high-pitched voice you are forcing your vocal chords to vibrate quickly.

Sound travels at 330 meters per second or 740 miles per hour. Sound travels the fastest through solids and the slowest through gases. The faster an object vibrates the higher the frequency, which causes the pitch of the sound to be higher. The higher the frequency sounds come from shorter wavelengths. A wavelength is one aspect of a sound wave. A wavelength is the length of one cycle of sound. The period of a sound wave is the time taken for one wavelength to pass a certain point before a new wave begins to pass by. Longer wavelengths have a lower pitch. The lowest tones that your ears can hear are about 16 vibrations per second, or 16 Hz. Amplitude specifies the sound's loudness. A low amplitude will produce a soft sound and a higher amplitude will produce a louder sound.14

SPEED OF SOUND

The speed of a sound wave refers to how fast the disturbance or wave is passed from particle to particle. Since the speed of a wave is defined as the distance which a point on a wave travels per unit of time, it is often expressed in units of meters/seconds (m/s). The speed of any wave depends upon the properties of the medium through which the wave is traveling. The density of the medium will affect the speed the wave will travel at. A sound wave will travel faster in a less dense material rather than in a more dense material. The equation for the speed of sound is speed = distance/time.

S = 330 meter/secondsS = (330 X 60 X 60 X 3.3)/5280S= 330M/s X 3.3ft./M X 3600sec/hr X 1 mile/5280ft.

This is probably the quality that is simplest to relate to a measureable quantity: the duration of a sound is the time interval between its beginning and end points. Our hearing system is capable of detecting and distinguishing a very short sound, even if it contains only a few cycles of air pressure oscillation.

DURATION

Another attribute of sound that is easily quantified is loudness. It is related to the amplitude of the pressure oscillation in a sound wave. Our perception extends over such a broad range of amplitudes (with the perceptible limits depending on frequency) that we use a logarithmic scale.

LOUDNESS

Noise pollution is excessive, displeasing human, animal or machine-created environmental noise that disrupts the activity or balance of human or animal life. The word noise comes from the Latin word nauseas, meaning seasickness.The source of most outdoor noise worldwide is mainly construction and transportation systems, including motor vehicle noise, aircraft noise and rail noise.Poor urban planning may give rise to noise pollution, since side-by-side industrial and residential buildings can result in noise pollution in the residential area.

NOISE POLLUTION

Noise health effects are both health and behavioral in nature. The unwanted sound is called noise. This unwanted sound can damage physiological and psychological health. Noise pollution can cause annoyance and aggression, hypertension, high stress levels, tinnitus, hearing loss, sleep disturbances, and other harmful effects.

Furthermore, stress and hypertension are the leading causes to health problems, whereas tinnitus can lead to forgetfulness, severe depression and at times panic attacks.Chronic exposure to noise may cause noise-induced hearing loss. Older males exposed to significant occupational noise demonstrate significantly reduced hearing sensitivity than their non-exposed peers, though differences in hearing sensitivity decrease with time and the two groups are indistinguishable by age 79. A comparison of Maaban tribesmen, who were insignificantly exposed to transportation or industrial noise, to a typical U.S. population showed that chronic exposure to moderately high levels of environmental noise contributes to hearing loss.

High noise levels can contribute to cardiovascular effects and exposure to moderately high levels during a single eight hour period causes a statistical rise in blood pressure of five to ten points and an increase in stress and vasoconstriction leading to the increased blood pressure noted above as well as to increased incidence of coronary artery disease.Noise pollution is also a cause of annoyance. A 2005 study by Spanish researchers found that in urban areas households are willing to pay approximately four Euros per decibel per year for noise reduction.

EFFECTS OF NOISE POLLUTION

Technology to mitigate or remove noise can be applied as follows:There are a variety of strategies for mitigating roadway noise including: use of noise barriers, limitation of vehicle speeds, alteration of roadway surface texture, limitation of heavy vehicles, use of traffic controls that smooth vehicle flow to reduce braking and acceleration, and tire design. An important factor in applying these strategies is a computer model for roadway noise, that is capable of addressing local topography, meteorology, traffic operations and hypothetical mitigation. Costs of building-in mitigation can be modest, provided these solutions are sought in the planning stage of a roadway project.

The sound tube designed to reduce roadway noise without distracting from the area's aesthetics.

BY

JYOTHIS

GEORGE