Sound Waves Ppt Free Download |BEST|
Alec Nigerson
A sound wave is the pattern of disturbance caused by the movement of energy traveling through a medium (such as air, water or any other liquid or solid matter) as it propagates away from the source of the sound.
Sound waves are created by object vibrations and produce pressure waves, for example, a ringing cellphone. The pressure wave disturbs the particles in the surrounding medium, and those particles disturb others next to them, and so on.
The pattern of the disturbance creates outward movement in a wave pattern, like sea water in the ocean. The wave carries the sound energy through the medium, usually in all directions and less intensely as it moves farther from the source.
The idea that sound moves in waves goes back to, at least, the first century B.C. The Roman architect and engineer Vitruvius and the Roman philosopher Boethius each theorized that sound may move in waves. The origin of the modern study of sound is attributed to Galileo Galilei (1564-1642).
When longitudinal waves travel through any given medium, they also include compressions and rarefactions. Compression occurs when particles move close together creating regions of high pressure. In contrast, rarefactions occur in low-pressure areas when particles are spread apart from each other. For example, a vibrating tuning fork creates compressions and rarefactions as the tines move back and forth.
A mechanical wave is transverse when all the particles of the medium, which are solid or liquid (and never gas), vibrate perpendicularly at right angles, up and down, and continue to move in the direction of the wave. For example, the ripples on the surface of a lake are transverse waves. Sound does not move through transverse waves except in special conditions.
When sound waves reach the outer ear, the auricle or pinna collects and channels them through the ear canal, amplifying the sound. The incoming soundwaves travel to an oval-shaped membrane at the end of the ear canal known as the eardrum.
Devices called bone conduction headphones bypass the outer ear by sending sound vibrations through a user's skull directly through the cochlea to the audio nerve. Here, bone -- in effect -- becomes the speaker.
Sound is produced when an object vibrates, creating a pressure wave. This pressure wave causes particles in the surrounding medium (air, water, or solid) to have vibrational motion. As the particles vibrate, they move nearby particles, transmitting the sound further through the medium. The human ear detects sound waves when vibrating air particles vibrate small parts within the ear.
A mechanical wave is a wave that depends on the oscillation of matter, meaning that it transfers energy through a medium to propagate. These waves require an initial energy input that then travels through the medium until the initial energy is effectively transferred. Examples of mechanical waves in nature include water waves, sound waves, seismic waves and internal water waves, which occur due to density differences in a body of water. There are three types of mechanical waves: transverse waves, longitudinal waves, and surface waves.
Why is sound a mechanical wave? Sound waves move through air by displacing air particles in a chain reaction. As one particle is displaced from its equilibrium position, it pushes or pulls on neighboring molecules, causing them to be displaced from their equilibrium. As particles continue to displace one another with mechanical vibrations, the disturbance is transported throughout the medium. These particle-to-particle, mechanical vibrations of sound conductance qualify sound waves as mechanical waves. Sound energy, or energy associated with the vibrations created by a vibrating source, requires a medium to travel, which makes sound energy a mechanical wave.
A pressure wave, or compression wave, has a regular pattern of high- and low-pressure regions. Because sound waves consist of compressions and rarefactions, their regions fluctuate between low and high-pressure patterns. For this reason, sound waves are considered to be pressure waves. For example, as the human ear receives sound waves from the surrounding environment, it detects rarefactions as low-pressure periods and compressions as high-pressure periods.
Transverse waves move with oscillations that are perpendicular to the direction of the wave. Sound waves are not transverse waves because their oscillations are parallel to the direction of the energy transport; however sound waves can become transverse waves under very specific circumstances. Transverse waves, or shear waves, travel at slower speeds than longitudinal waves, and transverse sound waves can only be created in solids. Ocean waves are the most common example of transverse waves in nature. A more tangible example can be demonstrated by wiggling one side of a string up and down, while the other end is anchored (see standing waves video below). Still a little confused? Check out the visual comparison of transverse and longitudinal waves below.
The amplitude of a sound wave determines it relative loudness. In music, the loudness of a note is called its dynamic level. In physics, we measure the amplitude of sound waves in decibels (dB), which do not correspond with dynamic levels. Higher amplitudes correspond with louder sounds, while shorter amplitudes correspond with quieter sounds. Despite this, studies have shown that humans perceive sounds at very low and very high frequencies to be softer than sounds in the middle frequencies, even when they have the same amplitude.
In music, duration is the amount of time that a pitch, or tone, lasts. They can be described as long, short, or as taking some amount of time. The duration of a note or tone influences the timbre and rhythm of a sound. A classical piano piece will tend to have notes with a longer duration than the notes played by a keyboardist at a pop concert. In physics, the duration of a sound or tone begins once the sound registers and ends after it cannot be detected.
When we measure sound, there are four different measurement units available to us. The first unit is called the decibel (dB). The decibel is a logarithmic ratio of the sound pressure compared to a reference pressure. The next most frequently used unit is the hertz (Hz). The hertz is a measure of sound frequency. Hertz and decibels are widely used to describe and measure sounds, but phon and sone are also used. A sone is the perceived loudness of a sound and a phon is the unit of loudness for pure tones. Additionally, the phon refers to subjective loudness, while the sone is the perceived loudness.
An air column is a large, hollow tube that is open on one side and closed on the other. The conditions created by an air column are especially useful for investigating sound characteristics such as intensity and resonance. Check out the video below to see how air columns can be used to investigate nodes, antinodes and resonance.
In physics, sound is a vibration that propagates as an acoustic wave through a transmission medium such as a gas, liquid or solid.In human physiology and psychology, sound is the reception of such waves and their perception by the brain.[1] Only acoustic waves that have frequencies lying between about 20 Hz and 20 kHz, the audio frequency range, elicit an auditory percept in humans. In air at atmospheric pressure, these represent sound waves with wavelengths of 17 meters (56 ft) to 1.7 centimeters (0.67 in). Sound waves above 20 kHz are known as ultrasound and are not audible to humans. Sound waves below 20 Hz are known as infrasound. Different animal species have varying hearing ranges.
Acoustics is the interdisciplinary science that deals with the study of mechanical waves in gasses, liquids, and solids including vibration, sound, ultrasound, and infrasound. A scientist who works in the field of acoustics is an acoustician, while someone working in the field of acoustical engineering may be called an acoustical engineer.[2] An audio engineer, on the other hand, is concerned with the recording, manipulation, mixing, and reproduction of sound.
Applications of acoustics are found in almost all aspects of modern society, subdisciplines include aeroacoustics, audio signal processing, architectural acoustics, bioacoustics, electro-acoustics, environmental noise, musical acoustics, noise control, psychoacoustics, speech, ultrasound, underwater acoustics, and vibration.[3]
Sound is defined as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sensation evoked by the oscillation described in (a)."[4] Sound can be viewed as a wave motion in air or other elastic media. In this case, sound is a stimulus. Sound can also be viewed as an excitation of the hearing mechanism that results in the perception of sound. In this case, sound is a sensation.
Sound can propagate through a medium such as air, water and solids as longitudinal waves and also as a transverse wave in solids. The sound waves are generated by a sound source, such as the vibrating diaphragm of a stereo speaker. The sound source creates vibrations in the surrounding medium. As the source continues to vibrate the medium, the vibrations propagate away from the source at the speed of sound, thus forming the sound wave. At a fixed distance from the source, the pressure, velocity, and displacement of the medium vary in time. At an instant in time, the pressure, velocity, and displacement vary in space. The particles of the medium do not travel with the sound wave. This is intuitively obvious for a solid, and the same is true for liquids and gases (that is, the vibrations of particles in the gas or liquid transport the vibrations, while the average position of the particles over time does not change). During propagation, waves can be reflected, refracted, or attenuated by the medium.[5]
9738318194