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Chegu vidyalayam: 

Chegu vidyalayam By P.Deveesujan, CH.Vineethsai,SK.Rasheed


Introduction Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid , liquid , or gas , composed of frequencies within the range of hearing. 1 Sound also travels through plasma .

Propagation of Sound: 

Propagation of Sound 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). Sound that is perceptible by humans has frequencies from about 20 Hz to 20,000 Hz. In air at standard temperature and pressure , the corresponding wavelengths of sound waves range from 17 m to 17 mm. During propagation, waves can be reflected , refracted , or attenuated by the medium.

Percipation of sound: 

Percipation of sound 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 although these limits are not definite. The upper limit generally decreases with age. Other species have a different range of hearing. 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 its unique sounds.

Physics of sound: 

Physics of sound The mechanical vibrations that can be interpreted as sound are able to travel through all forms of matter : gases , liquids , solids , and plasmas . The matter that supports the sound is called the medium . Sound cannot travel through a vacuum

Speed of sound: 

Speed of sound The speed of sound depends on the medium the waves pass through, and is a fundamental property of the material. In general, the speed of sound is proportional to the square root of the ratio of the elastic modulus (stiffness) of the medium to its density . Those physical properties and the speed of sound change with ambient conditions


Acoustics Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, 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 acoustics technology may be called an acoustical or audio engineer


Noise Noise is a term often used to refer to an unwanted sound. In science and engineering, noise is an undesirable component that obscures a wanted signal.


Pitch Pitch is a perceptual property that allows the ordering of sounds on a frequency -related scale . 1 Pitches are compared as "higher" and "lower" in the sense associated with musical melodies , 2 which require sound whose frequency is clear and stable enough to distinguish from noise. 3 Pitch is a major auditory attribute of musical tones , along with duration , loudness , and timbre

Doppler effect: 

Doppler effect The Doppler effect (or Doppler shift ), named after the Austrian physicist Christian Doppler , who proposed it in 1842 in Prague , is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession

Ultra sound: 

Ultra sound Ultrasound is a cyclic sound pressure wave with a frequency greater than the upper limit of the human hearing range . Ultrasound is thus not separated from "normal" (audible) sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is approximately 20 kilohertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz

Sound proofing: 

Sound proofing Soundproofing is any means of reducing the sound pressure with respect to a specified sound source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles , or using active antinoise sound generators


Phonons Normal modes of vibration progression through a crystal . The amplitude of the motion has been exaggerated for ease of viewing; in an actual crystal, it is typically much smaller than the lattice spacing . In physics , a phonon is a collective excitation in a periodic, elastic arrangement of atoms or molecules in condensed matter, such as solids and some liquids . Often referred to as a quasiparticle , 1 it represents an excited state in the quantum mechanical quantization of the modes of vibrations of elastic structures of interacting particles


Resonanse In physics , resonance is the tendency of a system to oscillate with greater amplitude at some frequencies than at others. Frequencies at which the response amplitude is a relative maximum are known as the system's resonant frequencies , or resonance frequencies . At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy .


Timbre In music , timbre ( -bər (American English), -bər (British English), or ) also known as tone color or tone quality from psychoacoustics , is the quality of a musical note or sound or tone that distinguishes different types of sound production, such as voices and musical instruments , string instruments, wind instruments, and percussion instruments. The physical characteristics of sound that determine the perception of timbre include spectrum and envelope

Sound Localisation: 

Sound Localisation Sound localization refers to a listener's ability to identify the location or origin of a detected sound in direction and distance. It may also refer to the methods in acoustical engineering to simulate the placement of an auditory cue in a virtual 3D space The sound localization mechanisms of the mammalian auditory system have been extensively studied. The auditory system uses several cues for sound source localization, including time- and level-differences between both ears, spectral information, timing analysis, correlation analysis, and pattern matching

Signal Tone: 

Signal Tone A signal tone or signalling tone (or signaling tone) is a steady periodic sound used to indicate a condition, for example on a telephone line or as an audible warning


Reverberation is the persistence of sound in a particular space after the original sound is produced. 1 A reverberation, or reverb , is created when a sound is produced in an enclosed space causing a large number of echoes to build up and then slowly decay as the sound is absorbed by the walls and air Reverberation


Beat Diagram of beat frequency In acoustics , a beat is an interference between two sounds of slightly different frequencies , perceived as periodic variations in volume whose rate is the difference between the two frequencies


Diffraction Diffraction refers to various phenomena which occur when a wave encounters an obstacle. In classical physics, the diffraction phenomenon is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings


Echo In audio signal processing and acoustics , an echo (plural echoes ) is a reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room


Music Music is an art form whose medium is sound and silence. Its common elements are pitch (which governs melody and harmony ), rhythm (and its associated concepts tempo , meter , and articulation ), dynamics , and the sonic qualities of timbre and texture . The word derives from Greek

Audio bit depth: 

Audio bit depth In digital audio , bit depth describes the number of bits of information recorded for each sample . Bit depth directly corresponds to the resolution of each sample in a set of digital audio data . Common examples of bit depth include CD quality audio, which is recorded at 16 bits, and DVD-Audio , which can support up to 24-bit audio

Auditory imagery: 

Auditory imagery Auditory imagery is a form of mental imagery that is used to organize and analyze sounds when there is no external auditory stimulus present. This form of imagery is broken up into a couple of auditory modalities such as verbal imagery or musical imagery. This modality of mental imagery differs from other sensory images such as motor imagery or visual imagery