Acoustics is the interdisciplinary sciences that always

 deals with the study of sound, ultrasound and infrasound (all mechanical waves in gases, liquids, and solids). A scientist who works in the field of acoustics is an acoustician. The application of acoustics in technology is called acoustical engineering. There is often much overlap and interaction between the interests of acousticians and acoustical engineers. 

Hearing is one of the most crucial means of survival in the animal world, and speech is one of the most distinctive characteristics of human development and culture. So it is no surprise that the science of acoustics spreads across so many facets of our society - music, medicine, architecture, industrial production, warfare and more. Art, craft, science and technology have provoked one another to advance the whole, as in many other fields of knowledge. This article is about audible acoustic waves. ... For other uses, see Ultrasound (disambiguation). ... Infrasound is sound with a frequency too low to be detected by the human ear. ... Acoustical engineering is the branch of engineering dealing with sound and vibration. ... Hearing is the following: Hearing is the sense by which sound is perceived. ... Look up speech, speaking, utter, gab in Wiktionary, the free dictionary. ...

The word "acoustic" is derived from the ancient Greek word ακουστός, meaning able to be heard (Woodhouse, 1910, 392). The Latin synonym is "sonic". After acousticians had extended their studies to frequencies above and below the audible range, it became conventional to identify these frequency ranges as "ultrasonic" and "infrasonic" respectively, while letting the word "acoustic" refer to the entire frequency range without limit. Sine waves of various frequencies; the lower waves have higher frequencies than those above. ...

History of acroustics

Early research in acoustics

The fundamental and the first 6 overtones of a vibrating string. Pythagoras was the first to study this phenomenon.

The science of acroustics had its beginnings in the Greek and Roman cultures between the 6th century BCE and 1st century BCE. It began with music, which had been practised as an art for thousands of years, but was not evidently studied in a scientific manner until Pythagoras took an interest in the nature of musical intervals. He wanted to know why some intervals seemed more beautiful than others, and he found answers in terms of numerical ratios. Aristotle (384-322 BC) understood that sound consisted of contractions and expansions of the air "falling upon and striking the air which is next to it...", a very good expression of the nature of wave motion. In about 20 BC, the Roman architect and engineer Vitruvius wrote a treatise on the acoustical properties of theatres including discussion of interference, echoes, and reverberation - the beginnings of architectural acoustics. Image File history File links Metadata Size of this preview: 576 × 599 pixelsFull resolution (6064 × 6309 pixel, file size: 1,016 KB, MIME type: image/jpeg) This is image is made by me and everybody is allowed to use it. ... Image File history File links Metadata Size of this preview: 576 × 599 pixelsFull resolution (6064 × 6309 pixel, file size: 1,016 KB, MIME type: image/jpeg) This is image is made by me and everybody is allowed to use it. ... A fundamental is something that cannot be built out of more basic things, which other things are built upon. ... Approximate harmonic overtones on a string An overtone is a natural resonance or vibration frequency of a system. ... Ancient Rome was a civilization that grew from a small agricultural community founded on the Italian Peninsula circa the 9th century BC to a massive empire straddling the Mediterranean Sea. ... Pythagoras of Samos (Greek: ; born between 580 and 572 BC, died between 500 and 490 BC) was an Ionian Greek mathematician[1] and founder of the religious movement called Pythagoreanism. ... For other uses, see Aristotle (disambiguation). ... Surface waves in water This article is about waves in the most general scientific sense. ... Marcus Vitruvius Pollio (born c. ...

The physical understanding of acoustical processes advanced rapidly during and after the Scientific Revolution. Galileo (1564-1642) and Mersenne (1588-1648) independently discovered the complete laws of vibrating strings (completing what Pythagoras had started 2000 years earlier). Galileo wrote "Waves are produced by the vibrations of a sonorous body, which spread through the air, bringing to the tympanum of the ear a stimulus which the mind interprets as sound", a remarkable statement that points to the beginnings of physiological and psychological acoustics. Experimental measurements of the speed of sound in air were carried out successfully between 1630 and 1680 by a number of investigators including Mersenne. Meanwhile Newton (1642-1727) derived the relationship for wave velocity in solids, a cornerstone of physical acoustics (Principia, 1687). This article is about the period or event in history. ... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... For the primes named after Marin Mersenne, see Mersenne prime. ... Look up vibration in Wiktionary, the free dictionary. ... For other uses, see Ear (disambiguation). ... For other uses, see Speed of sound (disambiguation). ...

The Age of Enlightenment and onward

The eighteenth century saw major advances in acoustics at the hands of the great mathematicians of that era, who applied the new techniques of the calculus to the elaboration of wave propagation theory. In the nineteenth century the giants of acoustics were Helmholtz in Germany, who consolidated the field of physiological acoustics, and Lord Rayleigh in England, who combined the previous knowledge with his own copious contributions to the field in his monumental work "The Theory of Sound". Also in the 19th century, Wheatstone, Ohm, and Henry developed the analog between electricity and acoustics. Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ... John William Strutt, 3rd Baron Rayleigh (12 November 1842 – 30 June 1919) was an English physicist who (with William Ramsay) discovered the element argon, an achievement that earned him the Nobel Prize for Physics in 1904. ...

The twentieth century saw a burgeoning of technological applications of the large body of scientific knowledge that was by then in place. The first such application was Sabine’s groundbreaking work in architectural acoustics, and many others followed. Underwater acoustics was used for detecting submarines in the first World War. Sound recording and the telephone played important roles in a global transformation of society. Sound measurement and analysis reached new levels of accuracy and sophistication through the use of electronics and computing. The ultrasonic frequency range enabled wholly new kinds of application in medicine and industry. New kinds of transducers (generators and receivers of acoustic energy) were invented and put to use. Methods and media for sound recording are varied and have undergone significant changes between the first time sound was actually recorded for later playback until now. ...

Fundamental concepts of acoustics

The study of acoustics revolves around the generation, propagation and reception of mechanical waves and vibrations.

The steps shown in the above diagram can be found in any acoustical event or process. There are many kinds of cause, both natural and volitional. There are many kinds of transduction process that convert energy from some other form into acoustical energy, producing the acoustic wave. There is one fundamental equation that describes acoustic wave propagation, but the phenomena that emerge from it are varied and often complex. The wave carries energy throughout the propagating medium. Eventually this energy is transduced again into other forms, in ways that again may be natural and/or volitionally contrived. The final effect may be purely physical or it may reach far into the biological or volitional domains. The five basic steps are found equally well whether we are talking about an earthquake, a submarine using sonar to locate its foe, or a band playing in a rock concert. This article is about the natural seismic phenomenon. ...

The central stage in the acoustical process is wave propagation. This falls within the domain of physical acoustics. In fluids, sound propagates primarily as a pressure wave. In solids, mechanical waves can take many forms including longitudinal waves, transverse waves and surface waves. A subset of the phases of matter, fluids include liquids and gases, plasmas and, to some extent, plastic solids. ... Longitudinal waves, also referred to as compressional waves or pressure waves, are waves that have vibrations along the their direction of travel. ... A light wave is an example of a transverse wave. ... In physics, a surface wave is a wave that is guided along the interface between two different media for a mechanical wave, or by a refractive index gradient for an electromagnetic wave. ...

Acoustics looks first at the pressure levels and frequencies in the sound wave. Transduction processes are also of special importance.

Wave propagation: pressure levels

In fluids such as air and water, sound waves propagate as disturbances in the ambient pressure level. While this disturbance is usually small, it is still noticeable to the human ear. The smallest sound that a person can hear, known as the threshold of hearing, is nine orders of magnitude smaller than the ambient pressure. The loudness of these disturbances is called the sound pressure level, and is measured on a logarithmic scale in decibels. Mathematically, sound pressure level is defined It has been suggested that this article or section be merged into Sound pressure. ...

where P_ref is the threshold of hearing and P is the change in pressure from the ambient pressure. The following table gives a few examples of sounds and their strengths in decibels and Pascals ^[1].

Wave propagation: frequency

Physicists and acoustic engineers tend to discuss sound pressure levels in terms of frequencies, partly because this is how our ears interpret sound. What we experience as "higher pitched" or "lower pitched" sounds are pressure vibrations having a higher or lower number of cycles per second. In a common technique of acoustic measurement, acoustic signals are sampled in time, and then presented in more meaningful forms such as octave bands or time frequency plots. Both these popular methods are used to analyze sound and better understand the acoustic phenomenon. For an alternative meaning, see ear (botany). ...

The entire spectrum can be divided into three sections: audio, ultrasonic, and infrasonic. The audio range falls between 20 Hz and 20,000 Hz. This range is important because its frequencies can be detected by the human ear. This range has a number of applications, including speech communication and music. The ultrasonic range refers to the very high frequencies: 20,000 Hz and higher. This range has shorter wavelengths which allows better resolution in imaging technologies. Medical applications such as ultrasonography and elastography rely on the ultrasonic frequency range. On the other end of the spectrum, the lowest frequencies are known as the infrasonic range. These frequencies can be used to study geological phenomenon such as earthquakes. Hz or hz may mean: Herero language (ISO 639 alpha-2, hz) Hertz, unit of frequency This is a disambiguation page — a list of articles associated with the same title. ...

Transduction in acoustics

An inexpensive low fidelity 3.5 inch driver, typically found in small radios

A transducer is just a device for converting one form of energy into another. In an acoustical context, this usually means converting sound energy into electrical energy (or vice versa). For nearly all acoustic applications, some type of acoustic transducer is necessary. Acoustic transducers include loudspeakers, microphones, hydrophones, sonar projectors, and ultrasound imaging equipment. Most of these are an electromechanical devices that converts an electric signal to or from a sound pressure wave. Image File history File linksMetadata Download high-resolution version (1024x768, 166 KB)By Richard Wheeler (Zephyris) 2007. ... Image File history File linksMetadata Download high-resolution version (1024x768, 166 KB)By Richard Wheeler (Zephyris) 2007. ... This article is about transducers in engineering. ... A loudspeaker is a device which converts an electrical signal into sound. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... A hydrophone is a sound-to-electricity transducer for use in water or other liquids, analogous to a microphone for air. ... This article is about underwater sound propagation. ...

One common example is a subwoofer used to generate lower notes in speaker audio systems. Subwoofers generate waves using a suspended diaphragm which oscillates, sending off pressure waves. Electret microphones are a common type of microphone which operate using a similar principle. As the sound wave strikes the electret's surface, the surface moves and sends off an electrical signal.

Divisions of acoustics

Countless subfields have been created as we have perfected our understanding of the underlying physics of acoustics. The table below shows sixteen major subfields of acoustics established in the PACS classification system. These have been grouped into three domains: physical acoustics, biological acoustics and acoustical engineering.

Acoustical engineering is the branch of engineering dealing with sound and vibration. ... Aeroacoustics is a branch of acoustics that deals with the study of aerodynamic sound. ... This article or section is in need of attention from an expert on the subject. ... Look up vibration in Wiktionary, the free dictionary. ... Bioacoustics is a cross-disciplinary science that combines biology and acoustics. ... This article or section does not cite its references or sources. ... The auditory system is the sensory system for the sense of hearing. ... Psychoacoustics is the study of subjective human perception of sounds. ... Bold text This article does not cite any references or sources. ... Signal processing is the processing, amplification and interpretation of signals, and deals with the analysis and manipulation of signals. ... It has been suggested that Acoustic transmission be merged into this article or section. ... The word transduction has several meanings: In developmental psychology, transduction is reasoning from specific cases to specific cases, typically employed by children. ... Ultrasound is sound with a frequency greater than the upper limit of human hearing, approximately 20 kilohertz. ...

See also

Wikisource has original text related to this article:

Acoustics

• Acoustic emission
• Acoustic impedance
• Acoustic levitation
• Acoustic location
• Acoustic thermometry
• Audiology
• Auditory system
• Diffraction
• Doppler effect
• Helioseismology
• Lamb wave
• Linear elasticity
• Medical ultrasonography
• Noise control
• Noise pollution
• P-wave
• Phonon
• Rayleigh wave
• Room Acoustics
• S-wave
• Seismology
• Sonochemistry
• Sound pressure
• Soundproofing
• Shock wave
• Sonic boom
• Sonoluminescence
• Surface acoustic wave
• Thermoacoustics
• Wave equation

Image File history File links Wikisource-logo. ... The original Wikisource logo. ... Acoustic Emission (AE) is a naturally occurring phenomenon whereby external stimuli such as mechanical loading generate sources of elastic waves. ... The acoustic impedance Z (or sound impedance) is a frequency f dependent parameter and is very useful, for example, for describing the behaviour of musical wind instruments. ... Acoustic levitation is a method for suspending matter in a fluid by using acoustic radiation pressure from intense sound waves in the fluid. ... Acoustic location is the art and science of using sound to determine the distance and direction of something. ... Acoustic Thermometry of Ocean Climate (ATOC) is an ambitious idea to observe the state the worlds oceans, and the ocean climate in particular, using long-range acoustic transmissions. ... Audiology is the branch of science that studies hearing, balance, and their disorders. ... The auditory system is the sensory system for the sense of hearing. ... The intensity pattern formed on a screen by diffraction from a square aperture Diffraction refers to various phenomena associated with wave propagation, such as the bending, spreading and interference of waves passing by an object or aperture that disrupts the wave. ... A source of waves moving to the left. ... A computer generated image showing the pattern of a p-mode solar acoustic oscillation both in the interior and on the surface of the sun. ... // Linear elasticity The linear theory of elasticity models the macroscopic mechanical properties of solids assuming small deformations. ... Sonography redirects here. ... Noise Control: Building Interior Noise Control Reduction of Reverberation is one function of noise control, most often refered to when speaking of building and room interiors. ... Noise pollution (or environmental noise in technical venues) is displeasing human or machine created sound that disrupts the environment. ... Plane P-wave Representation of the propagation of a P-wave on a 2d grid (empirical shape) One of the two types of elastic body waves (named because they travel through the body of the Earth) that are produced by earthquakes and recorded by seismometers. ... Normal modes of vibration progression through a crystal. ... Rayleigh waves, also known as the Rayleigh-Lamb Wave or ground roll, are a type of surface wave. ... A type of seismic wave, the S-wave moves in a shear or transverse wave, so motion is perpendicular to the direction of wave propagation. ... Seismology (from the Greek seismos(σεισμός) = earthquake and λόγος,logos = knowledge ) is the scientific study of earthquakes and the propagation of elastic waves through the Earth. ... In chemistry, the study of sonochemistry is concerned with understanding the effect of sonic waves and wave properties on chemical systems. ... Sound pressure is the pressure deviation from the local ambient pressure caused by a sound wave. ... Soundproofing is any means of to reducing the intensity of sound with respect to a specified source and receptor. ... Introduction The shock wave is one of several different ways in which a gas in a supersonic flow can be compressed. ... For other uses, see Sonic boom (disambiguation). ... Long exposure image of multi-bubble sonoluminescence created by a high intensity ultrasonic horn immersed in a beaker of liquid. ... A surface acoustic wave (SAW) is a kind of wave used in piezoelectric devices called SAW devices in electronics circuits. ... Sonic or thermoacoustic refrigeration is a technology that uses high-amplitude sound waves in a pressurised gas to pump heat from one place to another. ... The wave equation is an important partial differential equation that describes the propagation of a variety of waves, such as sound waves, light waves and water waves. ...

References

Benade, Arthur (1976), Fundamentals of Musical Acoustics, New York, NY, United States: Dover .

Rayleigh, J. W. S. (1894), The Theory of Sound, New York, NY, United States: Dover .

Wilson, Charles E. (2006), Noise Control, Malabar, FL, United States: Krieger Publishing Company .

Stephens, R. W. B. and Bate, A. E. (1966), Acoustics and Vibrational Physics, 2nd Ed., London, UK: Edward Arnold .