Without A Sound - Various - The Gas Collection 24
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In physicssound is a vibration that typically propagates as an audible wave of pressure, through a transmission medium such as a gas, liquid or solid. In human physiology and psychologysound is the reception of such waves and their perception by the brain.
Different animal species have varying hearing ranges. A sound wave is thus an acoustic wave that is audible to some ear, although not necessarily a human ear. Acoustics Without A Sound - Various - The Gas Collection 24 the interdisciplinary science that deals with the study of mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound, and infrasound.
A scientist who works in the field of acoustics is an acousticianwhile someone working in the field of acoustical engineering may be called an acoustical engineer. Applications of acoustics are found in almost all aspects of modern society, subdisciplines include aeroacousticsaudio signal processingarchitectural acousticsbioacousticselectro-acoustics, environmental noisemusical acousticsnoise controlpsychoacousticsspeechultrasoundunderwater acousticsand vibration.
Sound is defined as " a Oscillation in pressure, stress, particle displacement, particle velocity, etc. 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 see Longitudinal and transverse wavesbelow. 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 soundthus forming the sound wave. At a fixed distance from the source, the pressurevelocityWithout A Sound - Various - The Gas Collection 24 displacement of the medium vary in time. At an instant in time, the pressure, velocity, and displacement vary in space.
Note that 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 reflectedrefractedor attenuated by the medium. When sound is moving through a medium that does not have constant physical properties, it may be refracted either dispersed or focused. The mechanical vibrations that can be interpreted as sound can 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. Sound is transmitted through gases, plasma, and liquids as longitudinal wavesalso called compression waves.
It requires a medium to propagate. 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 rarefactionwhile transverse waves in solids are waves of alternating shear stress at right angle to the direction of propagation.
Sound waves may be "viewed" using parabolic mirrors and objects that produce sound. The energy carried by an oscillating sound wave converts back and forth between the potential energy of the extra compression in case of longitudinal waves or lateral displacement strain in case of transverse waves of the matter, and the kinetic energy of the displacement velocity of particles of the medium.
Although there are many complexities relating to the transmission of sounds, at the point of reception i. These fundamental elements form the basis of all sound waves. They can be used to describe, in absolute terms, every sound we hear. In order to understand the sound more fully, a complex wave such as the one shown in a blue background on the right of this text, is usually separated into its component parts, which are a combination of various sound wave frequencies and noise.
Sound waves are often simplified to a description in terms of sinusoidal plane waveswhich are characterized by Without A Sound - Various - The Gas Collection 24 generic properties:.
Sometimes speed and direction are combined as a velocity vector ; wave number and direction are combined as a wave vector. Transverse wavesalso known as shear waves, have the additional property, polarizationand are not a characteristic of sound waves. The speed of sound depends on the medium the waves pass through, and is a fundamental property of the material. The first significant effort towards measurement of the speed of sound was made by Isaac Newton. He believed the speed of sound in a particular substance was equal to the square root of the pressure acting on it divided by its density:.
This was later proven wrong when found to incorrectly derive the speed. The French mathematician Laplace corrected the formula by deducing that the phenomenon of sound travelling is not isothermal, as believed by Newton, but adiabatic. Thus, the speed of sound is proportional to the square root of the ratio of the bulk modulus of the medium to its density. Those physical properties and the speed of sound change with ambient conditions.
For example, the speed of sound in gases depends on temperature. The speed of sound is also slightly sensitive, being subject to a second-order anharmonic effect, to the sound amplitude, which means there are non-linear propagation effects, such as the production of harmonics and mixed tones not present in the original sound see parametric array.
If relativistic effects are important, the speed of sound is calculated from the relativistic Euler equations. A distinct use of the term sound from its use in Your Love - Various - Most Valuable New Players (In-store Play) is that in physiology and psychology, where the term refers to the subject of perception by the The Rockin Rewinds - Dole Queue Blues. The field of psychoacoustics is dedicated to such studies.
Webster's dictionary Las Delicias - Various - Tejano Roots : Orquestas Tejanas sound as: "1.
The sensation of hearing, that which is heard; specif. Sensation due to stimulation of the auditory nerves and auditory centers of the brain, usually by vibrations transmitted No Reason - Nick Lowe - Jesus Of Cool a material medium, commonly air, affecting the organ of hearing.
Vibrational energy which occasions such a sensation. Sound is propagated by progressive longitudinal vibratory disturbances sound waves. The physical reception of sound in any hearing organism is limited to a range of frequencies. Other species have different ranges of hearing. As a signal perceived by one of the major sensessound is used by many species for detecting dangernavigationpredationand communication.
Earth's atmospherewaterand virtually any physical phenomenonsuch as fire, rain, wind, surfor earthquake, produces and is characterized by its unique sounds. Many species, such as frogs, birds, marine and terrestrial mammalshave 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. 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. However, in sound perception it can often be used to identify the source of a sound and is an important component of timbre perception see above. Soundscape is the component of the acoustic environment that can be perceived by humans. The acoustic environment is the combination of all sounds whether audible to humans or not within a given area as modified by the environment and understood by people, in context of the surrounding environment.
There are, historically, six experimentally separable ways in which sound waves are analysed. They are: pitchdurationloudnesstimbresonic texture and spatial location. More recent approaches have also considered temporal envelope and temporal fine structure as perceptually relevant analyses.
Pitch is perceived as how "low" or "high" a sound is and represents the cyclic, repetitive nature of the vibrations that make up sound. For simple sounds, pitch relates to the frequency of the slowest vibration in the sound called the fundamental harmonic. In the case of complex sounds, pitch perception can vary. Sometimes individuals identify different pitches for the same sound, based on their personal experience of particular sound patterns.
Selection of a particular pitch is determined by pre-conscious examination of vibrations, including their frequencies and the balance between them. Specific attention is given to recognising potential harmonics. For example: white noise random noise spread evenly across all frequencies sounds higher in pitch than pink noise random noise spread evenly across octaves as white noise has more high frequency content.
Figure 1 shows an example of pitch recognition. During the listening process, each sound is analysed for a repeating pattern See Figure 1: orange arrows ShelteringE - Quarterhawk - Quarterhawk the results forwarded to the auditory cortex as a single pitch of a certain height octave and chroma note name.
Duration is perceived as how "long" or "short" a sound is and relates to onset and offset signals created by nerve responses Without A Sound - Various - The Gas Collection 24 sounds. The duration of a sound usually lasts from the time the sound Without A Sound - Various - The Gas Collection 24 first noticed until the sound is identified as having changed or ceased. For example; in a noisy environment, gapped sounds sounds that stop and start can sound as if they are continuous because the offset messages are missed owing to disruptions from noises in the same general bandwidth.
Figure 2 gives an example of duration identification. When a new sound is noticed see Figure 2, Green arrowsa sound onset message is sent to the auditory cortex. When the repeating pattern is missed, a sound offset messages is sent.
Loudness is perceived as how "loud" or "soft" a sound is and relates to the totalled number of auditory nerve stimulations over short cyclic time periods, most likely over the duration of theta wave cycles. Past around ms this is no longer the case and the duration of Without A Sound - Various - The Gas Collection 24 sound no longer affects the apparent loudness of the sound.
Figure 3 gives an impression of how loudness information is summed over a period of about ms before being sent to the auditory cortex.
Louder signals create a greater 'push' on the Basilar membrane and thus stimulate more nerves, creating a stronger loudness signal. A more complex signal also creates more nerve firings and so sounds louder for the same wave amplitude than a simpler sound, such Silly - PWR BTTM - Pageant a sine Home-Made Things - Cloud Car - Cloud Car. Timbre is perceived as the quality of different sounds e.
This identity is based on information gained from frequency transients, noisiness, unsteadiness, perceived pitch and the spread and intensity of overtones in the sound over an extended time frame. Even though a small section of the wave form from each instrument looks very similar see the expanded sections indicated by the orange arrows in figure 4differences in changes over time between the clarinet and the piano are evident in both loudness and harmonic content.
Less noticeable are the different noises heard, Without A Sound - Various - The Gas Collection 24 as air hisses for the clarinet and hammer strikes for the piano. Sonic texture relates to the number of sound sources and the interaction between them. However texture refers to more than this. The texture of an orchestral piece is very different from the texture of a brass quintet because of the different numbers of players. The texture of a market place is very different from a school hall because of the differences in the various sound sources.
Spatial location see: Sound localization represents the cognitive placement of a sound in an environmental context; including the placement of a sound If My Baby - Mista - Mista both the horizontal and vertical plane, the distance from the sound source and the characteristics of the sonic environment.
This is the main reason why we can pick the sound of an oboe in an orchestra and the words of a single person at a cocktail party.
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