A sound wave whose frequency is below the audible range of about 20 → Hz to 20,000 Hz. → sound wave; → ultrasound; → subsonic.
1) sedâ (#); 2) dorvâ
Fr.: 1) son; 2) sain
1) A physiological sensation received by the ear. It is caused by a vibrating
source and transmitted as a longitudinal pressure wave motion through a material
medium such as air.
1) M.E. soun; O.Fr. son, from L. sonus "sound," sonare "to sound;"
PIE base *suen- "to sound;" cf.
Av. xvan- "to sound;"
Pers. xvân-, xvândan "to sing, read;"
Skt. svana- "sound," svan-
"to sound," svanati "it sounds;" O.E. swinn "music, song"
1) Sedâ "sound," most probably a Pers. term, since it exists also in Indo-Aryan
languages: Skt. (late Vedic): sabda "articulate sound, noise,"
Pali and Prakriti: sadda "sound, noise," Sindhi: sadu, sado "shout, call,"
Gujrâti sad "call, voice, echo,"
Marathi: sad "shouting to," Konkani sad "sound,"
Sinhali: sada "sound." Therefore,
sadâ in Ar. "reverberating noise, echo" maybe a loan
from Pers., or a coincidence. Note that for the author of the classical Pers.
dictionary Borhân-e Qâte' (India, 1652 A.D.), the Ar. term is
a loanword from Pers.
divâr-e sedâ, varqe-ye ~
Fr.: mur du son
A sharp increase in aerodynamic drag that occurs as the speed of an aircraft approaches the speed of sound. Also called sonic barrier.
Fr.: énergie acoustique
The energy which → sound waves impart to a medium. Same as acoustic energy.
Fr.: champ acoustique
The distribution of → sound energy in a defined space.
Fr.: horizon sonore
The maximum distance a → sound wave could have traveled through the ionized plasma from the → Big Bang until the → recombination era. It is 150 → Mpc, or bout 500 million → light-years. Sound horizon is the equivalent of the concept of → cosmic horizon, where one replaces → electromagnetic wave by → sound wave. The sound horizon is a fixed physical scale at the → last scattering surface. Cosmological models relate the value of sound horizon to the angle it subtends on the sky today. Same as acoustic horizon and sonic horizon. See also → CMB angular power spectrum.
Fr.: intensité de son
The average → sound power passing through a unit area perpendicular to the direction that the sound is traveling. It is usually expressed in watts per square meter.
sound intensity level
tarâz-e dartanuyi-ye sedâ
Fr.: niveau de l'intensité de son
The expression of sound intensity in decibel units. The sound intensity level (LI), in decibels, is computed as: LI = 10 log (I/I0), where I is the measured sound intensity and I0 is the reference intensity (1 x 10 -12 watt per square meter).
Fr.: puissance de son
The → sound energy emitted by a source per unit time, usually expressed in → watts. Sound power causes → sound pressure.
sound power level
tarâz-e tavân-e sedâ
Fr.: niveau de la puissance de son
The sound energy emitted by a sound source per unit time and expressed in → decibels. Sound power, in → watts, is converted to sound power level in decibels (L), by L = 10 log (W/W0), where W0 is the reference power (1 x 10 -12 watt).
Fr.: pression de son
The periodic fluctuation above and below atmospheric pressure created by an oscillating body which provides the → sound power. Instantaneous sound pressure is the peak value of air pressure.
Fr.: qualité de son
The number of → overtones present in a sound and their respective intensity. Like → loudness, it is a subjective quantity and cannot be measured with instruments.
Fr.: vitesse du son
The velocity of propagation of a → longitudinal wave in a medium under specified conditions. Also known as sonic speed, sonic velocity, acoustic velocity, sound velocity, velocity of sound, speed of sound. The speed of sound is a thermodynamic property that relates to the change in pressure and density of the medium and can be expressed as C = (dP/dρ)1/2, where C is the sound velocity, dP is the change in pressure, and dρ the change in density. It can also be expressed as C = (E/ρ)1/2, where E is the bulk modulus elasticity. This equation is valid for liquids, solids and gases. The sound travels faster through media with higher → elasticity and/or lower density. If a medium is → incompressible the speed of sound is infinite. For → ideal gases, a simple relationship exists between the sound speed and temperature: C = (γR T)1/2, where γ is the → specific heat ratio (CP/CV), and R is the → gas constant. We see that for ideal gases it the speed is independent of pressure. In air at 0°C it is 332 m/sec. The speed of sound in a gas of hydrogen is 1315 m/s. → Mach number.
mowj-e sedâ (#)
Fr.: onde sonore
A → longitudinal wave which when striking the ear gives rise to the sensation of sound. Such waves can be propagated in solids, liquids, and gases. The material particles transmitting sound waves oscillate in the direction of propagation of the wave itself. There is a large range of frequencies within which longitudinal waves can stimulate the human ear and brain to the sensation of hearing. This range is from about 20 → Hz to about 20,000 Hz and is called the audible range. → ultrasound; → infrasound.
Fr.: sondage, radiosondage
1) In geophysics, any penetration of the natural environment for
From Fr. sonder, → sonde.
From gomâné, → sonde, + zani verbal noun of zadan "to do; to strike, beat; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *gwhen- "to strike, kill").
A small, free balloon sent into the upper atmosphere to measure, record, and transmit meteorological reports to a ground station.
1) The quality of being → sound.
Sound with a frequency lying above the audition frequency range, usually taken to be about 20 kHz. → sound wave.