Sound

Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure, caused by a sound wave.

Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz (hertz) or cycles per second, the "normal" limit of human hearing.

The speed of sound is the distance travelled per unit time by a sound wave as it propagates through an elastic medium.

Supersonic speed is a rate of travel of an object that exceeds the speed of sound (Mach 1).

The soundscape is the component of the acoustic environment that can be perceived by humans.

In linguistics, sound symbolism, phonesthesia or phonosemantics is the idea that vocal sounds or phonemes carry meaning in and of themselves.

Hearing, auditory perception, or audition is the ability to perceive sound by detecting vibrations, changes in the pressure of the surrounding medium through time, through an organ such as the ear.

Bloop was an ultra-low-frequency and extremely powerful underwater sound detected by the U.

Sound energy density or sound density is the sound energy per unit volume.

A purr is a tonal fluttering sound made by some species of felids, and two species of genets.

Concert pitch refers to the pitch reference to which a group of musical instruments are tuned for a performance.

A Shepard tone, named after Roger Shepard (born 1929), is a sound consisting of a superposition of sine waves separated by octaves.

Stridulation is the act of producing sound by rubbing together certain body parts.

Phonophobia, also called ligyrophobia or sonophobia, is a fear of or aversion to loud sounds—a type of specific phobia.

The precedence effect or law of the first wavefront is a binaural psychoacoustic effect.

An audio frequency (abbreviation: AF) or audible frequency is characterized as a periodic vibration whose frequency is audible to the average human.

(See also: Soundscape ecology) Acoustic ecology, sometimes called ecoacoustics or soundscape studies, is a discipline studying the relationship, mediated through sound, between human beings and their environment.

Atmospheric diffraction is manifested in the following principal ways: * Optical atmospheric diffraction * Radio wave diffraction is the scattering of radio frequency or lower frequencies from the Earth's ionosphere, resulting in the ability to achieve greater distance radio broadcasting.

Growling or growl is a low, guttural vocalization produced by predatory animals as a warning to others, as a sign of aggression, or to express anger.

Speech Transmission Index (STI) is a measure of speech transmission quality.

A hum is a sound made by producing a wordless tone with the mouth opened or closed, forcing the sound to emerge from the nose.