Auditory Information: the sensation produced in the ear or other organ of hearing by the vibration of the surrounding air or other medium. (Oxford) Mechanical vibrations transmitted by an elastic medium; the subjective sensation of hearing something; an audible event. (NCIt)

Physiological confirmation of “filling-in” by involuntary musical imagery has recently been obtained. (Researchers) used “fMRI” to scan the “auditory cortex” while their subjects listened to familiar and unfamiliar songs in which short segments had been replaced by gaps of silence. The silent gaps were not consciously noticed by their subjects, but the researchers observed that these gaps induced greater activation in the auditory association areas than did silent gaps embedded in unknown songs… true for gaps in songs with lyrics and without lyrics. (Sacks, 33) Also referred to as ‘sound.’

Loudness: a purely psychological construct that relates (in poorly understood ways) to the physical amplitude of a "tone." (Levitin, 15) Determined by the intensity, or ‘amplitude,’ of a sound wave. (Brooker, 97) The perceived attribute of a sound which corresponds to the physical attribute of intensity. (MeSH) Because our ears respond to “pressure” changes, any system for measuring loudness should be based on the measurement of pressure. Unfortunately, however, the earliest system of loudness  measurement was adapted from a method for measuring the decrease in strength of electrical signals after they had traveled down a mile of phone cable, so we ended up with a system based on ‘intensity’ rather than pressure. (Powell, 91)

Decibel: the unit of measurement of loudness. (Hockenbury, 96) Zero decibels represents the loudness of the softest sound that humans can hear. As decibels increase, perceived loudness increases. (Brooker, 97) Decibels are a physical measure, whereas loudness is psychological. (Goldstein, 265) A unit of measure representing the intensity of an electrical signal or sound. (NCIt)

Sound Waves: molecules of air vibrating at various frequencies. Do not themselves have pitch. (Levitin, 21) The physical stimuli that produce our sensory experience of sound. Usually produced by the rhythmic vibration of air molecules, but can be transmitted through other media, too, such as water. (Brooker, 97) Sets of "pressure" waves which pass through the air, one after the other, a speed governed by the “density” of the air. (Chapple, 227) Their motion and “oscillations” can be measured, but it takes a animal brain to map them to that internal quality we call "pitch." (Levitin, 21) A type of “non-ionizing radiation.” Sound (acoustic or sonic) radiation with frequencies above the audible range is classified as ‘ultrasonic.’ Sound radiation below the audible range is classified as ‘infrasonic.’ (MeSH)

Amplitude: height of a "sound wave." Measured in units called decibels. The intensity or amount of energy of a wave, reflected in the height of the wave; the amplitude of a sound wave determines a sound’s loudness. (Hockenbury, 96) The magnitude of an oscillation. (NCIt)

Frequency: the rate at which sound waves arrive at your eardrum. For example, the note ‘A,’ has been standardized to a wave arriving with a frequency of 440 vibrations per second. (Powell2, 4) The rate of vibration, or number of waves per second. Measured in units called "hertz." Hertz refers to the number of wave peaks per second. The faster the vibration, the higher the frequency, the closer together the waves are, and the higher the "tone" produced. If you pluck the high ‘E’ and the low ‘E’ strings on a guitar, you’ll notice that the low ‘E’ vibrates far fewer times per second than the high ‘E.’ (Brooker, 97)

Hertz (Hz): a “SI unit” derived unit of frequency; equal to one oscillation (one cycle) per second. (NCIt) The unit of measurement of frequency in cycles per second. After Heinrich Hertz, a German physicist who was the first to transmit radio waves. (Levitin, 19) Humans who are not suffering from any kind of hearing loss can usually hear sounds from 20 Hz to 20,000 Hz. The sound of the average male speaking voice is around 110 Hz, and the average female speaking voice is around 220 Hz. The sound that a singer hits when she causes a glass to break might be 1000 Hz. The lowest note on a standard piano vibrates with a frequency of 27.5 Hz. The highest around 6000 Hz. (Levitin, 22-24)

Spatial Location: where the sound is coming from. (Levitin, 15)