There are six experimentally separable ways in which sound waves are analysed, which are Pitch, Duration, Loudness, Timbre, Sonic Texture, and Spatial Location. Pitch is perceived as how “low” or “high” a sound is and represents the cyclic, repetitive nature of the vibrations that make up sound. Duration is perceived as how “long” or “short” a sound is and relates to onset and offset signals created by nerve responses to sounds. 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. Timbre is perceived as the quality of different sounds and represents the pre-conscious allocation of a sonic identity to a sound. Sonic Texture relates to the number of sound sources and interaction between them. Spatial Location represents the cognitive placement of a sound in an environmental context; including the placement of a sound on both the horizontal and vertical plane, the distance from the sound source and the characteristics of the sonic environment. Sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement through a medium such as air or water.
The type of medium sound passes through will determine its speed and wave type. Sound waves can come in the form of either transverse waves or longitudinal waves. Humans can hear sounds from approximately a range of 20 Hertz to 20 Kilo-Hertz. There is a lower pitch at 20 Hertz, and a higher pitch at 20 Kilo-Hertz. Humans can hear between approximately 0 Decibels and 160 Decibels, the measurement of quietness and loudness. The amplitude of sound waves determine the quietness or loudness of the sound exhibited.
Acoustic instruments generate sound physically whereas electronic instruments create sound electrically. There are for different types of acoustic groups: percussion (hit or shaken), wind (woodwind and brass; blown), string (bowed or plucked), and keyboard (played with fingers). An instrument creates sound when part of it vibrates rapidly. Several examples are: the column of air inside a wind instrument, the string of a string instrument, or the stretched skin of a drum all vibrate when played. These vibrations produce sound waves in the air, which we hear as different musical notes. Electronic instruments, such as electronic keyboards, do not make actually sounds in the way an acoustic instrument does. An electronic instrument produces an electric signal that is transmitted to an amplifier and then broadcast through a loudspeaker. Using a process called synthesis, electronic instruments imitate acoustic instruments or create their own noises.