by Danlee Mitchell and Jack Logan, Ph.D.

Measurable characteristics of sound are: Duration (length and periodicity), Pitch (highness and lowness), Amplitude (loudness and softness), and Timbre or Harmonic Profile (tone quality or tone color).
Duration of sound means length of sound in time. Duration of sound also deals with sound periodicity. Length of sound is self defining; however, periodicity is the aspect of duration wherein sound occurs in repeated patterns of lengths. Periodicity is the most useful aspect of duration because it gives beat and rhythm to music. A steady, periodic pattern gives beat or pulse (beat and pulse are interchangeable words) to music while repeated patterns of varying periodic lengths gives rhythm to music.
Periodicity is basic to life. It is experienced in every life cycle; for example, chronological age, heartbeat, walking, running, seasons of the year, months of the year, days of the month, hours of the day, and others. Sometimes the periodicity of life is steady and even, while at other times it is more or less uneven &emdash; both can be energizing. Music can be a metaphor for the life process, especially for its periodic aspects. Humankind enjoys the stimulus of music &emdash; it is a concentrated portion of life experience in sound.
Much music contains a steady pulse or beat. This pulse or beat occurs as a steady, reoccurring pattern of sound (for example, a heartbeat). "Beat" in music is very appealing because of its energizing quality - it provides a sense of inner security within the body while at the same time it inspires movement and dance.
If a steady beat is played with an accent (a longer and/or louder note) superimposed over the beat every second, third, fourth, fifth, or sixth beat the musical effect that is produced is called meter.
Sound may be measured by the number of vibrations-per-second (cps, or Hz/Hertz) produced by the vibrating body. If the vibration is steady (for example, 440 Hz), the musical effect produced is known as pitch, tone or note (all three words are interchangeable). Faster vibrating objects have higher pitches while slower vibrating objects have lower pitches. Pitch highness and lowness is relative. Many humans are capable of hearing pitches that range from 20 Hz to 20,000 Hz. Human hearing acuity deteriorates with age.