Monday, May 9, 2016

The Physics of Sound Pt 1



There are a myriad of pathways that one can take toward becoming a musician.  Some of us learn from family members, friends, books, instructional videos, listening to other musicians and so on.  Very often however we begin our journey with a teacher in or outside of an educational facility.  We are often initially taught the fundamentals of reading standard music notation and taught the techniques to recreate the tones and sounds that we see on paper without actually understanding what sound is and how it works.

According to the Encyclopedia Britanica, sound is; a mechanical disturbance from a state of equilibrium that propagates through an elastic material medium.  

Sound is defined by ANSI/ASA S1.1-2013 as "(a) Oscillation in pressure, stress, particle displacement, particle velocity, etc., propagated in a medium with internal forces (e.g., elastic or viscous), or the superposition of such propagated oscillation. (b) Auditory sensation evoked by the oscillation described in."

To expound upon this concept further; sound is a disturbance in air pressure; a vibration, energy.  For example, our vocal chords vibrate and cause a disturbance, change or fluctuation in air pressure.  The vibration in the form of a wave propagates from the source at a speed of 343.2 meters per second (1,126 ft/s; 1,236 km/h; 768 mph; 667 kn). Sound waves travel through the outer ear, are modulated by the middle ear, and are transmitted to the vestibulocochlear nerve in the inner ear. This nerve transmits information to the temporal lobe of the brain, where it is registered as sound.


The frequency of the sound is directly correlated to the speed of the vibration.  This vibration or frequency is measured in a unit of measurement called Hertz(Hz).  1 Hertz is one cycle or vibration per second.  A human being with optimal hearing can detect or hear sounds with frequencies between 20Hz to 20,000Hz (20kHz).  However due to hearing damage generally caused by exposure to loud sounds which is measured in decibels; after childhood adults can generally hear up to about 15kHz.

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