. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 472 Comparative Animal Physiology tion, the resulting wave of motion will be found to be the algebraic summa- tion of this fundamental and one or more of its multiples. The multiples of the fundamental are referred to as "; In this manner improper adjustment of the anatomical components of the ear (, loose coupling of middle ear bones; unequal tension on the ear drum or basilar membrane, or any other elastic structure) could give rise to harmonics when the stimulus consists of a pure tone
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 472 Comparative Animal Physiology tion, the resulting wave of motion will be found to be the algebraic summa- tion of this fundamental and one or more of its multiples. The multiples of the fundamental are referred to as "; In this manner improper adjustment of the anatomical components of the ear (, loose coupling of middle ear bones; unequal tension on the ear drum or basilar membrane, or any other elastic structure) could give rise to harmonics when the stimulus consists of a pure tone. The intensity of sound waves is defined as the rate of flow of energy through a unit area of the medium. Except for a few unusual conditions (especially those in which standing waves occur), the energy of a sound wave is proportional to the square of the root-mean-square value of the al- ternating pressure. The human ear is responsive to a very wide range in PARTICLE DISPLACEMENT y = ,1 sin (o/. PARTICLE VELOCITY INSTANTANEOUS PRESSURE p = Aiaf'i sin (u>t + 90") TIME Fig. 153. Curves showing various aspects of plane progressive sound waves, together with their equations, in which y=displacement; A=amplitude; w=angular velocity= 2 TT X frequency; trzitime; p,=velocity of particle; }9=alternating pressure; Po=;density of air; c=:velocity of sound. From Stevens and Davis.^" the energy of stimulation, and for convenience in expression and in plotting of data the scale used is logarithmic. A difference of one log unit (base 10) in energy is called a bel, and a difference of one-tenth log unit a decibel. The decibel (abbreviated db) is thus defined as ten times the logarithm of the ratio of two energies, but it can also be applied to two pressures, velo- cities, currents, etc., which are related to energy by a square law. The number of decibels in the ratio of two sound pressures thus become 20 times the loga- rithm of the ratio. The number of decibels (N) relating two
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