Nasalance

Nasalance is a measure of the degree of velopharyngeal opening in voiced speech [1] formed by computing the ratio of the amplitude of the acoustic energy at the nares, A_n, to amplitude of the acoustic energy at the mouth, A_m. The term nasalance usually refers to this ratio as a percentage,

${\displaystyle {\dfrac {A_{n}}{(A_{m}+A_{n})}}\times 100\%,}$

and thus may be more properly expressed as percent nasalance. The term originated in the work of Fletcher and his associates[2][3] and is now implemented in a number of commercially available devices.[4][5][6] There are small differences in the manner in which nasalance is computed in various devices, and differences[7] in the manner in which the oral and nasal acoustic energies are separated physically, as by a hard separator plate held against the upper lip vs. a two-chamber pneumotachograph mask. However, there have been no conclusive studies of the effect of these differences on a relevant underlying physical variable, such as the area of the velopharyngeal opening.