C 13 
XIX. On Sounds inaudible by certain ears. By William Hyde 
Wollaston, M. D. P. R. S, 
Read June 29, 1820. 
It is not my intention to occupy the time of this Society, 
with the consideration of that mere general dullness to the 
impression of all kinds of sound which constitutes ordinary 
deafness, but to request its attention to certain peculiarities 
that I have observed with respect to partial insensibility in 
different states of the ear, and in different individuals ; for I 
have found that an ear, which would be considered as per- 
fect with regard to the generality of sounds, may, at the 
same time, be completely insensible to such as are at one or 
the other extremity of the scale of musical notes, the hearing 
or not hearing of which seems to depend wholly on the 
pitch or frequency of vibration constituting the note, and not 
upon the intensity or loudness of the noise. 
Indeed, although persons labouring under common deaf- 
ness have an imperfect perception of all sounds, the degree 
of indistinctness of different sounds is commonly not the 
same ; for it will be found upon examination, tint they usu- 
ally hear sharp sounds much better than low ones ; they dis- 
tinguish the voices of women and children better than the 
deeper tones in which men commonly speak ; and it may be 
remarked, that the generality of persons accustomed to speak 
to those who are deaf, seem practically aware of this differ- 
