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AitT. XXV . — On Sounds inaudible by certain Ears*, By 
William Hyde Wollaston, M. D. F. R. S. 
It is not my intention to occupy the time of this Society, 
with the consideration of that mere general dullness to the im- 
pression of all kinds of sound which constitutes ordinary deaf- 
ness, 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 perfect with regard 
to the generality of sounds, may, at the same time, be complete- 
ly 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 consti- 
tuting the note, and not upon the intensity or loudness of the 
noise. 
Indeed, although persons labouring under common deafness 
have an imperfect perception of all sounds, the degree of indis- 
tinctness of different sounds is commonly not the same ; for it 
will be found upon examination, that they usually hear sharp 
sounds much better than low ones ; they distinguish the voices 
of women and children better than the deeper tones in which 
men commonly speak ; and it may be remarked, that the gene- 
rality of persons accustomed to speak to those who are deaf, 
seem practically aware of this difference, and, even without re- 
flecting tq)on the motives which guide them, acquire a habit of 
speaking to deaf persons in a shriller tone of voice, as a method 
by which they succeed in making them hear more effectually 
than by merely speaking louder. 
In elucidation of this state of hearing, which casually occurs 
as a malady, I have observed, that other ear& may for a time be 
reduced to the same condition of insensibility to low sounds. I 
was originally led to this observation, in endeavouring to inves- 
tigate the cause of deafness in a friend, by trial of different 
modes of closing, or otherwise lessening the sensibility of my own 
* From the Philosophical Transactions for 1820, part ii. p. 306. — 314» As 
this valuable paper is incapable of abridgment, we have presented it to our readers 
in its entire state. 
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