A NEW AND UNIFORM METHOD OF RECORDING THE 
HEARING POWER IN OTOLOGICAL PRACTICE. 
By J. S. Prout, M.D., Surgeon to the Brooklyn, Eye and Ear 
Hospital, &c. &c., Brooklyn, N. Y.- 
In otological practice we constantly feel 
the necessity for a reliable test for the hear- 
ing. For want of anything better we use 
the ticking of a watch, the voice spoken 
and whispered, tuning forks, &c. &c. The 
accuracy with which we measure the visual 
power by Snellen’s test-types, and record 
the results obtained, cannot be arrived at 
by means of any of the usual sound makers 
(sonofactors), nor will it be until an instru- 
ment can be made which shall always pro- 
duce uniform tones. These tones must be 
arbitrarily assented to as relatively, not ab- 
solutely, correct, just as the visual angle of 
five minutes, on which Snellen forms his 
test-types, is arbitrarily chosen, and “ does 
not afford us an absolute but only a rela- 
—tive value.’' For tins reason the attempt 
to invent a perfect sonofactor for testing 
the hearing power should be encouraged. 
In the mean time the sources of sound al- 
ready mentioned must continue to be used 
in recording our observations. 
A short formula for expressing the results 
thus obtained has long seemed to me to be 
necessary—something approaching the bre- 
vity of that used for recording the vision. 
This is based on the fact that the visual 
power is expressed by a fraction the nume- 
rator of which is the utmost distance at 
which the types are recognized (d), and 
the denominator the distance at which they 
appear at an angle of 5 minutes (D), thus 
giving the formula V = J. I hold it to be 
a mistake ever to reduce this fraction to 
lower terms. If not so reduced, V =-J, 
or Y = Ag, or V = §g, means that type 
No. 1, No. 10, or No. 20, was read at one, 
ten tor twenty feet, and expresses by its 
own terms, without any conventional un- 
derstanding , just what test was used. In 
ordinary usage, the formula Y == 1 is intend- 
ed to express the fact that type No. 20 was 
read at twenty feet, but it is more simple 
and straightforward to say in such a case 
V = §§, and it is very little more trouble. 
To return to the hearing : for nearly 
three years I have recorded the hearing 
power as a fraction, the numerator of which 
is the distance at which the particular 
sound is heard, the denominator the dis- 
tance at which it should be heard by an ear 
of good average hearing power. This de- 
nominator must vary according to the sono- 
factor used, and should generally be ex- 
pressed in inches. 
For still further simplification, and that 
the method may be adapted to international 
use, 1 suggest the following abbreviations : 
A. D., auris dextra, instead of right ear 
or R. E. ; A. S., auris sinistra; P. A., P. 
aud., potentia auditus, hearing power; V,, 
vox, the spoken voice; Y. S.. vox susur- 
rata, whispered voice—or simply S., susur- 
rus, a whisper ; H., horologium, the watch. 
If this system should become general, 
then the formula P A, A D, II, = -£§, would 
to all otologists represent the fact that a 
watch that should be heard at 36 inches 
was heard by the right ear of the patient 
at a distance of 12 inches ; the formula P A, 
A S, V S, = y would mean that the whis- 
pered voice was heard by the left ear at 6 
inches that should have been heard at 36 
inches. It is not necessary to multiply ex- 
amples. 
By referring to the records of the Brook- 
lyn Eye and Ear Hospital, I find that I 
commenced to record the hearing power 
for my watch as a fraction on the 15th of 
May, 1869. Its use by my colleagues and 
myself has been continued since then. On 
the 21st of September of the same year, 
I read a paper on the irffportance of early 
treatment of the diseases of the ear before 
the Medical Society of King’s County, in 
which the use of this fractional method was 
explained and advocated. [From Boston 
Medical and Surgical Journal, of Thursday, 
Feb. 29, 1872.