A popular essay on the laws of acoustics, and on the anatomy and physiology of the ear : followed by seventyseven cases of persons cured of deafness, being simple abstracts of each individual case / by Joseph Togno.

  • Togno, Joseph.
Date:
1834
Catalogue details

Licence: Public Domain Mark

Credit: A popular essay on the laws of acoustics, and on the anatomy and physiology of the ear : followed by seventyseven cases of persons cured of deafness, being simple abstracts of each individual case / by Joseph Togno. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    The pliancy and readiness with which air receives and transmits all the various inflections of sound, is really worthy of remark. It not only repeats every sound, but it transmits several at a time without con- founding them, although they may differ in power, pitch and timbre. Thus an experienced musician may distinguish which instrument is out of tune, or does not play correctly in a full orchestra. The sound is the more powerful the denser and warmer the air is. Thus in a cloudy day sounds are louder than in a clear one. Sausure relates that the report produced by the firing off of a pistol, while on Mount Blanc, where the air is uncommonly rare, was not greater than a common Chinese cracker. The rapidity with which the sonorous undulations of the air are com- municated through aerian molecules is immense and really astonishing. It has been reckoned at one hundred and seventythree fathoms in a se- cond of time, according to some experiments made near Paris ; and, ac- cording to English experimenters, sound travels eleven hundred and fortytwo feet in a second, or about a mile in four and a half seconds, or thirteen miles in a minute. Its velocity is the same whether it is strong or feeble; the sound of the human voice, or the report of a cannon; but in summer, when the air is not so dense as in winter, sound travels rather more rapidly ; so it does in elevated situations; while in cold foggy weather its progress is retarded. The difference in no case is, however, more than a few feet; and in a denser atmosphere, though the progress of sound is impeded, the same sounds are stronger than in thinner air; still there are many deaf persons who hear better in a clear dry atmosphere, than in a damp heavy one. This may be the reason why sounds are heard better at this season. When the earth is covered with several feet of snow, as was the case in the winter of 1830, the same sound is not half as strong. The snow prevents the vibrations of surrounding bodies, and it acts like the damper of a pianoforte. Our own pulse may be used as a measure of time. If we can see the flash of a cannon and count the pulsations between the flash and the moment when the report reaches our ear, and allow one thousand feet for each pulsation, we shall come very near the truth, as to the distance at which the cannon is from us. The tone of the sound does not influence its rapidity; for Mr. Biot had a person to play an air on the flute, atone extremity of the cylinder just mentioned, nine hundred and fiftyone fathoms long, and he, being at the other exiremity, heard it very distinctly ; which proves that the various tones had been propagated with equal swiftness. The disposition of the places traversed by the sound produces seve- ral phenomena. If the undulations of the air conveying a sound meets with a resist- ing surface, the sound is reflected in such a manner as to form an angle of reflection equal to that of incidence, and situate in the same plane. If the reflecting surface is sufficiently distant, so that the ear may have the time to receive the direct sound before the reflected one may reach the ear, then the same sound is heard twice, and there results a repeti- tion of sound, called an echo. It may be double; that is to say, the first reflected sound may be again reflected so as to be each time heard separately. This phenomenon has been observed in a great many parts of the world; but one of the most remarkable is the famous echo at the Mar- quis Simonetta's villa, near Milan. It is produced by the reflection of sound between the opposite parallel wings of the building, which are