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Alexander von Humboldt: „Comparative intensity of sounds“, in: ders., Sämtliche Schriften digital, herausgegeben von Oliver Lubrich und Thomas Nehrlich, Universität Bern 2021. URL: <https://humboldt.unibe.ch/text/1820-Sur_l_accroissement-06-neu> [abgerufen am 28.03.2024].

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Titel Comparative intensity of sounds
Jahr 1821
Ort London
Nachweis
in: The Leeds Correspondent, a Literary, Mathematical and Philosophical Miscellany 3:4 (Juli 1821), S. 228–230.
Sprache Englisch
Typografischer Befund Antiqua; Auszeichnung: Kursivierung.
Identifikation
Textnummer Druckausgabe: IV.2
Dateiname: 1820-Sur_l_accroissement-06-neu
Statistiken
Seitenanzahl: 3
Zeichenanzahl: 4909

Weitere Fassungen
Sur l’Accroissement nocturne de l’intensité du son. (Mémoire lu à l’Academie des Sciences le 13 mars 1820) (Paris, 1820, Französisch)
[Sur l’Accroissement nocturne de l’intensité du son. (Mémoire lu à l’Academie des Sciences le 13 mars 1820)] (Stuttgart; Tübingen, 1820, Deutsch)
A. v. Humboldt, über die Zunahme des Schalls während der Nacht (Jena; Leipzig, 1820, Deutsch)
Ueber die zunehmende Stärke des Schalls in der Nacht. (Eine Vorles. gehalt. am 13. März 1820 in d. Akad. d. Wiss. in Paris) (Leipzig, 1820, Deutsch)
On the Nocturnal Increase in the Intensity of Sound (London, 1821, Englisch)
Comparative intensity of sounds (London, 1821, Englisch)
Nocturnal Increase of Sounds (London, 1821, Englisch)
Nocturnal increase of sounds (London, 1821, Englisch)
Nocturnal increase of sounds (Philadelphia, Pennsylvania; New York City, New York, 1821, Englisch)
Sur l’Accroissement nocturne de l’intensité du Son (Paris, 1821, Französisch)
Nocturnal increase of Sounds (London, 1822, Englisch)
Over de meerdere sterkte die het geluid by nacht dan bij dag heeft (Amsterdam, 1823, Niederländisch)
Ueber die nächtliche Verstärkung des Schalls (Stuttgart; Tübingen, 1854, Deutsch)
|228|

COMPARATIVE INTENSITY OF SOUNDS.

The inhabitants of Atures and Maypures, what-ever the missionaries may have asserted in their works,are not more struck with deafness by the noise of thegreat cataracts, than the Catadupes of the Nile. Whenthis noise is heard in the plain that surrounds themission, at the distance of more than a league, youseem to be near a coast skirted by reefs and breakers.The noise is three times as loud by night as by day,and gives an inexpressible charm to these solitaryscenes. What can be the cause of this increased in-tensity of sound in a desert, where nothing seems tointerrupt the silence of nature? The velocity of thepropagation of sound, far from augmenting, decreaseswith the lowering of the temperature. The intensitydiminishes in air, agitated by a wind, which is con-trary to the direction of the sound; it diminishes alsoby dilatation of the air, and is weaker in the higher thanin the lower regions of the atmosphere, where thenumber of particles of air in motion is greater in thesame radius. The intensity is the same in dry air,and in air mingled with vapours; but it is feebler in|229| carbonic acid gas, than in mixtures of azot and oxygen.From these facts, which are all we know with any cer-tainty, it is difficult to explain a phenomenon observednear every cascade in Europe, and which, long beforeour arrival in the village of Atures, had struck themissionary and the Indians. The nocturnal tempera-ture of the atmosphere is 3° less than the temperatureof the day; at the same time the apparent humidityaugments at night, and the mist that covers the cata-racts becomes thicker. We have just seen, that thehygroscopic state of the air has no influence on thepropagation of the sound, and that the cooling of theair diminishes its swiftness.It may be thought, that, even in places not inhabitedby man, the hum of insects, the song of birds, therustling of leaves agitated by the feeblest winds, occa-sion, during the day, a confused noise, which we per-ceive the less because it is uniform, and constantlystrikes the ear. Now this noise, however slightlyperceptible it may be, may diminish the intensity of alouder noise; and this diminution may cease, if duringthe calm of the night the song of birds, the hum ofinsects, and the action of the wind upon the leaves, beinterrupted. But this reasoning, even admitting itsjustness, can scarcely be applied to the forests of theOroonoko, where the air is constantly filled by an in-numerable quantity of moschettoes, where the hum ofinsects is much louder by night than by day, andwhere the breeze, if ever it be felt, blows only aftersunset.I rather think, that the presence of the sun actsupon the propagation and intensity of the sound bythe obstacles which they find in the currents of air ofdifferent density, and the partial undulations of theatmosphere caused by the unequal heating of differentparts of the soil. In calm air, whether it be dry, ormingled with vesicular vapours equally distributed,|230| the sonorous undulation is propagated without difficulty.But when the air is crossed in every direction bysmall currents of hotter air, the sonorous undulationis divided into two undulations; where the density ofthe medium changes abruptly, partial echoes areformed, that weaken the sound, because one of thestreams comes back upon itself; and those divisionsof undulations take place, of which Mr. Poisson hasrecently developed the theory with great sagacity.It is not therefore the movement of the particles ofair from below to above in the ascending current, orthe small oblique currents, that we consider as oppos-ing by a shock the propagation of the sonorous undu-lations. A shock, given to the surface of a liquid,will form circles around the center of percussion,even when the liquid is agitated. Several kinds ofundulations may cross each other in water, as in air,without being disturbed in their propagation; littlemovements may ride over each other, and the real causeof the less intensity of sound during the day appears to bethe interruption of homogeneity in the elastic medium.During the day, there is a sudden interruption of den-sity wherever small streamlets of air of a high tempe-rature rise over parts of the soil unequally heated. Thesonorous undulations are divided, as the rays of lightare refracted, and form the mirage (looming,) whereverstrata of air of unequal density are contiguous. Thepropagation of sound is altered, when a stratum of hy-drogen gas is made to rise in a tube closed at one endabove a stratum of atmospheric air; and Mr. Biot haswell explained, by the interposition of bubbles of car-bonic acid gas, why a glass filled with Champagnewine is little sonorous so long as the gas is evolved,and continues to pass through the strata of the liquid.Humboldt’s Personal Narrative.