The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1856-08-22


cation Of the same Prncpk gives us ne explanation Of
mysterious Inus IN he reflection Of impulse from
the edge Of forest q trees each leaf properly situated
within range on ty fect OF the 'front.' plane OF renec
ton, will consprs produce distinct echo and these
would form the principal part Of the rejecting surfaces
OF dense iors for the remainder would be screened
arc beine ~ greater distance every ray which might
come rom Them would serve 70 produce merely low
conipasv on Of the sound.
On'hs same principle may at assert that the
panneyng Of room the introduction Of reflect
ing faces at different distances will not prevent the
eo6o provided they are parallel 70 each oher and tua
Hj relatively ~ each other within the limit OF per-
ceptbilty
rejecting surfaces behind the speaker We frequently
see churches TO diminish the effect OF the Voice OF
the preacher mass Of erapery placed directly 10 the
Of the pulpit However important this may be IN an
sstbetcs point Of view is Ger tsiny at variance with
correct acoustic arrangements-the great object OF
which should be 10 husband every articulation Of the
voice, and 70 ansmit it unmingled with other impulses
and with ~ little loss possible TO the ears Of the au
dieuce
Another effect of The Transmission ard reflection Of
sound that which 10 called revcrberaton which con
siss Of prolonged musical sound, and 10 much more
frequently the Of ndistinctnees Of perception Of
the srticulaons OF the speak the single echo
Reverberation 10 produced by repeated rejection OF
single dstonasion tkes place In the middle Of long
bal, with naked and perpendicular walls, an Impulse
viii pass IN each direction VIII Pc reelected from Inc
again reflected, and 80 until the original Impulse
entirely absorbed by the solid materials which conoe IT,
The impression will be retained upon the ear during the
interval Of the transmission past 1t Of two successive
waves and thus continued sound will be kept up, par
euaI i the walls Of any Of Tie Are ~ saoS
those produced by the rapid snaps Of the teeth OF
wheel against quill, be made In unison with the
result sufpose the wheel 70 be turned with
such velocity as TO cause . snap at the very
sppsra tus is placed The sec md sound viii combine With
the nrst, and thus loud and sustained vibration
viii be produced. will be evident from this that every
has key note and that an instrument be sounded
on thie II will resouud with great force. must be APP
par also that the continuance OF single sound ana
the tendency 10 confusion in distinct articulation de
pend on several conditions-arst on the of the
apartment second On the strength Of the SOUND Or .ee
Intensity Of the impulse third on the position OF the
rejecting surface and fourth on the nature Oh 1ne mae
rial Of the rejecting surfaces. .
In regard 10 the first OF these the larger the room the
longer time will be required for the impulse 70 reach y
wall along the axis and If we suppose that at each COLI
zion portion the original force absorbed, VIII re-.
quire couble the time 70 totally exsneush y N room o.
double the size the velocity Of sound being the
same, the number Of collisions ia agven time VIII De
nversey the distance through which the sound has
again that it must depend upon the loudness Of the
sound, or the insecurity of the impulse must be
evident when we consider that the cessation Of
The reflections is due to the absorption OF the
walls OF irregular reflection, and that consequently
the greater the amount OF original disturbance me longer
be the time required for its complete extinction This
principle sbundantly shown By our observations on
different rooms. .
upon the position OF the rejecting surfaces II these are
Dot parallel each other bat obhque as 70 reflect the
sound not to the opposite but 70 the adjacent wall with
out passing through longer Of the room will
evidently be sooner absorbed Any obstacle also which
may tend to break the wave and interfere with the
Election through the axis Of the room, will serve TO lessen
the OF the rtmcnt Hence though the pa
melting the ceiling snd introducing variety OF o0hque
surfaces may prevent olsed echo, provided the
distance be sufficiently great and the sound sufficiently
loud yet that they do bave A important effect 10 stop
ping the 10 evident from theory and expert
In n YopYn fact ou
Of single intense sound continued six seconds, where
cases and other objects were placed around the wall It's
continuance WAS reduced TO two seconds
Fourthly the duration the resonance will depend on
the Of the al Of the wall re.ec ION a.
ways place at the surface OF new medium, aud
The amount Of this will depend the elastic force or
10 resist compresson and the density OF the new
medium For example, Wall OF nitrogen, II such could
be found, would transmit nearly the whole OF wave OF
round In air, and reflect but very small portion par
ton Of tissue paper would produce nearly the same eff
feet. polf he'd wall Of steel, however OF sufficient
thickness prevent yielding would reflect for practical
purposes all the impulses through the air which might
au upon H. The rebound Of the wave is caused not by
The osoia the WALL but the elasticity and mobility
Of the air. single ray 81 sound striking aeains. yield
log board would probably Increase the ouiness OF the
reverberson, but not Its contn On tns point
OF experiments made by the OF the tuning
fork In this instrument the motion of the foot and OF
the two prongs give sonoroCs vibration TO the air
Which, receged upon another tuning fork OF precisely
The same sze and o.m, would reproduce the same vora
TONS
II is fact well established by observation, that
when two bodies are in perfect unison, and sefa-
rated from cecn o.her by space allied with air,
the vibrations OF the one vii be Transmitted TO
the other From this consideration Is probable that
ve.y nearly the same effect ought u be produced 10
irapsminng immediately the vibration Of tuning FORK 70
rejecting body 70 duration and intensity, IN the
Gaze OF Transmission through air. Ths conclusion Is
strengthened by floating fiat piece OF wool vessel
CT standing Upon sounding board placing strrng
FORK on this the Vibrations will DO transmitted 10 the
board through the and sounds will be produced
the .ame chscter as those e. I'd Shea the tuning fork
pended from due cambria thread vioraed Ia air and,
rom the mean Of mantle OF experiments was found
70 continue IN motion .52 seconds. in tbs experiment.
had tuning FORK been perfect vacuum suspended
without the OF string and further ha' the-e been
no Nhersl medium The ag .aiion Of which 80 nn. give
rise 20 right heat electricity other form u sne-
rial notion the ors would continue its vibT forever
The fok was next placed upoa args thin pine board
the top Of table, loud sound in ID IS case pro
cuec3 ahsh continued less than 10 seconds. me whole
table, as . system. Was isrown alto motion, and the
upper side Had the tuning fork been placed upon par.
tton Of this material, loud sound woai have been
heard In the adjoining room; this WIS proved by
ng the tuning FORK against door leading into closed
closet. The sound within apparently loud na,
without
the great amount Of tbs motive Of The FORK bsng
comm uric ued 70 . large mass OF wood The ed
sound due 70 the increased surface In ouer words
the shortness OF duration was compensated for by the
gresier intensity Of eif Ct produced.
Tie tuning fork next placed upon circular slab
Of marble about three feet In diameter and three
inch thick the sound emitted feeble, and the
fluctuations continued 1l5 seconds, as deduced from Tie
mean Of Xix experiments.
In all these experiments, except the in q vacuum
tie time a tho cessation Of tho tuning deter
min, by bringing the mouth ~ rcsoundng cavity near
the ert q the fork this cavity having previously been
adjusted 20 unison wtn the vibrations OF the fork gave
audible sound when could be heard b. the IN
aided
The tuning fork was next placed upon cube Of iai.
rubber and this upn the marble slab Tae sound emit
ted 10 this scarcely ihat IN the OF the
tuGing fork suspcnde1 from the cambria thread and
from this apaory OF the previous experiments .ht
at fret thought suppose The time Of dura,ion would be
great-bu this the case the Vibrations cor tnued
only forty seconds TIE question mag her, % asked
hat became 81 the impulses lost BY Tie gung fork
They were neither transmitted u the Ind rubber nor
given "a To the air The form 0f SOUND were prcba-
bly, cxI-nt cd IN producing cbalge IN tn matter OF the
India rubber. were converted into aeaL or both.
Though the inquiry did not tau strictly wilma tbs line Of
this series Of ipvestga vet II wa VI l0tercsuag
character In physical point 81 view, 70 deter nine who
ther beat actually produced, tia, the following
% riment was male
Acy hndric piece II India rubber about inches dia
meter, placed ln aubuat bottle with two openings,
ma ofhar M IA tan. n