Lecture 1 Acoustic Fundamentals
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Transcript of Lecture 1 Acoustic Fundamentals
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AcousticsFundamentals
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hat is ACOUSTICS?
“akouein”
It is the science of sound,
including its poduction,popagation and e!ects"
It is also de#ned as thegeneation, tansmission,and eception of eneg$ in
the fom of %i&ational
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(ain Su&)*iscipline of Acoustics
is the stud$ of aeod$namicsound, geneated 'hen a +uid +o'inteacts 'ith a solid suface o
'ith anothe +o'
AEROACOUSTICS
ARCHITECTURAL ACOUSTICS
BIOACOUSTICS
is the stud$ of ho' sound and&uildings inteact
is the stud$ of the use of sound&$ animals such as 'hales,
dolphins and &ats"
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(ain Su&)*iscipline of Acoustics
is the stud$ of the use of sound inmedicine"
BIOMEDICAL ACOUSTICS
LOUDSPEAKER ACOUSTICS
PSYCHOLOGICAL ACOUSTICS
is the engineeing discipline &ehind
the design of the loudspeake"
is the stud$ of ho' people eact tosound, heaing, peception and
localiation"
is the stud$ of the mechanical,electical and &iochemical function of
heaing in li%ing oganisms"
PHYSIOLOGICAL ACOUSTICS
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PHYSICAL ACOUSTICS
STRUCTURAL ACOUSTICS ANDVIBRATION
is the stud$ of the detailed inteactionof sound 'ith mateials and +uids SONOLUMINESCENCE and
THERMOACOUSTICS
is the stud$ of ho' sound andmechanical stuctues inteact
MUSICAL ACOUSTICS
is the stud$ of the ph$sics of musicalinstuments"
SO-O.U(I-/SC/-C/)the emission of light &$
&u&&les in a li0uid e1cited &$sound
T2/3(OACOUSTIC
S
(ain Su&)*iscipline of Acoustics
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is the stud$ of ho' sound isgeneated and measued &$loudspeakes, micophones, sonapo4ectos, h$dophones, ultasonic
tansduces, sensos"
TRANSDUCTION
WOLFFIAN ACOUSTICS
UNDERWATER ACOUSTICS
is the stud$ of salient featues ofpediatic ultasound
is the stud$ of the popagation ofsound in oceans"
(ain Su&)*iscipline of Acoustics
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is the stud$ of high fe0uenc$ sound
ULTRASONICS
ENVIRONMENTAL NOISE
SPEECH COMMUNICATION
is the stud$ of the soundpopagation in the humanen%ionment, noise health e!ects andnoise mitigation anal$sis"
the stud$ of ho' speech is poduced,the anal$sis of speech signals and thepopeties of speech tansmission,
stoage, ecognition and enhancement"
(ain Su&)*iscipline of Acoustics
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ACOUSTICAL MEASUREMENTSAND INSTRUMENTATION
(ain Su&)*iscipline of Acoustics
ACOUSTICS SIGNAL PROCESSING
ACOUSTICAL ENGINEERING
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3C2IT/CTU3A. ACOUSTIC
is a special &anch of science thatdeals 'ith the constuction ofenclosed aeas so as to enhance theheaing of 'anted sounds"
(A3CUS5IT3U5IUS
6O..IO
7OS/622/-38
WA..AC/ C./(/-T
SA9I-/“Fathe of (oden Achitectual
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hat is SOU-*?
is a ph$sical phenomenon thatstimulates the sense of heaing" It isan aual sensation caused &$ pessue+uctuations"
is a tem sometimes esticted tosuch ai&one %i&ational 'a%es,ho'e%e, moden ph$sicists usuall$
e1tend the tem to include simila%i&ations in othe gaseous, li0uid, osolid media"
is elemental that po%ides all sots ofco niti%e and a!ecti%e infomation"
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Speed of Sound
It is a pessue 'a%e that popagatesthough ai 'ith a speed of
appo1imatel$:
;;<mete=second
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Speed of Sound
In fuid dynami!" #$% !&%%d '( !'und ina fuid m%dium )*a! '+ ,i-uid. i! u!%d a!a +%,a#i/% m%a!u+% ('+ #$% !&%%d '( an
'01%# m'/in* #$+'u*$ #$% m%dium2 T$% !&%%d '( an '01%# di/id%d 0y #$%!&%%d '( !'und in #$% fuid i! a,,%d #$%
(ach num&e2
O01%#! m'/in* a# !&%%d! *+%a#%+ #$anMach1 a+% #+a/%,in* a# !u&%+!'ni
!&%%d!2
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Categoies of Sound
(USIC-OIS/
S6//C
2
/%e$thing aual
can &e gouped into thee categoies:
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Atti&utes of Sound
6ITC2 the atti&ute of audito$
sensation in tems of 'hich soundma$ &e odeed on a scalepimail$ elated to fe0uenc$"
highness o lo'ness of a musicaltone as detemined &$ the apidit$of the %i&ations poducing it"
UNIT3(/.
6oposed 9$:
ST/5/-S, 5O.>(A-- A-*-/W(A-- @;B
4"555 M%,! i! #$% &i #$ '( 4"555 H6 #'n% a# a!%n!a# i'n ,%/%, '( 75dB
The pitch of an$ sound 4udged &$listenes to &e “n” times that of a (/.
TO-/ is “n mels”"
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Atti&utes of Sound
.OU*-/SS is an o&se%eDs audito$
impession of the stength ofsound"
.oudness .e%el is measued &$the sound pessue le%el of astandad pue tone of speci#ed
fe0uenc$ 'hich is assessed &$
62O- i! #$% uni# '( ,'udn%!! ,%/%, 8$%n3
a2 T$% !#anda+d &u+% #'n% i! &+'du%d 0y a!%n!i0,y &,an% !inu!'ida, &+'*+%!!i/% !'und
8a/% 'min* (+'m di+%#,y in (+'n# '( #$%'0!%+/%+ and $a/in* a (+%-u%ny '( 4555H62
02 T$% !'und &+%!!u+% ,%/%, in #$% (+%%
&+'*+%!!i/% 8a/% i! %9&+%!!%d in dB a0'/%; ;
SO-/ i! #$% uni# '( ,'udn%!! 'n a !a,%d%!i*n%d #' *i/% !a,% num0%+! a&&+'9ima#%,y&+'&'+#i'na, #' #$% ,'udn%!!2
F'+ &+a#ia, &u+&'!%!" #$% !a,% i! &+%i!%,yd%?n%d 0y i#! +%,a#i'n #' #$% &$'n !a,%2
62O- E < G @< log H SO-/
UNIT3 62O- andSO-/
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Atti&utes of Sound
TI(93/ TO-/ CO.O3
is the chaacteistic tonal 0ualit$of sound
6U3/ TO-/ i! a !'und in 8$i$ #$% !'und&+%!!u+% /a+i%! !inu!'ida,,y 8i#$ #im%2
T$% 8a/%('+m may 0% +%&+%!%n#%d 0y a !in%
8a/%2
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Atti&utes of Sound
T/(6O
is the speed of sound
ho' fast o slo'
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Atti&utes of Sound
328T2(
elates to a sonic time patten,ma$ &e simple, constant, comple1o changing"
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Atti&utes of Sound
ATTAC>
is the 'a$ sound &egins
can &e had, soft, cisp o gadual
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Atti&utes of Sound
*U3ATIO-
efes to ho' long a sound &lasts
can &e shot o sustained sounds
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Atti&utes of Sound
*/CA8
efes to ho' fast sound fadesfom a cetain loudness
can &e 0uick, gadual o slo'
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Sound eneation
T3A-S(ITTI- (/*IU(
63/S/-C/ OF 5I93ATIO-3/C/I5/3 O3 /-* US/3
3e0uiements to 6oduceSound
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-atue of SoundSound is the sensation poduced &$ the
ea 'hen stimulated &$ a %i&atingo&4ect though a se0uence ofcompessions and aefactions in the aisuounding it"
CO(63/SSIO-)condensed egion of the mediumthough 'hich a longitudinal 'a%e
ta%els"3A3/FACTIO-)ae#ed egion o egion of
lessened pessue of the medium
though 'hich a longitudinal 'a%e
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O97/CTI5/.8:a puel$ phenomena consisting of'a%e motion in ai o an$tansmitting medium
Intepetation of Sound
SU97/CTI5/.8:
the sensation poduced &$ outsidestimulation on the ea"
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:5
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5elocit$ of 6opagation
Sound ta%els at di!eent%elocities depending upon themedium"
Since sound ta%els not onl$ in ai&ut also though pats of the
stuctue, it is of inteest to kno'the %elocities in othe media"
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5elocit$ of 6opagation
I- A AS (/*IU(:
s E
'hee:6o E is the stead$ pessue of the gas in -=mJHK E is the stead$ o a%eage densit$ of the gas in
kg=mJ; E atio of the speci#c heat of constant pessue to
that of the constant %olume
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5elocit$ of 6opagation
I- -O3(A. *38 AI3:
s E ;;@"L G
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5elocit$ of 6opagation
I- .IPUI*:
s E
'hee:> E li0uid compessi&ilit$ m)sJH=kg )
CO-STA-T
E B1@
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(ach -um&e
/3-ST (AC2
/3-ST WA.*F3I/* 7OS/F W/-R/.(AC2
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A!!i*nm%n#3
• Li!# ai++a(#! #'*%#$%+ 8i#$ #$%i+ Ma$Num0%+!
• A&&,ia#i'n! Mi,i#a+y" C'mm%+ia,"%#2
• Ima*%!
• D%/%,'&%+!
• L%n*#$ '( S%+/i%
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-atue of Speech
SOU-* 63/SSU3/ WA5/ OF S6//C2:
@
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A!!i*nm%n#3•
Ta0u,a#% !'m% !'und !'u+%! 8i#$#$%i+ 'm&u#%d &'8%+ and #$%i+'++%!&'ndin* !'und &'8%+ ,%/%," indB" +%(%+%n%d a# 454: 8a##!2
• E9am&,%3
(ust&edi!eent fom
thegi%endata inthe
handou
h
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Speech (easuement
5U (/T/3:It is the de%ice used to measue
speech %olume and designed to follo'speech le%els in elation to humanheaing 'ith a standad signal le%el ofGd9m on a M/3 O5/3 T2/C2A--/. d9m
6d9m E 5U eading V @" d9 G @<
Cl f S h
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Classes of Speech
5OIC/* SOU-*SAe poduced 'hen ou %ocal chods %i&ate as a
esult of ou lungs geneating sucient pessue toopen ou %ocal folds" Fo most people, the %i&ationfe0uenc$ of thei folds is 'ithin L< to
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Fe0uenc$ 6aametes
2A3(O-ICS
the integal multiples of thefundamental fe0uenc$
-th 2amonics E - 1Ff
F 6 t
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Fe0uenc$ 6aametes
O5/3TO-/
musical tem fo hamonics
-th O%etone E -G@1 Ff
F 6 t
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Fe0uenc$ 6aametes
OCTA5/fe0uenc$ inte%al of HIt is an inte%al &et'een t'ofe0uencies that ha%e a tonal ation of H
to @"It has a pitch inte%al of H:@It is the tone 'hose fe0uenc$ is t'icethat of the gi%en tone"
-th Octa%e E HJ- 1Ff -um&e of Octa%e E logH
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F 6 t
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Fe0uenc$ 6aametes
The human heaing ange fom H< 2to H< k2 has appo1imatel$ @< octa%e&ands"
The @< octa%es ae categoied as:
9ASS @st to th
(I*3A-/ Lth to Qth
T3/9./ th and @
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5ocal 3ange
5ocal 3ange
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5ocal 3ange
Appaent .oudness and .oudness
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Appaent .oudness and .oudness.e%el
.OU*-/SS
./5/.
A66A3/-T
.OU*-/SS5/38FAI-T
FAI-T(O*/3AT/
.OU*5/38.OU*
*/AF/-I-
< to @L d9
@L to ;< d9
;< to M< d9
M< to Q< d9
Q< to @;<d9
@;< d9
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Appaent .oudness and .oudness.e%el
T23/S2O.* OF2/A3I-
A5/3A/
CO-5/3SATIO-
T23/S2O.* OF 6AI-
6/3(A-/-T *A(A/TO 2/A3I-
< d9
M< d9
@H< d9
@L<
d9 S6. of Common Sound Souce
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S6. of Common Sound Souce
SOU3C/ S6. d9
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Sample 6o&lems
*etemine the speed of sound in ai atST6"-OT/ XST6:
E @" fo ai, E @"Hkg=mJ;,6 E @ atm
E @"
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Sample 6o&lems
A camea focuses using ultasound" If itfocuses pecisel$ at H< degee Celsius,ho' fa o! Y 'ill it &e at < degeeCelsius?
;"L;Y
Sample 6o&lems
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Sample 6o&lems
A +ute 'ith all of the holes closed can&e consideed as a tu&e 'ith &oth endsopen" It has a fundamental fe0uenc$ ofHM@"M 2 'hich is the middle C”"
Calculate the ;d
hamonic, ;d
o%etone,;d octa%es, and ;d decades of thefundamental fe0uenc$ calculated"
;d hamonic E BQ"Q
2;d o%etone E @"
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AcousticsFundamentals