-
7/25/2019 02 Sound Theory
1/25
BUILDING UTILITI
SOUND THE
-
7/25/2019 02 Sound Theory
2/25
RECAP
ACOUSTICS
- is a branch ! sci"nc" #ha# $"a%s &i#h #h" cn#r% an$
'r'a(a#is)n$*
Objectives of acoustics
# r"in!rc" n""$"$ s)n$
# "%i,ina#" )n&an#"$ s)n$
# 'r""n# )n&an#"$ s)n$# b" #rans,i##"$ in# an "nc%s"$
I#s a%% ab)#
-
7/25/2019 02 Sound Theory
3/25
SOUND THEORY
Wha# is a S)n$. s,"#hin( &" h"ar as a r"s)%# ! ibra#in !
a
an$ is cr"a#"$ b0 c,'r"ss"$ an$ "1'an$"$ air'r"ss)r"
)c#)a#ins*
-
7/25/2019 02 Sound Theory
4/25
SOUND THEORY
Wha# is a S)n$.ri(ina#"s !r, a ibra#in( b$0* I# is 'r"ss)r" haan
"%as#ic ,"$i),* I# is n# r"s#ric#"$/ i# s'r"a$s
)#&ar$ !r, i#s s)rc" in a%% $ir"c#ins $i,inishinin#"nsi#0
in"rs"%0 as #h" s)ar" ! #h" $is#anc" !r#h" s)rc" incr"as"s
-
7/25/2019 02 Sound Theory
5/25
SOUND THEORY
S)n$is""r0&h"r"4
Th"r" ar"5
Airbrn" s)n$s5 Th" ,"$i), is Air
S#r)c#)r"-brn" s)n$s5 Th" ,"$i), is Cncr"#"/ s#""&$/ (%ass
an$ c,bina#ins ! a%% #h"s"
-
7/25/2019 02 Sound Theory
6/25
SOUND THEORY
I# is a%&a0s ass),"$ #ha# #h" h"ar"r has a 'air !h"a%#h0
0)n( "ars &i#h #h" $ir"c#in ran(" ! 26 #
26/666 H7
-
7/25/2019 02 Sound Theory
7/25
PROPERTIES O8 SOUND
speed of velocity
992: !#;s"c a# 26
-
7/25/2019 02 Sound Theory
8/25
PROPERTIES O8 SOUND
frequency
is #h" n),b"r ! c0c%"s ! ibra#ins "1"c)#'"r s"cn$* H),ans can
h"ar s)n$s &i#hin@6 's # 9/666 's ran("
-
7/25/2019 02 Sound Theory
9/25
PROPERTIES O8 SOUND
frequency
D"'"n$in( n si7" ! s)n$ &a"s/ #h" r"'"a#"$%0 c0c%"a '"ri$ is
$i"r"n#* L& !r")"nc0 s)n$ is charac#"ri7b0 %n( s)n$ &a"s/
an$ cn#ain ,)ch "n"r(0/ &hi%" h!r")"nc0 s)n$ is charac#"ri7"$
b0 shr# &a"s/an$ c
%& "n"r(0*
-
7/25/2019 02 Sound Theory
10/25
PROPERTIES O8 SOUND
molecular absorption
- a s)n$ ,a0b" c"r"$ )' r absrb"$ b0 an#hs)n$* This 'h"n,"na is
ca%%"$ masking of souan$ #his is "r0 )s"!)% in ac)s#ics
- #h" s)n$ ,asin( is )s)a%%0 ! %&"r !r")"nc0 #h" s)n$ i#
,ass
-
7/25/2019 02 Sound Theory
11/25
PROPERTIES O8 SOUND
soporic eect
- #ha# ""c# br)(h# ab)# b0 a %&-s#"a$0 s)n$
-
7/25/2019 02 Sound Theory
12/25
PROPERTIES O8 SOUND
!A"# $#%&'T$is#anc" b"#&""n #& cr"s#s ! a
s)n$&a"
- lo( frequency soundsha" longer(avelengt)s#han hi(h
!r")"nc0
s)n$s* Th" &a"%"n(#h is a%s #h"$is#anc" #ra"%"$ b0 s)n$ in
n" s"cn$$ii$"$ b0 #h" !r")"nc0 ! #h" &a"
- "1a,'%"5
#h" &a"%"n(#h ! a 966 c0c%" &a" is a%i##%" ! "%""n !""#
%n( an$ a "
h)n$r"$ c0c%" &a"
!$? $is#anc#ra"%"$ b0 s&a" in n" s#h" !r")"nc0&a"
-
7/25/2019 02 Sound Theory
13/25
-
7/25/2019 02 Sound Theory
14/25
SOUND THEORY
*#'A"IO+ O, SOU%- I% A +OO.
Wh"n a sound (avein a r, s#ri"s a s)r!ac"r,/ 'ar# ! #h" "n"r(0
is re/ected/ 'ar# is
absorbed by t)e surfacean$ 'ar# is transmitto t)e surface
-
7/25/2019 02 Sound Theory
15/25
SOUND THEORY
+#,$#CTIO% O, SOU%- O% A SU+,AC#
A s)r!ac" #ha# is rigid/ /atan$ smoot))s)a%%0re/ects sound* Th"
r""c#in ! s)n$ n a s)r!a!%%&s #h" b"hair ! r""c#"$ %i(h#/
,"anin( #ha
t)e angle of incidence is equal to t)e angle ore/ection
-
7/25/2019 02 Sound Theory
16/25
SOUND THEORY
+#,$#CTIO% O, SOU%- O% ASU+,AC#
A s)r!ac" #ha# is rigid/ /atan$smoot))s)a%%0 re/ects sound*
Th" r""c#in ! s)n$ n as)r!ac" !%%&s #h" b"hair !r""c#"$
%i(h#/ ,"anin( #ha# t)eangle of incidence is equal tot)e angle of
re/ection
-
7/25/2019 02 Sound Theory
17/25
SOUND THEORY
&eometry of re/ectedsound
On" charac#"ris#ic ! s)n$ is#ha#/ %i" %i(h#/ i# can b"n$
ar)n$ an bs#r)c#in n&nas diraction of soundF*L& !r")"nc0
s)n$s ar"$irac#"$ ,r" "asi%0 #hanhi(h !r")"nc0 s)n$s
-
7/25/2019 02 Sound Theory
18/25
SOUND THEORY
Wh"n #h" &a"%"n(#h ! a s)n$is )s# #h" sa," as n" ! #h"r,s
$i,"nsins/ a s#an$in(&a" is cr"a#"$* Wh"n a s)n$c,"s !r, a
s)rc"
direct ororiginal sound
- !r, #h" s)rc" an$ $ir"c#%0$"%i"r"$ # #h" h"ar"r
re/ectedsound
- !r, a%% $ir"c#ins ! #h" r,
-
7/25/2019 02 Sound Theory
19/25
SOUND THEORY
!r a s)n$ # b" h"ar$ b0 a%is#"n"r c,!r#ab%0/ #h"r""c#"$ s)n$
,)s# c," #hi, n# %a#"r #han 0102 of a
secondr in #"r,s !$is#anc"/ #h" $ir"c# s)n$ an$#h" 'a#h ! #h"
r""c#"$ s)n$sh)%$ n# "1c""$ 23 ft1
-
7/25/2019 02 Sound Theory
20/25
SOU%- 4+O4A&ATIO% "#$OCIT5 I%"A+IOUS .#-IA
ELOCITY,"$i), ,"#"r '"r
s"cn$!""# '"r s"cn$
Air 3@@ 9936
Wa#"r 9@96 @2:
W$ 3366 96/J2:
Bric 366 99/J66Cncr"#" 366 92/966
S#""% @66 9/666
G%ass :666 9/@66
A%),in), :J66 9/666
A# 22
-
7/25/2019 02 Sound Theory
21/25
S4##- O, SOU%-
As s)n$ #ra"%s ,)ch s%&"r #han #h" s'""$ ! #h" r"s)%#in(
$"!"c#s in ,an0 r,s ar" ec)oesreverberations
Wh"n #h" r""c#"$ s)n$/ &hich r"ach"s anbs"r"r/ is $"%a0"$
,r" #han ab)# 6*6:J s"c
r"%a#i" # #h" $ir"c# s)n$s/ #h"0 ar" $is#in()ishas ec)oes*
+everberationcnsis# ! successivre/ections! s)n$s in a r,/ an$ sinc"
s)n#ra"%s n%0 ab)# 6670 ftr 788 m9sec/
-
7/25/2019 02 Sound Theory
22/25
+#SO%A%C#
Is &ha# ha''"ns # a b$0&h"n an#h"r ibra#in(b$0 ibra#"s
an$ini#ia#"s* Th" #h"r b$0# ibra#" in har,n0 &i#h
i# R"snanc" can b" )s"!)%
# r"in!rc" s)n$s a#s," s'"cic !r")"nci"s
-
7/25/2019 02 Sound Theory
23/25
+#SO%A%C#
This ha''"ns n%0h&""r/ i! #h" r"sna#in(b$0 r r"sna#r has
a$i,"nsin &hich is a,)%#i'%" ! #h"&a"%"n(#h ! #h"
s)n$&a" !r, #h" ri(ina#in(b$0
-
7/25/2019 02 Sound Theory
24/25
+#SO%A%C#
L& !r")"nci"s ha",r" r"snanc" #han #h"hi(h !r")"nci"s
b"ca)s"%& !r")"nci"s ha"%n("r &a"%"n(#hs an$
#h"r"!r" ,r" ,)%#i'%i"rs# #h" $i,"nsins ! #h"r, #han
hi(h!r")"nci"s
-
7/25/2019 02 Sound Theory
25/25
+#SO%A%C#
Y"#/ #h"r" ar" s)n$s #ha#r")ir" %"ss r"snanc" #(i" 'r"s"nc" #
#h"s)n$s
