-- —-_ I
7--:’,.
NATIONAL AI)WSORY COMMITTEE
-_
,
TECIINICA1. NOTE ●
— 1
No. 1358
1
.
I
,.
PROPELLER-LOUDNESS
CHARTS
By Harvey H. Hubbard
FOR
LIGHT
AIRPLANES
and Arthur A. Regier t
Langley Memorial Aeronautical Laboratory Langley Field, Va.
...
YqpJrj7
“ *
Washington July 1947
, .. . .
—.,
... .
,.
?WTIONAL ADUSORY
-*
CCMMITTEE FOR AERONAUTS
. *
PROPELIJZR-LOUDNESSC.MWIS NOR LIGHT AIRPLANES
.
By Harvey H. Hubbard and Arthur A. Regier STMMRY ( Calculations of the rotational-noise,snd vertex-noise loudness levels at distances of 300 and 1000 feet have been made for a largp nuznberof propellers in forward flight of ~ to 200 miles yer hour and for engine ratin&e of 10C to 300 horsepower. Propellers of two, four, six, and eight blades, diemeters of 6, 8, and 10 feet, and rotational speeds of 1000 to 3000 rpm are cons~dsred. CeLcuLatAd resul.tsae presented -in chart.form for convenience of desiprs of propellers for applications in which loudness is an important consideration:,
.
.
u
The theory for calculatin~ rotational sound pressures of a propeller operatizn~at zero forward speed was develo~d by Gutin in reference 1. A smlif’ication of the Gutin formula is @ven in reference 2 from which the sound-pressure level of a propeller may be easily calculated. This fozmmla shows that the rotatimal-soundpressure level of a propeller can be made as low as desired by reducing the tip speed and increasing the number of blades.
-4,
-h
9
.
.
*
u
INTRODUCTION
.
Recent tests of the sound emission frmm two-blade, four-Made, and seven-blade propellers (reference 3) show that the theory for rotational noise is in CI.OSOa~eement with experiment for a tip Mch number range between O.~ and 0.9 but Mb for lower tip Mach numbers the measwed over-all sound-pressure levels were much greater than the calculated rotatim.al-soundpre smre leve16. This discrepancy is due to the vortex noise of the propeller. Up to the present time, the sound output of practical propellers has been almost entire~ due to rotational noise and, consequently, vor’tx noise has nat been important. Because of public demand for a lsr~ reduction of airplane noise, it now becomes important to ind3cate the vortex-noise level of a propeller. In the present paper a tentative level of the vortex noise Is given for all propellers considered. This estimate is based on the work of references 4 and ‘j.
8
n ●
The loudness level rather than the sound-pressure level iS a letter criterion for ccmpe,ringthe noise from propellers. The method of Fletcher and Munson (reference 6) is used for calculating the loudness level. The calculation of the loudness of propellers is cumbersome. {“Inthe present paper the loudness levels of a large number of propellers in the U@t-airplane ran~ have been calculated and presented in chart-form. The rotational loudness level and the vortex-loudness level as well as the resultant loudness level may be obtained directly from the charty.
.
.
.
The efficiencies for this same class of pi?o~l.lersare given in refcmence 70 Since a larfy Qb.mberof combinations of propeller rotational speeds, diameter, and number of UadeO satisfy a given loudness level, the desigmr may choose’the combination which will stent give him a maximum of effici.ency and a minimumof loudness oonsi. with requkrements. .
SYMBOIS AND DEFINITIONS
Mt
ttp Mach number (rotatlcm only)
D
propeller dimeter,
9’
[email protected] of’observer from axis of rotation (0° in frent)
N
propeller rotational syeed, rpm
r~
engine rating, horsepower
v
airplane forwerd speed, miles per hovr
n
number of blades
s
distance fvom source of sound, feet
%-i
loudness levwl, decibels
n
propeller efficiency
Ti
ideal propeller efficiency
T
total +thrust,pounds ‘
Ab
total blade area, square feet
P
air density, slugs per cubic foot
feet
.—
.-
.
.-
“
. “
r
3
lthChKW No. 1358 9
--w
CL
..
1{ . .
propeller lift coefficient section veloci~
,. at 0.7 radius, feet per second
The terms’!noise,sound, and sound pressure&are used.synonymously. ..’ Sound-pressure level or sound-intensity level id the dedibel value Of.sound. The ~re8sure of 0.0002 ~ne per square cezW.meter -. Is O decibels. Loudness level of a sound takes into account the sensitivity of the ear to frequency and is equal to the intmwity level of the equallQvloud 1000-cycle reference tans. (see reference 6.) Rotational noise is the propeller noise due to the steady f~y.ces on me blade. ~ Gutin’s theory the noise “is divddbd into the torque and ‘bat components and the frequencie5” ,, are multiples of rotational syeed.
~go@~ic
.,.
Vortex noise,is the proyeller noise due to the oscillatory fotices on the blade associated,ti,ththe vortices in the Wake of an airfoil’ or the ,vortzcesbf a Karman vortex street. For propellers j the Vorpf= noise is.usually of mnch higlmr freqrmncy tham -the rotational noise ;: sad is distributed over a wide hand of frequencies. .. ,. .. :. ,. !,... ..... ANALYSIS AND ASSUMPTIONS ,. ●
✌✎
5
All equations used in sound calculations for this paper”have been yublished previously. Calculations are for standard sea~level conditions. t
> v *
~
Rotational IIOiSe.- The rotational noise of the propeller is the noise CILU3to the stmdy aerodynamic forces on ‘he llade. The .soti~ ~ from this source has been determined theoretically for a propeller Ot” v
/
.
NATIONAL ADVISORY COMMITTEE FORAERONAUTICS
.
. ●
●
.
.
kloulated sound pressures of flrat harmonlo from two-blade’ 1.propeller in simulated forward fli ht. B = 30 feet; D = 6 feet; Ht = 0.57; PH = 150 horsepower; % = 332 pound8; V = 150 tiles per hour.
Figure
I
.
%
4.
I
rl”’1 Loudnem
.6
.7
.8
17 leml
notational —
—
------
Vortex Total
.
n
iooo
1500
(d
2500 2000 u, * 6= yOrOOt.
3000
MOO
or promllen rotatlooal qwd ?lgum 2.. Loudnes; :s6af~otlon hour; ~=M)O ; V=50mileapm
1500
2000 m,
2500
30W
rpm
(b) o= MOOreet. for varlone nmber~ or bkleo. hors epowr.
I
1 t“
“d
,
,“
.
‘1,
,0
.
.5 ‘t .6
.4
.3
“ ●
I
?
.g
C) > El
Loudness
—— ------
level R&:::oMl Total
0 / ,‘
/
z gl . w co CJl CD
/
/
/
/ 0
/
I
/
,. ( /
/
I COMMITTEE FORAERONAU’rlCS -
iooo
1500
2000
‘N,rpm (a) s= 300 feet.
2500
3000
1060
1500
2500 2000 H, rpm (b) O= 1000 feet.
3(X)0
Figure3.- Loudnesm ag a runotlonof propellerrotationalepeed for variouanumbersof blades. D=6feet; T= 50 tilesper hour; FE= 150 horoqower.
Lodneas
J iooo
lpo
2500
2000
MOO
I
11111
level
I
I
rlgura
4.-
LoudneEs
feet;
I
I
2500
N, rpm feet.
as a funotlon
D=6
I
2000
Ii, rpm (a) s = 300
I
lp
V=
(b) 6=
of propeller rotational speed for various 50 milee per hour; PH = 225 horsepower.
1000 feet. numbare
of bklea.
I
# ,1’
,
*# 1
.
m~ L20
.4
‘~
.5
,(5
.7
.!3
3
n. ‘,6
.4
.
b I’I’lh’1
.tl 11’
z
g“ z=
100
/ / : 3 d i / 40
{ /
/
20
o-
10W
1500
2000 M, rpn
.?500
(.) B = yxl feet. Figure
5.-
Loudness aa a ronotion of propeller rotational V= 50 Miles per hour; D:6 feet; ~
1500
2500
20W u, mm
(b) B = 1000
feet.
speed ror VEIFIOW numbers - PO hmwepower.
or bladeo.
; . Cn
n
M~ .4
3
.6
5
.6
.7
n
/
/
/ /’
// / /
-
- /
/ /
/
1000
/
1500
3000
2500
mlo
1000
4’
~“,i.,’
6.-
Lotatneas :s6af~tion ; D
moo
2500
(b) # = 1000 feet.
(a) B = 3(X)roet. Fiwre
1500
II,-
N, ~
v=
,,
of propeller rotational speed for various numbers 100 miles per hour; ~ ❑ 100 horsepower.
q,
... S.,
*
of bl.adeo.
,,7
●
.
I t
~.~-,
I
,tJ
,)
1
m.
r I “’1r 4.
I
%6
.7
*L!
““
I
I
1 1
~
I (
iooo
UjOO
m
2500
low
1P
H, rpm
N, rpn (a) 8 = ~ Figure
7.-
2500
moo
feet.
(b) S = 1000
LoudneEn ae a f’unotion of propeller rotatioml speed for mriouo D = 6 feet; V = 100 mllea per hour; ~ = 19 horeepovem
feat.
nmmbbrg
of blmlem.
I
.4
120 ‘~
.5
%
.6
.7
&!
.8
m
n=
100 -
/
/
: ;
/ /
d
{
40
/
20 -
/ o
1000
mOO
1500 i, (a)
Figure
.’, .,
.,,,,,
s =
25m
1000
1500
rpm W
2500
2oofJ
U, rpm feet.
(b)
s =
1000
feet.
g.- Lotinens ma a fonotlon of propeller rotational Epeed for various numbern 100 mllee per hour; PJ.I= 225 horsepower. D=6 feet; V=
of blades.
) ,1
‘1
*,’J”V.8
,
,’
M.
iooo
1500
2000
2500
n, rpm (a) s = pa feet. Figure
I I
9.-
.3000
1000
1500
moo
2500
n, rpm (b) s= 1000 feet.
Loudnens a~ a funotlon of propeller rotational speed for various per hour; ~= 300horsepowar. D=6 feet; ‘?= 100mlles
numbers
of bladen.
3WIQ
la
,4
“~ .
.5
%
Nt .6
,m
.
.4
.3
.6
5
.g
.7
-
I I
t
LouaneM
1(MI
Rotational Vortex Total
—— -----I
lWB1
,
,
,
,
,
1
1
I
I
I
1
.
go
/
/
/
‘/
60
--
“-
‘-
/ /
f 20-
/ /
!
f
I
I
/
/
/
15W
?Oml
2000 n, rpa (a)
,,,
1000
I
I
1500
1111 I
.,.,
I
‘.
I
I
2000
I
1
2500
u, rpm (b)
feet.
a = 1000 feet..
10.- Loudness as a funotion of propeller rotational epaed ror various numbers V = 150 miles per hour; ~ = 100 hor~epower. D = 6 feet;
P@ure
,’,
s = p)
2500
I
I
NAT10t4AlADVISORY CONHITTEEFORAERONAUTICS—
t I
1
,> ...
of blade a.
),, \
*
1’
. .
1
lr~ .4
r’l
iooo
1500
2000 n, -
2500
(a) B = _&o feet. 61igure 11.- laxlneg~
.
.6
r!’!,
— — ------
Rotational vortex Total
1000
1500
.8
.
?!’;
20m n, rpm
2500
(b) B = 1000 feet.
:e6af~ctlon of propeller rotational Epeed for varioun numbers ; v= 150 mllee per hour; Pg = 150 hor~epower.
of blades.
yoo
%6
.4
I,20“~
1
7
.a
I
,
lm
/
.40 j-
/
20 /
I / n iooo
Figure
,’
,,
,
,. ,
12.-
2500 2000 H, rpm (a) 8 = po feet.
15fJ0
I.adness
poo
l&O
(b)
2500
2000
1500
a,
rp9
E =
1000
feet.
as a runotton of propeller rotational 6PI%%I for various numberE D = 6 feet; v s 150 miles per hour; PH = 225 hOIvaOPOWOr.
of bklea.
El z
iooo
1500
2&)o
2yo
poo
u, ~ (a) a = p
feet.
Flgwe 13.- Iawlnem ae a furmtlon D = 6 feet;
(b) o =
1000
feet.
of propeller rotational speed for varloue numbers V = 1~ mileo per hour; PH = ~o hornepowar.
of bkleo.
!5!
& .
P cd
.
.
iom
2500
2000
1500
1000
H, ~ (a)
1500
2500
2000 n, rQ8
(b) e = WOO
0 = y30 feet.
feet.
Figure 14.- Loudnese ae n funation of prop@ller rotational ~etl for varloun nuabers pH = lm horsepower. V = 200 MUM per hour; D= 6 feet;
‘ ,,
“’l
of bhdes.
,’! ,
,’, *
,,
I
‘t
,6
.7
I
.4
.3
.8
.
120
,5
‘t
.6
7
.6
I
I
Louluess level Rotational — — vortex ––- --- Total
100
/
-
00
J-w .
/ , /
/
,
/
/
4(
2(
I
o 1000
1500
2000
2500
WJJ
1000
I
I 1500
u, ~ (a)
e=
300 feet.
(b)
I
I
2000 M, rp9 s = 1000
I
I
1
2500 feet.
w .&
ml
.
Figure
15.- Loufioees as a funotlon of propeller rotatlooal epeed for various numbere 200 mi,lee par hour; ,% = 150 horsepower. D=6 feet; V=
of blades.
P 0
.-——
boo
1500
3000
2500
20W
n, ~ (a) s = yu
feet;
1500
moo
2500
Ii, rpB (b)
feet.
Figure 16.- LouMeE~ LW ~ fumtlon of propeller D=6
1000
200 miles
V=
a = 1000 feet.
rotational opeed f’or varloua nnmberB P~ = 225 horsepower. per hour;
cm
of blades.
WI
m
,. .’
.,.
.
.
“.,
$,
-.,
,
,
●
J
,, s,,.!
I
1000
1500
2500
2000
M, (a]
rigure 17.. Loulne8:
0 =
~
:s6ef&tlon ;
feet.
v=
3000
1(X)O
1500
2000 n, ~
2500
(b) e = 1000 feet.
of propeller rotational speed for various numbere PH ❑ ~0 honnepowar. 200 mllen per hour;
m #$ m
of bladee. w +
‘ Mt 5
120 +
7
.4
8
Loudnese — —— ------
100
.6
.5
.
1
.8
level
~M&mal
Total
I
80 -
,
/
/
, / : ,
:
,
,
~,~’/
/
d
_
_
_
_
/,#
_
~ 40
/
20
/ NATIONAL AINISORY UMMITTEE F@ AIMMAUTKS — /
:’
l!JW
1400
E200
26 o
/ I 1000
FIWJW
22C9
2600
H, rpm
El, rpm (s) B = PO
1800
1400
feet.
lt3.-Lowlness
(b) E
❑
1000 feet.
aE a function of propeller rotational speed for various numbers Pfi = 100 hor.eepower. D = S feet; V = 50 miles per hour;
of blmlea.
,.,
4 .,.., I
;
.,
, ,’
.
,J
1,
.,3
r
nt
Mt .6
“~
‘:
120
.7
.8
100
/
80 /
/
/
/
/ —
: g
~
‘
a i 40
/
‘o 10M
1400
1800
2200
2600
lm
1400
n, rpm
(a) Figure
s = 300 feet.
19.- I.c.udneoE:ngaf~tion ; D
2200
1800 n, rpm
(b)
E = 1000
of propeller rotational speed for varloue V = 50 ml.les per hour; PH : UjO horsepower.
reet.
numbers
of
bladee.
2600
Mt .4 120 -1
.6
.5
.7
.g
100
/ /
1
w
/
20
0 moo
Moo
MOO
N, (a) ?Igure
20.-
,. “’!
kudnecm
e =
W200
2600
UK@
Moo
as a funotlon of prop her rotational 50 mil 3 E per hour; ~ D=t$feet; v=
26@
H, rpm
rpm
3LM feet.
2200
1800
(b)
B = lWO
IJpeetlfor various = 225 horsepower.
feet.
numbers
of blmAem.
4 ,,. .
.!.. I
.
M*.
> 120
H
‘g
.IJ
.7
5
‘~
. ,, .,, {.
> H
z g .
100
P co m m
/ /
: :
/
e J? A_
40
_
_
_
_
_
.
20
0 1000
1400
MOO
2200
26OO
1000
1400
U,
Bl, * (a) s = ~oo feet. Figure
21.-
(b)
2.200
Isoo rp9
s = 1000
Loudnems an a funotion of propeller rotational speed for varloua D=g feet; V= 50 mllee per hour; PH = ~00 horsepower.
2600
feet.
numbeuw
of blades.
0? . M P
..-
Mt
Mt 5
12m “t
.6
.7
.4
●
.6
.5
.7
.8
I
I l! Lotiess
100
— — ------
.
le7el Rotatlooal Vortex Total
/
80 ~,= /
/ z s 4
/
TFwFFTH fJ
NATIONM ADVISORY WHHITTEE m AEmMAurlcs /
~~
10QO
lQOO
(n) Lmdnesa
22.-
2200
l&WO u,
Figure
/
D=
s=
26W
1000
rpB
(b) e= 1000 feet.
300 feet.
v=
2600
2200
1800
n,
rpa
asgaf~tlon ;
1400
of propeller rotational epeed for various numbers 100 miles per hour; ~= 100 horsepower.
of blades.
-. . .
.
. “’.
...!
.
~.,~.l
1
,,, .
, ,
,’
, i
lit
. ‘i.rl en 02
d
lm
lW
n,
(b) Pigure
22W
Moo
s=
26oO
rpm 1000
feet.
23.- Lomlness :ogaf~totion of propeller rotational speed for various numbers D ; v= 100 miles per hour; PH = 150 horsepower.
of blades. &
Mt .4
.5
.6
.7
.6
Lotlllrless 10TE1 —
I
2otatioMl Vortez
—
------
I
I
Total I
I
/ / # /
/’
/ / /
/
/
/ NATIONAL
ADVISORY
AEnoNAuTlcs
COMMITTEE m
10QO
1400
22m
1800
—
2600
u, rpm (b) a = 1~ Figure
,.
“r.
,..
2k.-
Loudness :sgar:u&i D ;
on of propeller rotational apoed for various numbers v= 100 tiles per hour; ~ = 225 horsepower.
.
‘ ,,
feet.
“ of blades.
,
1 ., .
-\l, ,
,
.
.,
8
, #
,
* ,, ,
*U, :
,
I
I
,4
::
.5
●IS
*7
El z
LOUQMIS6 level Rcktati-onal — — Vortox –-----Total
100
Ilo /’
/‘
/
/
3 . F UJ CJl al
,
I
I 0
(’/
-
/~ ‘ ~/ /
40
20 NATtONAL ADVISORY CONNITTEEF09AERONAUTICS
(
t
0
iooo
Moo
1400 (a)
Figure
2600
2200
1400
1000
2600 y $
(b] s=lOOO feet. of propeller
v=
2200
R,’rpa
II, rpm s = 300 feet.
2Lj.-Loudneae aagaf~tlon ; D=
MOo
100
miles
rotational per hour;
speed
for
varl,oue
PH = 300 horsepower,
numbem
of blades.
lx) Cn
.
.—
Mt
Ht
im
It,
Pigure
26.- kuinea;
2200
IJ?m
1400
(a)
s=
?pm
2600
“
PO feet.
:egat:W#tion of propeller rotational speed for varioua ; v= 19 mik3 per how; pH = 100 hOrEepWr.
nmbera
.
,. ““T,
...
—
‘
.1
‘\
.
of blndes.
. .,.’4.3
,,,
,.
.,,,
.
#
m
~,
.
.’,
,
*,C .
.
Mt 120 “?
100
. /
80
/
e ~ 40
/ 20
Loo
1400
2200
Moo
26m
1000
lW
lam
H, rpm (a)
●
=
300
u, feet.
(b)
S=
22W
26M
rpm
1000 foot.
W
6 ngm
27.- Loudnea;
a6gaf~tion = ;
v=
of propeller rotational epeed for various numbers 19 miles per hour; PH = 150 horsepower.
of blades.
‘M +
Mt 120 -“y
.g
7
.6
5
100 /
/
o : . a= 40
20 -
ho
lucre
1400
l?am
low
2600
II,rpm (a)
Flgura
a=
~0
,
(b] o = 1000
fret.
2S.. Louclness :sgmf:dlon D ;
v=
26W
2200
“\
fret.
of propeller rotational speed for various numbers 150 miles per hour; PH= 225 horsepower.
. ,,
1200 n, ~
. . “’, ,..
1400
.
of bl&rleo.
,
z
,.
.-
”...
.
● ✌✎ ✌✌✌
.,,!
*
,
‘,
b,
1203,
4
,6
.5
.7
.
.,,
i’
.
.8
100 I-J
.
,%
co
/ / /
/
0 / /
h
20
%X3
IMo
1400
h)
FIWM
29.- Lodlneaa
n,
rp
s=
WI
22W
100a
lIW
1400
2200
2600
II, rp feet.
(b)
S=
1000 fOOt.
as B function of propeller ~otational Epeed for varloun numberfl of bladea. D=g feet; V= 150 miles per how; ~ = ~0 horsepower.
g! ‘m co
.-
,4
.5
Iahinem —. —
—
.6
.7
d
level Rotational Vortex Total
— –—
I
/ ~ / / / I
NATIONAL
COWTITE
1000
1400
AOVISORY
FM AERONAUTICS
WO
2600
2200
w, ~ (b) Figure
...
,
,.
Jo.-
6
=
1000
feet.
Loudnemo an a funoti on of propeller rotational speed for variouo numberm D = 8 feet; V = 2CQ mllern per hour; PH ❑ 100 horsepower.
of blades.
. 4.,
‘
