Eu Respi J, 1996, 9, 2365–2370
DOI: 10.1183/09031936.96.09112365
P in ed in UK - all igh s ese ed
Copy igh ERS Jou nals L d 1996
Eu opean Respi a o y Jou nal
ISSN 0903 - 1936
AAccoouuss iicc aannaallyyssiiss oo ssnnoo iinngg ssoouunndd iinn ppaa iieenn ss wwii hh ssiimmppllee ssnnoo --
iinngg aanndd oobbss uucc ii ee sslleeeepp aappnnooeeaa
J.A. Fiz*, J. Abad*, R. Jané**, M. Rie a*, M.A. Mañanas**, P. Caminal**,
D. Rodens ein+, J. Mo e a*
Acous ic analysis o sno ing sound in pa ien s wi h simple sno ing and obs uc i e sleep
apnoea. J.A. Fiz, J. Abad, R. Jané, M. Rie a, M.A. Mañanas, P. Caminal, D. Rodens ein,
J. Mo e a. ©ERS Jou nals L d 1996.
ABSTRACT: Sno ing, a symp om which may indica e he p esence o he obs uc-
i e sleep apnoea synd ome (OSA), is also common in he gene al popula ion.
Recen s udies ha e sugges ed ha he acous ic cha ac e is ics o sno ing sound
may di e be ween simple sno e s and OSA pa ien s. We ha e s udied a small
numbe o pa ien s wi h simple sno ing and OSA, analysing he acous ic cha ac-
e is ics o he sno ing sound.
Se en een male pa ien s, 10 wi h OSA (apnoea/hypopnoea index (AHI) 26.2
e en s·h-1) and se en simple sno e s (AHI 3.8 e en s·h-1), we e s udied. Full nigh
polysomnog aphy was pe o med and he sno ing sound powe spec um was ana-
lysed.
Spec al analysis o sno ing sound showed he exis ence o wo di e en pa -
e ns. The i s pa e n was cha ac e ized by he p esence o a undamen al e-
quency and se e al ha monics. The second pa e n was cha ac e ized by a low
equency peak wi h he sound ene gy sca e ed on a na owe band o equen-
cies, bu wi hou clea ly iden i ied ha monics. The se en simple sno e s and wo
o he 10 pa ien s wi h OSA (AIH 13 and 14 e en s·h-1, espec i ely) showed he
i s pa e n. The es o he OSA pa ien s showed he second pa e n. The peak
equency o sno ing was signi ican ly lowe in OSA pa ien s, wi h all bu one OSA
pa ien and only one simple sno e showing a peak equency below 150 Hz
A signi ican nega i e co ela ion was ound be ween AHI and peak and mean
equencies o he sno ing powe spec um (p<0.0016 and p<0.0089, espec i ely).
In conclusion, his s udy demons a es signi ican di e ences in he sound powe
spec um o sno ing sound be ween subjec s wi h simple sno ing and obs uc i e
sleep apnoea pa ien s.
Eu Respi J., 1996, 9, 2365–2370.
*Se ei de Pneumologia, Hospi al Uni e si a io
Ge mans T ias i Pujol, Badalona, Spain.
**Ins i u o de Cibe né ica (UPC), Ba celona,
Spain. +Cliniques Uni e si ai es Sain Luc,
Uni e si é Ca holique de Lou ain, B ussels,
Belgium.
Co espondence: J.A. Fiz
Se ei de Pneumologia
Hospi al Ge mans T ias i Pujol
Ca e e a del Canye
s/n 08916 Badalona
Ba celona
Spain
Keywo ds: Acous ic analysis
obs uc i e sleep apnoea
sno e
Recei ed: Ap il 10 1995
Accep ed a e e ision June 20 1996
This wo k was suppo ed by g an 94/0625
FIS (Spain).
In he las 15 y s, sno ing has en e ed he ealm o
clinical medicine. Sno ing may dis u b he social and
amily li e o he sno e , who is unawa e ha he sno es.
Sno ing is a p e alen symp om, and abou 50% o he
adul popula ion sno es equen ly [1, 2]. One o i e
pe cen o he adul male popula ion su e om he
sleep apnoea synd ome, in which sno ing is a dominan
symp om. Se e al ea men s exis o simple sno ing
and o obs uc i e sleep apnoea (OSA), many o hem
mu ila ing o in asi e. Recen s udies ha e sugges ed
ha he acous ic cha ac e is ics o sno ing may di e
be ween simple sno e s and pa ien s wi h OSA. Heal hy
simple sno e s, wi hou apnoea episodes, showed a
powe spec um o sno ing signal wi h a ha monic s uc-
u e and a undamen al equency ha anged 110–190
Hz [3]. In sno ing pa ien s wi h OSA, equency com-
ponen s highe han 800 Hz we e ound [4].
We ha e s udied a small numbe o pa ien s wi h sim-
ple sno ing o OSA, and analysed he acous ic cha ac-
e is ics o he sno ing sound as well as he pa e n o
espi a o y dis u bances du ing sleep.
Ma e ial and me hods
Se en een li elong nonsmoking male pa ien s om
he sleep diso de s clinic o he Ge mans T ias i Pujol
hospi al in Badalona we e s udied. Ten o he subjec s
we e diagnosed as ha ing OSA and se en as ha ing
simple sno ing.
Lung unc ion es s we e pe o med using a spi o-
me e (PFT Ho izon Sys em) [5]. Re e ence alues we e
hose o ROCA e al. [6]. A e ial blood gas alues we e
measu ed using a blood gas analyse (Radiome e ABL).
Full nigh polysomnog aphy was pe o med acco d-
ing o s anda d me hods [7]. Sleep analysis was pe -
o med by isual inspec ion using RECHTSCHAFFEN and
KALES [7] pape sco ing. Elec oencephalog am (EEG),
elec o-oculog am (EOG) and chin elec omyog am (EMG)
we e ob ained om su ace elec odes. Tho acic and
abdominal espi a o y mo emen s, as well as hei sum,
we e ob ained using a induc i e ple hysmog aph (Respi-
ace NIMS, Miami, USA). Calib a ion was pe o med
by means o a d y spi ome e (S3371; Senso Medics,
J.A. FIZ ET AL.
2366
Table 1. – An h opome ic and espi a o y unc ion da a
o subjec s wi h simple sno ing and pa ien s wi h obs uc-
i e sleep apnoea
Simple sno ing OSA
Age y s 46±13 51±6
Heigh cm 171±9 166±7
Weigh kg 87±22 91±21
BMI kg·m-2 29.7±7.2 32.9±7.6
FVC L 4.4±1.1 3.5±0.6
% p ed 90±18 83±13
FEV1L 3.5±1.1 2.8±0.7
% p ed 93±20 85±17
FEV1/FVC % 81±3 78±8
Pa,O2kPa 12.2±0.8 10.6±2.1
mmHg 91.3±5.5 79.7±16.0
Pa,CO2kPa 5.0±0.3 5.4±1.0
mmHg 37.2±2.6 40.2±7.8
Sa,O2% 96±1 94±6
pH 7.37±0.0 7.39±0.0
Values a e p esen ed as mean±SD. FVC: o ced i al capaci y;
BMI: body mass index; % p ed: pe cen age o p edic ed alue;
FEV1: o ced expi a o y olume in one second; Pa,O2: a e ial
oxygen ension; Pa,CO2: a e ial ca bon dioxide ension; Sa,O2:
a e ial oxygen sa u a ion.
Table 2. – Sleep pa ame e s o subjec s wi h simple
sno ing and pa ien s wi h obs uc i e sleep apnoea (OSA)
Simple sno ing OSA
TST min 268±66 315±68
Awake % o TST 23±13 10±8*
S age 1 % o TST 41±18 28±17
S age 2 % o TST 28±18 51±16
S age 3&4 % o TST 1.3±3.3 0.3±0.9
REM % o TST 4.7±4.6 10.8±11.7
Lowe Sa,O2% 92±4 80±15
Mean Sa,O2% 95±2 90±6
AHI e en s·h-1 3.8±1.7 26.2±20.1
Maximum du a ion
o e en s s 26.7±16.5 42.7±27.3
Mean du a ion
o e en s s 17.7±3.7 20.5±3.9
Values a e p esen ed as mean±SD. TST: o al sleep ime;
REM: apid eye mo emen (sleep); Sa,O2: a e ial oxygen sa -
u a ion; AHI: apnoea/hypopnoea index *:p<0.05, o com-
pa isons be ween g oups (Kolmogo o -Smi no nonpa ame ic
es ).
Anaheim, USA). A e ial oxygen sa u a ion (Sa,O2) was
measu ed using a pulse oxime e (Oxy Shu le; Senso
Medics, USA) wi h a inge p obe. O onasal low was
assessed using he mis o s. All he signals we e eco d-
ed on pape using a Senso medics eco de .
In addi ion o he abo e, a minia u e mic ophone (MKE
3010; SennHeise , Ge many) was posi ioned upon he
neck, 1 cm la e al o he median line a he le el o he
c icoid ca ilage. The mic ophone was enclosed in a
plas ic hemisphe e, 3 cm in diame e and lea ing a 1 cm
dis ance be ween he mic ophone and he skin, a oiding
di ec con ac wi h skin su ace. The hemisphe e was a a-
ched o he skin using adhesi e ape. The mic ophone
had a la equency esponse be ween 40 Hz and 30 kHz
( ield ansmission ac o in open loop: 10 m ·Pa-1 ±2.5
dB).
An apnoea was de ined as he absence o ai low du -
ing ≥10 s. Apnoeas we e classi ied as obs uc i e o
cen al acco ding o he pe sis ency o absence o es-
pi a o y mo emen s, accompanied by a all in Sa,O2o
≥4%. Hypopnoea was de ined as a educ ion in idal
olume o ≥50% o hose eco ded du ing he p eced-
ing i e b ea hs o longe han 10 s, accompanied by
a all in Sa,O2o ≥4%. OSA was de ined as he p es-
ence o mo e han 10 apnoeas/hypopnoeas·h-1 o sleep,
and he o al numbe o episodes o apnoea and hypop-
nea pe hou o sleep ep esen ed he apnoea/hypop-
noea index (AHI).
The sound signal was il e ed wi h a band-pass il e
be ween 10 Hz and 6 kHz (KH 39188). The sound sig-
nal oge he wi h he low signal o he he mis o , was
s o ed using a ideo ape casse e (Racal V S o e CH)
a a speed o 7.5 in·s-1. Flow and sound signals we e
p ocessed using a pe sonal compu e (PC Compaq desk
368/20e) wi h a sampling equency o 12 kHz. Analysis
was limi ed o S age 1 and 2 non- apid eye mo emen
(REM) sleep.
Sno ing and low signals we e synch onized by means
o a digi al clock a ailable on ideo ape eco de . Th ee
episodes o h ee consecu i e b ea hs wi h sno ing we e
andomly analysed a e iden i ica ion o 10 pe iods o
sno ing. Analysis was pe o med using he a e age o
he h ee episodes. In pa ien s wi h OSA, sno ing co -
esponded o he 1s , 2nd and 3 d b ea h a e an apnoea.
Sno ing was iden i ied by lis ening o he sound. Fas
Fou ie T ans o m (FFT) was used o calcula e sound
spec a o he h ee successi e sound inspi a o y episo-
des o sno ing. FFT was applied on 1,024 samples.
Welch pe iodog am was applied using a Hanning win-
dow wi h an o e lap o 50%.
The ollowing pa ame e s we e measu ed: maximal
equency ( max), de ined as he uppe equency con-
aining 90% o he o al powe o he spec um; peak
equency ( peak) de ined as he equency wi h he max-
imum powe ; and mean equency ( mean) de ined as he
equency including hal he o al powe o he spec-
um. Ha monics we e de ined as b oad equency bands
in he spec um analysis [3, 4] wi h a undamen al e-
quency. Fo each pa ame e , he a iabili y was es i-
ma ed by calcula ing he coe icien o a ia ion (CoV)
indi idually o each subjec o pa ien . Compa isons
we e pe o med using he nonpa ame ic Kolmogo o -
Smi no es . Spea man's nonpa ame ic co ela ion co-
e icien was used o e i y he ela ionship be ween
sleep pa ame e s wi h acous ic spec al sound pa ame-
e s. Resul s we e conside ed signi ican i he p- alue
was lowe ha 0.05.
Resul s
Table 1 p esen s he an h opome ic as well as he
lung unc ion and blood gas alues o he pa ien s.
Pa ien s wi h OSA we e olde , and had somewha lowe
alues o o ced i al capaci y (FVC), o ced expi a-
o y olume in one second (FEV1) and a e ial oxygen
ension (Pa,O2) han pa ien s wi h simple sno ing. How-
e e , he e we e no s a is ically signi ican di e ences
be ween g oups.
Polysomnog aphic da a a e ep esen ed in able 2.
Sleep a chi ec u e was abno mal in bo h g oups, wi h
an excess o S ages 1 and 2 non-REM sleep and e y
ACOUSTIC ANALYSIS OF SNORING 2367
Fig. 1. – Analysis o sno ing signal om a simple sno e . a) Signal
(a bi a y uni s (au)) o i s b ea h; b) powe spec um (au) o i s
b ea h; c) signal (au) o second b ea h; d) powe spec um (au) o
second b ea h. The e is a undamen al equency and clea ly iden i-
ied ha monics.
Fig. 2. – Analysis o sno ing signal om an obs uc i e sleep apnoea
(OSA) pa ien . a) Signal (a bi a y uni s (au)) o i s pos apnoeic sno e;
b) powe spec um (au) o i s pos apnoeic sno e; c) signal (au) o
second pos apnoeic sno e; d) powe spec um o second pos apnoeic
sno e. Maximum ene gy is a ound he undamen al equency; no e
ha he e a e no inden i iable ha monics.
Signal au
-0.4
-0.2
0
0.2
0.4
a)
00.2 0.4 0.6 0.8 11.2 1.4 1.6 1.8 2.0
Time s
1.5
1.0
0.5
0
Powe spec um au
100 200 300 1000
900
400 500 600 700 800
0
F equency Hz
0.6
0.4
0.2
0
-0.2
-0.4
00.5 1.0 1.5 2.0 2.5
Time s
Signal au
b)
c)
0.1
0.2
0
Powe spec um au
100 200 300 1000
900
400 500 600 700 800
0
0.5
0.4
0.3
d)
F equency Hz
2
1
0
-1
-2
00.2 0.4 0.6 0.8 1.0 1.2
Signal au
Time s
2.5
2.0
1.5
1.0
0.5
00 100 200 300 400 500 600 700 800 900
F equency Hz
Powe spec um au
0
-1
-2
1
2
Signal au
00.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time s
25
20
15
10
5
0
0 100 200 300 400 500 600 700 800 900 1000
F equency Hz
a)
b)
c)
d)
1000
Powe spec um au
small amoun s o S ages 3 and 4 non-REM sleep. REM
sleep was be e p ese ed.
Spec al analysis o sno ing showed he exis ence o
wo di e en pa e ns. The i s pa e n was cha ac e -
ized by he p esence o a undamen al equency and
se e al ha monics h ough a b oad equency band ( ig.
1). The second pa e n was cha ac e ized by he clea
p edominance o sound ene gy sca e ed on a na owe
band o equencies, bu wi hou clea ly iden i ied ha -
monics ( ig. 2).
The se en simple sno e s and wo o he 10 pa ien s
wi h sleep apnoea showed he i s pa e n. The wo pa -
ien s wi h he less se e e OSA showed he i s pa e n
and had AHI o , espec i ely, 13 and 14 e en s·h-1 o
sleep. The es o he pa ien s wi h OSA showed he
second pa e n o sound spec um.
Table 3 p esen s he a e age equency indices cal-
cula ed o bo h g oups, as well as he mean o he indi-
idual CoVs o each pa ame e . The e was a signi ican
di e ence be ween pa ien s wi h simple sno ing and
pa ien s wi h OSA in peak equency ( able 3). Using a
h eshold o 150 Hz o he peak equency, all bu one
o he pa ien s wi h OSA, bu only one subjec wi h sim-
ple sno ing, showed alues below his h eshold.
All o he o he indices showed a endency o lowe
alues in pa ien s wi h OSA, bu he di e ences did no
each s a is ical signi icance ( able 3).
Signi ican nega i e co ela ions we e ound be ween
he numbe o AHI·h-1 o sleep and he peak and mean
equencies o he powe spec um ( ig. 3 and 4).
Discussion
In his s udy i was ound ha pa ien s wi h simple
sno ing had a sno ing sound spec um cha ac e ized by
a undamen al equency and he p esence o ha mon-
ics. Sno ing analysis was pe o med on he i s b ea hs
ollowing an apnoea in pa ien s wi h OSA. The pa e n
dec ibed o simple sno e s was only a ely seen in pa -
ien s wi h OSA, who ins ead seemed o ha e a spec-
um cen ed a ound a undamen al equency wi hou
ha monics. In addi ion, peak equency was lowe in
pa ien s wi h sleep apnoea. A h eshold o 150 Hz bes
iden i id pa ien s wi h sleep apnoea om simple sno -
e s. Finally, a signi ican nega i e co ela ion was ound
be ween he se e i y o he sleep apnoea synd ome,
assessed by he AHI, and he sno ing sound spec um.
Sno ing sound is p oduced by oscilla ions in he so
pala e, pha yngeal walls and epiglo is [8–10]. Sno ing
is always p eceded by low limi a ion [9]. Flow limi a-
ion has been a ibu ed o he sleep- ela ed dec ease in
pha yngeal muscle one. The pha ynx may be seen as
a collapsible ube. A dec ease in he one o i s walls
leads o a dec ease in i s c oss-sec ional a ea, wi h low
limi a ion ollowed by high equency oscilla ions in he
pha yngeal walls. In pa ien s wi h sleep apnoea, ade-
qua e ai low is comp omised and is es o ed wi h he
sno ing sound, only a e he a ousal ela ed eopening
o he pha ynx. A ha ime, he e a e pa ial and apid
closu es and openings o he pha yngeal lumen [11].
S udies on heo e ical models ha e ecen ly con i med
he abo e hypo hesis on sno ing p oduc ion p oposed
by LIISTRO e al. [11].
J.A. FIZ ET AL.
2368
Table 3. – Spec um equency pa ame e s o sno ing
in subjec s wi h o wi hou obs uc i e sleep apnoea syn-
d ome (OSAS)
Sno e s CoV OSAS CoV
%%
peak Hz 264±107 14 157±136 14
mean Hz 325±58 15 223±147 16
max Hz 462±85 8 455±199 8
Values a e p esen ed as mean±SD o he ele an da a, and
mean o he coe icien o a ia ion. peak: he equency wi h
he highes powe ; mean: he equency wi h he mean spec-
um powe ; max: he equency wi h 90% o o al spec um
powe ; CoV: in asubjec coe icien o a ia ion. *: p<0.05,
Kolmogo o -Smi no nonpa ame ic es .
600
500
400
300
200
100
0
010 20 30 40 50 60 70 80
AHI e en s·h-1
peak Hz
Fig. 4. – Rela ionship be ween apnoea/hypopnoea index (AHI) and
mean equency ( mean) o spec um in se en simple sno e s and 10
obs uc i e sleep apnoea (OSA) pa ien s. The e is a signi ican nega-
i e co ela ion (Spea man ank o de co ela ion: =-0.61; p<0.0089).
Fig. 3. – Rela ionship be ween apnoea/hypopnoea index (AHI) and
peak equency ( peak) o spec um in se en simple sno e s and 10
obs uc i e sleep apnoea (OSA) pa ien s. The e is a nega i e ela-
ionship. The e is a signi ican nega i e co ela ion (Spea man ank
o de co ela ion: =-0.70; p<0.0016).
AHI e en s·h-1
010 20 30 40 50 60 70 80
0
100
200
300
400
500
600
mean Hz
Acco ding o GAVRIELI and co-wo ke s [12, 13], col-
lapsible ubes may show low limi a ion and hen high
equency oscilla ions o wo di e en ypes: he walls
o he ube may oscilla e wi hou comple e collapse; o
he e may be oscilla ion wi h a comple e closu e in each
cycle o oscilla ion. Oscilla ion wi hou comple e clo-
su e co esponds o he sound o a wheeze, whe eas
oscilla ion wi h comple e closu e would co espond o
he sound o sno ing. In he p esen s udy, wo di e -
en ypes o sound spec a we e ound. The i s ype,
cha ac e ized by a undamen al equency and ha mon-
ics, was simila o he spec um obse ed du ing speech,
especially emission o owels [14]. I was cha ac e ized
by a high in ensi y peak co esponding o he unda-
men al equency, ollowed by a se ies o highe e-
quency peaks wi h he spec um occupying a b oad band
o equency ha monics, ( ig. 1).
The second pa e n o sound spec um was cha ac e -
ized by a low equency peak, wi h he es o he ene gy
o he sound spec um sca e ed a ound a na owe ange
o equencies, wi hou clea ly iden i iable ha monics
( ig. 2). This second pa e n could co espond o wha
has been called " elaxa ion oscilla ions" o "milking"
oscilla ion ubes [15].
In he p esen s udy, di e ences be ween peak e-
quency o bo h g oups ( able 3) we e obse ed. Al hough
his esul was signi ican , in e pa ien a iabili y was
high due o cha ac e is ics o peak equency. Mean e-
quency was highe in sno ing pa ien s bu no s a is i-
cally signi ican .
The p esen da a show subs an ial di e ences wi h
espec o he esul s o PEREZ-PADILLA e al. [4]. In hei
s udy, he peak equency in pa ien s wi h simple sno -
ing was lowe han in he p esen s udy, whe eas he
peak in pa ien s wi h OSA was highe . Mo eo e , in
pa ien s wi h OSA, hey also ound a esidual powe a
equencies a ound 1,000 Hz. Ne e heless, he esul s
o bo h s udies show some simila i ies: simple sno -
ing was cha ac e ized in bo h s udies by a undamen-
al equency and he p esence o ha monics ha a ely
exceeded 500 Hz. In pa ien s wi h obs uc i e sleep
apnoea, ha monics a e much mo e di icul o iden i y.
In he p esen s udy, he second b oade peak equen-
cy abou 1,000 Hz was no iden i ied.
The main di e ence be ween he p esen s udy and
he s udy by PEREZ-PADILLA e al. [4], a leas as con-
ce ns sno ing, es s on he me hod and eco ding equip-
men . They placed hei mic ophone on he manub ium
s e ni, whe eas we placed ou mic ophone abo e he la -
ynx. The il e ing e ec o he uppe ai way ca i ies is
qui e di e en om ha o he achea and main b onchi,
necessa y o he sound o each a mic ophone placed
on he manub ium s e ni. I is, hus, possible ha he
di e ences in he eco ding equipmen may be espon-
sible o he quan i a i e di e ences be ween he p e-
sen esul s and hose o PEREZ-PADILLA e al. [4]. The
di e ence in se e i y o he OSA be ween ou pa ien s
and hei s p obably canno explain he di e ences
be ween indings. Indeed, in he p esen s udy a sig-
ni ican co ela ion was ound be ween he se e i y o
he OSA synd ome exp essed as he AHI and a ious
indices desc ibing he noise spec um. This co ela ion
implies ha , he mo e se e e he OSA, he lowe he
equencies desc ibing he spec um. The e o e, one
would expec he pa ien s o PEREZ-PADILLA e al. [4].
who had a mo e se e e OSA synd ome, o ha e e en
lowe equencies han he pa ien s in he p esen sudy.
I is known ha in OSA he e is oedema o he so
pala e [16]. I can be hypo hesized ha , he highe he
AHI he mo e se e e he oedema, wi h a co esponding
inc ease in he mass o he so pala e. Vib a ing s uc-
u es emi a sound spec um which is ela ed o hei
mass, in such a way ha , he highe he mass he lowe
he equency spec um o he sound [10]. This could
explain he p esen esul s bo h in e ms o he lowe
equencies in OSA pa ien s compa ed wi h pa ien s wi h
simple sno ing, and in he nega i e co ela ion be ween
he se e i y o he AHI and he sound spec um.
Though he gene al spec a pa e ns a e di e en in
OSA pa ien s and simple sno e s, he wo pa ien s wi h
he leas se e e o m o OSA showed sound pa e ns
including ha monics. By con as , only one pa ien wi h
OSA showed a peak equency highe han 150 Hz, and
only one simple sno e showed equencies o less han
150 Hz.
An impo an ca ea should be bo n in mind con-
ce ning he p esen s udy. In pa ien s wi h OSA, only
he i s h ee b ea hs a e a comple e apnoea we e
analysed. Those h ee b ea hs gene ally ake place du -
ing he a ousal ha ends each apnoea. Sleep apnoea is
p ecisely cha ac e ized by he occu ence o apnoeas
ollowed by an a ousal ha allows esump ion o low.
Thus, we eel i jus i ied o ha e pe o med he p esen
s udy in his way. I u u e s udies con i m hese es-
ul s, hen au oma ed acous ic analysis o sno ing could
become a use ul ool in clinical sleep medicine o sepa-
a e indi iduals wi h apnoea om hose wi h simple sno -
ing.
In conclusion, we ha e ound signi ican di e ences
in he sound spec um o sno es be ween pa ien s wi h
simple sno ing and pa ien s wi h obs uc i e sleep apnoea.
These signi ican di e ences we e obse ed despi e he
p esence o some o e lap be ween he wo g oups. Mo e-
o e , he e was a signi ican co ela ion be ween indices
desc ibing he sound spec um and he se e i y o he
obs uc i e sleep apnoea synd ome.
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