Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/20.
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Tool De elopmen o Human Audible Spec um
Compensa ion
F ancisco Gonçal es, Filomena
Soa es
Algo i mi R&D Cen e
Uni e si y o Minho
Guima ães, Po ugal
[email p o ec ed]inho.p
Ví o Ca alho
Algo i mi R&D Cen e & *EST
Uni e si y o Minho & *IPCA
Guima ães, *Ba celos, Po ugal
ca [email p o ec ed]
José Machado
ME RICs R&D
Uni e si y o Minho
Guima ães, Po ugal
[email protected]
Abs ac — Communica ion elies on good unde s anding.
Humans ela e o each o he h ough isual, audible and ac ile
communica ion. I is impe a i e ha he audible communica ion
message eaches he ecei e in good condi ions, in o de o keep
a heal hy, smoo h and unde s andable speech. The e a e some
dis u bances in human speech and communica ion when hea ing
damage is p esen . Nowadays, hea ing loss is a equen inju y,
caused by noise pollu ion, daily s ess o noisy wo kplaces. Ye , i
can be ea ed by se e al ways. This p ojec consis s in
de eloping a ool ha cap u es he emi e 's oice audible
spec um, il e s he noise and o he equencies, and
compensa es he message, enabling he lis ene / ecei e
unde s anding. The pu pose o his esea ch is no aimed o
subs i u e no compe e wi h hea ing aids in he ma ke , which
a e well-de eloped, ce i ied and p esc ibed by
O o hinola yngology clinicians. The ocus o his s udy is o
iden i y he issues o human hea ing loss and o de elop an
algo i hm o hea ing compensa ion by using il e ing echniques
in a simula ed en i onmen applied o a hea ing model.
Keywo ds— digi al signal p ocessing; hea ing aid; noise
il e ing; speech; human ea .
I. INTRODUCTION
One o he big issues in human unde s anding is he abili y
o ealize he sounds so ha i is possible o ansla e he
message o he b ain [1]. I is e y impo an o humans o
ela e o each o he and eel com o able when
communica ing. Hea ing is one o he success’s key.
The abili y o hea is c i ical o unde s and he wo ld
a ound us as well as in e ac ing wi h each o he . Hea ing
impai men is he mos equen senso y de ici in human
popula ions and a ec s newbo ns, child en, adul s and elde ly
[2], [3].
Howe e , hea ing can be comp omised by issues ha may
lead o an ine icien ecep ion o he message. One cause is
he hea ing loss. The e a e many causes o hea ing loss.
Some imes i is jus a case o a ela i ely simple p ocedu e
like cleaning he audible canal in he ea , whe e i is wax
accumula ion ha should be emo ed. The e is also he
possibili y o an acciden o e en he use o an ibio ics. On
he o he hand, when he ne es a e a ec ed he e is no way o
eco e . Hea ing loss is one o he causes o social and
speech/unde s anding p oblems.
The esea ch objec i e o his pape aims o be a i s s ep
in o de o apply digi al signal p ocessing (DSP) and il e ing
echniques o a hea ing model in o de o enhance speech [4].
The pape is o ganized as ollows: Sec ion II desc ibes he
hea ing loss concep ; Sec ion III p esen s he spec um o
equencies o hea ing; Sec ion IV shows examples o hea ing
aids as well as some mobile applica ions and inally, Sec ion
V p esen s he inal ema ks.
II. HEARING LOSS
When desc ibing hea ing loss, we gene ally look a h ee
aspec s: ype o hea ing loss, deg ee o hea ing loss, and
con igu a ion o hea ing loss.
The e a e h ee basic ypes o hea ing loss: conduc i e,
senso ineu al, and mixed. Conduc i e hea ing loss occu s
when he sound is no sen easily h ough he ou e ea canal o
he ea d um and he iny bones (ossicles) o he middle ea .
Conduc i e hea ing loss makes sounds so e and less easy o
hea . This ype o hea ing loss can o en be co ec ed by
medically o su gically in e en ions. Some possible causes o
conduc i e hea ing loss a e [2], [3]:
 Fluid in he middle ea om colds o alle gies;
 Ea in ec ion (o i is media);
 Mal unc ion in he eus achian ube;
 Hole in he ea d um;
 Too much ea wax;
 Ex e nal o i is;
 Fo eign body in he ea canal (insec s, among o he s);
 Mal o ma ion o he ou e ea , ea canal, o middle
ea .
Senso ineu al hea ing loss (SNHL) happens when he e is
damage o he inne ea (cochlea) o o he ne e pa hways
om he inne ea o he b ain. Mos o he ime, SNHL canno
be medically o su gically co ec ed. This is he mos common
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ype o pe manen hea ing loss. SNHL educes he abili y o
hea ain sounds. Some possible causes o SNHL a e:
 D ugs ha a e oxic o hea ing;
 Hea ing loss ha uns in he amily (gene ic o
he edi a y);
 Aging;
 Head auma;
 Mal o ma ion o he inne ea ;
 Exposu e o loud noise.
Mixed hea ing loss occu s when a conduc i e hea ing loss
happens in combina ion wi h an SNHL. In o he wo ds, he e
may be damage in he ou e o middle ea and in he inne ea
(cochlea) o audi o y ne e [5].
Pa ien s wi h SNHL, howe e , also may expe ience
inni us, dizziness, o e en ue e igo. Ca e ul ques ioning
may e eal ha he pa ien has a speci ic di icul y
unde s anding speech. This may be appa en only in ce ain
si ua ions, such as when speaking on he phone o in a
con e sa ion in a noisy en i onmen o wi h ce ain
indi iduals (child en o women whose oices end o be mo e
silen and high pi ched).
Hea ing loss is an impo an public heal h conce n wi h
subs an ial economic and social cos s. In child en, hea ing
impai men delays language de elopmen and educa ional
p og ess. In adul s, i causes di icul ies in p o essional and
social li e as well as sel -es eem. Apa om consequences o
he indi idual pe son, hea ing loss also leads o high cos s o
socie y.
Hea ing impai men can be caused by a numbe o ac o s
including in ec ions du ing childhood such as measles, mumps
and meningi is, ch onic o i is media, exposu e o excessi e o
p olonged noise, head/neck inju ies, use o medica ions such
as ce ain ypes o chemo he apies and an ibio ics, indus ial
sol en s, congeni al abno mali ies and in ec ions and pe ina al
p oblems, ce ain nu i ional de iciencies, gene ic diso de s
and aging. Use o hea ing de ices [6] such as aids and
cochlea implan s as well as sign language, lip eading and
special ampli ica ion sys ems in schools a e s a egies o help
a ec ed people manage hei communica ion [7].
III. SPECTRUM OF FREQUENCIES
Hea ing is he abili y o pe cei e sounds. Sound occu s
o e a wide spec um o equencies. The human ea is
sensi i e o a equency band wi hin ha spec um exp essed
in decibels (dB). Humans a e capable o hea ing sounds om
a ange o equencies. The ange is ypically conside ed o be
be ween 20 Hz and 20000 Hz. F equencies highe han 20 kHz
a e conside ed as ul asonic, while equencies below audio
a e e e ed o as in asonic. Loss o he abili y o hea sound
equencies in he no mal ange o hea ing is called hea ing
impai men .
The e is a di e si y o de ini ions o hea ing impai men ,
hus, compa ison among s udies is di icul and may be
in alid. The de ini ion used by any s udy should always be
checked be o e a emp ing o make such compa isons. The
Wo ld Heal h O ganiza ion (WHO) de ines disabling hea ing
impai men in adul s as a pe manen unaided hea ing h eshold
le el (a e age o equencies 500 Hz, 1000 Hz, 2000 Hz,
4000 Hz) o he be e ea o 41 dB o g ea e (WHO, 2001).
In child en unde 15 yea s o age, disabling hea ing
impai men is de ined as pe manen unaided hea ing h eshold
le el (a e age o equencies 500 Hz, 1000 Hz, 2000 Hz,
4000 Hz) o he be e ea o 31 dB o g ea e [5]. Figu e 1
shows he equencies and h eshold le els o hea ing [8].
Fig. 1 – Hea ing Th eshold Le els [8]
Figu e 2 shows a ypical audiome ic examina ion o a
pa ien wi h mild o mode a e hea ing loss.
Fig. 2 – Audiome ic Examina ion Tes (example)
In his example, he e is no di e ence be ween he ai
conduc ion and he bone conduc ion h esholds; i indica es
ha he hea ing loss is due o a p oblem in he cochlea. This is
he mos common ype o hea ing loss in adul s and i is
known as a senso ineu al hea ing loss [9].
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IV. HEARING AIDS
Hea ing aids can be applied o o e come his impai men .
Because hea ing aids oday a e digi al and p og ammable, he
ampli ica ion can be ine- uned and ailo ed o each wea e .
Basic hea ing aids usually equi e some manual adjus men s
depending on he ype and deg ee o loss expe ienced by a
pe son. Basic hea ing aids allow o some cus omiza ion bu
a e limi ed in he amoun o adjus men s o i unusual pa e ns
o hea ing loss. Ad anced hea ing aids o e se e al di e en
le els o echnology. As he le el o echnology inc eases,
hea ing de ices a e mo e au oma ic, equipped wi h mo e
ea u es and allow o a mo e-pe sonal expe ience.
Some o he g ea es ad an ages o digi al signal
p ocessing in hea ing aids applica ions a e [10]:
 Gain P ocessing ( he po en ial o inc eased
audibili y o sounds o in e es wi hou discom o );
 Digi al Feedback Reduc ion (moni o o eedback
while he lis ene is wea ing he hea ing aid);
 Digi al Noise Reduc ion (in ended o educe gain in
he low equencies o bandwid h when noise is
de ec ed);
 Digi al Speech Enhancemen (a ela i ely new o
hea ing aid, i is in ended o imp o e empo al o
spec al con en o speech in o de o enhance
speech);
 Di ec ional Mic ophones and DSP (abili y o
di ec ional hea ing aids o imp o e he e ec i e
signal- o-noise a io p o ided o he lis ene );
 Digi al Hea ing Aids as Signal Gene a o s.
The hea ing aids p oduced oday u ilize wi eless
echnology. This allows wo hea ing aids o ope a e oge he
as one comple e sys em, ins ead o ac ing as wo independen
de ices. Addi ionally, wi eless echnology gi es hea ing aid
use s a g ea e abili y o cus omize hei expe ience and
p og am hei de ice.
Wi eless hea ing aids a e o en capable o wi elessly
communica ing wi h ex e nal de ices as well, as Blue oo h
echnology. Blue oo h enables hea ing aid wea e s o connec
pe sonal elec onic de ices such as mobile phones and s eam
signals di ec ly o he hea ing aid. Wi eless hea ing aids can
use compa ible assis i e lis ening de ices, o en called
s eame s, o p o ide a communica ion link be ween he
wi eless echnology in he hea ing aids and any Blue oo h-
enabled de ice.
A. Types o Hea ing Aids
While hea ing aids can be spli in o wo b oad ca ego ies –
in- he-ea s yles (ITE) and behind- he-ea s yles (BTE) – he e
a e se e al ypes a ailable wo n in di e en loca ions in o
behind he ea , allowing he wea e o ind he mos
com o able and bene icial i .
The ollowing hea ing aid ypes a e conside ed in- he-ea
s yles and a y om comple ely in isible and in he canal o
on he ou e edge o he ea bowl[11][12]:
 BTE – Behind he Ea . Placed behind he ea . Ve y
o en used in child en whe e sa e y is conce ned (Fig.
3).
Fig. 3 - BTE – Behind he Ea
 Behind-The-Ea Aid (Open Fi ing). Ve y simila o
he BTE bu wi h small and anspa en ube o
cosme ic easons (Fig. 4).
Fig. 4 – Behind The Ea (open i ing)
 ITC – In The Canal. De ice pa ially inside he canal
(Fig. 5).
Fig. 5 – ITC – In-The-Canal
 CIC – Comple ely in he canal. Almos as ITC, his
ype is enclosu e in a small box and comple ely
inside he canal. They o e he bes solu ions o
cosme ic pu poses (Fig. 5).
Fig. 5 – CIC – Comple ely In he Canal
 ITE – In The Ea . All pa s a e ou side he canal.
This ype is usually used by hose how a e no
com o able wi h CIC models (Fig. 6).
Fig. 6 – ITE – In-The-Ea
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B. Hea ing Aids in Mobile Applica ions
The e a e also hea ing aids a ailable as mobile
applica ions whe e i is possible o con ol some pa ame e s
ia Blue oo h [13], [14] (Fig. 7-8).
These mobile applica ions a e used o access o a as
a ay o pa ame e s con olling, ia Blue oo h. I is possible o
con ol olume, spa ial cus omized con igu a ions, among
o he s. They a e ee o cha ge and in ended o use wi h
Siemens hea ing aid p oduc s (Fig. 7) o GN ReSound (Fig.
8).
Fig. 7 – TouchCon ol App e easyTEK App om Siemens
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Fig. 8 – ReSound Con ol Mobile App om GN ReSound, a ailable o iOS.
The e a e some ools, in he o m o applica ion o mobile
de ices, usually limi ed, wi h some es s a ailable so ha he
use ha e an idea o his hea ing si ua ion. Some applica ions
(almos all o hem a e paywa e) can be used as a hea ing aid
as mobile’s headphones and mic ophone (Fig. 9 o Fig. 11,
cou esy o BioAidP ojec , Uni on Limi ed and Ginge Labs,
espec i ely).
This applica ion is in ended o gi e an audiome ic es so
ha he use may ha e an app oach o his/he hea ing loss and
hus, i necessa y, con ac he O o hinola yngology clinicians
o e alua e he p oblem.
Th ough a simple in e ace, he use can adjus a ew
pa ame e s o enchance hea ing.
Fig. 9 – Sc eensho om AUD1 [15], om BioAid P ojec , a ailable o iOS
de ices.
Fig. 10 – uHea [16] om Uni on Hea ing Limi ed
Fig. 11 – soundAMP R [17] om Ginge Labs
V. FINAL REMARKS
The esea ch objec i e is o apply DSP and il e ing
echniques o a hea ing model in o de o enhance speech.
Some echniques should be used like noise cancela ion,
ampli ica ion, comp ession, equency anspo a ion [18],
[19].
Hea ing aids a e based on complex algo i hms and well
de ined s uc u es. Algo i hms in ended o simula e he human
audi o y sys em ansla ing beha io s. Hea ing aids canno
o e come he pe cep ual dis o ions caused by hea ing loss bu
enables he use o unde s and he speech in a be e way [20-
23].

Recen Inno a ions in Mecha onics (RIiM) Vol. 2. (2015). No. 1-2.
DOI: 10.17667/ iim.2015.1-2/20.
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Acknowledgmen
This wo k has been suppo ed by FCT - Fundação pa a a
Ciência e Tecnologia in he scope o he p ojec : PEs -
UID/CEC/00319/2013.
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