ICSV Crn Autrl 9- July, 7 DIGIAL HEARING AID DSP CHIP PARAMEER FIING OPIMIZAION Soon Suk Jrng Dept. of Informton & Communton Eng. Choun Unverty Gwng-Ju 5-759, South Kore jrng@houn..kr Atrt DSP hp prmeter of dgtl herng d (HA hould e optmlly eleted or ftted for herng mpred peron. he more pree prmeter fttng gurntee the etter ompenton of the herng lo (HL. Dgtl HA dopt DSP hp for more pree fttng of vrou HL threhold urve pttern. A pef DSP hp uh Gennum GB3 w degned nd mnuftured n order to mth up to out.7 llon dfferent pole HL e wth omnton of 7 lmted prmeter. h pper del wth dgtl HA fttng progrm whh developed for optml fttng of GB3 DSP hp prmeter. he fttng progrm h ompleted feture from udogrm nput to DSP hp nterfe. he ompenton effet of the mrophone nd the reever re lo nluded. he pper how ome pplton exmple.. INRODUCION Herng mpred peron hve nreed HL threhold urve over udo frequeny nd, o tht ther herng mprment my e prtly ompented y HA. Before 99 nlog HA domnted HA mrket even though nlog HA re lmted n the HL ompenton eue they re not modfle. In nlog IE(In-he-Er type HA logrthm volume ontrol wth the only wy of modfton. here were ome onventonl fttng formul developed for etter hoe of mplfton nd ompreon []. he dvent of the ophtted emondutor tehnology well the etter undertndng of the herng phyology opened the ge of dgtl HA lt dede. Dgtl HA re modfle, tht, eh dfferent type of herng mprment n e preely ompented wth the me l of the dgtl HA. hee mult-purpoed dgtl HA re pole y doptng DSP ed IC hp degn nd mnufturng. DSP hp for dgtl HA re dvded nto two tegore; pef DSP hp nd generl DSP hp. he pef HA DSP hp w produed erler eue the mnture e of the hp pkge w requred for IE type HA frton []. Reently, generl DSP hp re gettng down n pkgng e wth lower power onumpton, o to e ppled to IE type HA [3, ]. A dgtl HA upport more funton nd flexlte, the fttng method of the dgtl HA eome mportnt ue n the herng d mrket. h
ICSV 9- July 7 Crn Autrl pper pple pef DSP hp uh Gennum GB3 (Fg. to dgtl HA frton nd how the reult of the optml prmeter fttng progrm development for the hp. he mn feture of GB3 re hnnel nonlner ompreve tve flterng nd extr lner qud flterng. hoe 8 tve dgtl flter re ued for fttng of vrou pttern of HL threhold urve. In th pper GB3 hp fttng progrm w developed for dgtl HA n whh the mot optml DSP hp prmeter were eleted from.7llon omnton of pole prmeter.. DSP PARAMEER FIING PROCEDURES AND RESULS Fgure. he ntl menu wndow of the dgtl HA fttng progrm. Audogrm Herng hrehold Fgure 3. he flow hrt of the prmeter fttng. he frt tep of the prmeter fttng to red the HL threhold of the herng mpred peron (Fg... Fttng Formul Fgure. Ar onduton HL threhold. x(left Er, o(rght Er. he eond tep to lulte the HA mplfton funton of frequeny y onventonl fttng formul uh FIG6. le how the nonlner Fg6 Formul []. le. Nonlner FIG6 Formul []. Input Level IG IG Gn. db SPL H < db HL H - H 6 db HL.5 H H >6 db HL 65 db SPL H < db HL.6( H - H 6 db HL.8 H -3 H >6 db HL H HL Input.
ICSV 9- July 7 Crn Autrl 95 db SPL H < db HL.( H -. H db HL Fg. 5 how the mount of the HA mplfton funton derved from the nonlner FIG6 formul. he three ontnuou lk thn lne of the fgure ndte how muh mplfton hould e done y the HA mplfer for three dfferent nput ound level. A the nput ound level gger, the reltve nrement of the mplfton eome mller eue of nonlnerty. If ny nlog mplfton hp n produe the mlr nonlner frequeny repone the fgure for prtulr herng mpred peron, the nlog hp peflly good enough for the peron. However every herng mpred peron hve eh dfferent mplfton requrement, o tht eh peron h to hve h/her own pef nlog hp. ht very uneonoml. Dgtl HA hp re degned to dpt to uh dvere requrement. ( Left Er ( Rght Er Fgure 5. HA mplfton funton derved from the nonlner FIG6 formul..3 DSP hp prmeter fttng he thrd tep to lulte DSP hp prmeter for fttng to the HA mplfton funton. he word, fttng, ometme onfued. In generl fttng men fttng formul n the eond tep. he prmeter fttng n the thrd tep men the proper djutment of the DSP hp prmeter n order for the DSP hp to reemle to the HA mplfton funton derved y the eond tep. Fg. 6 how the reult of the fttng formul (three lk thn lne nd the prmeter fttng (three olored thk lne y fttng progrm uppled y Gennum Co. he lue lne for db nput ound level, nd the green nd the volet lne re for 6dB nd 8dB nput ound level repetvely. he prmeter fttng eem to e ll rght t low frequeny nd, ut the prmeter fttng not well reemle to the HA mplfton funton t hgh frequeny nd. herefore th pper tred etter prmeter fttng thn Gennum. If we look t the opertonl prnple of the Gennum 3 DSP hp, ome etter optml prmeter fttng method ould e reulted. he Gennum 3 hp dvde the frequeny nd nto four hnnel. Eh hnnel oundry defned ro frequeny, CO, (Fg. 7. In Fg. 7 the red thk lne ndte HA mplfton funton. Eh hnnel of Fg. 7 ontrolled y eh dgtl flter; CHLow P (LP Flter, CHBnd P (BP Flter, CH3 Bnd P (BP Flter, CH Hgh P (HP Flter [5]. he four dgtl flter repone re ummed to reemle to the HA mplfton funton. 3
ICSV 9- July 7 Crn Autrl ( Left Er ( Rght Er Fgure 6. he reult of the fttng formul (thn lne nd the prmeter fttng (thk lne y fttng progrm uppled y Gennum Co. Blue: db Input Level, Green: 6dB Input Level, Volet: 8dB Input Level. he hnnel dgtl flter Butterworth type. he frt hnnel ompoed y the thrd order LP3 rd low p flter, f o. f ut-off frequeny nd o the frt ro frequeny. he eond hnnel ompoed y eond order hgh p flter well thrd/fourth order low ( HP nd LP ( 3 p flter, th HP f o nd LP f o f o rd f o. he thrd hnnel ompoed y thrd/ffth order hgh p flter well eond/thrd order low p flter, ( HP rd LP nd ( HP5 th LP3 rd 3 f o f o3 f o f o3 ( HP ( nd HP f o3 5th f o3 eond/ffth order hgh p flter,. he fourth hnnel ompoed y Fgure 7. Four hnnel eprtely formed y four dgtl flter. he four dgtl flter repone re ummed to reemle to the HA mplfton funton. le. Butterworth dgtl flter formul. N numer of order [5].. N th N -order Low-P Flter Even N / ω H ( k ω oφk ω Odd ( N / ω ω H ( ω k ω oφ k ω N th N -order Hgh-P Flter Even N / H( k ω oφk ω ( N Odd / H( ω k ω oφk ω Where f Frequeny, ω Cut-off ngulr frequeny, ω πf, jω, even, kπ φ k (N odd. N k π φ (. 5 k (N N Gennum 3 hp h three ro frequeny prmeter nd eh CF prmeter lgned wt h 69 fxed frequene (le 3. Alo eh hnnel h four prmeter; LH(Low hreh old, LLGAIN(Low Level Gn, UH(Upper hrehold, HLGAIN(Hgh Level Gn whh
ICSV 9- July 7 Crn Autrl re ued for nonlner ompreon (Fg. 8, le. Fgure 8. Nonlner ompreon reltonhp etween nput ound level nd output ound level. LH(Low hrehold, LLGAIN(Low Level Gn, UH(Upper hrehold, HLGAIN(Hgh Level Gn. he ntl mnmum numer of prmeter for the prmeter fttng re CF(6, CF(9, CF3(7, LLGAIN(3, LLGAIN(3, LLGAIN3(3, LLGAIN(3 whh generte.7 llon pole omnton of prmeter (.7 llon 6x9x7x3x3x3x3. hoe even DSP hp prmeter my e optmlly lulted y men qure method whh mnme the dfferene etween the dered HA mplfton funton nd the mpltude repone urve derved y pplyng dfferent prmeter et. he nput frequeny vrle nd we lmt the numer of the nput frequeny for fter lulton. Fg. 9 how the reult of the fttng formul (three lk thn lne nd the prmeter fttng (three olored thk lne y fttng progrm developed y uthor. In ompron wth Fg. 6 the optml prmeter fttng eem to e etter t ll frequeny nd thn Gennum. ( Left Er ( Rght Er Fgure 9. he reult of the fttng formul (thn lne nd the optml prmeter fttng (thk lne y fttng progrm developed y uthor. Blue: db Input Level, Green: 6dB Input Level, Volet: 8dB Input Level.. Compenton for the mrophone nd the reever he fourth tep to remove the reonne effet of the mrophone nd the reever. Fg. how the frequeny repone of the mrophone nd the reever repetvely. If the reonne effet of the mrophone nd the reever re dded to the optml prmeter fttng, the reultnt repone urve re hown n Fg.. he ummed reonne effet of the mrophone nd the reever reult n the feedk of the IE type HA. herefore the Gennum 3 DSP hp h nother four extr qud dgtl flter for the ompenton of the feedk reonne effet (Fg.. 5
ICSV 9- July 7 Crn Autrl Fgure. Frequeny repone of the mrophone nd the reever. Dotted lne re trunted repone. ( Left Er ( Rght Er Fgure. he reult of the fttng formul (thn lne nd the optml prmeter fttng (thk lne wth the reonne effet of the mrophone nd the reever. Blue: db Input Level, Green: 6dB Input Level, Volet: 8dB Input Level. Fgure. Four qud dgtl flter re extr flter for the ompenton of the feedk reonne effet. Eh qud dgtl flter degned y eond order IIR (Infnte Impule Repone dgtl flter hown n Fg. 3 [6]. Z Z ( H ( ( Z Z Fgure 3. he truture ( nd the formul ( of the dgtl qud flter. <,,,, <. le 5. he oeffent of the nlog qud flter ( H ( /( [6] he oeffent of the dgtl qud flter re dereved from the oeffent of the nlog qud flter ( H ( ( / where ω enter/ut-off ngulr frequeny, A n mplfton rto ( A >., Q qulty ftor (.779. he oeffent of 6
ICSV 9- July 7 Crn Autrl 7 the dgtl qud flter re lmted etween nd eue of 5 t gned reoluton lmt. herefore A nd Q hould e djuted to e wthn the lmt. he lner trnformton from S domn to Z domn, ( ( ( H ( ( ( H, done flowng equton; ( 8 ( (3 8 ( (5 where ( ( ( f f f π π tn, f 3 [H] Fg. how the reult of the optml prmeter fttng wth the reonne effet nellton of the mrophone nd the reever y four extr qud flter. In ompron wth Fg., Fg. how more pree fttng to the fttng formul urve thn Fg.. Fg. 5 how the nonlner nput-to-output ompreon urve for four dfferent frequene. And Fg. 6 how nonlner output ound preure level gnt nput ound preure level funton of frequeny. ( Left Er ( Rght Er Fgure. he reult of the fttng formul (thn lne nd the optml prmeter fttng (thk lne wth the reonne effet nellton of the mrophone nd the reever y four qud flter. Blue: db Input Level, Green: 6dB Input Level, Volet: 8dB Input Level. Fgure 5. Nonlner nput/output ompreon urve for four dfferent frequene. ( Left Er ( Rght Er
ICSV 9- July 7 Crn Autrl Fgure 6. Nonlner output ound preure level (db SPL gnt nput ound preure level funton of frequeny. 3. CONCLUSIONS h pper pple pef DSP hp uh Gennum GB3 to dgtl IE type HA frton nd how the reult of the optml prmeter fttng progrm development for the hp. Detl of hp prmeter re explned. he fttng progrm h ompleted feture from udogrm nput to DSP hp nterfe. he ompenton effet of the mrophone nd the reever re lo nluded. he ompron etween Fg. 6 nd Fg. 9 how tht the DSP hp prmeter uh.7 llon pole omnton of prmeter hould e optmlly hoen to reemle to the mount of herng threhold ompenton derved y the fttng formul. Extr dgtl flter need to e dded for the omplete fttng to the HA mplfton funton. Even though the preent DSP hp prmeter fttng progrm provde the et fttng for the fttng formul, the fnl pree fttng hould e mnully djuted y the uer, tht, the herng mpred peron [7,8]. ACKNOWLEDGEMEN h tudy w upported y rn Kore (BK, 7. REFERENCES [] Hrvey Dllon, "Herng Ad", Prnted y heme,. [] http://www.gennum.om/hp/dprodut/prgon/g3.htm [3] http://www.gennum.om/hp/dprodut/duet/g3.htm [] http://www.dpftory.om/tehnology/gnklrtehnology.html [5] Chewook Lee, Reent dgtl gnl proeng, pulhed y BookHll Co.,. [6] Gennum Co., Bqud flter n PARAGON dgtl hyrd, Do. No. 5-,. [7] B. Kollmeer nd V. Hohmnn, "Loudne etmton nd ompenton employng tegorl le," n Advne n Herng Reerh, G. A. Mnley, G. M. Klump, C. Köppl, H. Ftl, nd H. Oeknghu, Ed. Sngpore: World Sentf, pp. -5. 995. [8] S. Luner nd B. C. J. Moore, "Ue of loudne model for herng d fttng. V. On-lne gn ontrol n dgtl herng d," Int. J. Audol., vol., pp. 6-73, 3. 8