Pinna Reconstruction Filter for Behind the Ear Hearing Aids

van Hauen, Sigurd Møller

4. term

Acoustics and Audio Technology, Master

2018

2018-06-07

79

Øremuslingen (pinna) former lydbølgerne og giver vigtige ledetråde til at afgøre, hvor lyde kommer fra. I bag-øret-høreapparater sidder mikrofonerne bag øret, så lyden ikke naturligt formes af øremuslingen, og brugerne mister dermed rumlige ledetråde. Specialet undersøger overføringsfunktionen mellem høreapparatets mikrofoner og øregangen. Disse målinger danner grundlag for en pinna reconstruction transfer function (PRTF) – en metode til at genskabe øremuslingens påvirkning af lyden for høreapparatbrugere. Vi byggede en måleopstilling og indsamlede hovedrelaterede overføringsfunktioner (HRTF’er), dvs. hvordan hoved og ører ændrer lyden afhængigt af retning, fra 611 unikke lydretninger omkring fire forsøgspersoner. Ud fra målingerne syntetiserede vi pinna-rekonstruktionsfiltre. PRTF’ernes retningskarakteristik (hvordan følsomheden varierer med retning) adskiller sig markant fra en delay-and-sum beamformer, især som funktion af elevationsvinkel (op/ned-retning). Derudover udviklede vi en realtids testplatform til høreapparat-signalbehandling, så lokalisering med PRTF-filtrene kan evalueres og sammenlignes med delay-and-sum beamforming. Platformen blev afprøvet ved dynamisk binaural syntese, dvs. generering af rumlig to-øres lyd i realtid.

The outer ear (pinna) shapes incoming sound and provides important cues for locating where sounds come from. In behind-the-ear hearing aids, the microphones sit behind the ear, so the sound is not naturally shaped by the pinna and users lose spatial cues. This thesis investigates the transfer function between the hearing aid microphones and the ear canal. These measurements form the basis of a pinna reconstruction transfer function (PRTF), intended to restore pinna-related cues for hearing aid users. We built a measurement setup and collected head-related transfer functions (HRTFs)—how the head and ears change sound depending on direction—from 611 unique source positions surrounding four participants. From these measurements, we synthesized pinna reconstruction filters. The PRTFs’ directivity patterns (how sensitivity varies with direction) differ markedly from those of a delay-and-sum beamformer, especially as a function of elevation (up/down angle). In addition, we developed a real-time test platform for hearing-aid signal processing to evaluate localization with the PRTF filters and compare it to delay-and-sum beamforming. The platform was tested by performing dynamic binaural synthesis, i.e., generating real-time spatial two-ear audio.

[This abstract was generated with the help of AI]

høreapperat ; hørelse ; speciale ; projekt ; aau ; binaural ; synthesis ; auralization ; dynamic ; HRTF ; head-related transfer function ; measurements ; BTE ; HA ; BTE-HA ; real-time ; simulation ; acoustics

Download
View record in AAU Student Projects