Sound Localization and Lateralization by Bilateral Bone Conduction Devices, Middle Ear Implants, and Cartilage Conduction Hearing Aids.

Kimio Shiraishi

doi:10.3390/audiolres11040046

Abstract

Sound localization in daily life is one of the important functions of binaural hearing. Bilateral bone conduction devices (BCDs), middle ear implants, and cartilage conduction hearing aids have been often applied for patients with conductive hearing loss (CHL) or mixed hearing loss, for example, resulting from bilateral microtia and aural atresia. In this review, factors affecting the accuracy of sound localization with bilateral BCDs, middle ear implants, and cartilage conduction hearing aids were classified into four categories: (1) types of device, (2) experimental conditions, (3) participants, and (4) pathways from the stimulus sound to both cochleae. Recent studies within the past 10 years on sound localization and lateralization by BCDs, middle ear implants, and cartilage conduction hearing aids were discussed. Most studies showed benefits for sound localization or lateralization with bilateral devices. However, the judgment accuracy was generally lower than that for normal hearing, and the localization errors tended to be larger than for normal hearing. Moreover, it should be noted that the degree of accuracy in sound localization by bilateral BCDs varied considerably among patients. Further research on sound localization is necessary to analyze the complicated mechanism of bone conduction, including suprathreshold air conduction with bilateral devices.

Highlights

We are surrounded by many different sounds and we can know where they are and how far they are from us
The results showed that the response accuracy was significantly better with bilateral bone conduction device (BCD) (22%) than with unilateral BCDs (16%)
Most of the recent studies on sound localization and lateralization have shown that performance with bilaterally fitted devices was better than that with unilaterally fitted device for bilateral conductive hearing loss (CHL)

Summary

Introduction

We are surrounded by many different sounds and we can know where they are and how far they are from us The ITD is defined as the difference in arrival time between the two ears and is the most important cue to sound localization for low-frequency components [2]. Sound localization in the vertical plane is accomplished through filtering by the pinnae and the head itself This filtering can be expressed in “headrelated transfer functions (HRTFs)” [1]. With regard to hearing aids, there are differences in the HRTF depending on the angle at which the sound is presented from the loudspeaker when the device is worn, or where the device microphone is placed on the head. Sometimes the term “lateralization” is used to judge whether the sound appears from the right or the left when presented by a loudspeaker [3]

Methods

Results

Conclusion