Audibility and Interpolation of Head-Above-Torso Orientation in Binaural Technology

Head-related transfer functions (HRTFs) incorporate fundamental cues required for human spatial hearing and are often applied to auralize results obtained from room acoustic simulations. HRTFs are typically available for various directions of sound incidence and a fixed head-above-torso orientation (HATO). If-in interactive auralizations-HRTFs are exchanged according to the head rotations of a listener, the auralization result most often corresponds to a listener turning head and torso simultaneously, while-in reality-listeners usually turn their head independently above a fixed torso. In the present study, we show that accounting for HATO produces clearly audible differences, thereby suggesting the relevance of correct HATO when aiming at perceptually transparent binaural synthesis. Furthermore, we addressed the efficient representation of variable HATO in interactive acoustic simulations using spatial interpolation. Hereby, we evaluated two different approaches: interpolating between HRTFs with identical torso-to-source but different head-to-source orientations (head interpolation) and interpolating between HRTFs with the same head-to-source but different torso-to-source orientations (torso interpolation). Torso interpolation turned out to be more robust against increasing interpolation step width. In this case the median threshold of audibility for the head-above-torso resolution was about 25 degrees, whereas with head interpolation the threshold was about 10 degrees. Additionally, we tested a non-interpolation approach (nearest neighbor) as a suitable means for mobile applications with limited computational capacities

Using a one-dimensional finite-element approximation of Webster's horn equation to estimate individual ear canal acoustic transfer from input impedances

In many applications, knowledge of the sound pressure transfer to the eardrum is important. The transfer is highly influenced by the shape of the ear canal and its acoustic properties, such as the acoustic impedance at the eardrum. Invasive procedures to measure the sound pressure at the eardrum are usually elaborate or costly. In this work, we propose a numerical method to estimate the transfer impedance at the eardrum given only input impedance measurements at the ear canal entrance by using one-dimensional first-order finite elements and Nelder-Mead optimization algorithm. Estimations on the area function of the ear canal and the acoustic impedance at the eardrum are achieved. Results are validated through numerical simulations on ten different ear canal geometries and three different acoustic impedances at the eardrum using synthetically generated data from three-dimensional finite element simulations.Comment: 16 pages, 15 figure

On sound source localization of speech signals using deep neural networks

In recent years artificial neural networks are successfully applied especially in the context of automatic speech recognition. As information processing systems, neural networks are trained by, e.g., backpropagation or restricted Boltzmann machines to classify patterns at the input of the system. The current work presents the implementation of a deep neural network (DNN) architecture for acoustic source localization.EC/FP7/318381/EU/Experimenting Acoustics in Real environments using Innovative Test-beds/EAR-ITEC/FP7/284628/EU/Sounds for Energy Control of Buildings/S4ECoBEC/FP7/609180/EU/Energy efficient & Cost competitive retrofitting solutions for Shopping buildings/ECOSHOPPIN

A one-size-fits-all earpiece with multiple microphones and drivers for hearing device research

Earpieces that include one or more microphones and drivers are required in many research applications related to hearing devices, however suitable devices are often not readily available. In this contribution we present the development and evaluation of an earpiece for research on assistive hearing devices and hearables. The earpiece includes two balanced armature drivers as well as four microphones, which are built into a one-size-fits-all acrylic shell. It features custom transducer positioning at different positions inside a vent, as well as a microphone inside the ear canal. We discuss details on the earpiece design, present acoustic measurements, and discuss the eligibility for different applications. The earpiece is openly available both in a vented as well as an occluded version