Implementation of Sustainable Aviation Fuel. A PESTEL-analysis

Global climate changes are one of the greatest global threats affecting society. All sectors, from the largest ventures to the single individual, must aid in addressing and affecting these changes, resulting in a more sustainable and green future for the generations to come. Aviation currently stands for approximately 2.5% of global total anthropogenic CO2-emissions, which is rapidly climbing towards 24% by 2050, not even mentioning NOx, CO, other non-CO2 effects etc. The industry thereby also faces immense challenges to reach sustainability goals as set out by organizations, unions, and nations throughout the world. These considerable developments call for radical progresses in technology, innovation and development in all aspects of the industry. This thesis focuses on perhaps the most substantial means of developing the industry – replacing the means of propulsion. This thesis identifies the major component being transitioning to Sustainable Aviation Fuel (SAF) as a replacement to conventional kerosene Jet-A1. This study will analyze how SAF can reduce aviation’s overall emission footprint. This task will be undertaken using the PESTEL-analysis tool as a framework for uncovering barriers and challenges. Through an extensive literature review together with multiple expert interviews from various experts in the field, several conflicts from actors in the field has been identified and solutions presented under the different subparts of the PESTEL-analysis. Finally, an overview on the interaction between the different subparts will be discussed. This study identifies, among others, the lack of international legislation, vast production cost and supply of feedstock as major barriers needing a solution. It is evident that international cooperation and further political and economic incentives are necessary to drive an industry as complex and governed as aviation towards fulfilling the sustainability ambitions set out

Sensitivity to Angular and Radial Source Movements as a Function of Acoustic Complexity in Normal and Impaired Hearing

In contrast to static sounds, spatially dynamic sounds have received little attention in psychoacoustic research so far. This holds true especially for acoustically complex (reverberant, multisource) conditions and impaired hearing. The current study therefore investigated the influence of reverberation and the number of concurrent sound sources on source movement detection in young normal-hearing (YNH) and elderly hearing-impaired (EHI) listeners. A listening environment based on natural environmental sounds was simulated using virtual acoustics and rendered over headphones. Both near-far (‘radial’) and left-right (‘angular’) movements of a frontal target source were considered. The acoustic complexity was varied by adding static lateral distractor sound sources as well as reverberation. Acoustic analyses confirmed the expected changes in stimulus features that are thought to underlie radial and angular source movements under anechoic conditions and suggested a special role of monaural spectral changes under reverberant conditions. Analyses of the detection thresholds showed that, with the exception of the single-source scenarios, the EHI group was less sensitive to source movements than the YNH group, despite adequate stimulus audibility. Adding static sound sources clearly impaired the detectability of angular source movements for the EHI (but not the YNH) group. Reverberation, on the other hand, clearly impaired radial source movement detection for the EHI (but not the YNH) listeners. These results illustrate the feasibility of studying factors related to auditory movement perception with the help of the developed test setup

A framework for geometry acquisition, 3-D printing, simulation, and measurement of head-related transfer functions with a focus on hearing-assistive devices

Individual head-related transfer functions (HRTFs) are essential in applications like fitting hearing-assistive devices (HADs) for providing accurate sound localization performance. Individual HRTFs are usually obtained through intricate acoustic measurements. This paper investigates the use of a three-dimensional (3D) head model for acquisition of individual HRTFs. Two aspects were investigated; whether a 3D-printed model can replace measurements on a human listener and whether numerical simulations can replace acoustic measurements. For this purpose, HRTFs were acoustically measured for four human listeners and for a 3D printed head model of one of these listeners. Further, HRTFs were simulated by applying the finite element method to the 3D head model. The monaural spectral features and spectral distortions were very similar between re-measurements and between human and printed measurements, however larger deviations were observed between measurement and simulation. The binaural cues were in agreement among all HRTFs of the same listener, indicating that the 3D model is able to provide localization cues potentially accessible to HAD users. Hence, the pipeline of geometry acquisition, printing, and acoustic measurements or simulations, seems to be a promising step forward towards in-silico design of HADs

Temporal Fine-Structure Coding and Lateralized Speech Perception in Normal-Hearing and Hearing-Impaired Listeners

This study investigated the relationship between speech perception performance in spatially complex, lateralized listening scenarios and temporal fine-structure (TFS) coding at low frequencies. Young normal-hearing (NH) and two groups of elderly hearing-impaired (HI) listeners with mild or moderate hearing loss above 1.5 kHz participated in the study. Speech reception thresholds (SRTs) were estimated in the presence of either speech-shaped noise, two-, four-, or eight-talker babble played reversed, or a nonreversed two-talker masker. Target audibility was ensured by applying individualized linear gains to the stimuli, which were presented over headphones. The target and masker streams were lateralized to the same or to opposite sides of the head by introducing 0.7-ms interaural time differences between the ears. TFS coding was assessed by measuring frequency discrimination thresholds and interaural phase difference thresholds at 250 Hz. NH listeners had clearly better SRTs than the HI listeners. However, when maskers were spatially separated from the target, the amount of SRT benefit due to binaural unmasking differed only slightly between the groups. Neither the frequency discrimination threshold nor the interaural phase difference threshold tasks showed a correlation with the SRTs or with the amount of masking release due to binaural unmasking, respectively. The results suggest that, although HI listeners with normal hearing thresholds below 1.5 kHz experienced difficulties with speech understanding in spatially complex environments, these limitations were unrelated to TFS coding abilities and were only weakly associated with a reduction in binaural-unmasking benefit for spatially separated competing sources