Non-Invasive Intracranial Pressure Method and Monitor

The eyes are acoustically continuous with the brain and inner ear tissues in regard to matched impedances, based on tissue densities, thus, vibration of one site will be reflected in all sites. With this being the case, the vibrational energy response of the eye due to an external source can be used to determine a correlation or draw a conclusion concerning the vibrational energy response of the brain would be. And since there is a correlation between the vibrational energies, any changes in the acoustical energy in the eye can possibly be used to determine the changes in acoustical energy in the brain. Such an assertion was tested using the eye/balloon model, in which frequency specific tones can be used to analyze the vibrational response of the eye and the coupled brain. Changes in the intracranial pressure via the vibrational response induce changes in the intraocular pressure via the vibrational principle. Further, the model supports the observation that vibration delivered to the eye can be perceived as sound, if of sufficient intensity, resulting in an eye audiogram similar in degree to that obtained conventionally by bone conduction on the mastoid or forehead. The literature is suggestive that there is no positive correlation between IOP and ICP in terms of pressure, but there is a correlation when acoustical response is measured. This supports the possibility of measuring the changes in acoustical properties on the eye and within the cranium due to any external disruptions. The eye can therefore be considered an acoustical window to the brain and inner ear

Current Use and Future Perspectives of Spatial Audio Technologies in Electronic Travel Aids

Electronic travel aids (ETAs) have been in focus since technology allowed designing relatively small, light, and mobile devices for assisting the visually impaired. Since visually impaired persons rely on spatial audio cues as their primary sense of orientation, providing an accurate virtual auditory representation of the environment is essential. This paper gives an overview of the current state of spatial audio technologies that can be incorporated in ETAs, with a focus on user requirements. Most currently available ETAs either fail to address user requirements or underestimate the potential of spatial sound itself, which may explain, among other reasons, why no single ETA has gained a widespread acceptance in the blind community. We believe there is ample space for applying the technologies presented in this paper, with the aim of progressively bridging the gap between accessibility and accuracy of spatial audio in ETAs.This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement no. 643636.Peer Reviewe

A survey on hardware and software solutions for multimodal wearable assistive devices targeting the visually impaired

The market penetration of user-centric assistive devices has rapidly increased in the past decades. Growth in computational power, accessibility, and cognitive device capabilities have been accompanied by significant reductions in weight, size, and price, as a result of which mobile and wearable equipment are becoming part of our everyday life. In this context, a key focus of development has been on rehabilitation engineering and on developing assistive technologies targeting people with various disabilities, including hearing loss, visual impairments and others. Applications range from simple health monitoring such as sport activity trackers, through medical applications including sensory (e.g. hearing) aids and real-time monitoring of life functions, to task-oriented tools such as navigational devices for the blind. This paper provides an overview of recent trends in software and hardware-based signal processing relevant to the development of wearable assistive solutions

Binaural hearing with bone conduction stimulation

It has been argued that apparent masking-level differences (MLDs) in users of bilateral bone-anchored hearing aids (BAHAs) provide evidence of binaural hearing. However, there is considerably less acoustical isolation between the two ears with bone conduction (BC) compared to air conduction (AC). The apparent MLDs may have arisen, at least in part, from inter-cranial interference between signals arising from the two BAHAs (i.e. monaural effect). That might also explain some of the inter-individual variation in both the magnitude and the direction of the MLDs reported in BAHA users. The present study was composed of three experimental stages with the main aim to investigate the influence of interference in normal hearing participants by measuring masking level difference in AC and BC to explore the conditions contributing to the reported variation. An additional aim was to investigate the performance of a newly designed BC transducer; the balanced electromagnetic separation transducer (BEST), for bone conduction research as well as more general clinical use.Stage 1 evaluated the performance of the BEST in comparison to the clinically used RadioEar B71 in a series of acoustical (sensitivity and harmonic distortion) and psychoacoustical (hearing thresholds and vibrotactile thresholds) measurements. The results from these studies led to the use of the BEST in the second and third stages because they produced significantly lower harmonic distortion at low frequencies (mainly 250 Hz). The psychoacoustic measurements alluded to the need to use different calibration values with the BESTs.Stage 2 was a preliminary investigation comparing the MLDs with standard bilateral configurations between the AC and BC in nine normal-hearing participants. Signals were pure tones at one of three frequencies (250, 500, 1000 Hz), presented via AC or BC. Broadband noise (100- 5000 Hz) was always presented via AC at 70 dB SPL. Thresholds were estimated using a three-alternative forced choice procedure combined with an adaptive staircase. Transducers used were insert earphones and the BESTs for BC testing. The results from this stage showed a statistical significant difference between AC and BC MLDs at 250, 500 and 1000 Hz (mean difference is 9.4, 6.6 and 3.5 dB respectively). Evidence of the change in the MLDs direction is observed at 250 Hz in three participants.Stage 3 consisted of the investigation of inter-cranial interference in eighteen normal hearing participants. This stage was composed of three main measurements. The first measurement compared the AC and BC MLDs at three test frequencies. The second measurement evaluated the transcranial attenuation (TA). The third measurement was the novel feature of the study it evaluated the monaural interference effect through the measurement of the diotic and dichotic conditions in one test ear. A significant discrepancy was found between the AC and BC MLDs of approximately 6, 1.5 and 2.5 dB at 500, 1000 and 2000 Hz, respectively. The TA was found to be lower than 10 dB at the three test frequencies. Measurable MTLDs were reported in some of the participants, high inter-subject variability was observed in the direction of the MTLDs.The BEST can reliably replace the B71 in clinical setup. Formal adjustment of the reference equivalent threshold force levels is advised. Binaural hearing was achieved through bilateral BC stimulation to a lesser magnitude compared to AC MLDs in normal hearing participants. The discrepancy between the AC and BC MLDs was reduced with the increase in the frequency. The discrepancy can partially be explained by the cross-talk of the signal in one ear. The results showed that in some participants the magnitude of the monaural tone level difference was similar to the magnitude of the BC MLD. Further investigation is recommended to investigate the association of the transcranial delay with the discrepancy between the AC and BC MLDs. This investigation also recommends the investigation of the AC and BC MLDs in patients fitted with bilateral BAHAs

Computer assisted audiometric evaluation system

A computer-based audiometric evaluation system has been developed. The system makes use of an IBM PC/XT/AT compatible personal computer to perform pure tone and speech tests and · comprises a plug-in card and custom software. The card contains pure tone and masking noise generators, together with amplifiers for a. set of headphones .and bone conduction transducer, patient and audiologist microphone amplifiers and a hand-held infra-red remote-control unit. A voice-operated gain-adjusting device on the audiologist's microphone eliminates the need for a sound pressure level meter during speech tests. The software-based user-interface makes use.of overlaid pop-up menus, context sensitive assistance.and a text editor on a graphics screen. Pure tone and speech data are acquired and displayed on a dynamic audiogram and speech discrimination gram respectively. This data may be stored and later retrieved from a patient data base. Further audiometric tests may be incorporated at a later stage

Space Time Exploration of Musical Instruments

Musical instruments are tools used to generate sounds for musical expression. Virtual Reality (VR) and Augmented Reality (AR) musical instruments create sounds that may be spatially disjointed from the instrument controls. Spatial audio processing can be used to position the Extended Reality (XR) musical instruments and their corresponding sounds in the same space. This dissertation investigates novel ways of combining spatial reverb models to improve the naturalness of XR musical instruments. Seven spatial reverb systems, combinations of a shoebox spatial reverb model, a raytracing spatial reverb model, and measured directional room impulse response convolution reverb, were compared in a pilot study. A novel hybrid system of synthetic early reflections and directional room impulse responses was preferred for naturalness when tested over headphones with three instruments created by the author: AR electric guitar, AR drumset, and VR Singing Kite. This research culminated in a concert, Spherical Sound Search, which showcased the preferred hybrid system, the three XR musical instruments, and four re-contextualized spatial audio effects (spatial looping, spatial delay, spatial feedback, and spatial compression). The three pieces in the concert explored different aspects of XR modalities and presented the novel system with spatial audio effects to a larger audience by rendering to an octophonic loudspeaker layout

Virtual Heritage: Audio design for immersive virtual environments using researched spatializers.

This thesis work is based on a Virtual Heritage project being developed by the Systems of Representation research group. The objective of the project is to create a showcase demonstration on how the virtual reality (VR) could be used as an application for tourism in the heritage sector. In this context, my task was to develop a concept and prototype of how 'spatialized' sound could be used in a VR application. The initial location chosen for the concept was the ancient heritage burial site of Sammallahdenmäki, one of the Finnish heritage sites listed in the UNESCO register of World Heritage Sites. The thesis, that is written from an audio designer's perspective, focuses on three aspects of this project. First is the sound design for the Virtual Heritage project and the second is the quality of currently available 'spatializer' plug-ins used for headphone listening. In order to evaluate the process of designing 3D audio for virtual environments, the methods and principles within binaural rendering, sound design and immersion must be understood. Therefore, functions and theories within audio spatialization and 3D audio design are reviewed. Audio designers working on virtual reality content need the best possible solutions for creating believable 3D audio experiences. However, while working on the Virtual Heritage project, we did not find any comparative studies made about commercially available spatializer plug-ins for Unity. Thus, it was unknown what plug-in would have been the best possible solution for 3D audio spatialization. Consequently, two tests were conducted during this thesis work. First was an online test measuring which spatializer would be the most highly rated, in terms of perceived directional precision when utilizing head-related transfer functions without reverb or room simulations. The second was a comparative test studying if a spatialized audio rendering would increase immersion compared to non-spatialized audio rendering, when tested with the Virtual Heritage demonstration. The central aim in the showcase demonstration was to create an immersive virtual environment where users would feel as if they were travelling from the present, back to the Bronze Age, in order to understand and learn about the location’s unique history via auditory storytelling. The project was implemented utilising the Unity game engine. The research on music and other sound content used in the project’s sonic environment is explained. Finally, results of the project work are discussed.Tämä opinnäytetyö perustuu Virtual Heritage projektityöhön, joka on tehty Systems of Representation tutkimusryhmälle. Projektin tavoite on luoda malliesimerkki siitä, miten virtuaalitodellisuutta voitaisiin käyttää hyväksi turismisovelluksissa. Esimerkkikohteeksi projektille oli valittu Sammallahdenmäen hautaröykkiöt, joka on hyväksytty mukaan UNESCON maailmanperintöluetteloon. Tehtäväni oli toteuttaa Unity pelimoottorilla prototyyppi, jossa kartoitetaan virtuaalisen tilaäänen käyttömahdollisuuksia kyseisen teeman ympärillä. Opinnäyte on kirjoitettu äänisuunnittelijan näkökulmasta keskittyen kolmeen projektityöhön liittyvään keskeiseen osaan: prototyypin äänisuunnitteluun, immersion käsitteeseen sekä spatialisointi liitännäisten (plug-in) toimintaan ja laatuun. Virtuaalitodellisuuksiin sisältöä tuottavana äänisuunnittelijana tarvitsin parhaat mahdolliset työkalut uskottavan 3D äänimaailman luomiseen. Virtual Heritage projektia työstettäessä kävi kuitenkin ilmi, että ajankohtaista vertailevaa tutkimusta spatialisointi liitännäisten laatueroista ei ollut löydettävissä. Oli mahdotonta määritellä yksilöllisesti, mikä liitännäisistä on toimivin ratkaisu suurimmalle käyttäjäkunnalle. Täten oli tarpeellista toteuttaa kaksi tutkimusta. Ensimmäinen oli empiirinen verkkotutkimus, jolla arvioitiin spatialisointi liitännäisten suorituskykyä, kun mitataan subjektiivisesti äänen tilallisen sijoittumisen tarkkuutta kuulokekuuntelussa ilman kaikuprosessointeja. Tutkimuksessa parhaiten suoriutunut liitännäinen implementoitiin prototyyppiin. Toisessa kokeessa tutkittiin kuinka paljon implementoidun spatialisointi liitännäisen käyttäminen lisää virtuaalitodellisuuden immersiota verrattaessa spatialisoimattomaan ääneen, kun testialustana toimii Virtual Heritage prototyyppi. Projektin keskeisin tavoite oli luoda immersiivinen virtuaalitodellisuus, jossa käyttäjä voi kokea matkaavansa nykyajasta pronssikautiselle Sammallahdenmäelle ja oppia tällä tavoin kohteen ainutlaatuisesta historiasta äänikerronnan keinoin. Opinnäytetyössä esitellään äänikerronnan sisältöön ja toteutustapaan johtavat tutkimukset, tuotanto sekä ajatukset lopputuloksesta

The Acclimatization Effects of Earplugs on Acoustic and Perceptual Measures of University Singers' Vocal Performances in Choral and Solo Settings

ABSTRACT The purpose of this study was to assess with female university singers (N = 34) the potential acclimatization effects of wearing one brand of earplugs marketed to musicians on selected acoustic and perceptual measures of choral and vocal sound. Data were acquired during four data collection sessions across four weeks. Participants were members of two established women's choirs, Group A (n = 24) and Group B (n = 10). Each choir sang the same musical excerpt three times during weekly data collection periods: without-earplugs at rehearsal start, with-earplugs at rehearsal start, and with-earplugs at rehearsal end. For comparison purposes, Group A wore the earplugs at each of three rehearsals per week, while Group B wore the earplugs only during data collection rehearsals. Additionally, one-half of the singers, randomly selected, participated in weekly solo recording sessions that followed a similar protocol. Digital audio recordings of the choral and solo singing performances were used for analyses of long term average spectra (LTAS), intonation, and amplitude. Among primary results: (a) choral and solo LTAS data indicated significant differences in mean signal amplitudes between the no-earplugs and with-earplugs conditions, (b) solo amplitude means indicated a < 1 dB difference between conditions in 90% of the recordings, (c) choral pitch analyses indicated earplugs did not cause choristers to sing less in-tune, (d) fundamental frequency analyses indicated that earplugs did not cause soloists to sing significantly more or less in-tune, and (e) the majority of choral (87.50%) and solo singers (75%) reported being able to hear themselves best when not wearing earplugs during the weekly recording sessions. The results were discussed in terms of possible acclimatization effects, limitations of the study, and suggestions for future research