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Sensing the environment: development of monitoring aids for persons with profound deafness or deafblindness
Örebro University, School of Science and Technology. (Elektronik)
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Earlier studies of persons with deafness (D) and/or deafblindness (DB) have primarily focused on the mobility and communication problems. The purpose of the present study was to develop technology for monitoring aids to improve the ability of persons with D and/or DB to detect, identify, and perceive direction of events that produce sounds in their surroundings.

The purpose was achieved stepwise in four studies. In Study I, the focus was on hearing aids for persons with residual low frequency hearing. In Study II-IV, the focus was on vibratory aids for persons with total D.

In Study I, six signal processing algorithms (calculation methods) based on two principles, transposition and modulation, were developed and evaluated regarding auditory identification of environmental sounds. Twenty persons with normal hearing listened to 45 environmental sounds processed with the six different algorithms and identified them in three experiments. In Exp. 1, the sounds were unknown and the subjects had to identify them freely. In Exp. 2 and 3, the sounds were known and the subjects had to identify them by choosing one of 45 sounds. The transposing algorithms showed better results (median value in Exp. 3, 64%-69%) than the modulating algorithms (40%-52%) did, and they were good candidates for implementing in a hearing aid for persons with residual low frequency hearing.

In Study II, eight algorithms were developed based on three principles, transposition, modulation, and filtration – in addition to No Processing as reference, and evaluated for vibratory identification of environmental sounds. The transposing algorithms and the modulating algorithms were also adapted to the vibratory thresholds of the skin. Nineteen persons with profound D tested the algorithms using a stationary, wideband vibrator and identified them by choosing one of 10 randomly selected from the list of 45 sounds. One transposing algorithm and two modulating algorithms showed better (p<0.05) scores than did the No Processing method. Two transposing and three modulating algorithms showed better (p<0.05) scores than did the filtering algorithm. Adaptation to the vibratory thresholds of the skin did not improve the vibratory identification results.

In Study III, the two transposing algorithms and the three modulating algorithms with the best identification scores in Study II, plus their adapted alternative, were evaluated in a laboratory study. Five persons from Study II with profound D tested the algorithms using a portable narrowband vibrator and identified the sounds by choosing one of 45 sounds in three experiments (Exp. 1, 2, and 3). In Exp. 1, the sounds were pre-processed and directly fed to the vibrator. In Exp. 2 and 3, the sounds were presented in an acoustic test room, without or with background noise (SNR=+5 dB), and processed in real time. Five of the algorithms had acceptable results (27%-41%) in the three experiments and constitute candidates for a miniaturized vibratory aid (VA). The algorithms had the same rank order in both tests in the acoustic room (Exp. 2, and 3), and the noise did not worsen the identification results.

In Study IV, the portable vibrotactile monitoring aid (with stationary processor) for detection, identification and directional perception of environmental sounds was evaluated in a field study. The same five persons with profound D as in Study III tested the aid using a randomly chosen algorithm, drawn from the five with the best results in Study III, in a home and in a traffic environment. The persons identified 12 events at home and five events in a traffic environment when they were inexperienced (the events were unknown) and later when they were experienced (the events were known). The VA consistently improved the ability with regard to detection, identification and directional perception of environmental sounds for all five persons.

It is concluded that the selected algorithms improve the ability to detect, and identify sound emitting events. In future, the algorithms will be implemented in a low frequency hearing aid for persons with low frequency residual hearing or in a fully portable vibratory monitoring aid, for persons with profound D or DB to improve their ability to sense the environment.

Place, publisher, year, edition, pages
Örebro: Örebro universitet , 2009. , 85 p.
Series
Örebro Studies in Technology, ISSN 1650-8580 ; 35
Keyword [en]
Auditive identification, Deaf, Deafblind, Directional perception, Environmental sound, Filtering, Frequency transposing, Hearing aid, Hearing impairment, Modulating, Monitoring, Tactile perception, Vibratory aid, Vibratory identification
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Engineering and Technology
Research subject
Electronics
Identifiers
URN: urn:nbn:se:oru:diva-8136ISBN: 978-91-7668-688-1 (print)OAI: oai:DiVA.org:oru-8136DiVA: diva2:245969
Public defence
2009-10-30, HST, Örebro universitet, Örebro, 13:00 (English)
Opponent
Supervisors
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2011-04-29Bibliographically approved
List of papers
1. Auditive identification of signal-processed environmental sounds: monitoring the environment
Open this publication in new window or tab >>Auditive identification of signal-processed environmental sounds: monitoring the environment
2008 (English)In: International Journal of Audiology, ISSN 1499-2027, Vol. 47, no 12, 724-736 p.Article in journal (Refereed) Published
Abstract [en]

The goal of the present study was to compare six transposing signal-processing algorithms based on different principles (Fourier-based and modulation based), and to choose the algorithm that best enables identification of environmental sounds, i.e. improves the ability to monitor events in the surroundings. Ten children (12-15 years) and 10 adults (21-33 years) with normal hearing listened to 45 representative environmental (events) sounds processed using the six algorithms, and identified them in three different listening experiments involving an increasing degree of experience. The sounds were selected based on their importance for normal hearing and deaf-blind subjects. Results showed that the algorithm based on transposition of 1/3 octaves (fixed frequencies) with large bandwidth was better (p<0.015) than algorithms based on modulation. There was also a significant effect of experience (p<0.001). Adults were significantly (p<0.05) better than children for two algorithms. No clear gender difference was observed. It is concluded that the algorithm based on transposition with large bandwidth and fixed frequencies is the most promising for development of hearing aids to monitor environmental sounds.

Place, publisher, year, edition, pages
London: Taylor & Francis, 2008
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Medical Engineering
Research subject
Medicine; Electrical Engineering
Identifiers
urn:nbn:se:oru:diva-6995 (URN)10.1080/14992020802289776 (DOI)19085397 (PubMedID)
Available from: 2009-05-28 Created: 2009-05-28 Last updated: 2012-05-04Bibliographically approved
2. Vibrotactile identification of signal-processed sounds from environmental events
Open this publication in new window or tab >>Vibrotactile identification of signal-processed sounds from environmental events
2009 (English)In: Journal of rehabilitation research and development, ISSN 0748-7711, E-ISSN 1938-1352, Vol. 46, no 8, 1021-1036 p.Article in journal (Refereed) Published
Abstract [en]

Objective: To compare three different signal-processing principles (eight basic algorithms), transposing, modulating and filtering, and to find the principle(s)/al­go­rithm(s) that result in the best tactile identification of environmental sounds.

Subjects: Nineteen volunteers (9F/10M), deaf or profoundly hearing impaired, between 18-50 yr. 

Method: Sounds produced by 45 representative en­vi­ron­men­tal events were processed using the different al­go­rithms and presented to subjects as tactile stimuli using a wide-band stationary vibrator. Eight algorithms based on the three principles (one un­pro­cessed, used as reference) were compared. The subjects iden­ti­fied the sti­mu­li by choo­sing one among ten alter­na­tives drawn from the 45 events. 

Result and conclusion: Algorithm and subject were significant (RM-ANOVA, p<0.001) factors affecting the results. There were also large differences between individuals regarding which algorithm was best. The test-retest variability was small (Mean±95%CI: 8±3 percentage units), and no correlation between identification score and individual vibratory thresholds was found. One transposing al­go­rithm and two mo­du­lating al­go­rithms led to significantly (p<0.05) better results than did the unprocessed signals. Thus, the two principles of transposing and modulating were appropriate, whereas filtering was unsuccessful. In future work, the two transposing algorithms and the modulating algorithms will be used in tests with a portable vibra­tor for the deafblind.

Keyword
Deafblind, Environmental sound, Identification, Monitoring, Perception, Tactile, Transposing, Vibration
National Category
Signal Processing
Research subject
Electronics
Identifiers
urn:nbn:se:oru:diva-8126 (URN)10.1682/JRRD.2008.11.0150 (DOI)000274171000005 ()20157859 (PubMedID)2-s2.0-75749141318 (Scopus ID)
Projects
Sensing the environment
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-03-15Bibliographically approved
3. Vibrotactile identification of signal-processed sounds from environmental events presented by a portable vibrator: a laboratory study
Open this publication in new window or tab >>Vibrotactile identification of signal-processed sounds from environmental events presented by a portable vibrator: a laboratory study
2009 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Objective: To evaluate different signal-processing algorithms for tactile identification of environmental sounds in a monitoring aid for the deafblind.

Subjects: Two men and three women, sensorineurally deaf or profoundly hearing impaired with experience of vibratory experiments, age 22-36 years.

Method: A closed set of 45 representative environmental sounds were processed using two transposing (TRHA, TR1/3) and three modulating algorithms (AM, AMFM, AMMC) and presented as tactile stimuli using a portable vibrator in three experiments. The algorithms TRHA, TR1/3, AMFM and AMMC had two alternatives (with and without adaption to vibratory thresholds). In Exp. 1, the sounds were preprocessed and directly fed to the vibrator. In Exp. 2 and 3, the sounds were presented in an acoustic test room, without or with background noise (SNR=+5 dB), and processed in real time.

Results: In Exp. 1, Algorithm AMFM and AMFM(A) consistently had the lowest identification scores, and were thus excluded in Exp. 2 and 3. TRHA, AM, AMMC, and AMMC(A) showed comparable identification scores (30%-42%) and the addition of noise did not deteriorate the performance.

Conclusion: Algorithm TRHA, AM, AMMC, and AMMC(A) showed good performance in all three experiments and were robust in noise; they can therefore be used in further testing in real environments.

Keyword
Environmental sound, Identification, Narrow-band, Tactile perception, Transposing, Vibration, Vibrator
National Category
Signal Processing Engineering and Technology Computer and Information Science
Research subject
Signal Processing
Identifiers
urn:nbn:se:oru:diva-8129 (URN)
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2011-08-30Bibliographically approved
4. Vibrotactile detection, identification and directional perception of signal-processed sounds from environmental events: a pilot field evaluation in five cases
Open this publication in new window or tab >>Vibrotactile detection, identification and directional perception of signal-processed sounds from environmental events: a pilot field evaluation in five cases
Show others...
2009 (English)In: Iranian Rehabilitation Journal, ISSN 1735-3602, Vol. 6, no 7-8, 89-107 p.Article in journal (Refereed) Published
Abstract [en]

Objective: Conducting field tests of a vibrotactile aid for deaf/deafblind persons for detection, identification and directional perception of environmental sounds.

Method: Five deaf (3F/2M, 22–36 years) individuals tested the aid separately in a home environment (kitchen) and in a traffic environment. Their eyes were blindfolded and they wore a headband and holding a vibrator for sound identification. In the headband, three microphones were mounted and two vibrators for signalling direction of the sound source. The sounds originated from events typical for the home environment and traffic. The subjects were inexperienced (events unknown) and experienced (events known). They identified the events in a home and traffic environment, but perceived sound source direction only in traffic.

Results: The detection scores were higher than 98% both in the home and in the traffic environment. In the home environment, identification scores varied between 25%-58% when the subjects were inexperienced and between 33%-83% when they were experienced. In traffic, identification scores varied between 20%-40% when the subjects were inexperienced and between 22%-56% when they were experienced. The directional perception scores varied between 30%-60% when inexperienced and between 61%-83% when experienced.

Conclusion: The vibratory aid consistently improved all participants’ detection, identification and directional perception ability.

Place, publisher, year, edition, pages
Tehran: University of social welfare and rehabilitation sciences Evin, 2009
Keyword
Deaf, Deafblind, Directional perception, Environmental sound, Tactile perception
National Category
Signal Processing Other Health Sciences
Research subject
Electronics; Disability Science
Identifiers
urn:nbn:se:oru:diva-8131 (URN)
Projects
Sensing the environment
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-03-27Bibliographically approved

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Output format
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