| 1. |
- Amundin, Mats, 1947-, et al.
(författare)
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An echolocation visualization and interface system for dolphin research
- 2008
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 123:2, s. 1188-1194
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Tidskriftsartikel (refereegranskat)abstract
- The present study describes the development and testing of a tool for dolphin research. This tool was able to visualize the dolphin echolocation signals as well as function as an acoustically operated "touch screen." The system consisted of a matrix of hydrophones attached to a semitransparent screen, which was lowered in front of an underwater acrylic panel in a dolphin pool. When a dolphin aimed its sonar beam at the screen, the hydrophones measured the received sound pressure levels. These hydrophone signals were then transferred to a computer where they were translated into a video image that corresponds to the dynamic sound pressure variations in the sonar beam and the location of the beam axis. There was a continuous projection of the image back onto the hydrophone matrix screen, giving the dolphin an immediate visual feedback to its sonar output. The system offers a whole new experimental methodology in dolphin research and since it is software-based, many different kinds of scientific questions can be addressed. The results were promising and motivate further development of the system and studies of sonar and cognitive abilities of dolphins. © 2008 Acoustical Society of America.
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| 2. |
- Bjurström, Henrik, et al.
(författare)
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Comparative Seismic Laboratory and Non-Contact Field Measurements of Asphalt Concrete
- 2016
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Ingår i: 2016 Structural Materials Technology Paper Summaries.
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Konferensbidrag (refereegranskat)abstract
- Non-contact acoustic field measurements are performed on a newly built highway to characterize the real part of the dynamicmodulus of the asphalt concrete (AC) top layer. The in situ measurements are performed using an array of 48 micro-electromechanicalsystem (MEMS) sensors. Cores extracted from the field measurement positions are then examined in a laboratory usingseismic modal testing for comparison. The laboratory testing allows master curves to be constructed to characterize the AC over awide temperature and frequency range. It is demonstrated that the real parts of the dynamic moduli are consistent at the fieldtemperatures using the two test methods. The in situ measurements are also shown to be highly repeatable. The presentedcomparative study indicates a possible application for assuring the quality of AC based on mechanical properties using fast noncontactin situ measurements.
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| 3. |
- Bjurström, Henrik, et al.
(författare)
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Field and laboratory stress-wave measurements of asphalt concrete
- 2016
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Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 126, s. 508-516
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Non-contact surface wave measurements are performed on a new asphalt concrete (AC) pavement using 48 micro-electro-mechanical system (MEMS) sensors as receivers to estimate the real part of the dynamic moduli of the AC top layer. Laboratory measurements of core samples, extracted from the field measurement positions, are used to construct master curves for comparison with the field measurements. The real parts of the dynamic moduli from the two test methods are consistent at the field measurement temperatures, and the non-contact field measurements are highly repeatable. These results indicate a possible application for quality assurance of AC based on mechanical properties.
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| 4. |
- Bjurström, Henrik, 1983-, et al.
(författare)
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Implementering av seismiska ytvågsmätningar på vägbeläggningar
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Inom detta projekt har en ny metod för oförstörande profilerande mätningar av styvhetsmodulen på beläggningar demonstrerats och utvärderats på två kontrollerade vägsträckor. Resultaten visar att det nu är möjligt att mäta upp beläggningens styvhetsmodul och aktuell temperatur, vid en kontrollerad frekvens och töjningsnivå, genom rullande mätningar i trafik. Värdet av denna nya möjlighet är att heltäckande profilerande kvalitetskontroll av både nya och gamla vägar kan göras säkrare, från en vanlig bil, samt mer kostnadseffektivt genom att avspärrningar och stillastående provtagning kan undvikas eller minimeras. För en given beläggningstjocklek är styvhetsmodulen den viktigaste materialegenskapen i bundna asfaltlager och den egenskap som används som indata för att dimensionera beläggningens livslängd och underhållsbehov. Metoden bygger på kontaktlösa seismiska ytvågsmätningar med hjälp av mikrofoner. Uppmätt ytvågshastighet räknas om till dynamisk styvhetsmodul med hjälp av fundamentala viskoelastiska samband. Uppmätt ytvågshastighet och dynamisk styvhetsmodul har jämförts med konventionella stillastående mätningar och provning av borrkärnor i laboratorium. Resultaten visar på en god överrensstämmelse trots delvis okända temperaturprofiler i beläggningen. Rullande seismiska ytvågsmätningar har utförts i uppemot 50 km/h och ca 6 000 mätningar har samlats in på ungefär samma tid som en stillastående konventionell seismisk ytvågsmätning kräver.Inom detta projekt har endast ytvågshastigheten och styvhetsmodulen analyserats och jämförts med referensmätningar. Det finns dock potential att utveckla den automatiska analysen av rådata så att också beläggningens tjocklek och den viskösa delen av beläggningens styvhetsmodul kan utvärderas.
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| 5. |
- Hamilton, Rebecca A., et al.
(författare)
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Bottlenose dolphin communication during a role-specialized group foraging task
- 2022
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Ingår i: Behavioural Processes. - : Elsevier BV. - 0376-6357. ; 200
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Tidskriftsartikel (refereegranskat)abstract
- A division of labor with role specialization is defined as individuals specializing in a subtask during repetitions of a group task. While this behavior is ubiquitous among humans, there are only four candidates found among non-eusocial mammals: lions, mice, chimpanzees, and bottlenose dolphins. Bottlenose dolphins in the Cedar Keys, Florida, engage in role specialized “driver-barrier feeding”, where a “driver” dolphin herds mullet towards “barrier” dolphins. Thus trapped, the mullet leap out of the water where the dolphins catch them in air. To investigate whether dolphins use acoustic cues or signals to coordinate this behavior, vocalizations were recorded before and during driver-barrier feeding. Results of fine-scale audio and video analysis during 81 events by 7 different driver individuals suggest that barrier animals coordinate movements during these events by cueing on the driver's echolocation. Analysis of dolphin whistle occurrence before driving events versus another foraging technique, which does not involve role specialization, revealed significantly higher whistle production immediately prior to driver-barrier events. Possible whistle functions include signaling motivation, recruiting individuals to participate, and/or behavioral coordination. While the use of cues and signals is common in humans completing role-specialized tasks, this is the first study to investigate the use of vocalizations in the coordination of a role-specialized behavior in a non-human mammal.
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| 6. |
- Hamilton, Rebecca A., et al.
(författare)
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Separating overlapping echolocation : An updated method for estimating the number of echolocating animals in high background noise levels
- 2021
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966. ; 150:2, s. 709-717
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Tidskriftsartikel (refereegranskat)abstract
- Much can be learned by investigating the click trains of odontocetes, including estimating the number of vocalizing animals and comparing the acoustic behavior of different individuals. Analyzing such information gathered from groups of echolocating animals in a natural environment is complicated by two main factors: overlapping echolocation produced by multiple animals at the same time, and varying levels of background noise. Starkhammar et al. [(2011a). Biol. Lett. 7(6), 836-839] described an algorithm that measures and compares the frequency spectra of individual clicks to identify groups of clicks produced by different individuals. This study presents an update to this click group separation algorithm that improves performance by comparing multiple click characteristics. There is a focus on reducing error when high background noise levels cause false click detection and recordings are of a limited frequency bandwidth, making the method applicable to a wide range of existing datasets. This method was successfully tested on recordings of free-swimming foraging dolphins with both low and high natural background noise levels. The algorithm can be adjusted via user-set parameters for application to recordings with varying sampling parameters and to species of varying click characteristics, allowing for estimates of the number of echolocating animals in free-swimming groups.
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| 7. |
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| 8. |
- Reinhold, Isabella, et al.
(författare)
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Objective detection and time-frequency localization of components within transient signals
- 2018
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966. ; 143:4, s. 2368-2378
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Tidskriftsartikel (refereegranskat)abstract
- An automatic component detection method for overlapping transient pulses in multi-component signals is presented and evaluated. The recently proposed scaled reassignment technique is shown to have the best achievable resolution for closely located Gaussian shaped transient pulses, even in heavy disruptive noise. As a result, the method automatically detects and counts the number of transients, giving the center times and center frequencies of all components with considerable accuracy. The presented method shows great potential for applications in several acoustic research fields, where coinciding Gaussian shaped transients are analyzed. The performance is tested on measured data from a laboratory pulse-echo setup and from a dolphin echolocation signal measured simultaneously at two different locations in the echolocation beam. Since the method requires little user input, it should be easily employed in a variety of research projects.
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| 9. |
- Reinhold, Isabella, et al.
(författare)
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The scaled reassigned spectrogram adapted for detection and localisation of transient signals
- 2017
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Ingår i: European Signal Processing Conference. - 9780992862671 ; , s. 937-941
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Konferensbidrag (refereegranskat)abstract
- The reassigned spectrogram can be used to improve the readability of a time-frequency representation of a non-stationary and multi-component signal. However for transient signals the reassignment needs to be adapted in order to achieve good localisation of the signal components. One approach is to scale the reassignment. This paper shows that by adapting the shape of the time window used with the spectrogram and by scaling the reassignment, perfect localisation can be achieved for a transient signal component. It is also shown that without matching the shape of the window, perfect localisation is not achieved. This is used to both identify the time-frequency centres of components in a multi-component signal, and to detect the shapes of the signal components. The scaled reassigned spectrogram with the matching shape window is shown to be able to resolve close components and works well for multi-components signals with noise. An echolocation signal from a beluga whale (Delphinapterus leucas) provides an example of how the method performs on a measured signal.
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| 10. |
- Rydén, Nils, et al.
(författare)
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Vehicle based system for continuous non-contact surface wave testing of pavements in 50 km/h
- 2022
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Ingår i: e-Journal of Nondestructive Testing. - : NTD.net. - 1435-4934. ; 27:9, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Non-destructive seismic surface wave measurements can be used for quality control of civil engineering infrastructures such as pavements and bridges. The seismic wave speed is directly linked to the dynamic E-modulus of asphalt concrete providing valuable information for quality control of both old and new structures. Non-destructive pavement testing is here demonstrated using a vehicle based system for continuous non-contact surface wave testing of pavements in about 50 km/h. A 48-channel air-coupled microphone array is mounted on the tow bar of a normal car along with a surface temperature IR sensor and GPS. Two metal heads on plastic strips are bouncing on the surface while driving producing high frequency (5-40 kHz) seismic waves in the asphalt concrete. Results demonstrate that the system can record continuous repeatable surface wave measurements with about two measurement points per meter while driving in a speed of 50 km/h. This measurement system opens up the possibility to perform faster and more economically efficient automated measurements with minimal disruption of traffic.
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