Dummy Head Research Articles

The Accuracy of Implant Placement by Experienced Surgeons: Guided vs Freehand Approach in a Simulated Plastic Model

To investigate the difference in accuracy between freehand and guided single-implant placement in situations with one or more missing teeth as performed by experienced surgeons. A total of 80 implants were placed by 10 experienced clinicians in the anterior site of maxillary models, made of polyamide by selective laser sintering and mounted in a dummy head. Each clinician performed the same four single-implant cases via freehand surgery and then with a three-dimensional fabricated SIMPLANT Guide. Two of the four cases had a single anterior tooth missing and the other two models represented a partially edentulous situation with several missing anterior teeth. For all 80 implants the average vertical, lateral, and angular deviations between the virtually planned and the achieved implant positions were measured based on a cone beam computed tomography (CBCT) scan. Regarding the whole sample, angular deviation was 7.63 degrees for the freehand method and 2.19 degrees for guided surgery. The mean difference in angular deviation differed significantly between groups and was more than three times larger for the freehand method. Lateral deviation at the coronal level of the implants was 0.42 mm and 1.27 mm for the guided and freehand methods, respectively, and at the apical level was 0.52 mm and 1.28 mm for the guided and freehand methods, respectively; the deviation at the coronal and apical levels was significantly smaller for guided surgery than for the freehand method (P = .001). Differences in the depth deviation at the apical and coronal levels were smaller (guided vs freehand surgery at the coronal level: 0.54 mm vs 0.78 mm; apical level: 0.54 mm vs 0.73 mm) but also of statistical significance (P = .05). Differences in angular, global, and lateral deviations between the clinical situations (single vs multiple missing teeth) were also significantly smaller for guided surgery, whereas the deviations in depth did not reveal any statistically significant difference between both methods for the single-spaced units. In cases of one or more missing teeth in the anterior maxilla, guided surgery gives even experienced surgeons significantly higher predictability and accuracy than freehand surgery in transferring the virtual implant position to a model situation.

Evaluation of spherical microphone baffle with six hollows for omnibinaural recording

A binaural recording system records binaural sounds corresponding to plural listening orientations simultaneously. We devised and evaluated the binaural recording system. A binaural recording is generally performed with a dummy head; however, it can record for single listening orientation only. Moreover, an easy binaural recording system is desired because the dummy head is big, expensive, and difficult to handle. Therefore, we devised a cheaper and smaller omnibinaural recording system. In previous research, a spherical microphone baffle with two hollows was proposed, and the results addressed that it could be considered as a binaural recording system. In this study, a microphone baffle with six hollows was designed and evaluated. The proposed baffle has a spherical shape. Six hollows are located on three orthogonal axes originated from the center of the baffle. The acoustical features were examined by the numerical analysis. The results show that a difference between the previous research and the proposed baffle is small and the proposed baffle can achieve an omnibinaural recording.

Personalization of head-related transfer functions in the median plane based on spectral correction with pinna angle

Head-related transfer functions (HRTFs) are studied to realize high-precision sound field reproduction systems. These systems usually utilize the HRTFs of other listeners because self-measurement of one’s own HRTFs is a heavy burden. The localized sound accuracy of the listener, especially in the median plane, is degraded when the systems utilize the HRTFs of other listeners, which have different characteristics from the listener’s own ones. Thus, simple personalization of HRTFs is necessary for solving this problem. In this research, we focus on personalization of HRTFs in the median plane on the basis of spectral correction with pinna angles as anthropometric parameters. We first made analyses of the relationship between pinna angles and the spectral envelopes of HRTFs in the median plane through an experiment with a dummy head with a replicated pinna made from silicone. From these analyses, the spectral envelopes were confirmed to be affected by pinna angles. We then proposed a method for personalization of HRTFs on the basis of spectral correction with the pinna angles. Objective and subjective evaluation experiments were carried out in order to demonstrate the effectiveness of the proposed method. As a result, we confirmed improvement in the performance of sound image localization.

Individualization of head-related transfer functions by the principle component analysis based on anthropometric measurements

A binaural reproduction either uses individual or generic head-related functions (HRTFs). The assessment of individual spatial high-resolution HRTF datasets is very time-consuming and requires a special measurement setup. On the other hand, a generic HRTF dataset from a dummy head can lead to localization errors such as front-back confusions and in-head localizations. In the present work, the generation of individualized HRTF datasets using the principle component analysis and multiple regression analysis from a generic HRTF dataset is discussed. The individualized HRTFs reduce the localization errors by taking individual anthropometric dimensions of the head and pinna into account. The method is applied to 48 individual HRTF datasets to determine the principal components and their weights. The anthropometric dimensions are obtained from the 3D magnetic resonance imaging scans of the 48 subjects. The focus of the work is on the number of necessary principle components with respect to the measurement grid and redundancy of anthropometric dimensions.

Omni-binaural recording system for 360° video

A binaural recording system for 360° video is developed and evaluated. The 360° images can be stitched by using multiple cameras. A binaural recording generally uses a dummy head microphone or binaural recording microphones; however, the orientation of the dummy head needs to be changed depending on the selected view. Binaural recording corresponding to multiple orientations of a dummy head is very difficult and sometimes impossible. Therefore, we propose a binaural recording system that can simultaneously record the sound for the entire corresponding 360° video. The proposed equipment is cylindrical in shape and has four hollows that correspond to the cavity of the concha on the side. Binaural signals corresponding to a desired direction are generated by a weighted average of the recorded signals. Three types of weights, i.e., linear, spline, and optimum weights, were examined. The degree of suitability between the video and generated binaural signals was evaluated using subjective tests. Nine subjects a...

Binaural simulation using six channel reproduction based on the finite difference time domain room acoustic analysis

For auralization of room acoustics, various simulation-reproduction systems, such as ray tracing, cone tracing, image source methods, and wave-based numerical analysis for sound field simulation, and transaural system, multi-channel loudspeaker system for sound field reproduction, have been developed. As a sound recording-reproduction system, the six channel system has been developed, in which a sound signal is recorded by orthogonally located six directional microphones having a cardioid characteristics and the recorded signals are reproduced by orthogonally arranged six loudspeakers. To obtain binaural signals for auralization with headphones, the six channel reproduction was combined with binaural recording using dummy head microphones. The proposed concept can be efficiently applied to room acoustic simulation. As a room acoustic calculation method, finite-difference time-domain method was employed in this study. The calculated room impulse responses were reproduced by six channel reproduction system, and the binaural signals are recorded using dummy head microphones. In this presentation, the concept of the reproduction system is first stated and some examples on room acoustic problems are introduced.

Study of vertical sound image control with parametric loudspeakers

A parametric loudspeaker utilizes nonlinearity of a medium and is known as a super-directive loudspeaker. In this paper, the sound localization in the vertical direction using the upper and lower parametric loudspeakers is confirmed by listening tests and physical measurements. The differences in levels between the upper and lower parametric loudspeakers are varied as a parameter. The direction of sound localization in the vertical plane can be controlled not only when the acoustical axis is set to the right ear but also when it is set to at 5deg to the right of the right ear. The effect of the level difference between the upper and lower loudspeakers is weaker than the differences observed when using ordinary loudspeakers. We obtained interesting characteristics of the left-right sound localization in the horizontal plane with the upper and lower parametric loudspeakers in the vertical plane. It is found that by setting the parametric loudspeaker at the right ear (that is, the horizontal angle of a listener to it is only 3deg to the right), the direction of sound localization in the horizontal plane moved approximately 10deg to the right. Moreover, by setting the parametric loudspeaker 5deg to the right, the direction of sound localization moves approximately 20deg to the right. The ILD (Interaural Level Difference) using a dummy head is calculated from the measured left and right sound signals. It is determined that ILDs of the parametric loudspeaker are larger than those of the ordinary loudspeaker. A simple geometrical acoustic model is introduced and analyzed. The analysis helps to explain the measured characteristics.

A New Miniature Respirable Sampler for In-mask Sampling: Part 2—Tests Performed Inside the Mask

This paper is the second in a series of two describing the performance of a miniature and low-weight respirable sampler designed to fit inside filtering facepiece (FFP) and half-mask type respirators. The first paper described the design of the miniature sampler and evaluated the particle and collection performance of the miniature sampler. This paper assesses its comparability with the traditional inward leakage measurement technique, and its safe use. Simultaneous mass measurements of a respirable sodium chloride aerosol were taken inside a total inward leakage chamber by a miniature sampler and by sodium flame photometry. Direct side-by-side comparison of the two methods yielded excellent correlation (R 2 = 0.99), as did comparison when sampling from inside four different masks when worn by a breathing Sheffield dummy head. In addition, comparison tests were carried out using three models of FFP worn by human volunteers both with and without the miniature sampler, in order to test whether or not the presence of the miniature sampler negatively affected the protection offered. The difference between the tests carried out with the miniature sampler and without the miniature sampler was not statistically significant (P = 0.3). In all cases, the masks performed within their protection class, whether the miniature sampler was fitted or not. We therefore conclude that the miniature sampler does not significantly affect the protection offered by the masks. The miniature sampler may prove a viable option for in-mask measurements of respirable dust where low air concentrations of hazardous material are expected.

Evaluation of the influence of velocity on dynamic passenger loads during a frontal minibus impact against an obstacle

The safety of people travelling by minibus is a very complex issue, in which the decisive role is played by load-bearing vehicle structure, passenger seats, and personal protection means. In order to maximize the number of people transported, the seats are spaced very closely to each other and this may pose a hazard to the passengers. Based on an analysis of experimental test results, a computer model representing a system composed of a minibus floor segment, seats, and dummies was built. For the analysis, seats integrated with seat belts were adopted. A seat of this type was based on a high-rigidity frame necessary to bear, inter alia, the strong force exerted (during a collision) by passenger's torso on the shoulder seat belt and transmitted to the upper seat belt anchorage point on the seat backrest. Within this work, the frontal minibus impact against an obstacle with velocities ranging from 20 km/h to 70 km/h was considered.The analysis covered the motion of, and dynamic loads on, a test dummy representing a 50th percentile adult male (Hybrid III dummy). Within the analysis, realizations of dynamic loads caused by inertial forces and reactions exerted by a three-point seat belt were taken into account. Special attention was paid to the extreme values of the loads that acted on dummy's head, neck, and torso when the head hit the backrest of the preceding seat in the culminating phase of the vehicle impact against an obstacle. The values of biomechanical indicators HIC, ThAC, Nij, and FAC and of the joint injury risk indicator were calculated.

Speech Recognition in an Enclosure with a Long Reverberation Time

Abstract The aim of this work was to measure subjective speech intelligibility in an enclosure with a long reverberation time and comparison of these results with objective parameters. Impulse Responses (IRs) were first determined with a dummy head in different measurement points of the enclosure. The following objective parameters were calculated with Dirac 4.1 software: Reverberation Time (RT), Early Decay Time (EDT), weighted Clarity (C50) and Speech Transmission Index (STI). For the chosen measurement points, a convolution of the IRs with the Polish Sentence Test (PST) and logatome tests was made. PST was presented at a background of a babble noise and speech reception threshold - SRT (i.e. SNR yielding 50% speech intelligibility) for those points were evaluated. A relationship of the sentence and logatome recognition vs. STI was determined. It was found that the final SRT data are well correlated with speech transmission index (STI), and can be expressed by a psychometric function. The difference between SRT determined in condition without reverberation and in reverberation conditions appeared to be a good measure of the effect of reverberation on speech intelligibility in a room. In addition, speech intelligibility, with and without use of the sound amplification system installed in the enclosure, was compared.

Work of breathing using different interfaces in spontaneous positive pressure ventilation: helmet, face-mask, and endotracheal tube.

Noninvasive positive pressure ventilation (NPPV) using a helmet is expected to cause inspiratory trigger delay due to the large collapsible and compliant chamber. We compared the work of breathing (WOB) of NPPV using a helmet or a full face-mask with that of invasive ventilation by tracheal intubation. We used a lung model capable of simulating spontaneous breathing (LUNGOO; Air Water Inc., Japan). LUNGOO was set at compliance (C)=50mL/cmH2O and resistance (R)=5cmH2O/L/s for normal lung simulation, C=20mL/cmH2O and R=5cmH2O/L/s for restrictive lung, and C=50mL/cmH2O and R=20cmH2O/L/s for obstructive lung. Muscle pressure was fixed at25cmH2O and respiratory rate at20bpm. Pressure support ventilation and continuous positive airway pressure were performed with each interface placed on a dummy head made of reinforced plastic that was connected to LUNGOO. We tested the inspiratory WOB difference between the interfaces with various combinations of ventilator settings (positive end-expiratory pressure 5cmH2O; pressure support 0, 5, and 10cmH2O). In the normal lung and restrictive lung models, WOB decreased more with the face-mask than the helmet, especially when accompanied by the level of pressure support. In the obstructive lung model, WOB with the helmet decreased compared with the other two interfaces. In the mixed lung model, there were no significant differences in WOB between the three interfaces. NPPV using a helmet is more effective than the other interfaces for WOB in obstructive lung disease.

Design, construction, and evaluation of a binaural dummy head

Binaural-dummy-heads are often used as standard measurement devices where modeling of the human binaural hearing system is desired. The binaural-dummy-head imitates a human head (and torso) which is used in binaural recording as well as research areas such as hearing aids, sound localization, noise measurements, etc. Commercially available binaural heads are not economically efficient for some purposes. This paper outlines a less expensive binaural dummy head built using ANSI/ASA S3.36-2012 standard as a reference as part of an independent coursework. A hard plastic mannequin was used as head and torso, and the two ears were real human ear replicas casted out of water-based alginate gel. The complex Head-Related Transfer Functions (HRTF) of our dummy head were measured in an anechoic chamber to evaluate its spectral and directional properties and were compared to the same properties of the standard commercial dummy head.

Ultrasonic binaural echo perception of object's texture by human echolocation

Echolocating bats use frequency-modulated (FM) and/or constant-frequency (CF) sound for ultrasonic sensing depending on the situation during flight. We investigated discrimination ability of object’s texture for sighted subjects to understand acoustic clues for texture recognition in human echolocation. FM and CF ultrasonic echoes from six objects with different materials and surface structures were acquired by a 1/7-size miniature dummy head for presentation of 1/7-times pitch converted binaural audible sounds to listeners through headphones. In the results, averaged rate of correct answer in the case of extremely different surface condition (i.e., acrylic board versus artificial grass) was more than 90% while one in the slightly different surface condition (i.e., acrylic board versus foamed polystyrene) was under 40%. Furthermore, the rate of correct answers in the CF sound condition was approximately 13% lower than one in the FM sound condition. The correlation diagram among targets by multidimensional...

Impact attenuation of protective boxing and taekwondo headgear

This study aimed to compare the impact attenuation performance of boxing and taekwondo headgear in terms of peak linear and rotational acceleration. To measure the impact attenuation of headgear, a standardized (American Society for Testing and Materials (ASTM) F-2397) martial arts headgear striker was used to impart impacts to a 50th Percentile Male Hybrid III Crash Test Dummy head and neck complex. Two boxing (Adidas and Greenhill) and two taekwondo (Adidas and Nike) headgear, approved by the Association Internationale de Boxe Amateur and the World Taekwondo Federation (WTF), were selected. Each of the selected headgear was fitted to the Hybrid III head and subsequently subjected to five impacts at the front and side with a maximum impact interim time of 60 seconds by the rotating striker at 8 ± 0.3 m/s. Linear and rotational acceleration were recorded at 10,000 Hz. There were significant interactions of the impact location and brand on the rotational acceleration, F(3,40) = 6.7, p < .05. There were significant main effects of both impact location F(1,40) = 9.07, p < .05 and headgear brand F(3,40) = 9.9, p < .05 on the linear acceleration. Pairwise comparisons show significant differences between the front and side for both linear and rotational acceleration. The headgear tested failed the ASTM high impact test requirement to reduce the linear acceleration to below a threshold of 150 g. Further development of headgear to reduce impact linear and rotational acceleration magnitudes should be called for by the relevant sport governing bodies and initiated by headgear manufactures.

A Modified Hybrid III 6-Year-Old Dummy Head Model for Lateral Impact Assessment

Hybrid III six-year-old (6YO) child dummy head model was developed and validated for frontal impact assessment according to the specifications contained in Code of Federal Regulations, Title 49, Part 572.122, Subpart N by Livermore Software Technology Corporation (LSTC). This work is aimed at improving biofidelity of the head for frontal impact and also extending its application to lateral impact assessment by modifying the head skin viscoelastic properties and validating the head response using the scaled nine-year-old (9YO) child cadaver head response recently published in the literature. The modified head model was validated for two drop heights for frontal, right, and left parietal impact locations. Peak resultant acceleration of the modified head model appeared to have good correlation with scaled 9YO child cadaver head response for frontal impact on dropping from 302 mm height and fair correlation with 12.3% difference for 151 mm drop height. Right parietal peak resultant acceleration values correlate well with scaled 9YO head experimental data for 153 mm drop height, while fair correlation with 16.4% difference was noticed for 302 mm drop height. Left parietal, however, shows low biofidelity for the two drop heights as the difference in head acceleration response was within 30%. The modified head model could therefore be used to estimate injuries in vehicle crash for head parietal impact locations which cannot be measured by the current hybrid III dummy head model.

Comparison of optimisation strategies for the determination of precise dummy head trajectories based on the fusion of electrical and optical measured data in frontal crash scenarios

When determining the trajectory of the dummy head during a vehicle crash test, the head is not visible for all cameras during the whole movement, since it, e.g., dips into the airbag. Another possibility is to calculate the trajectory with acceleration and gyro sensor data. When using low-cost inertial measurement units, the calculated trajectory differs from the video analysis by 0.15 metres. The idea is to model possible electrical sensor errors and inaccurate known initial conditions and determine them in an optimisation process in which the video trajectory is taken as the target function. This paper deals with the optimisation process to determine if the optimisation function has a unique minimum. Based on that, several optimisation algorithms are compared and three of them are selected for a detailed comparison. The best of them is selected to show the calculation of a trajectory for a real world crash test.

Dummy head and TeleHead

Dummy head and TeleHead

次世代頭部ダミーにおける頭蓋内脳挙動の直接評価法の開発

次世代頭部ダミーにおける頭蓋内脳挙動の直接評価法の開発

Direction Judgment of Sound Source in Horizontal Plane using Dynamic Binaural Signal Recorded by a Steerable Dummy Head of which Rotation Angular Speed is Altered with a Listener&apos;s Head-rotation Speed : For Listeners who are Familiar in Sound Localization Using a Steerable Dummy Head

Direction Judgment of Sound Source in Horizontal Plane using Dynamic Binaural Signal Recorded by a Steerable Dummy Head of which Rotation Angular Speed is Altered with a Listener&apos;s Head-rotation Speed : For Listeners who are Familiar in Sound Localization Using a Steerable Dummy Head

Reciprocal measurement of acoustic feedback paths in hearing aids.

A reciprocal measurement procedure to measure the acoustic feedback path in hearing aids is investigated. The advantage of the reciprocal measurement compared to the direct measurement is a significantly reduced sound pressure in the ear. The direct and reciprocal measurements are compared using measurements on a dummy head with adjustable ear canals, different earmolds, and variations in the outer sound field. The results show that the reciprocal measurement procedure can be used to obtain plausible feedback paths, while reducing the sound pressure in the ear canal by 30 to 40 dB.