Dummy Head Research Articles

Computing Body Segment Trajectories in the Hybrid III Dummy Using Linear Accelerometer Data

An analytical method was developed and tested using several mini-sled and Hyge sled tests to calculate the planar trajectory of a Hybrid III dummy head. Aimed at expediting the Hybrid III test analyses, it may provide an opportunity for cost savings through reduced hardware and manpower on film analyses. Transformation from the moving coordinate to the laboratory coordinate is based on the angular positions integrated from the derived angular accelerations. Gravitational correction of the linear accelerometers was found to be insignificant. The computed head trajectories were compared to the ones obtained from the high speed film images. Accuracy of the calculated head trajectory relies heavily on the accuracy of the computed angular acceleration. Strain-gaged accelerometers are not dependable at all times during an impact and an ill-behaved signal for a very short period may create a significant drift in computed displacement due to double integrations. Accuracy of the currently available accelerometers is not high enough for an angular displacement calculation. A new generation of accelerometers with higher accuracy, or an angular velocity sensor may provide more accurate angular displacement for trajectory analyses. The redundancy of the in-line accelerations helps improve the isolation of erroneous outputs and improve accuracy of the procedure.

A Development of Dummy Head Recording System for Software Production of Virtual Reality

A Development of Dummy Head Recording System for Software Production of Virtual Reality

Spaciousness judgments of binaurally reproduced sound fields

Spaciousness is known to be a key subjective parameter in determining the acoustical quality of a concert hall. Spaciousness is described as the sense of being enveloped by the sound, or as an increase in the apparent width of the soundstage. Inter-aural cross correlations (IACC) and lateral energy fractions (LF) are two objective measures used to describe the relative spaciousness of concert halls. However, the two measures often do not correlate well with each other. In this study binaurally simulated sound fields were presented to listeners in paired comparison tests. Listeners were asked to identify the more spacious of the two sound fields. Binaural simulations of various North American concert halls were produced by convolving source material with impulse responses measured using a dummy head. The measured LF and IACC values are compared with the judged spaciousness. [Binaural impulse response data were obtained from a measurement tour partially supported by the Concert Hall Research Group.]

Relationships among various room acoustic indices

For the last 5 years, the authors have been making acoustical surveys of auditoria in the world at every opportunity. In these acoustical measurements, room impulse responses have been measured using a dodecahedral omnidirectional loudspeaker, monaural microphones, and a dummy head system (Neumann KU81i). In order to get accurate impulse responses with high S/N ratio, the sweep-pulse method and synchronous averaging technique were adopted. From the monaural and binaural impulse responses measured in a lot of concert halls and theaters, such acoustic indices as T60 (reverberation time), EDT (early decay time), D50 (definition), C80 (clarity), Ts (center time), and IACC (inter-aural cross correlation) were obtained, and the relationships among them were statistically investigated. As a result, it has been found that such indices as D50, C80, and Ts are highly correlated with each other and the correlations between IACC and other monaural indices are very low. The binaural impulse responses measured through the dummy head were convolved with dry music and speech signals by digital technique, and they are being used as the test signals for subjective experiments using a transaural reproduction system.

Effects of measurement equipment and procedure on IACC measurements

A series of binaural acoustical measurements were taken at several source locations and multiple receiver locations in eight concert halls using the Acoustical Research Instrumentation for Architectural Spaces (ARIAS) system and manikin developed at the University of Florida and the BRAM software system developed at NRC Canada with a B&K dummy head and torso. This paper will compare the results of room average data and several specific seat locations obtained from the two measurement systems with an analysis of the similarities and differences that arose. Correlations among various forms of IACC including IACCearly, IACClate, IACCwith direct sound, and IACCwithout direct sound were studied. A comparison of binaural reflectograms for locations within each room were also made. Summary graphs showing ranges of each measurement within each of the rooms and discussion of similarities and differences among the groups of rooms will be presented. [Work supported by the National Science Foundation and Concert Hall Research Group.]

The acoustic survey of British auditoria

By 1980 the understanding of acoustics for concert halls had reached an interesting stage. Two German studies at Göttingen and Berlin with dummy head recordings had gone a long way to determining the important subjective and objective dimensions. However the influence of architectural form on subjective acoustic conditions was much less well established. There were two possible routes: testing acoustic scale models or full-size auditoria. With access to sufficient full-size auditoria, the latter was the obvious choice since it also allowed true subjective assessment. The acoustic survey of British auditoria involved both objective measurements and subjective assessments in over 40 auditoria including concert halls, drama theaters, opera houses, and multi-purpose spaces. The whole exercise has now been published [M. Barron, AuditoriumAcousticsandArchitecturalDesign (Chapman & Hall, London, 1993)]. In concert halls a major conclusion of the subjective exercise was that halls with good reputations score well with regard to several attributes, such as reverberance, envelopment, and intimacy. Several novel observations on the effect of design details will also be discussed.

A simple method of calculating the interaural cross-correlation function for a sound field

A simple equation for calculating the interaural cross-correlation function at the two ears of a dummy head for octave bandpass-filtered noise (125 Hz–8 kHz) was derived. This can be applied for any single sound direction. Superposing such cross-correlation functions (weighted with the spectrum of a source signal), the interaural cross-correlation function and its magnitude for a sound field with multiple reflections may be calculated. This is called the IACC for music and continuous speech. Agreement of calculated IACCs with measured ones is satisfactory for these sound sources. When IACC values are measured with a dummy head and with real human heads, the difference in the size of heads is not critical.

How to measure the degree of interaural cross correlation as a physical factor for auditory source width

The degree of interaural cross correlation is well known as a physical factor for auditory source width (ASW). But, how to measure it is not yet described clearly. The degree of interaural cross correlation obtained by using a dummy head with an artificial ear simulator cannot explain the results by Barron and Marshall [J. Sound Vib. 77, 221–232 (1981)]. But, the degree obtained by using a dummy head without an artificial ear simulator can explain the results. Furthermore, it is impossible to explain ASW of stimuli that include the high-frequency components (higher than about 1.5 kHz) even if the latter degree is adopted. Finally, this paper proposes auditory processed interaural cross correlation (APICC) (the degree of interaural cross correlation obtained in consideration of the mechanism of binaural signal processing) as a physical factor for ASW.

The development of an audible simulator of sound fields and verification of simulation accuracy

A multichannel-type audible simulator with two special features, such as scattering sound and a way to determine production condition of reverberation, is developed. Using geometrical sound analysis with sound-scattering phenomenon, a sound field model of the simulator is composed of direct sound, initial reflection, reverberation, and scattered sound. Also, a new way to determine the production condition of reverberation is proposed. To examine the similarity between a simulated sound field and a real sound field, physical and psychological experiments are performed. It is found that acoustic indices, such as C80 (clarity), modulation transfer index (MTI), and time gravity (schwerpunktzeit), of simulated sound fields approximately agree qualitatively with those of the real sound field. The results of psychological experiments using dummy head recordings show that definition has good similarity, and it is necessary to improve reverberation.

遠隔操作法の実験とその評価

A remote operating system is required to control reliably and effectively, and to be used easily. As the remote operating system with legs, arms, hands, eyes and ears correspond to the human's ones is increasing the operation task, it is hard for only one human operator to control the operating tasks reliability and effectively. And so we consider it necessary the new method to operate with sensuous operation using the operator's knowledge and experience, and in this method, to control the slave-manipulator and ITV camera as if he felt with his own arms, hands, eyes and ears. In this paper, to develop the new method, we have made the experiments of ITV camara control test using joy stick lever, the voice command, operator's eyes and neck motion, and discriminating the direction of sound source test using ITV camera with the microphone. As the results, in the former test, it becomes clear that the voice command control mode and operater's neck control mode are able to be used instead of joy stick control mode, and we have extracted the factors of evaluating the operability. In the latter test, that is the dummy head that can be turned with the microphones is able to be used for discriminating the direction of sound source in the field, also is able to get the existence in the field.

A simple method of calculating IACC and its utilization for measurement in a concert hall.

Cross-correlation values using a dummy head for 1/1 octave bandpass noise (125 Hz–8 kHz) and for each single sound direction were measured. Summing up the measured values with the weighting of the sound energy spectrum of a source signal, the interaural cross-correlation function (IACC) for the stational noise and nonstational music as well as speech is calculated. Calculated results are compared with the measured values obtained in the Boston Symphony Hall. Agreement with measured results is satisfactory for stationary noise and also for music. Thus the presented method of calculating IACC can be utilized for any sound source in a concert hall. Also discussed is the correspondence between the measured IACCs and the results obtained by a simulation of the sound field using the plan and cross sections of the hall.

Measurement of impulse response and its applications in room acoustics

Impulse response includes almost all physical information of a linear system and it is also very important in room acoustics. Fortunately, owing to the recent development of digital signal processing techniques and instrumentation, it has become possible to make a precise and convenient measurement of impulse responses in rooms. In this paper, the practical techniques for this kind of measurement including scale model studies are introduced. For the measurement in real auditoriums, a sweep pulse is radiated many times from a dodecahedral omnidirectional loudspeaker and the responses are recorded on a DAT through an omnidirectional microphone or a dummy head system. From the recorded responses, impulse responses are obtained by synchronous averaging and deconvolution techniques. In scale model experiments, impulse responses are measured by using a spark discharge source and a scale model dummy head microphone. From the impulse responses measured in such ways, not only various room acoustic quantities are derived but also the sounds including the room response can be synthesized by making convolutions between the impulse responses and arbitrary dry source signals. This technique is effectively used for subjective evaluation of room acoustics. Some examples of the experimental results for real and scale model auditoriums will be demonstrated.

A miniature dummy head for binaural evaluation of tenth-scale acoustic models

Binaural room simulation in the form of a scaled-down model requires a sound receiver which precisely imitates the human external ear. By picking up the sound field in model spaces with such a sound receiver, it is not only possible to objectively predict the acoustic qualities of auditoria in the planning phase, but also to listen in to modelled spaces for auditory evaluation. The present paper deals with the design of a tenth-scale miniature dummy head and related problems. Special attention is given to equalization as well as to the application of this dummy head.

Ear‐adequate spectral analysis for noise evaluation

In numerous sound situations, sound quality cannot be determined by means of conventional measuring techniques. The frequent discrepancy between subjective judgment of sound events yielded by standard measurement procedures, can be explained by the difference between a sound situation as received by a single omnidirectional microphone, on the one hand, and as received by the human hearing, on the other hand. A new procedure using a dummy head and a special binaural analyzer has been developed for spectral analysis that realizes frequency and time resolution in the entire audio spectral range. This is comparable to the properties of human hearing, which is able to perceive quickly changing time structures and minor frequency differences at the same time. New approaches for ear‐adequate noise evaluation in order to judge noise quality can be achieved by means of psychoacoustic properties of human heating and binaural signal processing. The results of these investigations show that human hearing, which has two auditory paths with a complex directional characteristic and a binaural pattern recognition, gives a different judgment of noise quality as compared to conventional measurement methods, especially in complex sound situations with a spatial distribution of several sound sources and a sound‐pressure level below 85 dB.

Speech Intelligibility Enhancement by Interaural Magnification.

Hearing-impaired persons suffer from loss of speech intelligibility in noisy environments as well as from a decrease in binaural performance (e.g., interaural time and intensity discrimination). In order to improve speech intelligibility for spatially separated signal and noise sources by compensating for the reduced binaural performance, we implemented an algorithm increasing binaural dissimilarity on a digital signal processor. This algorithm is a modification of the proposal by Durlach & Pang (J. Acoust. Soc. Am. 1986; 80: 1849-1850). Speech discrimination experiments were performed under simulated spatial conditions with recordings of the speech material and the interfering noise source using a dummy head. With increasing complexity of the spatial masking condition, the binaural advantage as well as the benefits from the algorithm decreased for normal listeners. For four sensorineurally hearing-impaired listeners, only one spatial condition was tested. In addition, a battery of binaural tests (binaural masking level difference, interaural time and intensity discrimination) was performed. The results indicate that the benefits from the signal-processing technique are correlated with the remaining binaural performance.

Sound field reproduction by using dummy head microphones

Sound field reproduction by using dummy head microphones

Applicaiton of a dummy head to scale model experiments for designing of architectural acoustics

Applicaiton of a dummy head to scale model experiments for designing of architectural acoustics

Practical technique by dummy head recording

Practical technique by dummy head recording

Development of dummy head microphone for OSS

Development of dummy head microphone for OSS

Efficiency of ear protectors in laboratory and real life tests

The effectiveness of ten different ear-protectors (6 types of earmuffs and 4 types of earplugs) has been tested under laboratory conditions and in the real occupational environment. Three methods were used: (1) physical, utilizing a dummy head; (2) subjective, real-ear, executed on trained human subjects; (3) subjective, measuring TTS2 resulting from occupational, one-workday exposure. It could be shown that the ear protection efficiency ascertained on the basis of TTS2 measurements on workers exposed to noise in their occupational environment is, in nearly all cases, smaller than the efficiency expected, taking into account the sound damping of the same protectors, tested under laboratory conditions, using the physical or real-ear method. Measurements of TTS2 were found to give the best data needed to define the protectors' efficiency, since they include, simultaneously, the impact of various environmental factors, the subjective reactiveness, the nature of the professional task and the acoustical features of the protector used. Therefore this method enables the estimation of the real protection given to workers with a risk of noise-induced hearing loss.