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The presentation will illustrate the use of field programmable gate arrays (FPGAs) in microphone array digital signal processing for wireless acoustic beamforming in source localization. We have developed a prototype of a node composed of ten microphone channels interfaced with a Xilinx‐based FPGA board. The methodology involves basic signal conditioning and delay‐and‐sum beamforming programmed by VHDL. The prototype results illustrate significant increase in the sensitivity to acoustic sources in the direction of a signal, while rejecting noise from other directions. The sensitivity is also enhanced in relationship to the number of channels. This node prototype is a building block for a wireless sensor network, capable of distributed beamforming at about 10‐kHz sample frequencies. Each node is designed to maximize throughput so that broadband acoustic sources are accommodated. We are now performing parametric studies to optimize the node design and microphone array geometry to provide maximum bandwidth, dynamic range, and adequate special resolution, while preserving the ability to resolve time delays between the microphones.

Modeling head related impulse responses (HRIRs) to determine head‐related transfer functions (HRTFs) can be used to create a virtual auditory display through head phones. However, non‐individualized HRTFs can create errors in sound localization and perception of the source as coming from inside vs outside of the head. We present a method, based on model‐order reduction and principal component analysis, to “tune” generalized HRTFs derived from the CIPIC database of HRIRs in order to individualize an HRTF. The impulse response for each individual in the CIPIC database is modeled at given azimuth locations on the horizontal plane. Model order reduction is used to eliminate poles and zeros of the identified HRTF at high frequencies, while preserving the frequency response below ∼8000 Hz. Principal component analysis is then performed on the reduced‐order models in order to reduce the dimensionality of the dataset and identify a subset of weighting variables that are adjusted during HRTF customization. The sensitivity of weights on the frequency response is also studied in order to correlate weights with HRTF features. A prototype auditory display has been developed that allows a user to tune HRTFs in real‐time, while listening to a 44.1‐kHz source presented from a chosen azimuth.

Vehicle motion and tire force histories are estimated from an incomplete, noise-corrupted measurement set using an extended Kalman filter. A nine degree-of-freedom vehicle model and an analytic tire force model are used to simulate true vehicle motion, and a five degree-of-freedom vehicle model is used in the estimator. Simulation demonstrates that real-time filtering can provide state estimates required for advanced feedback control of ground vehicles. In addition, filtered histories of forces and motion can be used to construct tire models through off-line analysis. No prior knowledge of tire force characteristics or external factors that affect vehicle motion is required.

An adaptive leaky LMS algorithm has been developed to optimize stability and performance of active noise cancellation systems. The research addresses performance issues related to insufficient excitation, nonstationary noise fields, and signal‐to‐noise ratio. The algorithm is based on a Lyapunov tuning approach in which three candidate algorithms, each of which is a function of the instantaneous measured reference input, measurement noise variance, and filter length, provide varying degrees of trade‐off between stability and performance. Each algorithm is evaluated experimentally for reduction of low‐frequency noise in communication headsets and compared with that of traditional LMS algorithms. Acoustic measurements are made in a specially designed acoustic test cell which is based on the original work of Shaw, Brammer and co‐workers and which provides a highly controlled and uniform acoustic environment. The stability and performance of the ANR system, including prototype communication headsets, are investigated for a variety of noise sources ranging from stationary white noise to highly nonstationary measured F‐16 aircraft noise over a 20‐dB dynamic range. Results demonstrate significant improvements in stability of Lyapunov‐tuned LMS algorithms over traditional leaky or nonleaky normalized algorithms while providing noise reduction performance equivalent to that of the NLMS algorithm for idealized noise fields.

Data from the Southwestern sample of the Hispanic HANES are employed to evaluate the relationship of acculturation into the larger society with alcohol consumption. As in previous work, acculturation was not found to be related to alcohol consumption of Mexican American men, but was positively related to the consumption of younger Mexican American women. Among middle-aged women, acculturation was not important. However, we found evidence that middle-aged women might be turning to alcohol in response to marital disruption and poverty. In addition, middle-aged women who are not employed are less frequent drinkers but those who drink are heavier drinkers than employed women.

Stochastic robustness, a simple technique used to estimate the robustness of linear, time-invariant systems, is applied to a twin-jet transport aircraft control system. Concepts behind stochastic stability robustness are extended to stochastic performance robustness. Stochastic performance robustness measures based on classical design specifications and measures specific to aircraft handling qualities are introduced. Confidence intervals for both individual stochastic robustness measures and for comparing two measures are presented. The application of stochastic performance robustness, the use of confidence intervals, and tradeoffs between performance objectives are demonstrated by means of the twin-jet aircraft example.

Stochastic robustness is a simple technique used to estimate the stability and performance robustness of linear, time-invariant systems. The use of high-speed graphics workstations and control system design software in stochastic robustness analysis is discussed and demonstrated. It is shown that stochastic robustness makes good use of modern computational and graphic tools, and it is easily implemented using commercial control system design and analysis software. >

A custom designed shallow insert communication earplug for helicopter crews consists of a system based on a patented hybrid ANR feedback‐feedforward algorithm [Ray et al., J. Acoust. Soc. Am. 120(4), 2026–2038 (2006)]. The hybrid system provides the benefits of feedback ANR while extending the bandwidth and magnitude of total ANR performance with feedforward ANR, which improves attenuation of tonals. The development includes optimized algorithms, a custom earplug, and a miniaturized battery powered ANR module, weighing approximately 250 g. The hybrid ANR earplug requires two miniature microphones, one inside and one external to the earplug and an internal speaker to deliver the cancellation signal. The software automatically adapts the ANR algorithm to the transfer function characteristics of the system to both improve performance and accommodate individual human fitting differences. The testing protocol and results are based primarily on measurements with a HEAD Acoustics manikin in the Sound Innovations sound room [Duncan et al., Proceedings of Internoise 2006, December 2006]. MIRE testing is planned for the Spring of 2007. Results to‐date demonstrate comparable passive attenuation to a commercially available communication earplug and an added average active attenuation of approximately 6 dB for UH‐60 helicopter noise. [Work supported by U.S. Army.]

There is a need to establish a simple and accurate measurement technique for determining the transmission loss of sample materials for helmets over a frequency range of 300–3 kHz. Standard methods, e.g., ASTM E 90‐02, for measuring transmission loss of building materials and structures, based on adjacent reverberation chambers, are too costly and impractical. A 1.22‐m‐long double‐wall tube, packed with Owens Corning R13 insulation, has been fabricated using QUIK‐TUBETM cardboard concrete forms of 200 and 300 mm diameters. A circular sample of material, also 300 mm in diameter, is placed on the end of the tube and subjected to an external sound field. Transmission loss is established by external and internal microphones. This paper describes the measurement and analysis procedures and examines the associated variables and error terms. Results are presented for 16 material samples with surface weights covering a range from 0.3 to 14.7 kg/m2 and compared with analytical predictions including mass law models. The acoustical characteristics of commercial helmet materials and liners are evaluated in the context of hearing protection systems. The transmission loss measurement procedure has the potential for meeting standardization objectives.

Since the 1990s research and development of digital feedforward active noise reduction (ANR) based on least‐mean‐square (LMS) algorithms has shown that significant gains in noise reduction can be achieved for circumaural hearing protectors. However, to‐date digital feedforward hearing protection devices have not penetrated the market. This presentation reviews prior research in feedforward ANR for circumaural devices, along with the opportunities and challenges for commercialization of the technology. The effect of noise source characteristics, specifically stationarity and dynamic range, on stability and performance of LMS filters is examined. Research on hybrid ANR architectures combining LMS filters and digital feedback ANR is reviewed, showing that robust performance with stability margins required for a commercial product can be achieved with such systems. The role of ANR in enhancing speech intelligibility is outlined, along with research needed to develop standards for measurement of stability, ANR performance, and speech intelligibility afforded by digital feedforward ANR devices. The paper concludes with a presentation of opportunities offered by feedforward ANR in intra‐aural and supra‐aural hearing protection devices.

Smoking behavior was investigated with data from a three-generation study of Mexican Americans in San Antonio, Texas. Rates of smoking among the men were found to be higher than rates for other White men obtained in previous studies, while rates for women were slightly lower than those reported for other White women. However, the percentage of light smokers was considerably higher among Mexican Americans than among other groups. There was no evidence that acculturation was a consistent predictor of greater likelihood of smoking. However, there was evidence that the smoking behavior of younger Mexican Americans, particularly the women, was associated with the smoking behavior of their parents.

Sources of help and advice (other than one's spouse) and degree of intergenerational solidarity were investigated in a three-generation sample of Mexican Americans. It was found that elderly Mexican Americans are involved in strong helping networks with their children who rely a great deal on them for advice and help. In all three generations, there is a predominance of family as sources of support. Women are relied on for help regarding health matters and men regarding home repairs and upkeep. Help and advice regarding financial problems and personal problems fall primarily along same-sex lines. Scales measuring intergenerational solidarity, showed that all-female dyads have greater associational solidarity than all-male and cross-sex dyads. Few differences appear in affectual solidarity which was uniformly high. Finally, there appears to be minimum association and intergenerational helping between grandparents and grandchildren.

Determinants of physician utilization were examined using a three-generational sample of Mexican-Americans in San Antonio. A typical version of Andersen's causal behavioral model was moderately successful in predicting physician utilization in the middle and older generations and less successful in the younger generation. Consistent with the literature, need factors (health indicators) tended to affect utilization most directly. The authors also examined whether acculturation into the larger society positively influenced utilization regardless of need, as the literature suggested. While three separate measures of acculturation had no independent effects on physician utilization, acculturation did affect utilization indirectly via the need variables in the middle generation, although these effects were not consistently in the direction of greater utilization. Generational differences in determinants of physician utilization are discussed particularly in relation to the model's greater relevance for the middle and older generations.