Paul Calamia

Topological Sound Propagation with Reverberation Graphs

Reverberation graphs is a novel approach to estimate global soundpressure decay and auralize corresponding reverberation effects in interactive virtual environments. We use a 3D model to represent the geometry of the environment explicitly, and we subdivide it into a series of coupled spaces connected by portals. Off-line geometrical-acoustics techniques are used to precompute transport operators, which encode pressure decay characteristics within each space and between coupling interfaces. At run-time, during an interactive simulation, we traverse the adjacency graph corresponding to the spatial subdivision of the environment. We combine transport operators along different sound propagation routes to estimate the pressure decay envelopes from sources to the listener. Our approach compares well with off-line geometrical techniques, but computes reverberation decay envelopes at interactive rates, ranging from 12 to 100 Hz. We propose a scalable artificial reverberator that uses these decay envelopes to auralize reverberation effects, including room coupling. Our complete system can render as many as 30 simultaneous sources in large dynamic virtual environments.

Diffraction culling for virtual‐acoustic simulations.

Acoustic simulations of complex virtual environments typically are created with geometrical‐acoustics techniques. Such simulations can be augmented with edge diffraction modeling for improved accuracy, but not without a significant increase in processing time due to the additional propagation paths which must be considered and the computational complexity of the diffraction calculations. However, for a given modeling scenario, the contribution of a diffracted path to the overall impulse response can vary over a large range, suggesting that certain diffracted paths can be ignored, or culled, to reduce processing time with a limited effect on the accuracy of the simulation. In this talk, we first analyze the effects of diffraction culling through a precomputed, amplitude‐based ranking scheme. We then describe a simple procedure for identifying and culling insignificant diffraction components during a virtual‐acoustic simulation which approximates the performance of the precomputed ranking. Through numerical...

Edge diffraction in computer modeling of room acoustics

Computer modeling in room acoustics is typically based on geometrical acoustics techniques. Limitations with such methods include, among other things, a lack of diffraction modeling, which primarily leads to inaccuracies at low frequencies. The inclusion of diffraction modeling is quite straightforward for first‐order diffraction, which can be combined with specular reflections of any order. One impractical aspect, however, is that the number of diffraction components can be extremely high, and grows faster (with the reflection order) than the number of specular reflections does. At the same time, the importance, or magnitude, of the diffraction components will differ over an immense range. This variation can be exploited by estimating the importance of each diffraction contribution by the magnitude of its onset, and skipping the remainder of the calculations for those that are deemed too weak. This will be demonstrated for some typical geometrical cases including a set of overhead reflectors, an orchestr...

Fit testing of a hearing protection device with integrated in-ear noise exposure monitoring

In-the-ear hearing protectors are often used in high-noise environments, such as in military operations and during weapons training. The fit of such a hearing protection device in the ear canal can cause significant variability in the noise dose experienced, an important factor in characterizing the auditory health risk. Our approach for improved dose estimates under these conditions involves a portable noise recorder used to capture in-the-ear noise behind a hearing protector, and on-body noise, while assessing hearing protection fit throughout recording. In this presentation we describe evaluation of this system using ANSI S12.42 testing using a shock tube and an acoustic test fixture, to evaluate impulse peak reduction and for measurement validation. Also explored were angle dependent effects on the peak insertion loss and measurement accuracy of the on-body recorder. An exploratory study was conducted with a small sample of experimenters during a recent Navy-sponsored noise survey conducted at Marine ...

Noise exposure in berthing rooms of Naval ships

Noise on aircraft carriers is known to exceed hazardous noise levels as jets launch and land on the flight deck and loud machinery operates below deck. Crew members often reach their daily noise allowance while performing work duties but the conditions for auditory recovery onboard are not well understood. To address this gap, we assisted the Navy in recording 24h persistent noise measurements in several berthing rooms on the USS Nimitz (CVN-68). During flight operations, the 8h time-weighted average (TWA) noise levels in these below-deck living spaces ranged between 75 and 81 dBA. While the levels fall below the Department of Defense TWA limit of 85 dBA, these conditions may not support auditory recovery from temporary threshold shifts that occurred during work hours. Another potential noise hazard in these rooms is impulse noise from flight deck catapults and arresting wires, with peak levels as high as 143 dB. In this presentation, we describe an analysis of the 24h noise exposure from aircraft-carrier...

Predicting sound-localization performance with hearing-protection devices using computational auditory models

Evaluation of the effect of hearing-protection devices (HPDs) on auditory tasks such as detection, localization, and speech intelligibility typically is done with human-subject testing. However, such data collections can be impractical due to the time-consuming processes of subject recruitment and the testing itself, particularly when multiple tasks and HPDs are included. An alternative, objective testing protocol involves the use of a binaural mannequin (a.k.a an acoustic test fixture) and computational models of the auditory system. For example, data collected at the eardrums of such a mannequin outfitted with an HPD can be fed into a binaural localization model. If the performance of the model with such input can be shown to be similar to that of human subjects, the model-based assessment may be sufficient to characterize the hearing protector and inform further design decisions. In this presentation we will describe the preliminary results of an effort to replicate human-subject localization performan...

On-body and in-ear noise exposure monitoring

Accurately estimating noise dosage can be challenging for personnel who move through multiple noise environments. Dose estimates can also be confounded by the requirement to wear hearing protection in some areas, but not others. One concept for improved dose estimates under these conditions is to capture noise in-the-ear and on-body simultaneously. An additional benefit of this setup is that hearing protection fit can be assessed in real time. To evaluate this dual-microphone approach, we prototyped a noise dosimetry device for military environments where loud impulse noise such as weapons fire drives the need for high dynamic range and a high sampling rate. In this presentation, we describe a system where the in-ear microphone is acoustically coupled to a disposable foam or flange hearing protection eartip. Initial laboratory tests with a shock tube and acoustic test fixture (ATF) show more than 30 dB noise reduction between the on-body and in-ear microphones. Furthermore, in-ear levels are consistent with eardrum measurements in the ATF. One concern with body-worn dosimeters is their susceptibility to shock artifacts from microphone motion or handling. To address this issue, we also investigate co-locating an accelerometer with the on-body microphone to help remove shock artifacts. [Work supported by the Office of Naval Research.]Accurately estimating noise dosage can be challenging for personnel who move through multiple noise environments. Dose estimates can also be confounded by the requirement to wear hearing protection in some areas, but not others. One concept for improved dose estimates under these conditions is to capture noise in-the-ear and on-body simultaneously. An additional benefit of this setup is that hearing protection fit can be assessed in real time. To evaluate this dual-microphone approach, we prototyped a noise dosimetry device for military environments where loud impulse noise such as weapons fire drives the need for high dynamic range and a high sampling rate. In this presentation, we describe a system where the in-ear microphone is acoustically coupled to a disposable foam or flange hearing protection eartip. Initial laboratory tests with a shock tube and acoustic test fixture (ATF) show more than 30 dB noise reduction between the on-body and in-ear microphones. Furthermore, in-ear levels are consistent wi...

Concepts & Methods in Architectural Acoustics from the Classical Period to the Enlightenment

Herein is presented a critical examination of the early concepts in architectural acoustics in the western world. This study suggests that the historical extent of architectural acoustics is much more sophisticated than is generally considered. The presentation focuses on specific contributors and their discoveries in the nascent art of architectural acoustics. Among those studied are Marcus Vitruvius Pollio, the ancient Roman architect responsible for the tome De Architectura; German polymath Athanasius Kircher who delicately balanced empirical science with magic to explain acoustical phenomena in his two books, the Phornugia Nova and the encyclopedic Musurgia Universalis; and English architects‐cum‐scientists Sir Samuel Morland and Sir Robert Hooke whose wide and varied research often entered into acoustics. In the works of these gentlemen are elegant, precocious, and sometimes absurd revelations on the science of sound and surface.

Multiresolution geometrical‐acoustics modeling

Geometrical‐acoustics (GA) modeling techniques assume that surfaces are large relative to the wavelengths of interest. For a given scenario, practitioners typically create a single 3D model with large, flat surfaces that satisfy the assumption over a broad range of frequencies. Such geometric approximations lead to errors in the spatial distribution of the simulated sound field because geometric details that influence reflection and scattering behavior are omitted. To compensate for the approximations, modelers typically estimate scattering coefficients for the surfaces to account stochastically for the actual, wavelength‐dependent variations in reflection directionality. A more deterministic approach could consider a series of models with increasing geometric detail, each to be analyzed at a corresponding frequency band for which the requirement of large surface dimensions is satisfied. Thus, to improve broadband spatial accuracy for GA simulations, we propose a multiresolution modeling approach. Using s...

Frequency‐domain diffraction for edges of arbitrary length with efficient numerical integration

Frequency‐domain edge diffraction from an infinite wedge insonified by a point source has been widely studied, with various analytical solutions dating back nearly a century. In this talk we present an alternative frequency‐domain solution which can be used for finite as well as infinite edges. The expression, given as a line integral along the diffracting edge, is derived from an analytical time‐domain expression presented in [U. P. Svensson et al., J. Acoust. Soc. Am. 106, 2331‐2344 (1999)]. The new formulation is shown to be equivalent to an exact, analytical, contour‐integral formulation for the infinite wedge via a variable transformation. Results for various finite and infinite edge cases will be presented, and numerical integration using an efficient quadrature method for highly oscillatory integrals will also be discussed.