bluuebunny/crossref_metadata_2025 huggingface dataset:
The importance of the first 80 ms of room impulse responses: A historical review
Authors: Bradley John
Published: February 2014

The direct sound and reflections arriving within 80 ms after it are particularly important to the perceived quality of sound in rooms such as concert halls and auditoria and have been the focus of the majority of research on concert hall acoustics over the past 50 years. Most of the sound energy is usually concentrated in this time interval and this early sound energy determines many of the perceived characteristics of the hall. Although some remarkable early experiments date back to the 1850s, the major advances concerning how these early reflections are perceived have occurred more recently. Monaural effects including explanations of how our hearing system integrates early reflections, the precedence effect, and the development of measures of clarity and intelligibility have developed from initial work in the 1950s. A little more recently the binaural effects leading to perceived spatial impression have been explained and shown to be critical to achieving good concert halls. Physical measures have been developed that relate to both the monaural and binaural subjective phenomena. This work will review the development of our understanding of the importance of early arriving sound on the acoustical characteristics of concert halls and auditoria.
Edge diffraction and scattering in the early room impulse response
Authors: Torres Rendell R. , Kleiner Mendel , Svensson U. Peter
Published: February 2014

Although reverberation is a common and important measure of quality in architectural acoustics, the early part of a room’s impulse response is equally critical, as its spectrum and transient structure predominantly determine the initial filtering (i.e., the natural coloration) that a room endows on an (otherwise anechoic) source signal. Since this initial room filtering could make the difference between an acoustical impression that is, for example, either ‘‘clear and defined’’ or ‘‘murky and unfocused,’’ various studies have been performed to better understand and model the effects of edge diffraction and surface scattering on the early reflections in room impulse responses. These studies include auralizations with varying ‘‘diffusion’’ coefficients, computations and measurements of edge diffraction in early room impulse reponses, and application of ‘‘boss models’’ to compute hemispherical scattering in room acoustics auralization. Various results show that these effects can be clearly audible and that their audibility and perceived character depend on the input signal, among other factors. Conclusions are complemented with suggestions for future work. [Work supported by the Axson Johnson Foundation and Teknikbrostiftelsen, Sweden.]
An investigation of the spectral effect of multiple early reflections
Authors: Case Alexander U.
Published: February 2014

The interaction of a direct sound with a single reflection of short delay is well-understood. Comb filtering is a quantifiable, measurable, inevitable result. In actual auditoria, one rarely hears a single early reflection. Typically a volley of several reflections follows the direct sound. This paper presents an analytical evaluation of the change in frequency response due to, not one, but several reflections. The combination of a direct sound with several early reflections does not result in a more pronounced, more audible comb filter quality. Rather, the interaction of the direct sound with each of the several reflections in combination with the interaction among the many reflections themselves tends to average out or randomize the expected, comb filtered, spectral distortion.
The acoustics of the church San Francisco of Santiago of Chile
Authors: Delannoy Jaime
Published: February 2014

The church San Francisco, declared a national monument, is the most important representative of the colonial architecture that remains in Chile. The definitive construction data of 1618, and after supporting to earthquakes and fires, conserves its original central shape to the present time. The interest of diverse musicians to interpret its works in this enclosure was the reason for the accomplishment of this study. Measurements of the following objective parameters were made: EDT, C80, C50, D50, U50, ti, and NC. The results indicate that a high background noise exists (NC=46) and a poor intelligibility (D50 lower 0.34). Nevertheless its inner distribution provides an initial favorably short time delay gap (ti=22 ms) that provides an acoustic privacy that favors the execution of small orchestras. [Work supported by Department of Acoustics–Technical University Vicente Perez Rosales.]
Multibeam SONAR from the bottom and up
Authors: Condiotty Jeff , Bjorkheim Oywind (Irv)
Published: February 2014

Acoustic multibeam technology has traditionally been used for hydrographic surveying but is now being introduced as a useful tool in data collection within the water column. A new PC-based system operating at frequencies of 90 or 200 kHz allows visualizing targets within the water column for fisheries behavioral and enumeration studies as well as bottom characterization and profiling, at the same time. The system takes advantage of a wide sampling swath, up to 150 with up to 128 individual beams. The system can be operated in a wide beam mode or used in a Mill’s Cross mode to control the beamwidth in two dimensions. Data are displayed as a SONAR image in real time while raw data (pre-beamformed or beamformed) can be stored for further processing utilizing commercial software. The transducer can be either hull mounted, installed on a submersed vehicle, or attached to a pole mount on a small boat. Applications and data collection methodology to visual and measure target reflectors will be discussed along with calibration of individual beams to produce quantitative results.
Determination of fan inlet duct mode structure using in-duct microphone array measurement
Authors: Gerhold Carl H.
Published: February 2014

A methodology is developed in which the amplitudes of propagating modes are extracted from the sound measured in the duct. The method is derived from a beamforming technique in which the weighting function is the wave description of a chosen mode. The modal distribution that arises from the analysis is used to synthesize the sound propagating in the duct which is projected to the far field to estimate the sound radiated from the duct inlet. The methodology is tested using an array of dynamic pressure transducers in the inlet duct wall of a turbofan engine. The data show that the modal structure of the blade passage frequency tone at lower fan speeds is predominately from the interaction of the rotor with downstream obstructions. At higher speeds, when the fan blade tip speed becomes supersonic, many modes are excited. Good agreement is found between measured and estimated far field sound levels in the forward quadrant of the engine at the lower engine speeds. Significant divergence between measured and calculated far field sound occurs when the blade tip speed becomes supersonic. The methodology is a useful identification of the noise generation mechanisms present in the fan.
Radial temperature variations in cylindrical waveguides and implications for flow measurement
Authors: Willatzen Morten
Published: February 2014

A quantitative treatment of radial temperature variations in a cylindrical duct on ultrasonic flow meter performance is discussed in the laminar flow regime. First, based on the continuity equation, the Navier–Stokes equations, and an energy equation including loss mechanisms due to heat conduction and viscous effects, the steady-state temperature and flow spatial distributions are determined in two cases of practical interest: (a) cylinder wall temperature is maintained at a constant value, and (b) cylinder wall temperature decreases linearly with cylinder axial distance. It is shown that while radial temperature variations are insignificant in case (a), radial temperature gradients as large as 100–200 K/m are possible in case (b) for a fixed axial temperature gradient decrease of 0.1 K/m. Such strong temperature gradients have strong and unfortunate consequences for flow measurement. Large flow meter errors—up to several percentages—are possible using typical parameter values for water as medium. Finally, it is shown that effective ways exist such as to diminish the influence of temperature gradients on flow meter performance. Besides the obvious choice of insulating the flow meter tube, flow measurement errors due to radial temperature variations can be effectively suppressed by reducing the cylinder radius and/or ultrasound frequency.
The multiple source feedback of supersonic jet screech. IV. Space–time diagrams and the fast/slow waves of transitory wave theory
Authors: Powell Alan
Published: February 2014

In Part II [J. Acoust. Soc. Am. 108, 2588 (2000)] the space–time wave diagrams of multiple (point) source screech were elucidated, showing the condition for perfect, or nearly so, reinforcement of the feedback sound at the nozzle. In the transitory wave theory [J. Acoust. Soc. Am. 106, 2194 (1999)] the velocity modulation of a transitory instability wave as it traverses the periodic cell structure results in a continuous phased array which was resolved into fast (approx. sonic) upstream and slow downstream source waves (of constant sinuous amplitude, apart from the envelope factor), only the former radiating strongly, in the upstream direction. The two points of view are reconciled by constructing fast and slow waves in the space–time diagrams by: (a) introducing intermediate negative sources: (b) taking the sources at half strength and adding virtual sources at the zero positions on the fast wave traces, of the same sign as adjacent sources: (c) taking the other half-strength sources and adding virtual sources of opposite sign, the sources then being of the same sign along the slow wave traces. The implications of the need to introduce negative sources in the point source array are discussed.
Propagation of Lamb waves in a bonded plate
Authors: Wang Xiao-Min , Li Ming-Xuan
Published: February 2014

A solution to the propagation of Lamb waves in a two-layered elastic plate for a variety of interfacial conditions is obtained. The bond rigidity between the adjacent layers is accounted for by a spring model proposed by many researchers. Instead of being in the conventional form of a determinant, the resulting dispersion equation is given in a form of polynomials with the normal and tangential interfacial stiffness constants as the sum-coefficients. This novel expression of dispersion equation has an explicit physical interpretation and application for inversion of the stiffness constants. The influences of the variations of the stiffness constants on the propagation of Lamb waves are numerically studied. The results for different adhesive states show that the degradation of the bond rigidity may cause the decreasing velocity and the frequency-shifts of a given Lamb wave mode, thus having a possibility for inspecting adhesively bonded joints by using the ultrasonic wave velocity measurements. Experimental results to verify the theoretical analysis are given and the empircal relationship between the bond rigidity and the Lamb wave velocity of several lower modes is presented. [Work supported by the National Natural Science Foundation of China.]
Laser-induced weak shock in fused silica for destructive testing of thin films
Authors: Wang Junlan , Weaver Richard L.
Published: February 2014

Dynamic testing of the adhesion of thin films to solid substrates is a challenging problem. Work of the past decade testing such films by the impact of a compressive stress wave pulse generated by a laser pulse has determined that a critical parameter is the fall time of the stress pulse. Here we report the development of a variation that allows the necessary fall times to be readily achieved. A YAG laser of moderate power (100 mJ) and pulse duration (10 ns) illuminates a 0.4-μm aluminum layer on a fused silica substrate. A transparent 300-μm water–glass layer provides an inertial backing. The resulting compressive stress pulse that enters the substrate has a strain amplitude of the order of 2% and a duration of 10 ns. The negative elastic nonlinearity of the fused silica causes this pulse to evolve, over a distance of 1 mm, into a linear ramp followed by a weak shock that has a theoretical fall time of 10 ps. Interferometric measurements of the pulse, and observations of the failure of a micron-thick aluminum layer on the opposite side of the substrate, confirm this understanding. [Work supported by NSF.]
Dynamic information signals voicing for syllable-final stops
Authors: Nittrouer Susan , Taylor Sandy , Larive Lesley , Manning Carol , Mertes Tammy
Published: February 2014

Several acoustic properties can influence listeners’ judgments of voicing for syllable-final stops, including vocalic length. Developmental and cross-linguistic experiments have suggested that listeners with little experience about how vocalic length is related to final-stop voicing weight this property less than more-experienced listeners. For five (English, CVC) minimal pairs, we examined the acoustic consequences of final-stop voicing, as well as listeners’ weighting of two properties that signal voicing: vocalic length and syllable-offset transitions. First, an acoustic analysis of words showed that differences in vocalic length associated with final-stop voicing are attenuated when words occur in continuous speech, raising questions about how much experience any listener really has hearing vocalic-length differences correlated with final-stop voicing. Next, adults and children (3, 5, and 7 years old) labeled natural stimuli made from words that originally had voiced or voiceless stops, in which we modified vocalic length. Partial correlations revealed that listeners of all ages weighted offset transitions more than vocalic length. In fact, listeners were reluctant to label any stimulus that did not have transitions clearly indicating closure as ‘‘voiced,’’ and so the traditional ‘‘vocalic-length effect’’ was apparent only for originally voiced stimuli. We conclude that dynamic information takes precedence in this perceptual decision.
Change deafness: The inability to detect changes in a talker’s voice
Authors: Vitevitch Michael
Published: February 2014

Change blindness is a failure to detect a change in a visual scene. A shadowing task was used to demonstrate an auditory analog to change blindness–change deafness. Participants repeated words varying in lexical difficulty. After a rest-break they heard more words from either the same or a different talker. Answers to explicit questions about the change in talker and implicit measures of behavior (i.e., response latencies) demonstrate that processing is affected by the change, even if participants do not explicitly report a change in talker. Specifically, listeners who did not detect the change in the talker had a greater difference between conditions of lexical difficulty than listeners who noticed the change, or listeners who heard the same talker throughout. These results suggest that failures to detect changes are not limited to the visual domain and that processing at some level may be affected by changes in the environment. Furthermore, these results have implications for models of spoken word recognition.
Discrimination and labeling differences in audiovisual spech perception
Authors: Marrone Nicole L. , Carney Arlene E.
Published: February 2014

In an earlier report, Clement et al. [J. Acoust. Soc. Am. 107, 2887 (2000)] showed that listeners’ confidence ratings of the identity of audiovisual syllables produced with conflicting auditory and visual cues were typically lower than those for audiovisually congruent syllables. This occurred even when both types of syllables were labeled consistently as the same phoneme. Confidence ratings varied across listeners, suggesting a graded nature of auditory–visual integration even across listeners who exhibit visual bias. In the current experiment, listeners were asked to identify audiovisual tokens from two talkers who elicit a high proportion of visually biased responses [Carney et al., J. Acoust. Soc. Am. 106, 2270 (1999)] and to rate their confidence in their labeling judgment. Only listeners who exhibited strong visual bias were tested in a discrimination task in which a true audiovisual /di/ was a standard. Comparison stimuli were visual /gi/-auditory /bi/, visual /bi/-auditory /gi/, and true audiovisual /bi/, /di/, and /gi/. Listeners were able to discriminate the visually biased and true /di/ stimuli while labeling them both as alveolar tokens. Results support the notion of a graded perception of bimodal stimuli. [Research supported by NIDCD.]
Flexibility of acoustic cue weighting in children’s speech perception
Authors: Mayo Catherine , Turk Alice , Watson Jocelynne
Published: February 2014

Nittrouer and colleagues [Nittrouer, J. Phonetics 20, 1–32 (1992); Nittrouer and Miller, J Acoust. Soc. Am. 101, 2253–2265 (1997); Nittrouer et al., Percept. Psychophys. 62 (2000)] have found that in identifying certain syllable contrasts, young children make more use of syllable–internal formant transitions (relative to other available acoustic cues) than do older children and adults. The evidence for this change in the degree to which listeners weight, or use, certain cues comes predominantly from studies of fricative contrasts (e.g., /sV/–/∫V/, /sV/–/stV/, /Vs/–/V∫/). The current study tests the flexibility of children’s weighting of acoustic cues by examining cue weighting across a wider range of phonetic contexts. In particular, this study attempts to determine whether children’s focus of perceptual attention can be led away from transitions in contexts where such cues are relatively less salient. Additionally, the study tests children’s ability to identify phonemes in an extreme situation, in the complete absence of transitional information. [Work supported by Wellcome Trust.]
Spatial distribution of early reflections and speech intelligibility
Authors: Oh Yang-Ki , Jeong Dae-Up , Doo Se-Jin , Lee Hee-Won , Choi Chul-Min , Kim Lai-Hoon , Ko Il-Doo
Published: February 2014

The strong early reflections and short delay times have been known to improve the intelligibility of speech heard in rooms. D50 and C80, the most frequently used physical parameters, were developed taking this fact into consideration. However, these monaural parameters have limited applications for the practical design of rooms because of their lack of spatial information. The present work investigates how temporal changes in three-dimensional distribution of early reflections influence speech intelligibility in rooms. A new measurement method, using a five microphone array and an omnidirectional source setup, is employed, and a series of post-processing procedures are involved, for getting different early reflections in their spatial distributions. The changes were made for the impulse responses obtained through a five microphone array in the arrival times of early reflections from all, and the horizontal and vertical directions, respectively. Anechoic samples of the Korean language were convolved binaurally with the reproduced impulses by applying a head-related transfer function. A series of speech intelligibility tests, conducted for 22 university students, found that the percentage of correct responses significantly deteriorated by increasing delay times of early reflections from the vertical direction. The result suggests that vertical components of early reflections play a significant role in improving speech intelligibility. [Work supported by Korean Research Foundation Grant KRF-1999-1-310-004-3.]
Consonants and vowels discriminated differently even when acoustically matched
Authors: Kang A. Min
Published: February 2014

Vowels are reportedly discriminated differently from consonants, but there have typically been large between-class acoustic differences. Discrimination still differed when acoustic differences were reduced by removing the mostly vocalic center portion of CVCs [silent center (SC)] [A. M. Kang and D. H. Whalen, J. Acoust. Soc. Am. 107, 2855–2856 (2000)]. The present study compared consonant and vowel identification and discrimination of synthetic CVCs varying in equal-sized F2 steps along /b-d/ and /ε-ʌ/ continua (full syllables), and in truncated syllables corresponding to the initial 60 ms of the previously examined SC syllables. To lower listener uncertainty, only consonant, or only vowel, information was varied within a test block. Consonant discrimination for full syllables was much higher than in the earlier SC experiment; it was slightly higher for the truncated stimuli than for the full. Vowel discrimination was much higher than consonant, near ceiling for both full and truncated stimuli. Thus, even when acoustic steps are equalized and the speech presented (in the truncated stimuli) is limited to the syllable portion that contains most of the constant information, vowels remain better discriminated than consonants. This indicates a true difference processing of the two phonetic classes, even when the acoustics are well matched. [Work supported by NIH.]
The role of spectral contrast in the perception of stop consonants following vowels and their spectral complements
Authors: Coady Jeffry A. , Kluender Keith R.
Published: February 2014

The ability of listeners to recover speech information, despite dramatic articulatory and acoustic assimilation between adjacent speech sounds is remarkable and central to understanding perception of connected speech. In recent years, studies have revealed that, to some extent, auditory processes of spectral contrast compensate for assimilative effects of coarticulation. In the present studies, series of CV syllables varying acoustically in F2-onset frequency and perceptually from [ba] to [da] were identified either following front (e.g., [i], [e]) and back (e.g., [u], [o]) vowels or following complementary nonspeech spectra. These nonspeech stimuli were harmonic spectra in which the amplitudes of individual harmonics were the inverse of their amplitudes for those same harmonics in the vowels. A prediction of a spectral contrast account is that these complementary spectra should affect perception of following sounds in a manner complementary to that for the vowels from which they were modeled. This predicted effect was obtained. Nevertheless, one may expect that not all perceptual accommodation of coarticulation is explained by spectral contrast. In addition to these initial results, findings from experiments in which stimuli and task variables are manipulated to assess the influence of other processes will be reported. [Work supported by NIDCD DC04072.]
Infant-directed speech helps adults separate different streams of speech
Authors: Newman Rochelle S. , Weppelman Tammy
Published: February 2014

Infants, like adults, are frequently faced with multiple people speaking at one time. What cues help them separate different voices? One possible cue is infant-directed speech (IDS). Speech directed toward infants differs from adult-directed speech (ADS) in a number of ways. IDS typically involves higher pitch, wider pitch excursions, longer durations, and may involve greater amplitude variability [Aslin (1993); Fernald and Simon (1984); Fernald et al. (1989)]. Many of these same features have been shown to be important for adult musical streaming. Furthermore, IDS may serve to make the caretakers voice more distinct from background speech (which is likely to be adult directed). This suggests that it might be easier to separate IDS from ADS than it is to separate two ADS samples. To test this, adult listeners were asked to shadow a target voice while a distractor voice spoke in the background. Performance when one of the voices was infant directed was compared with that when both voices were adult directed. We found a significant effect of speech register on stream segregation, such that listeners found it much easier to follow the target voice when it (but not the distractor) spoke in an infant-directed manner. [Work supported by NSF.]
Automatic gender identification
Authors: Afshordi Dibazar Alireza , Liaw Jim-Shih , Berger Theodore W.
Published: February 2014

In this paper, a new automatic gender identification method is proposed as a part of an Automatic Speaker Recognition (ASR) system. The short time raw speech signal (180–450 ms) was filtered by the nine-order Butterworth low pass filter and decomposed to different frequency bands by the wavelet filter bank analyzer. The energy of the 120 sub-bands was used as a feature vector and applied to a standard classifier. This classifier was trained by the gradient descent method with 1594 utterances spoken by various males and females. The system was tested with different 2542 utterances giving 99.2% correct classification rate. The high performance and simplicity of implementation are the characteristics of this system in comparison to the other methods. [Work supported by DARPA.]
Efficient automatic recognition of spoken digit strings
Authors: O’Shaughnessy Douglas , Tolba Hesham
Published: February 2014

Automatic recognition of spoken digit sequences (such as credit card numbers) is now feasible even in speaker-independent applications over the telephone. However, all recognition tasks have lower performance in noisy conditions. If significant limitations are also imposed on the computational resources used for recognition, then robust speech recognition is still a significant challenge, even for a simple digit vocabulary. Since recognition of continuously spoken digits over telephone links is a very practical application, such recognition was investigated here under different conditions. Traditional hidden Markov model approaches with cepstral analysis were not used, because they are computationally intensive and have not always worked well under adverse acoustic conditions. Simpler spectral analysis was used, combined with a segmental approach. The analysis focuses on locations of spectral peaks, similar to formant tracking, but without the need to estimate peaks for all time frames. The limited nature of the vocabulary (i.e., ten digits) allows this simpler approach. High recognition accuracy is maintained despite being very efficient in both memory and computation. Recent progress will be reported.
Space resolution improvement in pulse crack location
Authors: Kazakov Vyacheslav V. , Zverev Vitaly A. , Sutin Alexander M.
Published: February 2014

The new method of space resolution increasing in pulse location method was suggested by Professor Zverev is applied for space resolution improvement of ultrasonic pulse location technique. According to this method, the spectrum of the received signal is divided to the spectrum of the reference radiated signal and the complex inverse Fourier transformation is applied to the divided spectrum. This approach extends the frequency band used for analysis and highly increases the space resolution of crack location. The feasibility test was conducted with pulse ultrasonic device working with carried frequency about 3 MHz. The suggested processing was applied to the rectified signal so the frequency band of processing was restricted by 700 kHz. Even in this not optimal processing we observed the shortening of the signal reflected from a crack more than 20 times. The suggested technique was also used for spatial resolution improvement of nonlinear modulation crack imaging based on modulation of ultrasonic pulses by a crack vibration. [Work was partially supported by International Science Technical Center Grant No. 1369.]
Improvement in matched field processing by the CLEAN algorithm
Authors: Song H. C. , de Rosny J. , Kuperman W. A.
Published: February 2014

Matched field processing can be improved by the CLEAN algorithm [Astron. Astrophys. Suppl. 15, 417–426 (1974)], introduced into radio astronomy for image restoration. The CLEAN algorithm is based on the a priori assumption that most images of radio sources are essentially blank sky with point-source components distributed in small regions. A simple iterative approach is employed to find the positions and strengths of these point sources. On convolving the point-source components with a ‘‘clean’’ beam, a final image known as the ‘‘clean’’ map is derived. In this paper, we apply this approach to match field processing where the ambiguity surface corresponds to the astronomical map. The initial ambiguity surface called a ‘‘dirty’’ map is evolved to a clean map through the iteration process. Numerical simulations demonstrate that matched field processing combined with the CLEAN algorithm provides better performance especially when a weak source is hardly visible due to sidelobes generated by a much stronger source.
Source localization through knowledge of the scattered field near two air-filled spheres: Numerical modeling results
Authors: Lepper Paul A. , D’Spain Gerald L. , Hodgkiss William S.
Published: February 2014

Knowledge of the complex nature of the underwater sound field measured near two scatterers that are in the far field of an acoustic source may provide valuable information on the location of the source. Traditional techniques of source localization such as time-of-arrival (phase) and amplitude differences measured by multiple receivers are complicated when placed within the near field of an acoustic scatterer due to effects such as diffraction and scattering. The use of the interference pattern field due to the presence of the scatterers is proposed to enhance traditional source localization techniques. Numerical results are presented using a 2-D finite-difference time-domain (FDTD) scheme for scattering from two fluid-loaded, thin-walled, air-filled elastic spheres for multiple source aspect angles and frequencies. Matched field processing techniques are used to quantify the source localization capabilities. [Work supported by ONR.]
Array element localization for towed marine seismic arrays
Authors: Dosso Stan E. , Riedel Michael
Published: February 2014

This work presents a new approach to array element localization (AEL) for the sensors of a towed marine seismic array based on regularized inversion of direct and bottom-reflected acoustic ray travel times picked from recorded seismic sections. Depth-sensor measurements at a number of points along the array are included as a priori estimates (with uncertainties) in the inversion. The smoothest array shape consistent with the acoustic data and prior estimates is determined by minimizing the array curvature or roughness. A smooth array shape is physically reasonable; in addition, minimizing array curvature provides an a priori model for the correlation between hydrophone positions that allows the estimation of both the offset and depth of hydrophones that record only one (or even no) acoustic arrival due to the shadowing effects of water-column refraction or reflection from arbitrary bathymetry. The AEL inversion is applied to a 102-sensor, 1.2-km towed array to correct receiver positions in the seismic velocity analysis of a seabed gas hydrate survey.
Demonstration experiments, videos and audios for teaching acoustics
Authors: Rossing Thomas D. , Hansen Uwe J.
Published: February 2014

Since the time of Pythagorus, if not before, experiments have been used by physics teachers to illustrate acoustic phenomena and important acoustic principles. We owe much to Michael Faraday who established a rich tradition of lecture demonstrations at the Royal Institution in London. Lord Rayleigh, in addition to his well-known papers on the theory of sound, published a number of short notes which he entitled ‘‘Acoustical Observations.’’ A potpourri of acoustics experiments will be demonstrated by a team of college and high school teachers with instructions for doing these experiments with simple equipment. Reproduction of these demonstrations may be useful in a formal educational setting for teaching acoustics, and should be useful also in any number of informal venues—including ones not always thought of as ‘‘teaching.’’ Videos and audios demonstrating acoustics also will be previewed.
Acoustic test facilities of the Underwater Sound Reference Division
Authors: Van Buren A. Lee , Drake Robert M. , Jenne Kirk E.
Published: February 2014

The acoustic test facilities of the Underwater Sound Reference Division (USRD) of the Naval Undersea Warfare Center will be described. The USRD serves as the U.S. standardizing activity in the area of under-water acoustic measurements, as the National Institute of Standards and Technology does in other areas. It is the Navy’s primary activity for underwater acoustic calibration, test, evaluation, and reference measurements on transducers and related devices and materials. In this role the USRD maintains specialized measurement facilities with the capacity to simulate real-world ocean environments. It also maintains transducer standards to help ensure the accuracy of measurements made both at USRD and elsewhere. This presentation will describe the Acoustic Pressure Tank Facility, the Low-Facility Facility (with its three test vessels), the Acoustic Open Tank Facility, the Long-Line Hydrophone Calibrator, the Conical Shock Tube Facility, the Leesburg Facility, and the Transducer Standards Loan Program.
Acoustic measurement facilities at the Applied Research Laboratory
Authors: Bradley David L.
Published: February 2014

Acoustic measurement facilities, ranging from a water tunnel that is also listed as an ASME Historic Landmark to a new ultrasonic measurement system, are illustrated and described with a brief explanation as to size, measurement equipment available, and frequency ranges that are typically employed. The facilities include a high-pressure tank for hydrophone tests ‘‘at depth,’’ the ultrasonics tank, an anechoic tank for hydrophone calibration, the water tunnel, an air acoustic anechoic room and a large, multipurpose underwater measurement facility.
Designing acoustic facilities for education
Authors: Raichel Daniel R.
Published: February 2014

An acoustic laboratory in a university generally serves two functions: education and research. In planning, budgetary considerations constitute a decisive factor. A low budget can result in the laboratory being relegated to fairly simple measurements but some degree of ingenuity can widen the scope of experimentation, as has been proven in Take Five demonstrations at ASA meetings. A more elaborate facility would enable measurements in the ultrasonic region in addition to those in the audio range. The cost of maintenance and eventual upgrading should be figured into the planning and design of any facility. Necessary instrumentation include means of measuring sound pressure levels and intensities, executing spectral analyses (preferably in real time), generating and synthesizing signals, performing fairly standard measurements for sound absorption coefficients; and it would be desirable that specific enclosure conditions be simulated (viz., through the use of anechoic and reverberation chambers). Research programs generally require more sophisticated instrumentation, but fortunately fairly recent advances in microelectronics permit integration of acoustic monitoring functions into personal computers at considerably lower cost than would be the case if individual measurement instruments were purchased separately.
NASA Glenn Research Center Acoustical Testing Laboratory
Authors: Cooper Beth A.
Published: February 2014

The Acoustical Testing Laboratory (ATL) at the National Aeronautics and Space Administration (NASA) John H. Glenn Research Center in Cleveland, Ohio supports the low-noise design of science experiment payloads developed for the International Space Station (ISS). The ATL consists of a 100-Hz vibration-isolated hemianechoic test chamber with 21-ft by 17-ft by 17-ft (h) interior working dimensions and removable floor wedges that allow the facility to be configured as either a hemianechoic or fully anechoic chamber. A separate, sound-isolated control room with outside dimensions of 23-ft by 11-ft by 12-ft (h) doubles as a noise control enclosure when testing articles that require remote connections to high-noise support equipment and services. These characteristics, along with very low design background sound levels, enable the acquisition of accurate and repeatable acoustical measurements on test articles, up to a full ISS rack in size, that produce very little noise. The ATL provides a comprehensive array of acoustical testing services, including sound power level in accordance with precision and engineering grade standards. These capabilities employ a PC-based acoustical data acquisition system that has been customized to perform simultaneous acquisition and real-time analysis of multiple channels of acoustical signals.
Riverbank Acoustical Laboratories
Authors: Moyer David L.
Published: February 2014

Riverbank Acoustical Laboratories (RAL) is located in Geneva, Illinois. Constructed in 1918, RAL became the world’s first independent laboratory dedicated to the science of architectural acoustics. Riverbank owner, philanthropist Colonel George Fabyan, built the laboratory for its designer, professor Wallace Clement Sabine. The scientific efforts of this renowned Harvard physicist earned him two distinguished titles, acknowledged today as the father of the science of architectural acoustics and the first ‘‘modern day’’ acoustical consultant. The unit of absorption is a Sabin. When the professor died in 1919, his distant cousin, Dr. Paul Earls Sabine, became RAL’s director. Retired in 1947, Dr. Sabine turned the operations over to the IIT Research Institute. RAL provides a wide range of acoustical testing services for over 600 clients. The majority of RAL tests are industrial related. RAL provides clients with an accredited, independent testing facility, not associated with any manufacturer or product. Part of RAL’s outstanding credibility reflects upon their policies of maintaining strict confidence and proprietary rights for all clients. RAL is accredited by NVLAP, The City of Los Angeles, and others. Also of interest to many clients is RAL’s museum dedicated to the Science of Architectural Acoustics. The ASA officially sanctioned the museum in 1989.
Signal processing by echolocating dolphins
Authors: Au Whitlow W. L.
Published: February 2014

Many different types of target discrimination experiments have been performed with echolocating dolphins in order to understand and model their echolocation capabilities. However, not many experiments have been performed that measured differential performance as a function of the magnitude of a single target variable, thus making it very difficult to extract limits of various auditory discrimination capabilities. Nevertheless, sufficient information exists that could provide some insight on important echo cues utilized by dolphins and what the signal processing may be. Furthermore, other types of experiments emulating some dolphin experiments have also been conducted. Stretched versions of echoes from target used in dolphin experiments have been used in human listening experiments to determine salient cues present in the echoes. Neural network experiments have also been conducted using echoes from the same target used in the dolphin experiments. The most pertinent of these experiments involving dolphins, humans, and neural networks will be discussed in order to gain insight into important target cues and the manner in which these cues might be processed by echolocating dolphins. The discussion will be conducted in light of the results of a recent experiment in which the auditory filter shape of a dolphin for different frequencies was determined.
Roles of neural oscillation in time domain processing in the bat inferior colliculus
Authors: Galazyuk Alexander V. , Feng Albert S.
Published: February 2014

Central auditory neurons in echolocating bats exhibit pulse-echo delay-tuned responses. Sullivan (1982) proposed that paradoxical latency shift (PLS), characterized by an increase in response latency to loud sounds, is important for this attribute. At present, the mechanism underlying PLS is unclear. The goal of the present study was to identify the mechanism underlying PLS. The responses of 92 neurons in the inferior colliculus of little brown bats to brief tone pulses at the unit’s CF over a wide range of sound levels were studied. Of these, 16 neurons displayed unit-specific periodic oscillatory discharges at high sound levels with a characteristic period of 1.3–6.7 ms. The 27 neurons exhibited unit-specific PLS, with quantal latency shift of 1.2–8.2 ms. In 14 neurons showing PLS, unit’s responses before, during and after iontophoretic application of bicuculline were investigated. Application of bicuculline abolished the PLS and transformed it into periodic discharges, suggesting that neural oscillation in combination with ordinary inhibition may be responsible for PLS. To further investigate whether intrinsic neural property was responsible for PLS, unit’s responses to sounds having different durations were investigated. The result indicates that both intrinsic and extrinsic mechanisms are likely involved in creation of PLS. [Work supported by NIH R01DC00663.]
An investigation of the pulses produced by the least shrews (Cryptotis parva)
Authors: Jalili Mersedeh S. , Thomas Jeanette A.
Published: February 2014

Most echolocation studies have focused on bats and dolphins. Because of technological improvements in ultrasonic sensing and recording equipment, there now are cost-effective approaches towards examining ‘‘other’’ groups of mammals for possible echolocation abilities. In this study, we suggest that echolocation is a primitive characteristic, first appearing in insectivores, the ancestor of all other placental mammals. A few other studies and anatomical, behavioral, and physiological attributes suggest that shrews are likely to echolocate. In captivity, least shrews (Cryptotis parva) produce series of pulses. We used a board divided into an inner and outer box of equal area to run 8 least shrews through a set of foraging and orientation experiments. Experiments were in the dark and we monitored the circumstances under which shrews produced pulses using a night-vision video camera. An ANABATII bat detector monitored the presence of pulses, a Marantz cassette recorder documented the sounds, and Audioscope software on a laptop computer provided real time sonogram and oscillogram displays. The number of pulses and trains, the typical waveform, power spectrum, peak frequency, and bandwidth (−3 dB) were examined among the experiments. Results provided strong evidence that least shrews use simple pulses for both orientation and foraging.
Experimental simulation of binaural object classification by dolphins
Authors: Quentin Gerard J. , Au Whitlow W. L.
Published: February 2014

We used the experimental setup designed to simulate ultrasound transmission and binaural reception by dolphins at the Marine Mammals Research Program. Three composite piezoelectric transducers, located in the same plane, were placed at the corners of a triangle such that a distance of 14 cm separates the two receivers. This approximates the presumed spacing between the dolphin sound entrances. The two receiving channels approximate those of dolphins (e.g., similar spectral responses, different receiving patterns between the two receptors). Transmitted signals were similar to dolphin clicks and echoes were recorded simultaneously at the two receivers and digitized at 1 MHz using two data acquisition boards housed in a portable computer. We sought to identify different targets in these preliminary experiments: a 3-in. stainless steel spherical shell filled with water and two copper cylindrical shells with outer diameters equal to 1.63 and 1 in., respectively. The last two samples have the same thickness (1/16 in.) and are filled either with water or with air. The scattered signals are processed via a simple Fourier transform and analyzed using the resonance scattering theory. A preliminary study of the results is presented.
A two-way integral equation approach to a shelf break problem
Authors: Knobles David P. , Stotts Steven A.
Published: February 2014

Benchmark solutions play an important role in the development, testing, and application of numerical models for range-dependent problems in underwater acoustics. To produce benchmark accuracy propagation solutions requires careful attention to both the theoretical formalism and numerical implementation. The focus of this research is a ‘‘benchmark’’ solution for a two-dimensional (2-D) shelf-break problem in ocean acoustics. The method employed to construct a solution is a two-way energy-conserving coupled mode approach in the form of coupled inhomogeneous integral equations. Solutions of the coupled equations are obtained using a powerful approach originally introduced in nuclear theory and also used to solve simple nonseparable problems in underwater acoustics. The basic integral equations are slightly modified to permit a Lanczos expansion to form a solution. The solution of the original set of integral equations is then easily recovered from the solution of the modified equations. Benchmark quality demands that the errors in each step of the numerical calculation be well quantified, so that the resolution in the transmission loss can be determined. Consistency checks are made in the form of using different numerical schemes to compute the adiabatic or free propagator and mode coupling matrix operator.
PE solutions to some internal-wave benchmark problems
Authors: Ebbeson Gordon R. , Thomson David J. , Brooke Gary H.
Published: February 2014

Benchmarking underwater acoustic propagation models is a necessary stage in the evolution of numerical modeling codes. Candidate benchmark problems should challenge the capabilities of existing models in order to promote the development of improved techniques for reliably simulating sound propagation in realistic oceans. In this paper, a parabolic equation (PE) model is applied to the suite of internal-wave test cases that are offered for numerical consideration by the organizers of the Benchmarking Range Dependent Numerical Models session. The PE calculations are carried out using a code that was originally developed for matched-field processing applications [G. H. Brooke et al., ‘‘PECan: A Canadian parabolic equation model for underwater sound propagation,’’ J. Comput. Acoust. (2001)]. The capability of PECan to propagate sound accurately through the benchmark environments is examined for both tonal and broadband signals. The discussion will address issues related to reciprocity, interpolation of the internal-wave sound speed structure, and convergence of solutions as a function of Padé order and range and depth step sizes. Where possible, PECan will be validated against other well-known propagation models to assess its accuracy as well as to appraise the suitability of the proposed internal-wave benchmark problems to test the limits of existing propagation codes.
Verified acoustic propagation predictions for a shelf-break case
Authors: Evans Richard B. , King David B.
Published: February 2014

A comparison is made between transmission loss computed with stepwise couple modes and the parabolic equation for several shelf-break cases. The close agreement between these two diverse approximate solutions of the wave equation can be interpreted in one of two ways: Either both are producing the correct result or they are making identical errors. The low probability of the second coincidence is interpreted as verification of both results. The difficulties encountered in obtaining verified propagation results are discussed.