bluuebunny/crossref_metadata_2025 huggingface dataset:
Current Status of the Diagnostic Rhyme Test
Authors: Voiers William D.
Published: October 2005

The diagnostic rhyme test, a two-choice test of consonant discriminability, has been subjected to extensive experimental evaluation during the past 6 years. On the basis of this evaluation it has undergone a succession of refinements of content and scoring technique. This report summarizes the major results of this evaluation and presents a version of the diagnostic rhyme test, along with various scoring options, based on these results.
The Use of Isolated Vowels as Auditory Stimuli in Eliciting the Verbal Transformation Effect.
Authors: Lass Norman J. , Golden Sheila S.
Published: October 2005

The purpose of this investigation was to determine the effectiveness of single isolated vowels as auditory stimuli in eliciting perceptual illusory changes in subjects, a phenomenon referred to by Warren [Brit. J. Psychol. 52, 249–258 (1961)] as the verbal transformation effect. Three vowels, /i/, /u/, and /æ/, were individually presented to a group of 24 normal adult listeners in a single experimental session. Each vowel was repeatedly presented via headphones for a period of 5 min. The order of presentation of the three vowels was randomized for each subject. Results indicate that single isolated vowels are capable of eliciting verbal transformations in normal listeners. However, the transformations often differ from those obtained using more complex auditory stimuli. The nature of the verbal transformations, average number of alternate forms perceived and transitions employed, and average number of repetitions of the stimulus required prior to the onset of transformations are discussed. Comparisons are also made with the findings of previous investigations.
The Fundamental Frequency of Sustained Vowels under Different Production Conditions
Authors: Woood C. A. , Michel J. F.
Published: October 2005

Studies have shown that phonations of high vowels have a consistently higher fundamental frequency (F0) than low vowels. This study examined whether this phenomenon was due to production or perception variables. Sustained vowels /i, a, æ, u/ were produced under four conditions: (1) spontaneous “natural” production, (2) auditory masking, (2) matching the “pitch” of a reference signal, (4) matching the F0 of a reference signal using a visual frequency aid. It appears from the data that whatever is causing the vowel/F0 relationship is intrinsic to the production and not the pitch perception of the vowel. No matter if the auditory perception was masked during production or enhanced by an auditory cue, the speakers' F0s did not change significantly from the “natural” vowel productions. Given enough cues, auditory and visual, speakers can voluntarily overcome the intrinsic vowel F0s. However, the results obtained by just asking speakers to match pitch to a reference tone indicate that the intrinsic production factors are fairly strong and require a concentrated effort to overcome them. Implications of the results for source tract interaction are discussed.
Temporal Masking of Speech
Authors: Charan K. K.
Published: October 2005

Temporal effects of 50-msec wideband and narrow-band noise bursts on the perception of three voiceless stop consonants in CV syllables, /pa/, /ta/, /pu/, /tu/, and /ku/, were investigated. In each trial a single noise burst was presented in a specified temporal relation with a syllable. The time intervals between the beginning of the syllable and the end of the noise burst were studied in a range between −600 msec (burst before the syllable) and +150 msec (burst completely within the syllable). The listening tests were conducted at 88 and 96 dB noise burst SPL and seven S/N ratios ranging between −22 and −50 dB. The results demonstrated appreciable masking within ±150-msec interval. Maximum masking occurred when the noise burst overlapped a part of the frictional noise of the stop consonant. Forward masking, measured as decrease in intelligibility, decreased linearly as the logarithmetic function of interval. Consistent relations were found between the noise spectra and the amount of masking and the type of substitution errors. Differences as a function of talkers and vowels were also observed.
Cross-Language Differences in the Perception of Natural Vowel Sounds
Authors: Terbeek Dale , Harshman Richard
Published: October 2005

Recent studies of perceptual vowel spaces deal strictly with steady-state stimuli. In most cases, these stimuli were acoustically similar to vowels in the listeners' native languages. In this experiment, listeners from different native language backgrounds performed triadic comparisons on 12 natural vowel stimuli, produced with falling intonation and stress in the context [bəb__] in order to place listeners in a speech-perception mode. Also, for any listener, the stimulus set included vowels not present in his native language. The stimuli were presented under listener control by a PDP-12 computer. Listeners' judgments were converted to relative difference matrices, supplied with additive constants according to Cooper's best-fit technique, and transformed into scalar products of vectors. The resulting data were factor analyzed by the multimodal PARAFAC procedure (Harshman, this meeting), which provides highly constrained solutions of more theoretical interest than are provided by traditional multidimensional scaling. Factor solutions for 1 through 5 factors were obtained and compared. Results across listeners grouped according to native language have implications for the concept of a “universal” perceptual space.
Air and Bone Conduction Pure Tone Detection Thresholds for Squirrel Monkey
Authors: Wilpizeski C. R. , Young I. M.
Published: October 2005

Probe microphone equivalents of monaural pure tone MAP thresholds were determined for seven squirrel monkeys trained to track thresholds by means of a shock avoidance conditioning procedure. Three animals were fitted with audiometric-type bone vibrators cemented permanently to stainless steel screws tapped into the parietal bones, and bone conduction thresholds were obtained. Stimuli were steady and pulsed pure tones from 125 Hz through 16 000 Hz. Head attenuation (cross hearing) and effective contralateral masking levels for broad-band noise were measured. Validity of bone conduction thresholds was checked under conditions of experimentally induced conductive and sensorineural deafness. [Work supported in part by U. S. Veterans Administration and by National Institute of Neurological Diseases and Stoke.] (This paper was originally scheduled for presentation at the Eightieth Meeting, but was not delivered.)
Lateralization of Tone Stimuli by Rhesus Monkeys
Authors: Wegener J. G.
Published: October 2005

Six monkeys were trained to sit quietly in a chair wearing a tight-fitting plastic helmet. Sounds were delivered to either ear separately or to both ears simultaneously via condenser microphones placed in the helmet and directed toward the auditory meatus. To date we have examined single-ear thresholds for a 500-Hz tone doubled at the transducer to a 1000-Hz tone. We have also determined the interaural intensity thresholds and have begun the study of phase difference lateralization. Sound levels with a monkey head in the helmet have not yet been determined. Measurements with an open helmet, including normal sound room ambient noise, averaged 61 dB re 0.0002 dyn/cm2 at the frequency used and at 0-dB attenuation. The 75% correct level of performance for all single ears averaged 27.8 dB below the measured 0-dB level (range: 24.8–30.5 dB). The average difference between ears of the same animal was 1.9 dB (range: 0.6–3.0 dB). The average 75% correct interaural intensity threshold for six monkeys was 1 dB (range: 0.9–1.3 dB). [Supported by NINDS grant.]
Hearing in Two Species of Wild Rodents
Authors: Heffner Henry , VanOeveren Ronald , Masterton Bruce
Published: October 2005

As part of a systematic study of the auditory capacities of mammals, behavioral audiograms were determined for two species of wild rodents: the cotton rat (Sigmodon hispidus) and the house mouse (Mus musculus). The method of conditioned suppression was used to assess thresholds for frequencies ranging from 0.5 to 91 kHz. Comparisons of the two audiograms with each other and with an updated sample of those of other mammals yield support for two previously discovered (inverse) relationships between high- and low-frequency hearing and between high-frequency hearing and interaural distance (maximum Δt). However, a partial correlation in which high-frequency hearing is held constant reveals that low-frequency hearing is not related to maximum Δt. The updated sample of mammalian audiograms now provides firmer ground for concluding what does and what does not constitute a bizarre auditory adaptation. For example, bats are neither unique nor bizarre in their ability to hear extremely high frequencies nor in their inability to hear low frequencies.
Narrow-Band CW/FM Echolocation in Bats
Authors: Simmons J. A.
Published: October 2005

The horseshoe bat, Rhinolophus ferrumequinum, emits sonar cries that rise slightly in frequency to about 83 kHz, remain constant at 83 kHz for 10–50 msec or so, and then during the last millisecond or two sweep downward to 65 or 70 kHz. Other laboratories have reported that the bat adjusts its outgoing CW frequency to keep the returning echo frequency at 83.4 kHz regardless of Doppler shift. Discrimination experiments indicate that Rhinolophus uses the terminal FM signal for target ranging, achieving an acuity of about 30 mm with a cross-correlation sonar receiver. The FM and CW signals are separated by sharply tuned auditory mechanisms into different populations of neurons. Such separation is vital in a correlation receiver to prevent contamination of the FM signal with the CW signal and consequent loss of acuity in ranging. Doppler-shift compensation is necessary because the narrow-band FM waveform of Rhinolophus is subject to intolerably large Doppler ranging errors. Other bats that use correlation receivers avoid severe Doppler ranging errors by transmitting broad-band FM signals.
Model Studies of Aircraft Noise Propagation in the City
Authors: Lyon R. H. , Pande L.
Published: October 2005

A series of model studies of the propagation of V/STOL noise in urban areas have been initiated. The scaling is approximately 1:32. Frequencies of interest in the model study are 1–100 kHz. Diagnostic experiments using a spark source and simulation experiments using a continuous noise source have been carried out. Description of the models and results from the experiments are presented. [Research supported by Department of Transportation, under contract.]
Criteria for Selection of Measurement Positions for Maximal Jet Aircraft Sideline Noise
Authors: Galloway William J.
Published: October 2005

Present FAA noise certification requirements for subsonic jet aircraft specify uniquely the measurement locations for takeoff and approach noise. A third set of measurements is required to determine the maximum noise produced on the ground to the side of the flight path. The regulation specifies only the offset distance from the runway, requiring the applicant to determine where, longitudinally, measurements should be taken and to demonstrate that a maximum value is obtained. Based on three separate test programs for turbojet powered business aircraft, we show that the maximum sideline noise will occur when the angle between the ground and the aircraft is approximately 10°. Further, when reported as effective perceived noise levels, the sideline noise varies extremely slowly with distance along the runway after this angle is achieved. With very coarse assumptions as to the aircraft noise directivity pattern, a sideline noise measurement location can be selected which will meet the FAA requirements. A design chart for measurement point selection, using aircraft performance estimates as input data, is provided.
Speech Intelligibility in the Presence of Time-Varying Aircraft Noise
Authors: Williams C. E. , Pearsons K. S. , Hecker M. H. L.
Published: October 2005

There has been some question as to whether the relationship between the articulation index (AI) and intelligibility test scores established for steady-state noise can be used to predict intelligibility scores that would be obtained in the presence of time-varying aircraft noise. For various aircraft flyovers, speech intelligibility scores and various noise measurements were obtained as functions of time. In addition, intelligibility scores and measures of AI were obtained for steady-state simulated aircraft noise. The relation between AI and speech intelligibility for flyover noise was different from the relation obtained for the steady-state noise. The various noise measures were almost equally effective in predicting speech intelligibility in the presence of flyover noise. There is an appreciable disruption of contextual speech when the peak level of a flyover exceeds 88 PNdB, an SIL of 68 dB, and an A-weighted sound-pressure level of 76 dB. [Work supported by Federal Aviation Administration.]
Scaling Aircraft Noise Perception
Authors: Ollerhead J. B.
Published: October 2005

An experiment was undertaken to evaluate various methods for calculating the perceived level of aircraft flyover sound. One hundred and twenty recorded sounds of jets, turboprops, piston engined aircraft, and helicopters were compared in a paired comparison test. The “complex” procedures developed by Stevens, Zwicker, and Kryter were found to be superior to other scales, particularly when integrated to include a signal duration allowance. The main advantage of these methods over the more convenient weighted sound-pressure level scales lies in their ability to cope with signals over a wide frequency range. However, Stevens' loudness level scale and the perceived noise level scale both overestimate the growth of perceived level with intensity. A simple correction is proposed which is based on Zwicker's theory and which will enable these scales to account properly for the experimental observations. It is recommended that the search for an improved sound level meter scale be continued, not as a replacement for the more complex perceived level procedures, but to supplement them. Despite deficiencies which cannot be overcome by refined weighting circuits, it is clear that the weighted sound-pressure level provides a powerful scale for comparing the sounds of aircraft. [Work supported by the National Aeronautics and Space Administration and the Federal Aviation Administration.]
Future Trends in Airport Noise
Authors: Eldred K. M.
Published: October 2005

The existence of noise problems around existing major airports is well known. In some cases, the land area in which residents complain about noise is very large, on the order of 40 square miles or more. In these situations, attainment of compatibility through land use conversion is economically, politically, and sociologically untenable, and other solutions must be found. This paper discusses some of the available tools for obtaining compatibility for existing large and smaller jet airports through operational changes and the development of quieter aircraft. Future trends are projected over the next 10 and 20 years and illustrated by examples of noise exposure forecasts for a single runway operation.
A Unique Program of Research and Education in Noise Acoustics
Authors: Wright S. E.
Published: October 2005

Recently, a pilot scheme was established at the NASA Langley Research Center to determine the feasibility of an off campus full time graduate training program. The students spend approximately half of their time on course work and half on research, making use of the excellent NASA research facilities. The students also have the academic advantages of belonging to a university system, as the teaching is carried out by professors who spend the majority of their time at NASA Langley. Much interest is focused on this educational experiment, for if successful, it could pave the way to further expansions. The program is the result of cooperation between the George Washington University, NASA Langley Research Center, and the internationally known Institute of Sound and Vibration, England. Noise Acoustics was chosen as the initial area in order to increase the number of trained people able to help combat noise pollution. The many aspects of this topic include noise sources, transmission studies, and the effect of noise on man and structures. A description of the program—its hopes, its possibilities, and the success so far—is given after nearly two semesters of operation.
Computer Analysis of Fan-Induced Turbofan Engine Noise
Authors: McNeill Harry
Published: October 2005

Three different sounds can be identified within the noise field of a modern turbofan engine. Most noticeable is a high-pitched whine which seems to be imposed on the background of a loud hissing sound. Occasionally a multiple tone, resembling a buzz saw, can also be heard with some engines. Many observations have been made regarding these sounds in research programs conducted by Pratt and Whitney. It was observed that with high by-pass ratio turbofan engines, fan generated sound has been identified as the dominant noise source. When investigating the consequence of test programs using rig data or in engine mock-up development programs, a problem of central importance is the separation of the field into the classifications described. In this way, parametric changes can be associated with their effects on a particular component of the noise field. Fan-induced noise from a turbofan engine is analyzed by a digital computer using time series data taken by microphones placed in the noise field. Analysis in the frequency domain permits separation of the noise field into passing tones, combination tones, and broad-band noise. The results of the analysis are presented in both plots and computer data listing. The frequency distribution of passing tones and combination tones are shown in the listing with fitted polynomial coefficients for broad-band noise. The data is also integrated over 1-oct and 13-oct bandwidths to permit comparison with other methods of analysis.
Calibration System for Pressure and Pressure Gradient Hydrophones at Infrasonic and Audio Frequencies
Authors: Ensign Thomas H.
Published: October 2005

A complete measurement system for the calibration of pressure and pressure gradient hydrophones over the frequency range 5–3000 Hz with static pressures to 1000 psi is described. Measurement of hydrophone amplitude, phase, and directional response to a plane progressive wave is made within a stiff-walled cylindrical sound channel terminated by active transducers. Sound-pressure levels to 140 dB above 1 Pa may be employed. Adequate plane-wave operation in the infrasonic region is assured by the separation and individual alignment of the even and odd pressure distributions that compose a plane wave. Each wave component is monitored by a symmetric distribution of pressure responsive probes in an amplitude sensitive alignment technique. An analysis of required pressure field tolerances and subsequent termination transducer drive tolerances is discussed. The low frequency limit of the system is shown to be a direct function of the field tolerances and sound channel length. Two complete systems have been fabricated, and data have been collected on a large number of moving coil gradient hydrophones.
A Digital-Readout Sound Level Meter with Automatic Range Switching
Authors: Sullivan C. E. , Knowd M.
Published: October 2005

One of the main problems confronting sound engineers who must make a noise survey armed only with a sound level meter is the determination of the effective level of a noise that fluctuates through a wide range. If the range of variation is more than 15 dB, or if changes occur very rapidly, it is nearly impossible to arrive at a reasonable average figure. Therefore, a sound level meter was developed that not only automatically switches ranges according to the input level, but also provides a digital readout for on-line or off-line linkage to a computer. Problems of integration time and frequency of readout are discussed in terms of present knowledge concerning what constitutes the “effective level” of time-varying noise.
Development of a Portable Acoustic Impedance Meter
Authors: Jhaveri A. G.
Published: October 2005

It is shown that the proposed portable acoustic impedance meter, based on simple design and concepts, can not only measure complex impedance of various acoustical lining configurations and resonator panels, but can also determine acoustic efficiency of assembled units within the framework of nondestructive type testing.
Radiation from a Source in a Short Circular Duct
Authors: Zorumski William E. , Clark Lorenzo R.
Published: October 2005

An analytical and experimental study is made of the sound field from a point source in a short circular duct. The analytical model is a duct, with a finite number of acoustically treated sections, which terminates in an infinite baffle. A modal solution is given which includes all reflections between sections and at the open end of the duct. Analytical and experimental SPLs are compared inside and outside of the duct.
Interaction between the Vibration of a Thin Elastic and Fluid-Loaded Plate and the Sound Field inside a Closed Cavity
Authors: Obermeier Frank
Published: October 2005

The sound field inside a closed rectangular cavity behind a thin elastic plate excited by a turbulent flow is discussed. The results obtained show a certain analogy to the well-known behavior of an undamped dynamic vibration absorber. While, in general, the sound pressure inside the cavity remains small compared with the pressure fluctuations of the turbulent flow and the plate motion depends in a first approximation only on the flow pressure, in the resonant case the sound pressure increases to the level of the corresponding turbulent pressure fluctuations, while the corresponding components of the displacement of the plate decrease to zero. This is true even if a resonant frequency of the plate is equal to a resonant frequency of the cavity.
Scattering of Acoustic Waves by a Periodically Supported Plate
Authors: Garrelick Joel M. , Feit David
Published: October 2005

An idealization of a structural system that is commonly used in aerospace and marine vehicles is that of a thin skin that is periodically supported by parallel rib stiffeners. If we consider such a structure placed in an acoustic medium, an interesting problem that arises is a consideration of how such a structure scatters an incident sound field. The scattering structure is taken as an elastic plate of infinite extent, representing the thin skin, which is periodically supported in such a way that the displacement and slope of the plate vanish at the support points (clamped supports). Thus as a first approximation we have modeled the stiffeners as being of infinite mass and of infinite torsional rigidity. For a normally incident pressure whose wavelength is larger than the interstiffener length, the theory predicts a scattered pressure in the specular direction whose magnitude is equal to that of the incident pressure and hence independent of the elastic parameters of the plate. At higher frequencies nonspecular as well as specular reflections are found, and their magnitudes are dependent on the elastic properties of the plate.
An Integral Equation Approach to Acoustic Wave-Elastic Body Interaction Problems
Authors: Shaw R. P.
Published: October 2005

The scattering of acoustic waves by obstacles of arbitrary shape has been treated by an integral equation formulation for several forms of boundary conditions, e.g., rigid, free, Robin (inertial), and impedance. The advantage of the integral formulation in reducing the dimensionality of the problem to only surface values of the unknowns is well understood. It is proposed here that the same approach be employed for the study of scattering of acoustic waves by elastic bodies of arbitrary shape. Such studies to this point have been essentially limited to separable geometries such that a modal approach might be employed. The present formulation would employ a velocity potential in the acoustic fluid and displacement potentials in the elastic solid, all of which satisfy wave equations for which an integral formulation is available. The coupling at the boundary for thin-walled elastic shells is simplified in that the same surface and, therefore, influence coefficients can be used for both media.
Transient Acoustic Scattering by a Pressure Release Sphere
Authors: Shaw R. P. , English J. A.
Published: October 2005

The early time, i.e., first two transits, surface velocity field on a pressure release sphere scattering a plane step incident acoustic pressure pulse is calculated by a Kirchhoff time retarded potential integral equation. Modal solutions of the same problem have not been published in numerical detail, but a comparison can be made to the first three mode sum of the analagous pressure release sphere bisected by a free surface found by Baron and Bleich in a report. Agreement is very good except at very early times, where the modal solution converges slowly and, therefore, where the integral equation solution is more accurate. Solutions are also given for an incident plane step acoustic pressure pulse, which decays exponentially, and for an incident spherical step acoustic pressure pulse. [This research has been supported by the Office of Naval Research under Contract.]
Acoustic Scattering by an Axisymmetric Thin Elastic Shell
Authors: Chang S. , Chambers B. S. , Maxum B. J.
Published: October 2005

A technique is presented for predicting acoustic scattering by an axisymmetric, but otherwise generally shaped, thin elastic shell immersed in an infinite ideal homogeneous fluid. It is assumed that the shell is illuminated by a monochromatic plane wave and that linearity and the thin-shell theory are applicable. The problem is formulated by coupling the Lagrangian equations of motion for the shell to the surface Helmholtz integral equation. In this problem, both the surface pressure and the body displacements are unknowns. The pressure and displacements are expressed in terms of subsectional basis functions where the coefficients of the displacement basis functions become the generalized coordinates of the system. In this manner the integro-differential equations are reduced to a set of linear algebraic equations, which are then solved. Finally, farfield pressure is computed from which the bistatic scattering pattern is found. Numerical results are obtained for sperhical and hemispherically capped cylindrical shells. The numerical results for the spherical shell are compared with the exact analytic solution for that geometry. This comparison serves as a test of the validity of the technique. [Supported by Cornell Aeronautical Laboratory, Internal Research.]
Dynamic Analysis of Large Structural Systems
Authors: Rosen R. , Rubenstein M. F.
Published: October 2005

The techniques used in predicting the time history response of structural systems subjected to a dynamic environment have seen major modifications in the last 10 years. The increased capabilities of digital computers have been the impetus for improved numerical techniques and computer codes. Direct decomposition methods for the solution of linear equations have replaced iterative techniques like relaxtaion and Gauss-Seidel. Eigenvalue and eigenvector extraction methods like inverse iterations, Q/R, L/R, and A/P have received a great deal of attention, and many standard computer codes utilizing these methods are available. The present generation of computers offers the user a large variety of hardware and software options. The CDC 6600 with a 60-bit word and 130 000 core words is an ideal machine for large dynamics analysis programs, while the IBM-360 series with a 32-bit word size is inadequate and double precision must be used. Computer programs such as STARDYNE, NASTRAN, SAMIS, and SRUDL are capable of solving dynamic structural problems with thousands of degrees of freedom. It is important for the analyst to understand their capabilities and shortcomings in order to make effective use of them.
Mathematical Model for the Free Vibration of an Arc with Varying Radius of Curvature
Authors: Rutledge James R. , Royster L. H.
Published: October 2005

A mathematical model for the symmetric and antisymmetric free vibrations of an arc with varying radius of curvature is developed. The arc is approximated by a discrete set of equations, and the model is developed for varying cross-sectional geometry (taper and thickness). Digital computer solutions for the matrix eigenvalue problem are discussed for the pinned-pinned and clamped-radially guided boundary conditions. Vibration coefficients are presented for various elliptical cases with taper and thickness variations. [Work was partially sponsored by the Office of Naval Research, Acoustics Programs, and by the Naval Underwater Sound Laboratory.]
Noise Exposure Site Assessment Techniques
Authors: Winzer George E.
Published: October 2005

Sites proposed for housing and other Departmental programs sometimes are located in noisy areas. Over the past several years, a number of “problem cases” have resulted from commitments, often made 5–10 years ago, to such sites without adequate preliminary screening of the noise environment. In most cases, legislative limitations on unit costs often preclude additional expenditures for incorporation of special noise control features. Because of the large number of applications handled by field personnel and the complexity of the many issues facing them, instrumental measurements of noise exposure at every proposed site is practically impossible. Indeed, such measurements would be of little value in projecting noise exposure where land use is undergoing change, e.g., pastoral to the urban residential and industrial new community. Techniques have been developed for use by field personnel and applicants who have no technical training in acoustics. These “screening tools,” which are based upon various noise sources and factors affecting the generation and propagation of sound, will be described. An example of their application to an Operation Breakthrough prototype site in Memphis will be given.
Considerations in Residential Building Design for High-Level-Noise Sites
Authors: Goodfriend L. S.
Published: October 2005

Contemporary urban planning and building design for single and multiple dwellings to be located in areas of high level noise are only now beginning to account for the planning, legal, and architectural constraints that perpetrate inadequate isolation from exterior noise at every price level. Current exterior construction and glazing techniques provide little basic isolation. Conventional penetration of the exterior for air conditioning intakes, vents, kitchen and bathroom exhausts, and attic vents would, in any case, destroy the effectiveness of a well-designed exterior. To add to the designers problems, modern urban planning has, to date, been more concerned with social and civil engineering aspects of site evaluation. Working toward correcting this situation some planning, architectural, and engineering activity is under way. Several major airport regions and highway projects have been evaluated on a noise basis as part of the planning. Among architectural ideas that have been developed are wall systems. These include cavity walls of medium density block, fenestration designs for a high-rise as well as single-family housing using a minimum of exposed glass for maximum light, and roof designs that optimize acoustical isolation in thermally appropriate exterior systems. Finally, control of inadvertant penetrations of the building combined with operable closures that really close, can, along with the other measures cited, improve interior isolation 15 and possibly 20–25 dB over conventional building design.
The Acoustical Design of Structures above or Adjacent to Railroad Tracks
Authors: Blazier W. E.
Published: October 2005

Current urban redevelopment trends in both the USA and Canada are resulting in the construction of more and more buildings adjacent to or above railroad tracks. At the present time several such building sites are being developed, the economic success of which is strongly dependent upon how effectively the airborne and structureborne noise, due to nearby heavy freight train activity, is isolated from interior sensitive spaces. This paper reviews what has been done, both architecturally and structurally, to incorporate noise and vibration isolation controls in the source-to-receiver paths on several current projects. The measured performance of a completed structural isolation system that uses neoprene pads is discussed. In addition, data are presented on a recent field evaluation of the quantitative differences between continuous-welded rail and conventional jointed track with respect to both the generation of acoustic noise and the relative levels of ground-induced vibration. Data are also shown which demonstrate how the source noise and vibration levels vary as a function of train speed, car weight, and maintenance condition of the wheels for typical freight traffic.
Acoustical Modeling for Large Area Community Noise Control
Authors: Ortega Jose C. , Veneklasen Paul S.
Published: October 2005

Rarely does it occur that noise exposure over a structure is uniform. Beyond the simplest shapes, sound diffraction is much too complex for mathematical analysis. Yet, economical design requires acoustical balance, i.e., the treatment of various surfaces in proper relation to their outside exposure. Acoustical modeling permits a rapid and precise determination of relative exposures for exterior surfaces of the most complex configurations and for the trajectory of a moving sound source. Practical examples impress the designer with the large degrees of self-shielding occurring over ordinary structures. Examples are given to illustrate the meaning of balanced acoustical design and the economic significance. The spreading of shielding benefits over surrounding areas leads to the suspicion that the need for widespread noise control measures for individual structures over large areas might be reduced or eliminated by concentrating the sound control in specific building barriers, with great economic savings. As an example, sidelines of airports are considered with limited model data. An outline is given of other technical and economic factors that accompany the acoustical prospects.
Building Design for University Campus near Major Airport
Authors: Salter C. M. , Bruce R. D.
Published: October 2005

In this paper we discuss the acoustical problems associated with locating a university campus near a major airport. The site selected for the campus is located three miles from the airport and is directly beneath a flight path of the major runways. By 1975, it is anticipated that there will be about 200 jet operations per day over the campus at altitudes of 1000–3500 ft. The paper presents a description of the prediction scheme used to estimate the noise level out of doors due to the aircraft flyovers. The procedure used to develop the acoustical criteria is discussed. Methodology for determining the required construction for the various spaces is presented along with examples of actual constructions to be utilized.
A simple Method for Acoustically Designing a Dwelling against Aircraft Noise
Authors: Donato R. J.
Published: October 2005

A method is described whereby a dwelling unit may be designed to reduce the noise produced by aircraft to an acceptable level. The individual components contributing to the transmission of sound are chosen so that their effects on the total sound produced are equal. The total sound field may then be calculated by the application of simple weighting factors. The method, although somewhat restricting, has the great advantage that the choice of elements in the design may be made by unskilled personnel. Tables are given showing the insulation factors of various elements and the effect of their relative surface area on the total sound field.
Intrusive Automotive Noise in Buildings over Arterial Highways
Authors: Anderson Grant S. , Jensen Paul
Published: October 2005

A recent experiment indicates that the intrusive automotive noise levels in air-rights buildings can be predicted from the floor slab transmission loss and the 50-ft truck levels published in Report 78 of the National Cooperative Highway Research Program. Correlation between data and predictions was used to determine an average effective source height for truck noise. A design goal for this intrusive noise was determined from spectrum shape and the expected ambient air-handling noise within the building. The impact was evaluated in terms of A-level, preferred speech interference level, and NC rating. The prediction procedure was used to develop floor slab recommendations for a proposed future air-rights building over a section of planned urban interstate highway. Use of the STC rating to design against air-rights intrusive noise was evaluated.
Intensity Discrimination of Tactile Stimuli
Authors: Craig James C.
Published: October 2005

The difference threshold for intensity of tactile stimuli was measured using a 2IFC procedure. Two types of tactile stimuli were delivered to the right index fingers of Ss: (1) taps, approximately 10 msec in duration, and (2) 200-msec bursts of sinusoidal vibration, 160 Hz. Difference thresholds were measured at stimulus intensities of 14, 21, 28, and 35 dB SL. Difference thresholds for taps were higher at lower intensities than the difference thresholds measured at the same intensity for the bursts of vibration. Difference thresholds were also measured for taps and bursts in the presence of extraneous vibration. The difference thresholds were elevated when signal intensities were low and the extraneous vibration was strong. The extraneous vibration raised the difference threshold for bursts more than for taps. These results may be compared to results obtained by Raab and Taub [J. Acoust. Soc. Amer. 46, 965–968 (1970)] with auditory stimuli in which the presence of noise under some conditions caused a reduction in the difference threshold for clicks.
Short-Term Human Autocorrelation: Some Preliminary Experimental Evidence
Authors: Pastore Richard E.
Published: October 2005

The detectability of an interrupted bandlimited (150–2400 Hz) noise signal was studied as a function whether the interruption process was periodic or aperiodic. A standard two-alternative temporal forced choice detection procedure was employed. The low amplitude 250-msec signals were presented monaurally in a continuous uncorrelated masking noise with a slightly wider band width (100–300 Hz) than the signals. The noise signals were interrupted either periodically or aperiodically at an average rate of 200 times per second. The periodic and the aperiodic signals possessed identical power spectra, but differed with respect to the presence of a peak in the autocorrelation function of the periodically interrupted signal. The psychometric function for the periodic signal exhibits a more rapid growth than the aperiodic signal. The results are interpreted in terms of the ability of the auditory system to effectively perform a short-term autocorrelation on the input waveform.
Discrimination of Temporal Gaps
Authors: Abel Sharon M.
Published: October 2005

Ss were asked to discriminate between two time gaps, T and T+ΔT msec in duration. The gaps were silent intervals bounded by noise bursts. In the first of two experiments the duration of the noise bursts was 10 msec. The function relating the Weber fraction (ΔT/T for 75% discrimination) and the base gap T is nonmonotonic, showing a local minimum of 0.5 at approximately 4 msec and a local maximum of 0.6 at 10 msec. The function reaches a value of 0.2 after a slow decline from 10 to 640 msec. In the second experiment the noise bursts were 300 msec. The results are essentially similar to those of the first experiment, except that the local maximum at 10 msec is raised to 1.9. The data are compared with the results of Small and Campbell (1962), and with the predictions of Creelman's (1961) Poisson counter model. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare while the author was a National Research Council of Canada Postdoctorate Fellow.]
Perception of Phase Differences among Two-Component Auditory Stimuli
Authors: Hall J. L.
Published: October 2005

Subjects were required to distinguish among two-component auditory stimuli of the form cosω1t+cos(ω2t+φ) [cf., J. H. Craig and L. A. Jeffress, “Effect of Phase on the Quality of a Two-Component Tone,” J. Acoust. Soc. Amer. 34, 1752–1760 (1962)]. The frequency ratio ω1:ω2 was 2:3, and the only difference among stimuli presented in a given session was the phase φ. Stimuli were presented monaurally at low frequency (range 100 Hz–1 kHz) and high intensity (range 60–90 dB SPL). Stimuli were generated and the experiment was controlled by a Honeywell DDP-516 computer. Subjects made dissimilarity judgments using the method of triadic comparisons, and they also made paired-comparison judgments of subjective attributes, such as apparent pitch and timbre. The relationships between these subjective attributes and phase of the stimulus change systematically as stimulus frequency or intensity changes. Dissimilarity matrices obtained from the triadic comparisons can be related to pitch and timbre of the stimulus.
The Detection of Phase Changes between Dichotically Presented Signals
Authors: Christensen I. P.
Published: October 2005

Subjects listened to a 400-Hz signal and a 200-Hz signal presented simultaneously and dichotically. In the reference condition these signals were in phase; in the stimulus condition they were out of phase by an amount varying from 12° to 60°. The pattern of an experimental trial followed that used by Nixon et al. [J. Acoust. Soc. Amer. 48, 554–556 (1970)]: a presentation of the reference condition (600 msec) was followed, after a short break, by the observation interval (300 msec) containing either the reference condition or the stimulus condition. After another break the reference condition was presented again for 600 msec. Subjects reported whether the contents of the observation interval were the same as, or different from, the two reference presentations. As Nixon intimated, the first reference condition is essential in providing information for the comparison. This information clearly degrades rapidly over time; the results of this study showed that for a given phase angle, performance deteriorated as the interstimulus interval increased from 40 to 320 msec. With constant interstimulus interval, performance improves rapidly as the phase angle increases, being around chance at 12° and almost 100% at 60°. Two possible models for this process are discussed.
Detection, Lateralization, and the Phase Angle α: 250 Hz
Authors: McFadden Dennis , Jeffress Lloyd A.
Published: October 2005

At the 78th and the 80th Meetings of the Society, we reported two experiments in which we measured detection and lateralization performance for several values of the phase angle α, the angle at which the signal was added to the masker. In both of the experiments, the same narrow band of noise (50 Hz wide centered at 500 Hz) was used as both masker and signal. The present experiment is essentially a replication of the previous two using a 50-Hz noise band centered at 250 Hz. Detection data were taken for N0 S0, α=0° (increments) and α=180° (decrements), and both detection and lateralization data were taken for several values of α for N0-Sπ. A single-interval psychophysical method was used throughout. As in the previous experiments, detection performance for N0-Sπ was better for some subjects when there was only an interaural level difference (α=0°) and for other subjects when there was only an interaural time difference (α=90°). These differences in sensitivity to level and time were evident in the lateralization data as well, particularly at values of greater than 90°, where the time and intensive cues are in opposition. Masking-level differences were positive for all values of α, and they ranged, across subjects, from 12 to 25 dB. [This research was supported in part by a grant from the Public Health Service, National Institute of Neurological Diseases and Stroke.]
Interstimulus Interval in Monaural Detection with and without Contralateral Cue
Authors: Taylor M. M. , Smith S. M.
Published: October 2005

Performance in the monaural detection with contralateral cue (MDCC) task has been described as due to two separate detection mechanisms. One acts like an energy detector and operates also in simple monaural detection or amplitude discrimination; the other responds to phase differences between the signals to the two ears and acts rather like a correlator. These two mechanisms may oppose or may aid one another in the MDCC situation, resulting in performance, respectively, worse than or better than that obtained without the cue. When an amplitude discrimination task is performed monaurally, performance declines for interstimulus intervals (ISI) smaller than 150–300 msec (depending on the subject). Performance also declines with short ISI for cued detection at masker levels where the monaural detector cannot operate, but the break point is below 50 msec. If the decline in performance for short ISI is owing to the second stimulus cutting short the processing of the first, then lateralization must be processed appreciably faster than is intensity. Work is in progress to define how the two detection systems interact at various phases with short ISI.
Internal Delay Discrimination
Authors: Yost William A.
Published: October 2005

Listeners were asked to discriminate between two pulsed sinusoids, one presented with an interaural temporal delay T and the other presented with a longer delay T+ΔT. Frequency of the sinusoid ranged from 250 to 4000 Hz. The difference threshold for ΔT was defined as the dependent variable. This threshold increased as T increased from 0 μsec to half the period of the sinusoid, then decreased as T was further increased to a full period of the sinusoid. As T was increased to half the period of the sinusoid, the lateral image appeared to shift away from midline, but as T was increased beyond half a period of the sinusoid, the lateral image appeared to shift toward the midline. Similar results were obtained at all frequencies; they are compared to data obtained from localization studies. [This research was supported by the National Institutes of Health, Public Health Service, U. S. Department of Health, Education, and Welfare and by an NSF postdoctoral fellowship.]
Interaural Time-of-Arrival JND Threshold Functions for Periodicity-Perturbed Pulse Trains
Authors: Sullivan Roy F.
Published: October 2005

Psychometric functions for interaural Δt thresholds were obtained by Yes/No method of constant stimuli from three subjects at three representative sensation levels incorporating selected rms values of unilateral Gaussian stimulus periodicity perturbation or jitter. These functions, whose parameters are external jitter (Je) and SL(y), are characterized by slope in μsec/d′. Data were obtained in relative temporal quiet [d′(Jiy)] and with unilateral jitter [d′(Jty)]. The latter results are well predicted from a simple model rating subject's performance against an internal-noise-free ideal statistical observer attending multiple stimulus presentations. Parameters estimated from the data include: number of stimulus pulses effectively utilized by the subject (Ne, constant across SL, and effective internal noise level (Jiy), inversely related to SL: Ne = (Je)max2/[d′(Jty)2−[(d′(Jiy)]min2], Jiy = d′(Jiy) (Ne12. Considered as a signal-detection task in rms temporal masking, the obtained function slopes [d′(Jty)] may be predicted: d′(Jty) = [(Je2+Jiy2)/Ne]12.