bluuebunny/crossref_metadata_2025 huggingface dataset:
Cavitation in Liquid Helium
Authors: Finch R. D.
Published: September 2005

Ultrasonic cavitation has been induced in liquid helium over the temperature range 1.2°–4.2°K, using plane and cylindrical standing-wave systems at 90 and 46 kc/sec, respectively. The threshold for cavitation noise measured with the plane wave system is only of the order of millibars of root-mean-square pressure amplitude, rises sharply near the λ point, and is insensitive to variations of static pressure, addition of solid air or imposition of electric fields. Visible cavtation, obtained most readily with the cylindrical standing wave changes dramatically in nature in different temperature regimes. The results are compared with those obtained using “hyrodynamic” techniques, and the theoretical implications of the work are briefly discussed.
Research on Cavitation Nuclei
Authors: Sette D.
Published: September 2005

Two researches on cavitation nuclei are reported. The first (Sette-Wanderlingh) concerns a thermodynamic theory for the creation of nuclei by high-energy particles. Starting from the statistical existence of gas embryos in a liquid, the thermodynamic conditions are studied for their growth to larger sizes. In pure liquids in metastable conditions, as in bubble chambers, an embryo able to grow can be found in the hot regions produced by energetic particles. In the case of nuclei for cavitation, the particle should furnish the energy for both processes: (1) bringing a large region to high enough temperature, (2) to produce a hotter spot in which is formed an embryo able to grow in that region. The energy required is too high. If, however, instead of pure liquids one considers liquid containing dissolved gases, the difficulty is removed and values of energy deposit needed for the creation of 1-μ nuclei in water are calculated to be of the order of 4–5 MeV, in remarkable agreement with experiment. The second research (Messinò, Sette, Wanderlingh) intends to clarify the action of solid particles on cavitation nuclei. The study of distribution functions of nuclei has been carried out in water differently treated (normal, with lead screen, neutron irradiated, with uranyle salt addition) and to which calibrated solid particles were added. The results with unwettable impurities support Harvey's theory of stabilization of nuclei in cracks of these solid particles. The action of impurities is not, however, simply a stabilizing one, because it affects the size distribution of nuclei; the unwettable impurities increase the concentration of large nuclei, while the wettable ones shift the distribution towards the region of small-size nuclei. To explain the results, one has to assume a collision process between particles and nuclei created by radiation and the existence of an intrinsic stabilization mechanism that allows an independent existence of a microbubble at least for the time required to experience a collision with a solid particle.
Radiation-Induced Ultrasonic Cavitation
Authors: Greenspan Martin , Tschiegg Carl E.
Published: September 2005

Exposure of a liquid to high-energy neutrons yields a reproducible threshold if the liquid is clean enough. The cavitation rate rises sharply with stress, and at a fixed stress is proportional to neutron flux. The events are random. No appreciable induction or decay times are observed, even in water. For “Freon TF” (F2 Cl C C Cl2 F), the threshold is 2.7 bar from 12 to 45 kHz. Isopropanol at 40 kHz has a neutron threshold of 9.8 bar, a well-defined α-particle (thorium salt dissolved) threshold of 17.4 bar, and a poorly defined fast-fission threshold at <3.1 bar. Other neutron thresholds (Pu-Be source) are methanol, 6.1 bar; ethanol, 7.5 bar; water very high (to be supplied). All results are for about 30° C. The dissolved gas content had little effect. The test liquid was contained in a cylindrical resonator forming part of a self-sustained, programmable oscillator. [Work supported in part of U. S. Office of Naval Research.]
Threshold Adaptation following Brief Recovery and Békésy Audiometry in Impaired Ears
Authors: Lotterman Stephen H. , Kasten Roger N. , Revoile Sally G.
Published: September 2005

The study examined the relationship of Békésy audiometric tracings to threshold adaptation following brief recovery periods in sensorineural ears. Fixed-frequency interrupted and continuous self-recorded threshold tracings were obtained at 500, 2000, and 4000 Hz. Threshold adaptation was induced through the introduction of steady-state adapting tones 10 dB above the midpoint of the interrupted threshold tracing. Each decrease of the perceived signal to inaudibility resulted in the introduction of a 125-, 250-, 500-, 1000-, or 2000-msec interruption (25-msec rise/decay times) in the presentation. The subjects were exposed to five test runs of 2 min each at 500, 2000, and 4000 Hz. The influence of interruption duration upon subsequent tonal perception and its relationship to Békésy audiometric patterns is discussed.
Temporary Threshold Shifts under Two Interaural Phase Conditions of Binaural Exposure Signals
Authors: Melnick William
Published: September 2005

Binaural exposure to intense signals has been observed to produce less temporary threshold shift (TTS) than monaural exposure. The mechanism responsible for this decrease in TTS was been proposed to be more vigorous contraction of the middle-ear muscles during binaural exposure. If an interaural phase effect on TTS could be demonstrated, then the argument for middle-ear-muscle activity as the sole causative factor would be weakened. With 15 listeners, recovery from TTS was recorded monaurally for 4 min at 1000 Hz, following 2 min of exposure to 750 Hz at 110 dB SPL in three sessions under each of three exposure conditions-monaural, binaural 0° phase difference, and binaural 180° phase difference. Seven of these listeners then participated in similar sessions for one trial at the three exposure conditions using a 500-Hz exposure signal and a test signal of 750 Hz, while the other seven subjects traced thresholds for 6000 Hz following exposure to 4000 Hz. Results indicate a difference between TTS for monaural and binaural exposures but no systematic difference between the two binaural phase conditions.
Pitch of Bands of Noise
Authors: Small Arnold M. , Daniloff R. G.
Published: September 2005

The pitch of low-pass and high-pass noise bands was determined as a function of cutoff frequency at 40 dB SL (sensation level). Because of the difficulty of direct pitch-matching using a sinusoidal comparison stimulus, and on the assumption that a subjective octave relates exclusively to pitch sensation, 10 naive listeners made octave judgments with respect to noise bands differing only in cutoff frequency. For a particular standard, the listener adjusted the cutoff frequency of a second band of like configuration until its pitch was (a) an octave above and (b) an octave below that of the standard. As a control condition, the same procedure was used with sinusoidal stimuli. Pitch functions determined in this manner indicate that, over a large range (0.08–10 kHz for low-pass and 0.6–10 kHz for high-pass), the pitch of noise bands corresponds to cutoff frequency. These general results are in accord with von Békésy's [J. Acoust. Soc. Am. 35, 588–601 (1961)] observations and suggest the operation of a pitch mechanism using a place rather than frequency (volley) principle.
Busy or Ringing? Parameters Used in Tone Interpretation by Telephone Users
Authors: Schoeffler M. S. , Sheridan J. A.
Published: September 2005

Foreign telephone systems have somewhat different tone signals from those used in the USA to inform a caller as to whether the distant telephone is ringing or busy. In order to prepare for the eventual extension of American direct dialing to overseas points, we measured the effect on user interpretation of frequency, modulation rate, repetition period, and ON/OFF ratio of the telephone tones. Test subjects identified a large set of tones as being ringing, trunks busy, lines busy, or none of these. The set included most of those tones which are currently in use in various countries. The data were used to provide a 2-dimensional mapping of the signals. The results indicate that low repetition rates are interpreted to mean “ringing” and high repetition rates mean “busy,” regardless of any modulation of the fundamental frequency of the tone. However, for intermediate repetition rates, a modulation that makes the tone sound rough increases the tendency to interpret such signals as “ringing.” Fundamental frequency of the tones and ON/OFF ratio were found to be relatively less important variables.
Computer-Simulated Cepstrum Pitch Detection for Vocoder Excitation
Authors: Noll A. Michael
Published: September 2005

The basic concept of the cepstrum (the power spectrum of the logarithm of the power spectrum) for vocal-pitch detection was described previously [J. Acoust. Soc. Am. 36, 296–302 (1964)]. The present paper reviews the method and describes its application to deriving the excitation signal for a computer-simulated vocoder. The excitation signal is derived from successive cepstra by automatically picking those cepstral peaks that correspond to the pitch periods of the voiced speech intervals. The maximum cepstral peak is compared with a variable threshold, and suitable logic is used to eliminate such undesired pitch-period indications as isolated cepstral peaks and pitch-period doubling due to very small alternations in pitch period lengths. Examples of actual speech spectra and cepstra are used to illustrate the development of the algorithms for the cepstral pitch detector.
Evaluation of a Method for Measuring Conversational Speech-Activity Patterns
Authors: Pruzansky S.
Published: September 2005

A method of automatically measuring time patterns of two-way conversations is described. First, fast-acting detectors continuously indicate whether each party is speaking or silent. The output states of the two detectors are sampled simultaneously every 5 msec and the result is recorded on digital tape. This tape, which constitutes a description of a conversation in terms of four mutually exclusive states, is then processed by computer programs. The first stage of computer processing fills in stop-consonant gaps and other short interruptions related to the mechanics of speech production. The next stage defines and measures durations of various types of speech events and silences. Histograms and cumulative frequency distributions of durations of these events are plotted automatically. Corresponding sets of measurements were obtained by visual inspection of oscillograms of several conversations. The oscillographic measurements were used to help evaluate the effects of varying the detector sensitivity, fill-in time, and sampling rate.
Effects of Transmission Delay on the Fine Temporal Structure of Conversation
Authors: Bricker Peter D.
Published: September 2005

Subjects worked in pairs on a task that required them to communicate over a four-wire voice circuit, 14 pairs served under each of three conditions, which differed only in the amount of pure transmission delay inserted. The efficiency of verbal encoding was adversely affected by the extreme condition (1.8-sec roundtrip delay), but subjects in the 0.6-sec-delay condition did not differ from those in the zero-delay condition, either in efficiency or in their responses to a post-experimental questionnaire. However, several measures derived from an automated analysis of the speech-activity patterns reflected systematic differences among the three conditions. The finding that the temporal patterns of conversations were modified by an amount of delay insufficient to produce changes in the other variables is relevant to any attempt to characterize conversational behavior.
Speech Band Compression by Analytic-Signal Rooting
Authors: Schroeder M. R. , Flanagan J. L. , Lundry E. A.
Published: September 2005

Speech is filtered into contiguous passbands. The signal s(t) in each passband is represented as Re[σ(t)], where σ(t) is the analytic signal corresponding to s(t). By definition, σ(t)=(t)+jŝ(t), where ṡ(t) is the Hilbert transform of s(t). The nth root of the analytic signal is formed, and the real part of the rooted signal is confined to a fraction of its original frequency range. After transmission, the rooted signals are restored to their original frequency positions by raising to the nth power. The restored signals from each channel are then combined to synthesize an approximation to the original speech signal. A complete transmission system has been simulated on a digital computer, and the results of restricted bandwidth transmission are demonstrated.
Pulse Distortion in a Refracting Medium
Authors: Hirsch Peter
Published: September 2005

There has been continuing recent interest in the question of whether or not a totally internally reflected ray suffers an additional π/2 phase shift over that predicted by ray theory. It can be shown that the phase depends on whether the ray touches a caustic. If it does, the extra π/2 (with the attendant pulse distortion) will be found. If it does not, then ray theory predicts the exact phase (provided, of course, that the medium is “slowly varying”). The existence of a relevant caustic depends on the medium and, in some cases, on the initial angle of the ray. These effects are well illustrated in the family of media described by a sound speed c, which varies with depth z as c2=c02 [1−(αz)β]−1, where c0 is the speed at z=0, and α and β are parameters. [Work supported by the Office of Naval Research, U. S. Navy.]
Ray and Mode Dispersion for a Model of the SOFAR Channel
Authors: Bucker H. P.
Published: September 2005

A four-parameter velocity profile v−2(z)=A sech2 (z/H)+B tanh (Z/H)+D was fitted to a typical Atlantic deep-ocean profile. The normal-mode solution to this problem has been given by Gazarian [Soviet Phys.—Acoust. 3, 135–149 (1957)] and Deavenport [Radio Sci. 1, 709–724 (1966)]. Curves are presented showing the arrival time, at a given range, for the various modes as a function of frequency. The arrival of typical rays are plotted on the same graph for comparison. It is clear from the curves that the expected signal duration is about the same from either ray or mode theory and that the duration will be the same for narrow- or wide-band receiving equipment.
Ray Propagation in a Linearly Moving Inhomogeneous Layered Medium
Authors: Hayre H. S. , Tripathi I. D.
Published: September 2005

A sample model of the ocean is assumed to consist of three portions. The top portion is assumed to be moving with a linear velocity and to have no change in speed of sound with depth. In the next layer, the water is assumed to have a constant physical velocity, and the sound velocity decreases linearly with depth. The bottommost layer is assumed to have a constant velocity of mass motions and an unchanging speed of sound with depth. The vector eikonal equation has been used to find the ray path in this stratified inhomogeneous moving medium. The expression for ray path and its slope are derived and plotted. Previous work in this field is reviewed, and their scope of coverage is discussed. Furthermore, a more complex model of the ocean is offered for analysis and some current results of this work are also included. [Work sponsored by the U. S. Office of Naval Research.]
Sound-Transmission Paths to a Hydrophone in the Body of the Deep Sea
Authors: Urick R. J.
Published: September 2005

Two series of measurements of explosive sound transmission to a hydrophone in the body of the deep sea have been made. In one, a series of explosive charges detonating at 800 ft was dropped from an aircraft at 1-mile intervals out to 110 miles from a hydrophone at depths of 2350 and 5800 ft in water 15 600 ft deep. This series of shots shows the expected succession of double convergence half-zones, with a convergence gain of 5–10 dB over spherical spreading in the 800–1600 oct for the first pair of zones at 30 miles, and near 0 dB for the third pair at 100 miles. In the second series, the depth of detonation was varied at a few selected ranges. Seven detonation depths from 800 to 12 000 ft were employed, using charges dropped at 5, 20, 40, 60, 80, and 100 miles. Here, the pattern and energy density of the arrivals can be readily identified with the ray diagram at the shorter ranges, but become increasingly complex for easy identification at the longer ranges.
Horizontal Range Difference Method of Locating Hydrophones Forming a Near-Vertical Array
Authors: Ricard James H. , Rosenthal Felix
Published: September 2005

A method for determining the difference in horizontal position between two hydrophones, A and B, on a nominally vertical array, is discussed. The difference in horizontal range from a distant underwater sound source to A and to B, plotted in polar coordinates, as a function of bearing angle from the source to the array, describes two coincident circles, one diameter of which passes through the origin and the horizontal coordinates of B relative to A. Experimental results, using a surface ship and a taut-wire hydrophone array, were obtained. Successive runs using the same hydrophones, and an independent least-square determination of the coordinates, show consistent results. Results of an error analysis indicate that the method requires only approximate average speed of sound data, and approximate source and array depth information, although accurate values of the vertical separation of the hydrophones is required. The method is computationally suited to on-site determination of the relative horizontal location of hydrophones using a small low-speed computer.
View to the Future in Auditorium Design
Authors: Veneklasen Paul S.
Published: September 2005

The essential requirements for good acoustical performance for all uses of auditoriums are rather clearly emerging in terms of essential physical requirements and methods. Terminology still needs clarification for communication in design and clarification of musical objectives and results. We believe that clarity, envelopment, and reverberance are essential listening factors, which can be designed for. Optimal balance and mixture of these factors are not quantitatively formulated, and greatly affect public reaction. The greatest challenge is to assure accomplishment of objectives using modeling techniques and measurements in advance of construction. Optimizing sound projection, while retaining cohesion for the players on a stage, requires compromise. Apparent frequency balance must not be destroyed by inadvertent absorption or diffraction. The physical limitations resulting from large size need defining. Fixed reverberation time that is adequate for music will be too great for essential intelligibility of lyrics. Economical provision of adjustable reverberation is a challenge. Cooperative effort and research by acousticians with musicians and further research on instrument directivity are essential to improving orchestral balance and perspective. Adequate sound reinforcement for staged performances needs research and more effective application in order to win acceptance.
Transmission Loss of Plasterboard Walls
Authors: Northwood T. D.
Published: September 2005

Although test data are available for many variations of the typical plasterboard wall, there are enough minor variations in construction or test technique that it is difficult to deduce accurately the effects of the various parameters. Accordingly, a systematic study has been made of a number of experimental and practical walls. Tests were first made on single leaves (a leaf consisting of one layer of material or several layers laminated together). The next phase was a study of two such leaves separated by an air space. Finally. the modifications introduced by stud and connector systems and space fillers were investigated. Results from the first phase are found to correspond well with theoretical calculations.
Field Survey of Sound Transmission between Offices
Authors: Benasutti Roger , Sabine Hale J.
Published: September 2005

Sound-transmission measurements were made in 15 pairs of occupied offices with suspended acoustical ceilings and continuous plenum in high-rise buildings in several areas of the USA. The tests were made to determine typical noise-reduction (NR) values between offices as found in present-day construction. Measurements of NR and background noise were made in octave bands. The STC contour curve was used to determine one-number ratings of the measured NR curves. NR values ranging from 24 to 48 STC were observed, the latter value being obtained with a ceiling of acoustical tile adhered to gypsum board. NR's were strongly influenced by the type and location of return-air plenum openings and ducted connections between rooms. Background-noise levels from 34 to 46 dbA were measured, these being due almost entirely to air-conditioning noise. A simple but accurate speech-intelligibility test was conducted at each site to relate speech privacy to background levels and NR's. The measured intelligibility correlated quite well with a figure obtained by adding the value of background noise in decibels A-scale to the NR expressed as STC.
Noise in Apartments from Services and Utilities
Authors: McKay Ronald L.
Published: September 2005

A field survey has been made to ascertain typical noise levels in urban high-rise apartments due to certain services and utilities. Data are presented on the sound-pressure levels and vibration acceleration levels produced by kitchen and bathroom equipment, by elevator hoistway and lift equipment, by trash chute use, and by garage operations. Measurements were taken near the various sources and at remote positions horizontally and/or vertically. For several sources, an analysis is made of the relative importance of airborne versus structure-borne sound transmission. Data are presented on losses associated with the transmission of vibration along typical concrete constructions. A tentative system is suggested for estimating radiated airborne-noise levels in a space remote from a source, if source vibration levels and the details of interconnecting structure are known.
Measurements on the Effect of Transducer Size on the Resolution of Boundary-Layer Pressure Fluctuations
Authors: Geib F. Ellsworth
Published: September 2005

The measured values of the power spectral density are known to decrease with increasing transducer diameter. Measurements of this effect have been made on a wall adjacent to a turbulent boundary layer for a range of transducer diameters. Data were taken in a 3-Hz bandwidth for a Reynolds-number range, based on boundary-layer displacement thickness, from 2100 to 9300. The ratio of transducer radius to boundary-layer displacement thickness ranged from 0.09 to 4.3. Strouhal numbers based on angular frequency, displacement thickness, and wind-tunnel speed ranged from 0.07 to 12. The data are presented in dimensionless form and are compared with the theoretical correction curve of Corcos. General agreement is found.
Spatial Resolution Effected by a Recessed Microphone
Authors: Fitzpatrick Hugh M.
Published: September 2005

In spatially resolving the fluctuating pressure on a wall (e.g., a wall adjacent to an aerodynamic boundary layer), a small hole in the wall leading to a microphone recessed in a cavity is equivalent to a rigid microphone whose sensitivity varies over its face in the same way as the normal efflux velocity that would result (at the actual opening in the wall) if a source were placed at the location of the microphone in the cavity. The wall may be curved and compliant.
Scaled Spherical Transducer Array
Authors: Ehrlich Stanley L. , Heimann J. H.
Published: September 2005

A scale model of a large truncated spherical transducer array has been designed and fabricated to provide means for obtaining design data in a test tank. Scaled transducer elements are mounted on a scaled supporting structure with a removable dome. Modular amplifiers drive an array aperture in transmission or preamplify in reception. Delay lines used with aperture selection cable harnesses form beams directed along the acoustic axes of the apertures and steered slightly from these axes. Horizontal beam patterns at depression angles of 0°, 15°, and 45° and vertical beam patterns at azimuth angles of 0°, 60°, and 120° may be measured. Transmitting and receiving responses at scaled operating frequencies for all system modes can be determined. In transmitting, measurements of voltage, current, and phase to each transducer element can be used to determine element input power and impedance. Scaling parameters are outlined. Effects of aperture shape, the dome, element acoustic interaction, and manufacturing tolerances are reviewed. Available data are presented. [Work supported by U. S. Navy Underwater Sound Laboratory.]
Computed Diffraction Characteristics of a Sonar Baffle
Authors: Kreisle L. F. , Moyer W. C.
Published: September 2005

The diffraction characteristics of sonar baffles are investigated with a simple, two-dimensional model consisting of a single-frequency plane wave incident on an opaque baffle. The configuration of the baffle is taken to be an arc of a circle. The diffracted field of the baffle is computed on a cylindrical surface (transducer) located behind the baffle as with typical baffle-transducer installations. It is assumed that the surface on the forward side of the baffle is rigid and that the rear surface, or surface toward the transducer, is a pressure-release surface. Results for the diffracted field are obtained for varying baffle width, baffle-transducer separation, and radius of curvature of the baffle. The results indicate that for fixed baffle width and baffle-transducer separation, usually prescribed by the dimensions of the sonar dome, considerable reduction in the acoustic field incident on the transducer is obtained through the use of minimum radius of curvature for the baffle.
Quick Characterization of the Directional Response of Point Arrays
Authors: Lowenstein Carl D. , Anderson Victor C.
Published: September 2005

The directional response of a 2- or 3-dimensional point array is a function of two space variables and also a function of frequency. A suitable mapping of these three parameters into a pseudodirection and a pseudofrequency allows one to examine the major- and minor-lobe structure of the array response with only a two-parameter computation. This method has been applied during the design of a 32-element planar array, to permit adjustment of the element positions for a minimum and uniform minor-lobe structure.
Directional Microphones
Authors: Olson Harry F.
Published: September 2005

A comparison of gradient, and end-fired line, and crossfired surface-wave microphones has been carried out. These considerations include the following subjects: namely, the directivity as a function of the dimensions and frequency, the problem of obtaining a uniform directional pattern with respect to frequency, and the ambient-noise response and relative pickup distances of directional microphones.
Flush-Diaphragm Condenser Microphone for Aerospace Measurements
Authors: Ortega Jose C.
Published: September 2005

A special-purpose microphone has been developed for measurement of pressure fluctuations in the boundary layer of high-speed vehicles. The design permits flush-mounting of the diaphragm on the vehicle surface, very high values of recovery temperature over a wide region of Mach number and altitude, minimal and predictable change in calibration with operating conditions. Solutions of operational requirements and calibration methods are described.
Performance of a Head-Contact Microphone in Wind Noise
Authors: Sebesta G. J. , Mellen A. J. , Carlisle R. W. , Wadsworth William B.
Published: September 2005

A small variable-reluctance transducer, only 0.440×0.220×0.160 in., has been developed for use in military microphones under conditions where propeller downdraft and other wind noise make the use of boom microphones impossible. A unique mounting arrangement enables the transducer to be used on top of the head without appreciable loss over forehead positions. Field experience indicates acceptable performance for speech communication.
Reduction of Compressor-Noise Radiation
Authors: Lowson M. V.
Published: September 2005

The noise radiated by a compressor is the result of a complex acoustic source interacting with complex propagation characteristics. However, this very complexity of the noise gives rise to a large number of potential methods for its reduction. The mechanisms underlying the noise radiation by a compressor are reviewed, with particular emphasis on the potential noise-reduction methods. Many independent methods appear to be feasible, but only a few of these have received serious investigation. Use of all these possible methods could give reductions in compressor noise radiation of well over 20 dB.
Study of Acoustical Treatments for Jet-Engine Nacelles
Authors: Marsh Alan H.
Published: September 2005

Discrete-frequency compressor noise radiated from fan-discharge and inlet ducts is a major factor in the perceived noisiness of current, operational jet transports. A design of a nacelle treatment suitable for the P&WA JT3D turbofan engine has been studied with careful consideration given to aerodynamic as well as acoustical criteria. Inlets with lightbulb-shaped centerbodies, providing narrow duct dimensions and increased surface area for the addition of acoustical treatment, were evaluated by analytical aerodynamic studies and wind-tunnel model tests. Duct-wall sound-pressure levels were measured during a ground runup of a JT3D engine. Laboratory tests were run to determine the airflow resistance, acoustical impedance and absorption coefficient of various duct-lining treatment configurations. Transmission-loss tests were conducted to determine the attenuation achieved by several configurations of inlet and fan-discharge duct models; duct airflow velocities ranged from 75 to 465 ft/sec. Based on these test, a broad-band-resonator concept was developed, offering the potential for high absorptivity over a wide frequency range with minimal weight and drag penalties. [Work supported by NASA-Langley Research Center.]
Experimental Comparison between Several Threshold-Measuring Procedures
Authors: Levitt H.
Published: September 2005

Threshold and difference-limen measurements for a 250-cps tone in quiet and in broad-band noise were obtained using four different procedures: (i) the standard von Békésy method; (ii) a modified von Békésy procedure [L. R. Rabiner, S.M. thesis, Mass. Inst. Technol., pp. 22–24 (June 1964)]; (iii) the sequential Up-Down-Transformed-Response (UDTR) procedure [G. B. Wetherill and H. Levitt, Brit. J. Math. & Statist. Psychol. 18, 1–10 (1965)]; and (iv) modified UDTR procedure in which a refernce tone was switched on between presentations of the stimulus. Each method was found to have its own specific merits and disadvantages.
Factors Affecting the Slope of Empirical ROC Curves
Authors: Markowitz Joseph , Swets John A.
Published: September 2005

Receiver-operating characteristics (ROC) curves obtained at six different signal-to-noise ratios showed that the function relating the slope of the ROC curve (on normal-normal coordinates) to the signal strength differed, depending upon whether a confidence rating or a binary response was solicited from the observers. This difference appeared to be largely independent of the particular stimulus presentation procedure used—single interval, or two-interval with and without a pedestal. Because the binary curves were swept out with varying presentation probabilities, while the rating curves were all obtained with a fixed, symmetric presentation probability, a subsequent study was undertaken to observe the effects of varied presentation probabilities on rating ROC curves. The results indicate that the slope of these rating ROC curves is dependent upon the presentation probability. The use of a cueing procedure tended to mitigate this dependency. [Work supported by NASA-Ames Research Center, Human Performance Branch.]
Effect of Duration upon Detection with Gated and Continuous Noise and Signal
Authors: Tucker Ann , Evans Rand B. , Jeffress Lloyd A.
Published: September 2005

A 2AFC procedure was used to study the effect of duration on signal detectability under two conditions: gated noise and signal, and continuous noise and gated signal. The durations employed were 10, 20, 50, 100, 200, and 500 msec, with (2E/N0)12 held constant. Each observed performed under both conditions. In the gated noise-and-signal condition, the data show a higher d′ at short durations than they do for a continuous noise. At long durations, the d′s are about equal. [Work supported through a contract with the U. S. Navy Bureau of Ships and a grant from the National Aeronautics and Space Administration.]
Central Masking: On Time and Intensity Interaction
Authors: Zwislocki J. J. , Johnson E.
Published: September 2005

In previous papers, it was shown that the contralateral threshold shift produced by central masking rapidly decays as the time delay from the masker onset increases. In the present paper, we discuss the interaction between this decay and the masker sensation level. Our data indicate that both the threshold shift at the masker onset and the rapidity of its decay increase with the masker intensity. A critical band of random noise centered at 1000 Hz was used as the masker. The threshold shift was determined by means of 10-msec bursts of a 100-Hz tone with the help of a method of forced-choice tracking.
Detection of a Narrow-Band Noise as a Function of the Interaural Correlation of Both Signal and Masker
Authors: Wilbanks W. A.
Published: September 2005

This study is an extension of some work that we reported at the St. Louis Meeting of the Society [J. Acoust. Soc. Am. 38, 929(A) (1965)]. The signal, a 135-Hz noise centered at 250 Hz, was partially masked by continuous wide-band noise. The correlation of both signal and masker were varied between +1.00 and zero. With a correlated masker (N0), detection is about 14 dB better with an uncorrelated signal (SU) than with a correlated signal (S0), and about 16 dB better than with both signal and masker presented monaurally (NmSm). These masking-level-differences (MLD's) diminish as the correlation of the signal is increased to unity, and as the correlation of the masker is decreased to zero. The results suggest that sizeable MLD's are obtained under those conditions where the addition of the signal results in a decrease in the correlation between the stimulus events at the two ears and, presumably, decreased synchrony between the neural inputs to the binaural detection mechanism.
Effect of Warping of the Reed Tip on Clarinet Tone
Authors: Backus John
Published: September 2005

In a previous paper [J. Acoust. Soc. Am. 39, 1220 (A) (1966)], there were described several parameters associated with the clarinet reed that influence the harmonic structure of the tone produced. In addition to these, another important effect has been found. The aperture between reed and mouthpiece does not actually close completely during this part of the cycle that the reed is in contact with the mouthpiece, due to a certain amount of warping usually present. That part of the reed not in contact with the mouthpiece can then still oscillate with a small amplitude at a high frequency. A harmonic of the internal standing wave near this frequency can then be produced at a relatively high amplitude by the same regenerative mechanism that produces the fundamental frequency with the entire reed. The magnitude of this effect will be unpredictable for cane reeds.
Open Tones of Musical Horns
Authors: Young Frederick J.
Published: September 2005

A computer program is presented that calculates the frequencies of the open tones of musical horns from the dimensions of the horns. The program also allows for the consideration of the additional tubing added by the valve slides. The calculations are executed for several different horns. For a given bell and untapered portion of the horn diameters, the ratio of the length of the untapered portion to the total length of the horn is varied and the resonant frequency is calculated. In these calculations, the tapered portion of the horn varies as r(x)/r(o) = (1+x)−α, where r is the radius, x the distance from the mouth of the bell, and α the taper constant. The effect of varying the taper is investigated by letting r(x)/r(o) = (1+xp)−α, where p is varied but the bell diameter and the length of the cylindrical tubing is held constant. The effect of temperature upon intonation is evaluated in several cases.
Spatial Chords
Authors: Julesz B. , Levitt H.
Published: September 2005

A spatial chord is similar to a conventional musical chord, except that the component tones differ in spatial position as well as in pitch. Spatial chords of this type were simulated using binaural techniques. Five simultaneous tones at frequencies of 250, 297, 354, 421, and 500 cps were presented dichotically, each tone having an associated interaural delay of either −1.0, −0.5, 0, 0.5, or 1.0 msec; negative values indicate delay to the left ear. This stimulus corresponds to a chord of tones spaced at minor-third intervals where the spatial positions of the tones are distributed between the two ears. Different spatial chords were obtained by keeping the tonal frequencies fixed but interchanging the associated interaural delays. Each of the spatial chords was heard as a fused sound of a gestaltlike character. An AB test between various pairs of chords of 500 msec duration was performed. Differences in the spatial arrangement of the component tones were perceived as changes in the quality of the resulting chord. Ease of discrimination depended on the total sum of changes in interaural time delay.
Influence of Blade Shape on Compressor Noise
Authors: Hulse Bruce T.
Published: September 2005

Sound-level and air-flow measurements were made for flat, cambered, and twisted blades. For the types of blades tested, the change of sound level with relative tip speed appears to be independent of blade shape. The inlet guide-vane wake strength did not affect this result. In the régime studied, under 0.5 Mach number, blade thickness did not appear to contribute significantly to noise. By suitable IGV design or by changing the IGV-rotor spacing, it is possible to diffuse the wake-velocity profile. The consequent reduction of the rotor-blade/wake interaction results in lower sound level.
Fans and Pure Tones
Authors: Nordby Knut S. , Woehrle K. K.
Published: September 2005

The pure-tone power levels for several types of axial flow fans of less than 12-in. diameter have been determined under different loads and mounting conditions. The method described by Maling and Nordby [Paper J65 in Proceedings of the Fifth International Congress on Acoustics, 1965, Liège, D. E. Commins, Ed. (Imprimerie Georges Thone, Liège, 1965), Vol. 1b; J. Acoust. Soc. Am. 38, 921(A) (1965)] for measuring pure-tone power level (PWL) in a reverberation chamber was modified. A source-substitution procedure was employed that permits a faster determination of the PWL than with the original method. The effect of different radiation impedance of fans and the “substitution source” is considered. From the data obtained, a set of preferred design trends and mounting recommendations for reducing the generation of pure tones in fans was developed. A reduction in pure-tone power by more than 10 times has been achieved in some applications. Empirical data for scaling from the PWL to sound-pressure levels at 1 m distance from a machine are discussed.
Sound Duration and Its Affect on Judged Annoyance
Authors: Little J. W. , Mabry J.
Published: September 2005

Results are presented from two experimental studies in which a total of 120 subjects judged the annoyance of sounds. The experiments were based on a factorial design and a nested factor, mixed model. The factors studied were (1) sound-pressure level (SPL), (2) sound spectrum, (3) duration within 10 dB of peak OA-SPL, (4) rise time, (5) test technique, and (6) subject instructions. The results have been analyzed by analysis of variance and other appropriate statistical techniques. The most significant results are that interactions exist between most of the factors studied; i.e., no factor acts independently of others in its affect on judged annoyance. For example, the affect of duration on judged annoyance can vary from 0.25 dB per duration doubling to 4.5 dB per duration doubling, depending on the level of other factors. The results of this work are compared with other studies of sound-duration effects.
Correlation of Objective Measures with Subjective Ranking of Motor-Vehicle Noise
Authors: Hillquist Ralph K.
Published: September 2005

A subjective ranking experiment in which 20 observers judged 100 truck passby noises using paired-comparison techniques was conducted to determine the correlation between various objective measures of noise and subjective response. Sound levels having the weightings A, B, C, DIN 3, and N, and octave-band levels for the 1-kHz and combined 0.5/1/2-kHz bands, were measured; in addition, loudness levels by the ARF and Stevens Mark II and Mark VI methods and perceived-noise level (PNL) were determined. Correlation coefficients and variances relating these objective measures and the subjective ranking-scale values were computed. Best correlation is obtained with loudness and PNL's and A-weighted sound level, with lesser correlation for the other direct measures. Of interest is the ordered decrease in correlation coefficients for the various sound levels with both increasing and decreasing passband width referenced to A-weighting. Variances of individual observers are greater than those of the various objective measures. In conclusion, A-weighted sound level represents both the optimum of direct measures and adequate approximation of subjective rating for truck passby noise.
Noise Environments Encountered within Two- and Four-Engine-Powered Fixed-Wing Aircraft: Influence of Power Plant and Power Plant-to-Vehicle Matings on the Character of Internal Noise
Authors: Gasaway Donald C.
Published: September 2005

The noise levels encountered at different stations within various fixed-wing aircraft are varied. This paper demonstrates characteristic differences found in noise levels measured at comparable internal locations within 10 categorical types of two- and four-engine-powered aircraft. A total of 45 different aircraft were classified into 10 groups from which noise envelopes were derived. The aircraft types studied include those used for cargo-passenger, search-rescue, training, utility, and weather-reconnaissance rôles. Depending upon aircraft-to-engine profile and where feasible, the noise envelopes represent noise levels measured: (1) in the cockpit; (2) forward of the propeller plane; (3) within the propeller plane (or forward of the wing); (4) in the midwing areas; and (5) aft of the wing area. The measurements that compose the envelopes represent noise levels encountered during conditions of normal cruise. This information and data provide knowledge concerning differences in noise exposures associated with the airborne operation of various types of two- and four-engine-powered military aircraft.
Use of Acoustical Modeling in Airport-Noise Studies
Authors: Simmons Duane R.
Published: September 2005

The determination of the exterior noise exposure around a complex building form is accomplished by acoustical modeling, simulating aircraft in taxiing, docking, and takoff, and helicopters in approach, landing, and takeoff. The deviations from free-field inverse-square pressure spectra are essential to proper design for interior residual-noise criteria.
Measurements of Pressure Fluctuations in a Turbulent Shear Flow
Authors: Potter R. C.
Published: September 2005

A technique of using two opposing airflows, to produce a turbulent mixing region where the highest shear occurs at a point with zero mean velocity, has been utilized to allow probe-microphone measurements of the shear-flow fluctuating pressure field with zero convection velocity. The method also removes the problem of the microphones disturbing the mean flow of the turbulent mixing region. The program has included a study of various microphone configurations to investigate the effect of the microphone disturbance of the turbulent velocity fluctuations on the pressure signals measured. The results indicated a normalized pressure-fluctuation spectrum, which has more power at high frequencies as compared to the corresponding longitudinal turbulent-velocity spectrum. This is in agreement with the earlier results reported for the weaker shear flow of turbulent wakes, and contrary to theoretical predictions based on studying isotropic turbulence and applying a velocity gradient to the results to represent a turbulent shear flow. [Work supported by National Aeronautics and Space Administration, George C. Marshall Space Flight Center, Huntsville, Alabama.]
Implementation of a Self-Adapting Echo Canceler
Authors: Presti A. J.
Published: September 2005

An echo canceler was designed at Bell Telephone Laboratories for use in long-line telephone systems. Echoes are generated in a telephone connection owing to impedance mismatching at various points in the network. The instrumentation of this echo canceler is described, which will cancel the echoes with a minimum of transmission interference.
Speech-Loudness Judgments: A Multidimensional Analysis
Authors: McDermott B. J.
Published: September 2005

Listeners judged the loudness of speech processed by 22 different circuits, including both linear and nonlinear distortions. Listeners heard pairs of sentences, each processed by a different circuit, and indicated which of the pair sounded louder. The analysis produced solutions in one through eight dimensions. A χ2 test for goodness of fit showed that the data were not satisfied by a unidimensional solution. The analysis showed that the loudness of circuits with added noise is ambiguous and that listeners differed in their interpretation. Listeners also differed in their judgments about some of the nonlinear distortions. Additional dimensions representing the attributes of these two types of circuits accounted for most of the residual variability. The results of this analysis are compared to those of a previous experiment, which indicated that loudness is a major factor influencing preference judgments of the same circuits.
Relation between Intelligibility Scores for Various Test Methods and Different Types of Speech Distortion
Authors: Williams Carl E. , Hecker Michael H. L.
Published: September 2005

Several intelligibility tests are currently being used to evaluate speech-communication systems. Individuals engaged in the development of such systems would often like to compare the performance of a system evaluated with one test with the performance of another system that has been evaluated with a different test. A study has been conducted to examine and quantify the relation between scores obtained with four intelligibility tests (the Harvard PB-Word Test, the Fairbanks Rhyme Test, the Modified Rhyme Test, and the Harvard Test Sentences) for various levels of three types of speech distortion (additive speech-shaped noise, peak clipping, and vocoderization). Recordings by two adult male speakers of the different test materials were processed by the three distortion systems, and output recordings were administered to a group of listeners. The results of the study demonstrate that the relation between the various test scores is not unique but depends considerably on the type of speech distortion employed. [Work supported by Decision Sciences Laboratory, Electronic Systems Division, Air Force Systems Command, Bedford, Massachusetts.]