bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of the Source of a Monophonic Signal Presented on a Four-Channel System
Authors: Gunn Walter J. , Schnapf Nathan
Published: October 2005

In the course of attempting to recreate realistically the sounds of jet aircraft overflights, it was discovered that a monophonic recording of a jet takeoff or landing, when presented through a four-channel system (one speaker in each corner of the room), gave the sensation that the sound was coming from a single source directly overhead. This seemed a rather interesting phenomenon, since the four speakers were below the level of the listener's head. A study was then conducted, using several 1-oct wide bands of noise as well as some meaningful sounds, to determine more definitive aspects of this phenomenon. The results of these studies will be reported.
Loudspeaker Bass Response in Small Cabinets
Authors: Brociner Victor
Published: October 2005

Small loudspeaker systems are capable of good performance at low frequencies if loudspeaker and cabinet size are properly related. Both calculation and experiment indicate that bass response is not proportional to the size of the loudspeaker, contrary to intuitive expectations.
Playback Losses and the Design of Wide-Band Phonograph Pickups
Authors: White James V.
Published: October 2005

Mechanical playback losses in phonographs fall into two categories, termed pickup loss and scanning loss. Pickup loss is due to resonances in the mechanical system formed by the tone arm, pickup, and compliant groove walls. Scanning loss, on the other hand, arises because of the finite areas of contact between the stylus and each of the groove walls. Pickup loss can be reduced to arbitrarily low levels by making the driving-point impedance of the stylus much smaller than the groove impedance. Scanning loss, however, can be reduced only by reducing the effective interaction, or scanning, area between the stylus and the groove wall. The rational design of wideband phonograph pickups will be discussed in light of our present understanding of these losses.
Review of the High-Frequency Playback Limits of Mechanically Recorded Disks
Authors: Bubbers John J.
Published: October 2005

The extension of the upper frequency limit of the playback stylus is reviewed from a theoretical and measured review of the published work of C. R. Bastaians and subsequent additional data presented by J. White. From these apparent limits the discussion of the newly introduced high-frequency playback techniques developed at Teldec are reviewed. [C. R. Bastiaans, “Factors Affecting the Stylus/Groove Relationship in Phonograph Playback Systems,” J. Audio Eng. Soc. 15, 389–399 (October 1967); Offenlegungsschrift 1 574 489, German Patent Office, 10 September 1970).]
Discrimination of Aviation Headsets
Authors: Joscelyn Edwin R.
Published: October 2005

The often quoted phrase “good books stand the test of time” is equally applicable to headsets. Daily contact with headsets by the author has resulted in a study of the reasons for the popularity of certain types of airborne headsets. Under discussion are five specific headsets which are judged by their individual merits. Topics include price, comfort, performance of earphones (response curve and sensitivity), and available options. Detailed discussion of transducers showing exploded view illustrations of each headset are presented showing equivalent circuitry as well as respective responses and parameters. The specific headsets described are those used in general aviation, commercial aviation, and military aviation. They are generally categorized as ear insert, supra-aural, and circumaural types using magnetic, balanced armature, or dynamic elements. Each headset type will be available for demonstration following the meeting.
Ultrasonic Degradation of Biopolymers in Solution
Authors: Coakley W. T.
Published: October 2005

The degradation of synthetic polymers and biopolymers in the presence of the detectable effects of ultrasonic cavitation may be explained in terms of the mechanical forces, with perhaps some contribution from free radicals, resulting from cavitation. Therefore, the threshold sound intensity for degradation, in these cases, depends upon the cavitation threshold. Persisting degradation of polymers, when precautions have been taken to suppress cavitation, has been offered as evidence for a noncavitational mechanical interaction between ultrasound and the polymers. These experiments are reviewed in the light of the care taken to suppress cavitation and the sensitivity of the methods used to monitor its disappearance. Several proposed mechanisms for a noncavitational effect are discussed briefly. Experimental evidence is presented associating DNA degradation quantitatively with cavitation activity at intensities greater than 500 W/cm2 at 1 MHz.
Thresholds for Biological Effects Resulting from Sonically Induced Shearing
Authors: Rooney James A.
Published: October 2005

The treament of biological cells in suspensions has recently been investigated under conditions where sonically produced viscous shear stresses are important mechanisms. In experiments using a stable oscillating bubble with its associated acoustic streaming a threshold displacement amplitude was found for hemoglobin (Hb) release from erythrocytes in suspension. Corresponding to this amplitude for room-temperature conditions a velocity gradient of 104 sec−1 and a shear stress of about 3500 dyn/cm2 were calculated using acoustic streaming theory. These values decrease with increasing temperature. Williams et al. (1970) treated cell suspensions using a transversely oscillating wire driven at ultrasonic frequencies and found similar results at room temperature. Values from these experiments may be compared with those obtained with purely hydrodynamical shearing. Nevaril et al. (1968), using Couette flow found a critical stress of 3000 dyn/cm2 for Hb release and P. L. Blackshear (1965) using jets, found a critical velocity gradient of the order of 105 sec−1. Morphological changes occurring during shearing of erythrocytes in hydrodynamical fields compare well with experiments on shearing of oil droplets by F. D. Rumscheidt and S. G. Mason (1961).
Ultrasonic Exposure Thresholds for Changes in Cells and Tissues
Authors: Hill C. R.
Published: October 2005

Biological change consequent on ultrasonic exposure may arise through three distinct modes: thermal, cavitational (including stable bubble), and “other.” The thermal mechanism is quite well defined and predictable. Wide divergencies occur between different authors on values of cavitation thresholds, but these may be due, in part, to differences in criteria used. Our results are reported for dependence of “stable cavitation” on intensity, frequency, pulsing parameters, ambient pressure, and nature of the medium (liquid, gel, or organized tissue). Evidence is reviewed for the existence of, and relevant thresholds for, other mechanisms that are effective in living cells and tissues irradiated by ultrasonic beams.
Mechanisms of “Surgical” Lesion Production by Focused Ultrasound
Authors: Lele P. P.
Published: October 2005

Reproducible and consistent structural and functional alterations can be produced in different biological tissues by irradiation with a single beam of focused ultrasound of 1- to 5-MHz frequency and 200- to 1000-W/cm2 average focal intensity. Mysterious mechanical mechanisms have recently been invoked to explain the formation of these lesions. However, experimental studies show that the lesions are, in fact, thermal in origin. Furthermore, the development of the lesions and their size and shape for varying values of ultrasonic constants and controllable variables can be predicted analytically, assuming a purely thermal model. The dimensions of the lesions in the brain, as in other tissues with different acoustical and thermal properties, resulting from ultrasonic irradiation at different freqencies, intensities, and dosage regimens are directly related to the resultant temperature rise and its duration. Histological and ultrastructural studies indicate that, contrary to the general belief, the lesions are instantaneous in development, show no evidence of mechanical cellular disruption, and can be duplicated by a purely thermal radiation. [Supported by a USPHS grant.]
Studies on Structural and Functional Alteration of Biological Materials by Ultrasonic Irradiation
Authors: Taylor K. J. W. , Pond J. B. , Newman D.
Published: October 2005

Investigations have been performed on the effects of ultrasound on biological structures including lever, peripheral nerve, spinal cord, and Ehrlich cell suspensions. These studies have shown the existence of two mechanical noncavitational ways by which ultrasound can cause both functional and structural changes in biological materials. Three forms of dosage are employed in diagnostic ultrasonography: the sonar dose form, the Doppler, and the sonar-Doppler modes. In the authors' experiments, the range of frequencies used (12–6 MHz) includes the range predominantly used in all three diagnostic dose forms. The range of peak intensities (10–50 W⋅cm−2) is similar to those used in the sonar and sonar-Doppler modes, while the pulsing regime used lies somewhat between the sonar and the Doppler forms. The results of these investigations indicate short-term accumulation of mechanical strains even when two subliminal doses are separated in time. By extrapolation, an approximate estimate may be given of total safe exposure time for diagnostic usage. It was also shown that the presence of hypoxia renders tissue more susceptible to damage by ultrasound. Absolute threshold intensities for functional and structural changes are being determined. Further experiments on Ehrlich cells show that ultrasonic irradiation can modify the net surface charge of the cell coats external to the plasma membrane.
The Importance of the Pinna to Auditory Localization
Authors: Markey P. R. , Moshier S. L.
Published: October 2005

Measurement of the impulse response of live pinnae were made in an anechoic space. The responses of the near-side and far-side ears were recorded on paper punch tape for about 390 locations in the right hemisphere. Live and remote listening tests with single clicks and with noise bursts as stimuli were conducted. Interaural time differences were measured in 10° increments at 0° azimuth and at 0° elevation. Pinna impulse responses show a systematic change of structures as a function of azimuth and elevation. The localization data indicate that errors in elevation judgments and azimuth judgments are not correlated. These data suggest that separate mechanisms may be used to estimate azimuth and elevation. The importance to localization of the pinna transfer function, head motions, and interaural time differences are discussed.
The Role of the External Ear in the Hearing of the Guinea Pig
Authors: Sinyor Albert , Laszlo Charles A.
Published: October 2005

The acoustic transmission characteristics of the outer rim of the pinna (flap), the concha, and the external auditory meatus of the guinea pig were measured in the frequency range 100 Hz–15 kHz using a PDP-12 computer. The experiments were performed on anesthetized guinea pigs suspended in a sound field. The orientation of the field relative to the experimental animal was varied and the localization properties of the pinna recorded. To measure the amplitude and phase of the input and transmitted sound, two identical acoustic probes were used. One probe was placed at the entrance to the ear canal, and the other probe was surgically implanted in front of the tympanic membrane. The results of ten experiments indicate: (1) that the flap does not provide any significant amplification in the frequency range of measurement, (2) that the concha provides a significant amount of boost (10 dB) in the 5–9 kHz region, (3) that the ear canal itself can be represented by an open-ended tube of appropriate dimensions, and (4) that in the guinea pig, two pressure maxima are observable at the tympanic membrane owing to the loading effect of the middle ear. These maxima occur at approximately 2.4 and 5.0 kHz. In similar measurements on humans, no corresponding peaks have been observed. This difference can be explained by anatomical dissimilarities between the human and guinea pig middle ears.
Morphological Relationship between the Tectorial Membrane and the Organ of Corti—Scanning and Transmission Electron Microscopy
Authors: Lim David J.
Published: October 2005

The exact mechanism involved in initiating action potential in the cochlea is not yet clearly understood. It is generally believed that the wave motion of the basilar membrane causes displacement of the organ of Corti which shears against the tectorial membrane. Since the tectorial membrane and the organ of Corti should share the same shearing motion, their fixed relationship to each other becomes increasingly important. This report shows that: (1) The tectorial membrane is attached to the organ of Corti at the level of the Hensen-Deiter junction and inner phalangeal-inner border cell junction areas. The attachments are not continuous but interrupted as the trabeculae. (2) Only the tallest rows of the sensory hairs of the outer hair cells are solidly attached to the tectorial membrane, whereas the sensory hairs of the inner hair cells did not show any evidence of strong attachment as did the outer hair cells. Physiological implications of this finding will be discussed. [Supported in part by an Air Force contract from WPAB and by the Deafness Research Foundation.]
Summating Potentials in the Three Cochclear Scalae
Authors: Dallos Peter , Cheatham M. A. , Schoeny Z. G.
Published: October 2005

Summating potentials (SP) in response to tone bursts were measured from all three scalae of the first, second, and third turns of guinea pig cochleae. Both the intensity and frequency of the stimulus were varied over a wide range of values, and averaging techniques were used to obtain the summating potential. The scala media response (SM) was compared to the scala tympani (ST) and vestibuli (SV) responses, as well as to the potential gradient across the cochlear partition and the common potential of the two perilymphatic scalae. The former of these quantities is defined as DIF = (SV−ST)/2, while the latter as AVE = (SV+ST)/2 [Dallos et el., Science 170, 641–644 (1970)]. It was demonstrated that at any cochlear location the potential gradient across the cochlear partition (DIF) and the scala media response are best correlated in the dependence of response magnitude and polarity upon stimulus parameters. Aside from the similarities in the response patterns, some significant differences were also noted. Probably the most important of these is that the width of the characteristic negative summating potential bands in the vicinity of the best frequency for a given electrode location is greater in SM than when recorded from the perilymph with the differential electrodes. [Supported by grants from the National Institute of Neurological Diseases and Stroke.]
The Origin of Fractional Distortion Components in the Cochlea
Authors: Boston J. R. , Dallos Peter
Published: October 2005

This paper describes the properties of pairs of fractional distortion components that are generated in chinchilla and guinea pig cochleas and suggests a possible source of these pairs. The pairs consist of two components with frequencies that are equally spaced around one-half the excitation frequency and that sum to the excitation frequency. The pairs exhibit a threshold of appearance, their frequencies can drift with time, and at excitation intensities well above threshold the pairs develop into noisy bands instead of remaining as discrete frequency components. An analysis of the stability of an acoustic flow over a flexible boundary suggests a possible source of these pairs. The analysis shows: (1) for a sufficiently large acoustic excitation, the flow is unstable owing to an exponentially growing one-half subharmonic wave, and (2) pairs of fractional components may appear in the flow just before the flow becomes unstable. On the basis of this analysis, it is suggested that the fractional distortion pairs observed in the cochlea are related to a developing flow instability. [This work was performed at the Biomedical Engineering Center and supported by the NIH.]
A Comparison of Cochlea Anatomy and Electrophysiology in Agoutis and Guinea Pigs
Authors: Peterson E. A. , Feng A.
Published: October 2005

Certain differences in cochlear anatomy between the agouti Dasyprocta puctata and guinea pig Cavia porcellus provide an empirical test of models dealing with inner-ear mechanics. The basilar membrane of agouti, for example, is about 60% longer and somewhat narrower than that of the guinea pig. Based on the work of von Békésy and others, velocity of the traveling wave should be greater in the agouti than it is in the guinea pig. In addition, a greater proportion of the basilar membrane of the agouti should be devoted to reception of higher-frequency stimuli. The cochlea microphonic (CM) was used as the index of basilar membrane response in 18 agoutis and 12 guinea pigs. Scala media recordings were made from each turn, and differential recordings were made from each turn but the apex in both species. CM latencies to tone pips and clicks were measured. Sensitivity functions were also taken. As predicted by several models, latency per unit length of basilar membrane was shorter for agoutis than for guinea pigs. For each turn agouti sensitivity to low-frequency tones was less and to high-frequency tones greater than was that of the guinea pig.
Comparison between Measured and Calculated Cochlear Microphonics
Authors: Strelioff D. , Honrubia V. , Ward P. H.
Published: October 2005

A computer model of the generation of cochlear microphonics in the guinea pig cochlea, with the mechanical response based upon von Békésy's measurements and with electrical properties simulated by a three-dimensional network incorporating the variable hair cell impedance concept, was used to simulate electrical responses of the cochlea to pure tone stimuli. Whereas the amplitude and phase of the calculated current flow through the organ of Corti at any position along the length of the model accurately reflected the amplitude and phase of the cochlear partition displacement at that position, the calculated potentials were found to be poor indicators of partition displacement. Thus, since potentials, but not currents, can be measured experimentally in the guinea pig cochlea, the study of the generation and spatial distribution of cochlear microphonics requires an appropriate cochlear model. Comparison will be made between potential variations calculated with the cochlear model and cochlear microphonics measured in the four turns of the guinea pig scala media.
Dynamics of the Peripheral Vestibular Apparatus in the Squirrel Monkey
Authors: Goldberg Jay M. , Fernández César
Published: October 2005

It is usually assumed that the dynamics of the semicircular canals are described by a heavily damped torsion pendulum. A torsion-pendulum model, while it may describe the mechanics of the cupula-endolymph system, does not provide an adequate depiction of the response dynamics of peripheral vestibular neurons. Two additional factors must be considered. First, the neurons, in responding to prolonged angular accelerations, exhibit sensory adaptation. Adaptation is reflection by preacceleratory response declines and by postacceleratory secondary responses. Second, in their response to high-frequency sinusoids (1.0–8.0 Hz), the neurons show a gain enhancement and a progressive phase lead. The high-frequency deviation suggests that the afferents are sensitive to both the amplitude and velocity of cupular displacement. The peripheral adaptation is similar to that seen in human psychophysical experiments. The velocity sensitivity may permit the peripheral system to compensate for the dynamic loads represented by the various vestibular reflex pathways. [Supported by NIH grants.]
Recovery of Single Auditory-Nerve Fibers from Sound Exposure
Authors: Young E. D. , Sachs M. B.
Published: October 2005

The rate of response of single fibers in the cat auditory nerve to tone bursts was measured prior to and following 1-min exposure to a tone at the fiber's characteristic frequency. Measurements were made for several levels of the exposure tone. Ten test bursts, at near threshold levels, preceded exposure and 90 followed it. In some runs the test bursts were omitted so that the recovery of spontaneous activity could be studied. The last postexposure burst was followed by a silent period of at least 80 sec before the next test. Following exposure, response rate to the test bursts was less than the pre-exposure value. Response rate recovered to at least 80% of the pre-exposure level within 2–15 sec after exposure. Complete recovery of the rate to the pre-exposure level occurred within 2 min. Both the amount of rate reduction and the time course of recovery could depend on exposure level. [Supported by the National Institute of Neurological Diseases and Stroke and the U. S. Air Force Office of Scientific Research.]
Endolymphatic Changes Associated with the Inception of Hearing
Authors: Bosher S. K. , Warren R. L.
Published: October 2005

Cochlear microphonics, nervous activity, and behavioral responses to sound stimulation are known not to be present in laboratory mammals until the end of the second week after birth. The electrochemical changes in the cochlear endolymph were therefore investigated in rats aged 8–18 days. The ionic concentrations were already fully mature at the beginning of this period, but the endocochlear potential was insignificant before the 12th day, when a 50-mV increase occurred in 48 h. The processes underlying this rapid change remain obscure, but a sudden increase in the cochlear duct electrical resistance seems the most likely possibility. Osmotically induced water movements revealed no evidence of major intercellular shunt pathways, but demonstrated free water permeability. Existing evidence suggests this early attainment of the adult chemical composition may be concerned with hair cell integrity. The separate development of the endocochlear potential, which coincides with the inception of hearing, confirms it is an essential feature of cochlear mechanoelectric transduction.
Measurement of the Rate of Perilymph Replacement by CSF in the Guinea Pig Cochlea
Authors: Moscovitch David H. , Gannon R. P.
Published: October 2005

The large open lumen of the cochlear aqueduct in the guinea pig establishes communication between the subarachnoid space of the brain and the perilymphatic system of the inner ear. The rate of perilymph displacement in scala tympani by cerebrospinal fluid was measured by recording the advance of the meniscus in calibrated silicone-treated glass micropipets sealed into the cochlea. Measured flow rates were typically 0.8–1.00 mm3/min (range 0.5–1.4 mm3/min). Flow rates were temporarily increased during short periods of respiratory depression and could also be influenced by body orientation. Our results indicate that a single opening made into the cochlea at the apex can result in the displacement of all the perilymph in scala tympani (8.0 mm3) by an equal volume of cerebrospinal fluid in 6–16 min. The technique of intracochlear injection in the study of ion and drug actions on hearing is therefore complicated by the continuous displacement of perilymph and consequent removal of the substance being studied from its site of action in the cochlea. For substances introduced into scala tympani, the duration of action will be shorter in the basal turn than at more apical locations.
A New Development for Shock and Random Vibration Testing
Authors: Usher Theron
Published: October 2005

Equalization of amplifier-shaker-specimen frequency response characteristics has been a requirement for random and shock vibration testing due to the resonant behavior of the shaker and specimen. Such equalization has heretofore been accomplished by different systems for random signals and for shock signals. A presentation of the design criteria which led to the development of EROS, a fully automatic Equalizer for either Random Or Shock vibration testing is included. The philosophy of shock spectrum synthesis as it applies to EROS is discussed. Novel system features include narrow-band equalization for both signal types, simplified display techniques, self-calibrating procedures, use as a spectral analyzer, and wide frequency range (1–10 000 Hz).
Transverse Vibration of Nonuniform, Internally Damped Cantilever Beams
Authors: Kerlin R. L.
Published: October 2005

The Bernoulli-Euler theory of transverse beam vibration, suitably extended to take into account internal damping, has been used to derive closed-form expressions for the driving-point impedance and force transmissibility of three types of nonuniform cantilever beams: (1) those of rectangular section with constant breadth and a depth of increasing or decreasing linear taper, (2) those of rectangular section with linearly tapered depth and a breadth appropriately varied to maintain constant cross-sectional area, and (3) those with three discontinuous stages of arbitrary but uniform cross section. In each case, the beams are driven at their free end by a sinusoidally varying point force, and the frequency dependence of their impedance and transmissibility has been calculated. Representative results are presented for internal beam damping of the solid type for which the Young's modulus and associated damping factor are independent of frequency. The mass and length of the beams have been held constant and the graphical results compared in terms of the wavenumber of an equally massive reference beam of uniform section. [Investigation sponsored jointly by the U. S. Naval Ordnance Systems Command, the U. S. Naval Ship Systems Command, and the U. S. Office of Naval Research.]
Power Flow and Energy Difference for a Simple Coupled System
Authors: Davies Huw G.
Published: October 2005

An exact result is obtained for the spectral density of power flow between two beams coupled by a rotational spring of arbitrary strength. It is shown that by averaging this result over narrow bands of frequency, and by suitably defining a modal coupled energy, the basic power-flow energy-difference result of statistical energy analysis can be recovered.
Frequency-Averaged Power Flow into a One-Dimensional Acoustic System
Authors: Scharton T. D.
Published: October 2005

This work shows the effect of the drive point impedance of a finite acoustic system on the power delivered by a realistic source. At low frequencies when the modal overlap of the system is small, the frequency-averaged power delivered by the source can be much less than the power which the source would deliver to an equivalent semi-infinite system. An analysis of the power flow into a finite one-dimensional wave tube is used to explain the observation that broad-band high-intensity acoustic drivers deliver less low-frequency power to small reverberation chambers than they deliver to progressive wave tubes. The analysis indicates that the modal overlap also plays a central role in the determination of the ratio of space-averaged to drive point response.
Some Experiments on the Large-Amplitude Response of Thin Rectangular Plates to Pulse-Type Loads
Authors: Rajagopal Ganesh , Taylor Stanley B. , Lowery R. L.
Published: October 2005

An experimental study of the large deflection response of thin rectangular glass plates to N-wave-type pulse loads is described. A plane-wave tube coupled to a pulse generator is used for creating pulse loads up to 1-psi magnitude on the plate. The reflected Moivé grid technique is applied to obtain a whole field picture of the plate response. The experimental results are compared with an existing finite difference solution of the Von Kármán plate equations and simper one-mode models for the plate.
Revision of Noise Criteria Curves
Authors: Beranek L. L. , Blazier W. E. , Figwer J. J.
Published: October 2005

The noise criteria (NC) curves (L. L. Beranek et al., “Ventilation System Noise,” J. Acoust. Soc. Amer. 25, 313–321 (1953); L. L. Beranek, “Criteria for Office Quieting,” J. Acoust. Soc. Amer. 28, 833–852 (1956); L. L. Beranek, “Revised Criteria for Noise in Buildings” Noise Control 3, 19–27 (Jan. 1957)] were developed both as a method for evaluating existing noise situations and as a means for specifying design goals for noise control. They have also influenced the N ratings used abroad. It has been demonstrated that if a background noise whose spectrum conforms to an NC curve shape is deliberately generated, it does not sound to a listener as a pleasant or neutral noise, but is both “hissy” and “rumbly.” A recent tendency in consulting practice, therefore, has been to specify noise levels that are lower than NC curves at both low and high frequencies. Also, the original NC curves were derived using Stevens' Mk. I method of calculating loudness level from noise levels measured with the old octave bands, the lowest of which was the “below-75-Hz” band. A re-examination of the noise criteria curves has been undertaken using Stevens' Mk. VI method and the new octave bands. The result is a new set of curves, called “preferred noise criteria (PNC) curves,” having levels in the bands below 125 Hz and above 1000 Hz that are lower than those of the 1957 NC curves by 2–5 dB. The new set also takes into account the engineering realities of achieving the specified noise levels with conventional air handling equipment. The results of a number of recent noise control projects in building are presented for comparison.
Sound Absorption of an Audience on Unupholstered Seating
Authors: Hegvold L. W.
Published: October 2005

A 1:8 scale model auditor was developed to simulate a seated person dressed in light- to medium-weight clothing and used to determine the sound absorption of an audience on unupholstered seating. Using scale model techniques the variables of seating density, seating rake, perimeter per unit area of seating block, edge absorption, and selective low-frequency absorption were independently examined. From the results a series of curves were developed from which the total absorption of any audience on unupholstered seating may be determined.
Application of the Landscape Equation for Acoustical Design
Authors: Sulewsky James E. , Krishnan P. V.
Published: October 2005

Using the landscape equation, design graphs are made relating signal(speech)-to-noise ratio with distance from the speaker with barrier (screen) attenuation and directivity index of the speaker as parameters for a noise background of NC-40. Design graphs are also given relating articulation index with distance from the speaker for a noise background of NC-35, NC-40, and NC-45. The effects of the directional characteristic of the speaker on the acoustic environment of the landscape space are discussed and shown by polar plots of equal privacy contours for a noise background of NC-40. Slides of acoustically designed typical landscape spaces will be shown.
Three Recent Experiences in Open Office Planning
Authors: Pirn Rein
Published: October 2005

Theoretical considerations have led to the design and completion of three acoustically successful open-plan offices. With but minor compromises, each was treated with highly absorptive materials to reduce and to localize the sounds of speech and other activities. In two of the three cases, a steady level of background noise is generated and distributed electronically. Partial-height barriers are employed to maximize privacy between work stations. This paper briefly reviews the acoustical principles employed, methods adopted, and results achieved. Specifically, it deals with the questions of surface absorptivity and background noise. The findings include observations on the level and uniformity of background noise, the level of activity sounds, sound attenuation with distance, and barrier performance. While there has been no opportunity to collect and tabulate occupant response, the over-all results are very encouraging. They largely substantiate the validity of the approach taken and reinforce the value of exact acoustical design.
Impulse Measurements of Transmission through and Diffraction around Simple Panels Using Correlation Techniques
Authors: Schomer P. D.
Published: October 2005

The impulse pressure response of various path—including both transmission and diffraction separately—was measured using the technique of correlating white noise. Meaurements were performed on various common simple panels such as plywood and gypsum board. These tests were made as a function of distance and angle. In all cases, the distance of both the source and receiver from the panel was less than the smaller panel dimension. In addition, the “frequency responses” of these various paths were calculated from the correlation measurements by means of computer-aided transform techniques. When practical, swept sine wave measurements were made to compare with the transforms of the correlation measurements. Agreement between these two methods of measurement was satisfactory.
A Model for the Conduction of Vibration from Floor to Floor through Building Columns
Authors: Ver I. L.
Published: October 2005

A simple two-plate column system is used to model the actual building structure. The floor-to-floor vibration attenuation defined as the logarithmic ratio of the space-average velocity of the respective floor slabs is given in terms of the physical properties of the structural elements.
A Method of Calculating the Relative Sound-Pressure Levels as a Location-Dependent Function in Irregularly Shaped Rooms
Authors: Chernjawski M.
Published: October 2005

A numerical method has been developed for determining the sound-pressure level (SPL) as a function of the locations and acoustical characteristics of the source, the receiver, and the various room boundaries of an irregularly shaped room. The technique is based on the acoustical image method, where the sum of the energies passing through the first, second, and higher-order images contributes to the overall reverberent energy at the receiver. The technique considers the shape of the room and the absorption characteristics of each individual boundary surface. A computer model has been developed which calculates the total relative SPL at any predetermined location in a room. The technique is applicable to long rectangular, L-shaped, T-shaped, and other irregularly shaped rooms. As an example, a numerical solution is presented for a long rectangular room (200 ft×10 ft×12 ft) with walls, ceiling, and floor each having different acoustical characteristics. The SPL is determined at one extreme end and at several intermediate locations, with the source situated at the opposite end.
The Interaction of an Acoustic Feedback Channel with the Transient Sound Field in a Rectangular Enclosure
Authors: Tunbridge B. J. , Stephens R. W. B.
Published: October 2005

A single filtered acoustic feedback channel similar to those used in the “assisted resonance system” in the Royal Festival Hall, London, to prolong reverberation time was set up in a simple model enclosure scale 1:20. The frequencies studied corresponded to the range 100–400 Hz in a full-scale concert hall. The channel was phased for positive feedback at a single frequency, part of the feedback loop being the steady-state sound field transmission characteristic between the channel loudspeaker and microphone. The sound field at a point in the enclosure was studied in response to a tone burst from a loudspeaker to observe if the feedback channel, set up in the steady state, would interact favorably with the transient sound field. The center frequency of the tone burst was at, or close to, the channel frequency and the pulse length was varied between 6.3 mS and 50 mS. (The R.T. of the enclosure was 180 mS.) With acoustic feedback the decay was prolonged but the envelope of the pressure was not exponential, with or without feedback, and was significantly longer than the corresponding exponential decay rate for decays from the steady-state sound field excited at the feedback frequency.
The Effect of Boundary Conditions on the Statistical Properites of the Sound Field in Enclosures
Authors: Tichy Jiri
Published: October 2005

The paper reports on part of the extensive research program sponsored by ASHRAE on the sound field in reverberant chambers generated at single frequencies. The statistical properties of the sound field characterized by cumulative distributions and autocorrelation function are discussed. Experimental data obtained for various damping of modes and boundary conditions varying with time are presented. Practical conclusions with respect to the sound power measurements are considered.
Session WI. Speech Communication I: Workshop on Multidimensional Scaling
Authors: Bricker Peter D. , Kruskal J. B. , Wish M.
Published: October 2005

The speakers will concentrate on the practical problems of how to use multidimensional scaling (including individual differences scaling). In a nutshell, the basic aim of this technique is to determine a spatial configuration of points, one for each stimulus, that best reflects measured similarities among the stimuli. The similarities (or dissimilarities) may be based on direct physical measurements or on psychological judgments (such as similarity rating or sorting, or stimulus-response confusions). In general, objects that the data indicate to be more similar are closer to each other in the space. Most multidimensional scaling techniques are quite robust against typical difficulties that occur in real data. In practice, the potential user must solve several problems, which the speakers will discuss. (1) Is multidimensional scaling appropriate for his data? (2) What program should he use; how does he get it; and how does he use it? (3) How does he choose among the plethora of options and parameter values? (4) How does he decide on dimensionality? (5) How does he “interpret” the configuration produced by the program? Although the speakers refer to other programs briefly, they will emphasize the Kruskal-Shepard M-D-SCAL program [Psychometrika 29, 1–27, 115–129 (1964)] and the Carroll-Chang INDSCAL (individual differences scaling) program [Psychometrika 35, 283–319 (1970)]. They will also briefly discuss the numerical procedures that underlie these programs. A configuration can be interpreted by direct inspection, by multiple linear regression, and by other techniques. Interpretation often involves relating the dimensions of the configuration to perceptual attributes. These matters of interpretation will be illustrated with real data on speech and other sensory stimuli. Dimensionality is generally chosen on a rule-of-thumb basis. Newly available tables of stress distribution (analogous to t and F tables) can now help in making this choice, though the tables are severely limited. Both the rules of thumb and the tables will be discussed.
Inheritability of Ultrasonic Effects—a Review
Authors: Dyer Hubert J.
Published: October 2005

Occasionally reports have appeared of biological systems, treated with ultrasound, which exhibited changes from normal, the changes being then passed on to offspring. These cases will be reviewed, with emphasis on the mutations produced in the author's laboratory. A tentative mechanism whereby low-intensity ultrasound might induce nonlethal mutations will be presented.
Ultrasonic Absorption in Biological Media
Authors: O'Brien William D. , Dunn Floyd
Published: October 2005

For the full potential of ultrasonic energy to be realized as a medical diagnostic and therapeutic tool, and in order to assure safe and efficacious procedures, the mechanisms by which this form of energy interacts with living systems must be well understood. The processes by which ultrasound is absorbed in biological media are basic to the understanding of these interaction mechanisms. Until the mid 1950s, investigators devoted much attention to studies of the frequency dependence of the ultrasonic absorption coefficient in biological tissues, and it was found that the loss per cycle α/f was largely constant, at least within the frequency range 0.2–10 MHz, and that as the complexity of the biological media increased, so did the ultrasonic absorption behavior. An additional early finding was that the protein content was largely responsible for the observed ultrasonic absorption, although contributions from the structural features of tissue were also apparent. The more recent studies have dealt with molecular models to explain the latter observations. To date the ultrasonic properties of only a few biologically important macromolecules in solution have been examined extensively, mainly globular proteins, and to a much lesser extent carbohydrates and nucleic acids. Three mechanisms have been suggested to explain the excess ultrasonic absorption in aqueous protein solutions, viz., proton transfer reaction, solvent-solute interaction, and shear viscosity relaxation, and a fourth mechanism, helix-coil transition, has been suggested in reference to polyaminoacids.
Ultrasonic Examination of the Hemoglobin Dissociation Process
Authors: O'Brien William D. , Dunn Floyd
Published: October 2005

The ultrasonic absorption and velocity were determined in aqueous solutions of hemoglobin (Hb) undergoing dissociation. The dissociation of Hb in aqueous solutions of the strong electrolyte guanidine hydrochloride (GuHCl) has been studied extensively [K. Kawahara, A. G. Kirschner, and C. Tanford, Biochemistry 4, 1203 (1965)]. With increasing concentration of GuHCl to 0.7M (molar), the Hb molecule dissociates into half-molecules without loss of tertiary structure. At GuHCl concentrations greater than 2.5M, the Hb molecule dissociates further into its four individual polypeptide chains with complete loss of tertiary structure. The acoustical absorption coefficient within the frequency range 1–50 MHz appears to be insensitive to these conformational changes. Within the neighborhood of 2-M GuHCl concentration, a maximum in the excess ultrasonic absorption coefficient occurs which does not correspond to dissociation or expansion of the Hb molecule, and it is speculated that this maximum can be attributed to the proton transfer reaction.
Disorganization and Disruption of Mammalian and Amoeboid Cells by Acoustic Microstreaming
Authors: Williams A. R.
Published: October 2005

Single-cell suspensions of mouse Ehrlich ascites carcinoma and the amoeba Hartmanella castellanii were subjected to the small-scale acoustic microstreaming field set up around a partially submerged transversely oscillating wire. A resonant length (1.69 cm) of thin steel wire (0.023-cm diam) was driven transversely from one end at 20 kHz and a system of flexural standing waves developed. The free end of the wire was immersed in 0.3 ml of the dilute cell suspension and the maximum displacement amplitude of the submerged portion measured with a traveling microscope. The amoebae and mouse cells were disrupted in a reproducible manner when the maximum wire displacement amplitude exceeded the critical values of about 10 and 28 μm respectively. Electron micrographs of amoebae sonicated for 5 min at displacement amplitudes close to the critical value for disruption suggest that some form of intracellular streaming might have occurred. However, this is unlikely in the mouse cells where intracellular adhesion is so strong that the cell membrane may be partially or completely removed without dispersing the cell contents. Intact sonicated mouse cells exhibit a variety of changes which suggest that a small alteration in fluid transport has occurred.
Frequency-Dependent Examples of Wave Propagation
Authors: Wood D. H.
Published: October 2005

With the current interest in low-frequency wave propagation, it is highly desirable to know frequency-dependent solutions of the reduced wave equation in at least a few idealized situations. For point sources in layered unbounded media with sound speeds satisfying [c″(z)/c(z)]′=0, we find approximate solutions with frequency (ω) dependence, a(x,y,z) exp[iωt(x,y,z)]×[1+b(x,y,z)/ω+c(x,y,z)/ω2]. The leading term is the ray acoustics field, that is, t(x,y,z) is “travel time” and a(x,y,z) is “intensity.” The additional terms correct ray acoustics for finite frequency; for example, b(x,y,z) provides a measure signal distortion for brief signals. All our results are parameter-less explicit functions of ω, x, y, z found without using rays, ray equations, or ray parameters.
Survey of Modern Digital Correlation Techniques
Authors: Langenthal Ira M.
Published: October 2005

Although correlation techniques have been a known and accepted signal-processing technique for many years, it is only recently that the advent of digital technology has progressed to the point where an all-digital correlation processor can be built efficiently as an instrument. Although this emergence is nowhere near the breakthroughs resulting from the advent of FFT techniques, it has opened up many interesting areas of application. The background, present status, and future direction of digital correlation techniques will be outlined. The processing techniques utilized in the digital correlator will be described with particular emphasis being given to the flexibilities that are achievable and the attendant areas of application. Additionally, comparisons will be made between the FFT method of calculating correlation functions and that utilized by the direct method.
Interdisciplinary Design Effort to Control Building Mechanical Equipment Noise
Authors: Salter C. M. , Rosenfeld S. I.
Published: October 2005

When locating a government building complex with its requisite power generating capabilities in a very quiet residential community, extensive interaction was required between the architect, mechanical and electrical engineers, and acoustical consultant. The success of the design was dependent on achieving acoustical compatibility with the neighborhood consistent with aesthetic, legal, and budgetary considerations. This case study is presented to highlight the interdisciplinary effort necessary to satisfy the various constraints imposed by the community, client, and designers. The maximum noise-level criterion established for the mechanical and electrical equipment was based on the existing ambient, and guidelines contained in U. S. Army Manuals TM 5-805-4 and TM 5-805-9. The noise levels of the air-cooled chillers, transformer, and engine-generator, all located in an outdoor equipment yard, were estimated using procedures elucidated in the Army manuals. This information was augmented by acoustic field measurements of similar equipment, plus manufacturers' SPL and power-level data. The noise-control treatments required to achieve the aforementioned acoustic criterion and their individual costs are discussed along with a description of the engineering modifications to the equipment.
Reverberation and Sound Intensification under a Large Outdoor Dome
Authors: Campanella A. J.
Published: October 2005

Modern architectual structures occasionally produce unique acoustical qualities—perhaps unintentionally. A 30-ft2 dome of spherical shape covering a drive-in bank was found to reinforce vehicular noise, thus interfering with patron transaction communications. The reinforced fiberglass shell reflected sound, and the focal point of the sphere was found near waist level. Sound-pressure levels with vehicles as well as reverberation times of the flutter echo were made with basic equipment. Several echo suppression schemes were proposed. Esthetic and durability considerations constrained their selection for their implementation during 1973.
Acoustic Tracking of Individual Fish
Authors: Johnson Richard K.
Published: October 2005

A system developed to study sound scattering from fish and other marine organisms is used to track individual fish against backgrounds of noise or reverberation. Multifrequency target strength information is used to classify the fish by size. Results are reported for studies in the California Current near San Diego.
The Relation of Shock Structure to Airborne Noise Generation
Authors: Mull H. R.
Published: October 2005

Airborne noise generation from shocks can be related to the structure of the shock system. Radiated sound power and spectra can be estimated from the geometry of the system. Methods of noise control for explosive decompression of tanks and valves involve expansion, absorption, and shock breakup.