bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of Ultrasound with Amniotic Liquid
Authors: Zana R. , Lang J.
Published: May 2012

The increasing use of ultrasound in obstetrics and gynecology for diagnostic purposes led us to undertake a study of the interaction of ultrasound with amniotic fluid. The following properties were investigated: (1) Velocity—1510 m/sec at 5 MHz and 25°. This velocity is quite close to that of water. (2) Absorption—in the range of medical interest (1–15 MHz) the amniotic fluid shows a relaxational excess absorption. The effect of frequency, concentration, and pH indicates that this excess absorption is mostly due to the protein content of the amniotic liquid. (3) Ultrasonic vibration potential (uvp)—at 200 kHz the value of the uvp is 0.8±0.2 μV/(cm/sec). The effect of the amniotic liquid concentration and of the concentration of added electrolyte was studied. All of the results indicate that the uvp is due to the NaCl content of the amniotic liquid. It must be pointed out that ultrasonic irradiations performed for gynecologlcal purposes are likely to give rise to uvp's in vivo. This uvp may be involved in the phenomenon recently observed by other workers (Wackert, Quentin, Morin, and Pollak) during the irradiation of the foetal heart in vivo.
Test for 1-kHz Relaxation in Lake Superior
Authors: Fisher F. H. , Levison Stuart A.
Published: May 2012

Samples of Lake Superior water obtained from a municipal water supply were examined by the temperature-jump method which revealed the 1-kHz relaxation due to boric acid in the ocean [F. H. Fisher, E. Yeager, J. Miceli, and R. Bressel, J. Acoust. Soc. Am. 53, 364 (1973)]. No relaxation was observed corresponding to the 1-kHz acoustic relaxation reported by D. G. Browning, E. N. Jones, R. H. Mellen, and W. H. Thorp [Science 162, 1120–1121 (1968)]. [This report is the result of research sponsored by the Office of Naval Research. The measurements were made at Scripps Clinic and Research Foundation by Dr. Levison and Mr. A. Hicks.]
Sensory Aids for the Blind Using Acoustics
Authors: Murphy E. F.
Published: May 2012

Blind people long have used acoustic cues and echoes, plus oral descriptions or reading, Talking Books, or recordings. To supplement a long cane or dog, an experimental ultrasonic sensor warns of objects at chest height. Binaural ultrasonic “spectacles” sense the environment and aid mobility. A laser cane using optical triangulation provides audible signal of overhead objects, major drops, and objects ahead of the user. LED “spectacles” provide audible warning of an object at head height. The ultrasonic spectacles provide comprehensive but complex signals; the other devices provide go-no-go information. For reading, the latest direct translator of letter shape to tone patterns is a portable, relatively inexpensive stereophonic aid, with bass boost in the left ear and treble in the right. A more complex optical character recognizer, also intended for individual ownership, uses spelled-speech output, coalescing into wordlike groups at higher speeds. Synthesis of easily understood English speech from letter recognition, automatic grapheme-phoneme dictionary, and rules for intonation and inflection will require computer-based library-type operation. These experimental devices have reached user trials. Further clinical studies and education of teams in prescription and training methods should lead to wide use.
Thermodynamics of Viscous Damping in Inelastic Fiber Composites
Authors: Chung T. J.
Published: May 2012

Recently, viscoelastoplastic fiber-reinforced shell structures and thermodynamical behavior of inelastic isotropic solids have been studied. The present paper is concerned with the thermodynamics of inelastic glass fiber composites exhibiting significant viscous damping characteristics combined with plastic deformations. The construction of a theory describing the rate-dependent inelastic behavior must be based on irreversible thermodynamic processes since the viscous damping is greatly affected by temperature changes. However, such an attempt encounters a basic difficulty in the form of a free energy function which, in general, is not smooth. In the present study, an incremental theory is developed such that anisotropic properties of the material associated with dissipative process may be defined within a small discretized time domain. The explicit material kernels representing rate-dependent inelastic behavior are nonexistent. It is possible, however, to propose a form of free energy function considered smooth within a small time increment which contains all possible sources of energy depicting properties of elasticity, viscosity, and plasticity, under nonequilibrium thermodynamic processes. The present study is a step toward practical applications of rational thermodynamic theory to rate-dependent inelastic anisotropic composite structures. The finite element method is employed to obtain extensive numerical solutions.
Measurement of the Glottal Pulses
Authors: Sondhi M. M.
Published: May 2012

The glottal pulse shape is usually estimated either by inverse-filtering the speech wave or by taking a motion picture of the vocal cord vibration. We present a much simpler alternative based on the following idea: The effect of the vocal tract resonances on the glottal pulse is considerably reduced by speaking into a reflectionless uniform tube. If, in addition, the tract is held in a neutral position, the effect is almost entirely eliminated and the glottal pulse may be recorded by a microphone in the uniform tube. A number of examples are presented of glottal pulses recorded in this manner. Results of spectral analysis of these pulses are also presented.
Automatic Determination of Time Direction in Speech
Authors: Neuburg Edward P.
Published: May 2012

In research leading to the automatic extraction of speech parameters, some tasks are best done on a computer very differently from the way people do them. In fact there are some speech tasks that a computer can do better than a human, and even some that a computer can do that a human cannot do at all, generally because there is no evolutionary reason why a human should be able to perform such a task. An example of this type of task is determining whether a passage of recorded speech is being played back forwards or backwards. There are passages for which a human finds it difficult or even impossible to make a determination, while a simple computer program has no difficulty at all. Examples of such speech passages are given, and simple methods of determining direction described. The intended implication of the paper is that lines of research or justifications of projects should not be overly influenced by how or how well people perform speech tasks.
Early Acoustic Detection of Laryngeal Pathology
Authors: Markel J. D. , Koike Y.
Published: May 2012

Most studies on the early detection of laryngeal pathology have been based upon perception. The few acoustical studies performed have been based upon pitch perturbation, amplitude perturbation, or inverse glottal wave filtering. Each of these techniques has rather severe limitations depending upon the degree of the pathology being studied. In this study a new measure is introduced for early detection of laryngeal pathology based upon a linear speech production model. The signal of interest is referred to as a residue signal and is obtained by extracting both the vocal tract characteristics (as with inverse glottal wave filtering) and the smoothed or trend characteristics of the glottal volume velocity and lip radiation characteristics. The analysis technique is easily automated and even though it does not resolve difficult problems such as source-tract inseparability for severe cases, it has been demonstrated to be a fairly sensitive indicator of laryngeal disease in a study of ten normal and ten pathological speakers. Physical properties of this technique will be given along with examples. [This research has been supported by the National Institutes of Health under Grant No. RO-NB-08177.]
A Computer-Assisted Hot Wire Technique for Measuring Oscillating Velocity Profiles
Authors: Elder S. A.
Published: May 2012

The need for detailed knowledge of conditions at the interface of the free stream at the mouth of a cavity resonator has led to the development of a computer-assisted technique for velocity profile measurement. Basically, hot wire data are recorded simultaneously with sound pressure microphone data so as to permit later sorting out: of local velocity readings as a function of phase in the acoustic cycle. From the ensemble of stored surveys, turbulent velocity fluctuations can be averaged out and the time sequence of oscillating profile configurations can be reconstructed. By subtracting the mean profile from each element of the sequence, the profile of the underlying instability wave is exposed. Another use of the results is the determination of the fluctuating component of volume flow into the cavity by numerical integration. [Sponsored by Naval Ship Systems Command under a GHR contract administered by NSRDC]
Intensity Discrimination of Noise in the Presence of Band-Reject Noise
Authors: Viemeister Neal F.
Published: May 2012

Weber's law holds over at least an 80-dB range for intensity discrimination of 200-msec noise bursts. Weber's law also holds over at least an 80-dB range when information regarding intensitive differences is effectively restricted by the addition of a band-reject noise to a range of frequencies for which pure-tone absolute thresholds are relatively constant. In particular, no saturation effects at high intensities were observed. These results indicate that spread-of-excitation across frequency is not necessary for the auditory system to maintain a large dynamic range. These data, together with recent indications of limited variability of absolute thresholds for VIIIth nerve units of a given characteristic frequency, further suggest that the system can maintain this large dynamic range even when no “fresh” fibers are available for recruitment.
Steady-State Responses and Circumferential Echoes from Cylinders
Authors: Ryan William W.
Published: May 2012

The steady-state response functions are calculated for the infinite cylindrical shells having a b/a ratio of 0.916 where b and a are the inside and outside radii, respectively. For the aluminum and Lucite cylinders, ka was from 0+ to 132; for brass and Armco iron, ka was from 0+ to 66. Experimental results from eight aluminum shells (b/a = 0.916; 4<ka<100) are presented and are in good agreement with the computer curves. Theoretical echoes were also calculated for these cylindrical shells using a 10-μsec incident pulse. The echo for the aluminum was calculated and measured at two frequencies (ka=−9.26 and 39.1). The echoes observed at each frequency were circumferential echoes. The low-frequency echo is associated with a low-velocity circumferential mode (v≈2000 m/sec); and the high-frequency echo is associated with a high-velocity circumferential mode (v≈5600 m/sec). Good agreement was observed between theory and measurements for both frequencies. [Work sponsored by Naval Ship Systems Command.]
Scattering of a Plane Wave by a Sphere Surrounded by a Thin Spherical Shell
Authors: Pond H. L. , Hoy R. W.
Published: May 2012

The scattering of a plane wave by a thin spherical shell surrounding a solid sphere is determined. The results are given for shells of uniform thickness and axially symmetric cases for shells of nonuniform thickness. For a shell of uniform thickness the method of separation of variables can be applied, but for shells of nonuniform thickness the more general method described must be used. Numerical results are given for the scattering coefficients, target strength and farfield pressure distribution. It is shown that replacing a solid sphere by a thin spherical shell of the same diameter which surrounds a smaller internal solid sphere can lead to variations in the target strength of the order of ±10 dB. The results depend on the interaction between waves reflected from the inner body and the shell. Thus, important parameters are the spacing between body and shell and the wavelength. As body spacing and frequency are increased, the effect is to increase the average target strength.
Where Do Lateral Waves Come from?
Authors: Hudimac A. A.
Published: May 2012

Wave theory indicates that the first round from a point source reaching a point in the ocean (at a distance'many times the depth) is directed upward from the bottom at the critical angle and has the phase of a signal leaving the source at the critical angle, propagating just inside the bottom at the bottom speed, and exciting at the critical angle. Ordinary ray theory does not account for this field. A modified ray theory [A. A. Hudimac, J. Acoust. Soc. Am. 49, 77(A) (1971)] indicates that the errors of ray theory can be corrected by distributing simple sources in the bottom with density whose phase is that of the rays and whose magnitude is proportional to the Laplacian of the ray amplitude. The principal contribution to the rays ensonifying the observation points comes from the source distribution near the interface, below the observation points and toward the source. Sample calculations show that the resulting “diffraction” field is essentially that predicted by wave theory.
Detection and Classification with Unipolar Pulses
Authors: Toulis W. J.
Published: May 2012

Unipolar type of echo-ranging systems may be designed in the manner of most any type of conventional sonar/radar detection system by omitting, absorbing, rectifying, or reflecting one of the two radiated polarities. In general, the signal returns are also similar if the bandwidth in the unipolar and bipolar receivers is the same. However, the returns with a unipolar detection system contain highly distinctive low-frequency signals which are not self-cancelling in the manner of the usual bipolar detection systems. Such returns may be used to recreate (both instantly and closely) the sound-speed profile that exists at sea. Similarly, targets may be classified unambiguously from such low-frequency returns as long as the signal is detectable and, especially, if the target has a “ringing” signature. Various means for generating and radiating unipolar pulses will be discussed also. [Reference: U. S. Patent 3,686,669.]
The Sound Field Scanner Revisited
Authors: Harvey F. K.
Published: May 2012

A series of photographs displaying sound wave space patterns, made with a sound field scanner at Bell Laboratories, was first shown publicly to the Acoustical Society of America at its 40th Meeting, November 1950, by Kock and Harvey [J. Acoust. Soc. Am. 23, 149(A) (1951); Bell Syst. Tech. J. 30, 564–587 (1951)]. Because of renewed interest, the scanning techniques are recalled with regard to the mechanics of motion, the registration of the photographic image, the calibration of the gray scale and the electronics needed to delineate the amplitude and phase patterns. The initial pictorial results are presented from examples on file, including some not previously given. (More displays from later experiments are described by W. E. Kock in a following paper.) In addition, a 16-mm film loop portraying a progressive wave in transit through a focal area is shown.
The HEARSAY Speech Understanding System
Authors: Reddy D. Raj , Erman Lee D. , Fennell Richard D. , Lowerre Bruce T. , Neely Richard B.
Published: May 2012

This talk describes the present state of performance of the HEARSAY system. [For more complete descriptions of the system see D. R. Reddy, L. D. Erman, and R. D. Neely, “A Model and a System for Machine Recognition of Speech,” IEEE Trans. Audio Electroacoust. AU-21, 229–238 (1973) and D. R. Reddy, L. D. Erman, R. D. Fennell, and R. B. Neely, “The HEARSAY Speech Understanding System : An Example of the Recognition Process,” Proc. 3rd Int. Joint Conf. on Artificial Intelligence (Aug. 1973)]. The system uses task and context-dependent information to help in the recognition of the utterance; this system consists of a set of cooperating parallel processes, each representing a different source of knowledge (e.g., acoustic-phonetic, syntactic, semantic). The knowledge is used either to predict what may appear in a given context or to verify an hypothesis resulting from a previous prediction. Performance data of the system on several tasks (e.g., medical diagnosis, news retrieval, chess, and programming) will be presented. For example: The voice-chess task contains a 31-word vocabulary with about 5 000 000 possible sentences. One particular set of data contains 19 utterances of three to nine (mean =4.5) words each. Seventy-nine percent of the utterances are correctly recognized (at about four times real time on a PDP10 computer); removing the semantic source of knowledge (but leaving the syntactic and acoustic-phonetic) reduces recognition to 42%.
Representation and Use of Acoustic-Phonetic Knowledge in the HEARSAY System
Authors: Erman Lee D. , Lowerre Bruce T. , Reddy D. Raj
Published: May 2012

The HEARSAY speech understanding system uses acoustic-phonetic knowledge at basically four levels: lexical, syllabic, phonemic, and subsegmental. The lexicon is a list of phonemic spellings of all the words of the given language, possibly with alternates. The system recognizes possible word juncture problems from the phonemic dictionary; for example, the juncture between the words “got to” may be realized with one or two stop releases, and the system is sensitive to both possibilities. At a (roughly) syllabic level, the speech is segmented into the three classes of “voiced,” “silent,” and “fricated” (voiced or unvoiced). (In addition, a “voiced” segment is further subdivided if it contains a significant amplitude minimum between significant maxima.) This segmentation, while crude, is very reliable for many first-lever approximations. At the phonemic level, the system matches an expectation derived from the dictionary spelling to the actual utterance; each candidate word is rated as a function of the goodness of this phonemic-phonetic match. At the subsegmental level, a label is assigned to each 10-msec sample of speech. The inventory of labels is intended to correspond to the steady-state portions of the sustained phone types of English. This labeling is used to characterize each 10 msec for the further higher-level processing.
An Experiment in Automatic Isolation and Identification of Vowels in Continuous Speech
Authors: Kameny Iris , Weeks R.
Published: May 2012

Results of a vowel isolation and identification experiment provided tentative answers to some acoustic phonetic questions concerning continuous speech. The experiment indicated that (1) automatic techniques can be employed to isolate vowels in the speech signal; (2) vowels consistently reach an approximate target in terms of their first three formants; (3) it is possible to locate a “steady-state” portion of the vowel that corresponds closely to the vowel target; (4) a single spectrum extracted in the steady-state region of the vowel locates that vowel reliably with respect to the three-dimensional formant space; and (5) comparison of the vowel formants with a previously compiled, speaker-dependent table of vowel formants provides a satisfactory method of identifying the vowel.
Report of a Workshop on Machine Segmentation and Labelling of Connected Speech
Authors: Erman Lee D. , Reddy D. Raj
Published: May 2012

Approximately 45 people, representing 12 groups (most of which are active in speech recognition research), attended this workshop in Pittsburgh in July 1973. The common data were 31 different utterances (3 sec average), recorded by eight talkers under a variety of recording conditions. Each group was provided with the same data: either as a digital tape (at 10K or 20K) or as a copy of the analog tapes. Eight of the groups submitted machine-generated labeled segmentations of the data. At the workshop, the participants were provided with spectrograms, oscillograms, and a manually performed segmentation and phonetic labeling of each utterance, as well as the 11 different machine-generated labeled segmentations which were submitted. All of these displays were aligned and synchronized in the time domain. The general results are encouraging; although most of the groups claimed that their techniques are “still rough and preliminary,” (1) most segments and boundaries were found by a majority of the schemes, (2) classification at a gross level (e.g., “strident fricative,” “front or mid vowel,” or “stop”) was quite good, and (3) finer classifications (at about the broad phonetic level) were generally close. Particularly because of the common data, a great deal of interaction among the participants occurred.
Phonemic and Morphemic Variability in Connected Speech
Authors: Reddy D. Raj
Published: May 2012

One observes three types of variability in connected speech: (1) the actual features present in a segment are different from the expected features; (2) an expected segment is entirely missing; or (3) an unexpected segment is present. Much of this variability is rule governed, i.e., allophonic variability (incorrect features), extreme cases of consonant and vowel reduction (missing segments), or extreme movements of the articulators (extra segments). One also occasionally observes significant free variation which cannot be satisfactorily explained by rules. This talk illustrates these different types of variability at the phonemic and morphemic levels with examples from natural and synthetic speech, and discusses the implications for recognition and synthesis strategies.
The Design of Sound Absorptive Materials to Meet Special Requirements
Authors: Wirt L. S.
Published: May 2012

Bulk sound-absorbing materials are not suitable for many applications involving liquids, air flow, elevated temperature, vibration, and severe space limitations. In aircraft all of these design constraints can occur together. The simplest alternative to the bulk absorber is the laminar absorber, comprising a permeable facing sheet over a closed compartmented air space. Laminar absorbers meet some of the above design requirements but their impedance-versus-frequency characteristic is inherently inferior to that of a good bulk absorber. A wide variety of improved absorption characteristics may be attained by utilizing more acoustical elements and parallel as well as series connections among the elements. The use of resistance paralleled by inductive resistance provides a facing sheet whose resistance increases with frequency while the positive reactance decreases. Dissimilar air cavities arranged in parallel provide air space reactance that remains near zero over a broad range of frequency. The cutoff characteristics of miniature acoustic horn arrays may be exploited to provide a dual-frequency range of absorption. The upper frequency range resembles that of a laminar absorber, whereas the low-frequency absorption occurs in a controllable region of considerable bandwidth. These novel sound-absorbing structures may provide practical solutions to such diverse problems as fan jet engine buzzsaw noise, combustion noise, and noise due to cooling towers and car wash installations.
Temporary Threshold Shift and Loudness Recruitment
Authors: Young I. M.
Published: May 2012

Ears of normal-hearing subjects and patients with sensorineural hearing loss were exposed to uninterrupted stimuli, e.g., pure tone(s), broad-band noise, and narrow-band noise for a duration of 1–5 min at over-all intensity of 80–120 dB re 0.0002 μbar. Thresholds were measured by conventional pure tone test and Békésy audiometry at various frequencies both before and after exposure. Althernate binaural and/or monaural loudness balance tests were performed for various frequencies showing threshold shift. Following exposure to stimuli, normal ears revealed asymptotic recruitment and ears with sensorineural loss showing straight-line recruitment before exposure showed asymptotic and straight-line recruitment. Reverse recruitment (decruitment) in ears showing abnormal adaptation before exposure changed to asymptotic and reverse recruitment. From these findings it is assumed that temporary threshold shift is considered as a discrete lesion and may be comparable to absolute scotoma in the eye. Ears showing straight-line recruitment, e.g., Ménière's syndrome, may be similar to relative scotoma of diffuse lesion. Different conditions of sensorineural lesion probably give rise to different types of recruitment curve and may lead to new insight into the nature of loudness recruitment.
A Report of Acoustic Admittance Parameters in Normal Ears
Authors: Feldman A. S.
Published: May 2012

The acoustic measurement of middle ear function is presently accomplished with electroacoustic instruments which measure the difference in flow of acoustic energy through the middle ear as a function of variable air pressure gradient across the tympanic membrane. The result is displayed in the form of a curve called a tympanogram, which may be analyzed by its configuration, or may provide the computational basis for the determination of static acoustic impedance or its parameters. Descriptive data has previously been defined in reactive or resistive components of the acoustic impedance, or the acoustic impedance itself, depending upon the instrumentation used. The present study explores the clinical measurement of acoustic admittance, which is the reciprocal of acoustic impedance, and compares the results of this measurement on 100 normal human middle ears with the previously developed normative data. Normal ranges for the acoustic susceptance and acoustic conductance, as well as the complex acoustic admittance, are developed which will serve as ranges for the clinical study of static acoustic admittance of the middle ear. The results compare well with data previously developed with mechanical acoustic instrumentation and also provide evidence of the source of variability in certain pathological conditions.
Results of the Investigations of Two Speech Parameters in the Detection of Emotional Stress/Tension
Authors: Fuller Fred H.
Published: May 2012

Initial research started ten years ago or the extraction of non-verbal speech parameters as numerical assessors of emotional/physical states of the speaker. Initial research concentrated on energy changes occurring in different frequency regions when the speaker or the experiencing emotional stress. It was determined that the optimal frequencies were the 100–120 and 500–800 Hz regions. Subsequent research and field studies explored additional parameters and other emotional states of the speaker. A second parameter has been shown to be correlated with the tension of the speaker. It has been shown to successfully discriminate different levels of confidence of the speaker in his statements and his attitudes to social issues as well as the different emotional stress levels occurring in polygraph examination. The precise property of speech corresponding to the second parameter has not as yet been identified, although active research is continuing. A current study shows excellent correlation with interpretations of polygraph data, although the voice parameter does not appear to correlate highly with any of the three conventional physiological parameters used in polygraph examination. The first and second speech parameters discussed in this paper appear to be independent (Pearson product moment correlation equals +0.05).
Nonlinear Sound Propagation in a Duct with Resonator Lining
Authors: Galaitsis A. G. , Ingard U.
Published: May 2012

The attenuation and phase velocity of sound in a duct with non-linearly responding walls were measured at different frequencies and sound pressure levels. The duct lining was a locally reacting surface consisting of a perforated metal sheet with a partitioned air backing; the linear and nonlinear components of its impedance were extracted by direct measurements in an impedance tube. The phase velocity and the attenuation of sound in the duct were obtained theoretically by incorporating the Morse charts in a computer program, and were in good agreement with the experimental findings. [This work was supported in part by the U. S. Department of Transportation under Grant Agreement DOT-OS-30011 and in part by the U. S. Navy (Office of Naval Research) under Contract N00014-67-A-0204-0019.]
Difference Frequency Radiation from a Cavitating Parametric Source
Authors: Konrad W. L. , Moffett M. B.
Published: May 2012

A cavitating projector radiating two primary frequencies exhibits much higher efficiency in the generation of difference frequency energy than the conventional noncavitating parametric source. The results of experimental work using a mean primary frequency of 25 kHz demonstrate essentially omnidirectional patterns with source levels considerably higher than the on-axis levels obtained from the same source operating at the same input power at depths sufficient to prevent cavitation. The spectrum of the signal exhibits energy strongly concentrated at the difference frequency and its harmonics.
Relations between Velocity and Attenuation in Sea Water and in Sediments
Authors: Horton C. W.
Published: May 2012

The Kramers-Kronig dispersion relations between velocity and attenuation are applied to various cases of interest in underwater acoustics. The phase velocity is calculated for a medium for which the attenuation has the form afn nepers/meter where a and n are constants and f is the frequency. It is shown that the phase velocity is independent of frequency when n = 2 and n = 1. The case n = 2 corresponds to ideal water with viscous losses, and n = 1 corresponds to many earth materials and is the value favored by E. L. Hamilton for ocean sediments [J. Geophys. Res. 76, 579 (1971)]. For other values of n the phase velocity depends on frequency. The dispersion relationships are applied to the MgSO4 relaxation phenomenon in sea water.
The Relationship of Transducer Apertures and Separation Distances to the Composite Directivity Patterns in the Nearfield Region
Authors: Mikeska E. E. , McKinney C. M.
Published: May 2012

In many acoustic systems, the aperture dimensions of the projecting and receiving transducers are comparable. The variation of received signal level with separation distance along the acoustic axis in the transition region between near- and farfields has been studied by several workers, but apparently little has been published on the composite directivity patterns for this case. This paper presents the results of an experimental investigation of the composite directivity patterns for a series of projector-hydrophone pairs of various ratios of apertures as a function of range from the nearfield to the farfield. Relevance of the results to several applications, including transducer calibration, acoustic communications, and range determination, is discussed. Criteria for separating the nearfield and farfield regions for both axial pressure level variation and directivity patterns are discussed. [This work was sponsored by the U. S. Navy Department.]
An Exact Expression for Lommel's Diffraction Integral
Authors: Van Buren A. L. , Rogers Peter H.
Published: May 2012

A number of authors have obtained diffraction corrections for a circular piston source by numerical or graphical integration of an approximate expression for the piston field attributable to E. Lommel [Abhandl. Bayer. Akad. Wiss. 15, 233 (1886)]. Lommel's expression gives the piston field in terms of trigonometric functions and Lommel functions of two variables, the latter being defined as infinite sums involving cylindrical Bessel functions. It is shown here that the required integral of Lommel's expression can be evaluated analytically to obtain a simple closed form expression for the diffraction correction. The extrema of this expression are obtained as roots of simple transcendental equations. It is also shown that the same expression can be obtained by taking the limit as ka → ∞ (where k is the wavenumber and a is the piston radius) of Williams's exact integral expression for the diffraction correction [J. Acoust. Soc. Am. 23, 1 (1951)]. Finally, it is shown both analytically and by numerical integration of Williams's exact expression that the simple closed form expression is a good approximation for all distances from the source provided that (ka)12 ≫ l.
Effect of Diffuseness of Incident Sound Field on the Measurement of Airborne Sound Transmission Loss
Authors: Holmer C. I.
Published: May 2012

Much of the literature on airborne sound transmission loss (TL) indicates that TL of a panel at a given frequency is dependent on distribution of sound intensity with angle of incidence in the incident sound field. Observed TL in most laboratory tests employing a “diffuse” sound field yields data which may be described as lying between that to be anticipated if the energy in the sound field were concentrated at normal incidence, and that expected if the sound field were uniformly distributed over all angles of incidence (Random Incidence). An ad hoc approach to dealing with this phenomenon has involved the postulation of a “field incidence” sound field, which assumes that the distribution of incident intensity is uniform up to a limiting angle of 75° to 80° from the normal to the panel. This approach provides a means for calculating TL which agrees with measurements, but no satisfactory analytical model has evolved which provides justification for this approach. Some careful experimental evaluations involving convolution of the cross correlation of the incident pressure field with an analytic model of panel response have shown that the fundamental approach is reasonable, but still provides no basis for explaining this phenomenon. In this paper, the recent published and unpublished data of a number of authors are reviewed, which imply that TL is more sensitive to local perturbations from a diffuse incidence sound field than from gross perturbations in the source room. One hypothesis which seems to correlate with these observations is that the aperture in which a panel is tested should be viewed as a spatial filter which limits the incident sound field in addition to the effects of “diffusivity” present in the source room. It is postulated that the limitations produced by the aperture are more significant than those provided by the room for a “reasonably reverberant” source room.
Acoustic Response of External-Ear Replica at Various Angles of Incidence
Authors: Shaw E. A. G.
Published: May 2012

Simple progressive waves at grazing incidence are generated by a special source which can be placed at various orientations in the plane of the ear [J. Acoust. Soc. Am. 51, 150(A) (1972)]. Response curves for an ear replica under various conditions of measurement have been recorded at 11 angles of incidence spanning an arc of 135°. The primary purpose of the experiment was to determine the transfer functions from a variety of probe positions to the eardrum position. Measurements of pressure are judged useful only where the transfer function is substantially independent of the source angle and hence the form of the incident sound field. With an open ear canal, pressure measurements at most positions in the concha are correlated with measurements at the eardrum within 1 dB up to 5–6 kHz. Measurements at the “blocked meatus” are correlated within 1 dB up to 9–10 kHz and within 5 dB up to 12–14 kHz. A careful choice of probe position is clearly necessary if one wishes to determine the angular properties of the external ear at the higher frequencies.
Extraction of the Fundamental Component in Speech with. a Nonlinear Circuit Model for the Cochlea
Authors: Stewart J. L.
Published: May 2012

Distributed nonlinearities in a circuit model for basilar membrane vibrations demodulate the envelope component in speech in a cumulative way. Induced components propagate to the normal place of localization where they may be extracted. Waveforms and recordings for this component are demonstrated with well-known sentences under various conditions of speech pre-filter bandwidths and imposed noise. The extracted fundamental is comparatively reliable and tolerant of speech bandwidth variations. Specific demonstrated bandwidths are 30–5000 Hz, 300–3000 Hz, and 600–3000 Hz. Raising the lower frequency cutoff has little effect on voicing extraction except for a gradual weakening of /u/, /i/, and the nasals. Extending upper cutoff above 3000 Hz has little value. Experiments using the extracted voicing component as a tactile deaf aid are described, with plosive cues also present.
Category Boundaries for Speech and Nonspeech Sounds
Authors: Sawusch J. R. , Pisoni D. B.
Published: May 2012

Recent experiments employing an adaptation paradigm have demonstrated the possibility of phonetic feature detectors in speech perception (Eimas and Corbit, 1973). These results could be explained by Adaptation Level Theory (ALT), assuming the reference for categorizing a speech sound is external. In the present experiment, identification functions were obtained for a series of synthetic speech sounds ranging perceptually from /ba/ to /pa/ and a series of tones varying in intensity from 60 to 84 dB SPL. The distribution of occurrences of each stimulus in a series was varied for both tones and speech stimuli. The category boundaries for the tones shifted as a function of the relative number of occurrences of each tone as predicted by ALT. However, the phonetic boundaries for the speech stimuli failed to show the analogous shift. These results suggest that the response criteria for phonetic boundaries may be mediated by an internally generated reference. In contrast, the reference for the nonspeech category boundaries is under external stimulus control.
Variability in Aircraft Flyover Noise Measurements
Authors: Bishop Dwight E.
Published: May 2012

The increasing interest in aircraft flyover noise measurements and in noise monitoring around airports has raised questions as to the variability in in aircraft flyover noise measurements. This paper reviews the results of repeated aircraft noise measurements for two major classes of observations: Repeated measurements of a single aircraft flown by a skilled flight test crew, made over short time periods under controlled conditions (measurements typical of those required for FAA noise certification tests); and repeated noise measurements extended over periods of one to 30 days at civil airports during routine operating conditions, where there is no special control of operations or detailed information as to exact aircraft configurations. As might be expected, the variability in the later class of observations is inherently greater than in measurements under carefully controlled conditions. Results are reported for several different noise measures, including the effective perceived noise level, the single event level, and the maximum A-level. Comparisons are made between two methods of averaging noise level data, arithmetic and energy averaging, since both methods are of interest depending on the study application.
Blown Flap Noise Using Velocity Decayer Nozzle
Authors: Reddy N. N. , Swift G.
Published: May 2012

Experiments were conducted in the anechoic chamber to investigate the radiated sound of a model blown flap configuration (lower surface blowing) u:iing a velocity decayer nozzle. The nozzle is contoured to have two dissimilar halves: the upper half is a multilobe mixer and the lower half is semi-elliptical. The wing/flap is two dimensional with triple-slotted flaps. The jet flow impinging on the flaps comes primarily from the upper half of the nozzle which is designed to provide greater velocity reduction in the axial direction as compared to any conventional nozzle. The various parameters studied are the jet Mach number, the flap angles, and the distance between the nozzle exit plane and the flaps. The radiated sound is measured at various angles on the flow side of the wing/flap configuration. The results are presented in the form of the variation of OASPL with jet Mach number and 2/3-octave spectra and compared with the equivalent conical nozzle data. These results indicate that as the flap angle increases, the sound pressure levels increase, the spectral peaks shift to higher frequencies, and bandwidths increase. The OASPLs are higher directly below the wing (flyover conliguration) than the wing plane (side line condition).
The Mammalian Cochlea
Authors: Lim D. J.
Published: May 2012

A marked differentiation between the outer and inner hair cells is one of the characteristics of the mammalian cochlea. These two groups of cells are separated by Corti's tunnel, which is presumably filled with Corti's lymph. Communication between Corti's tunnel and the scala tympani is thought to be accomplished by Schuknecht's channel, the presence of which in mammals was confirmed in the present study. It was also confirmed that the endolymphatic spaces of fresh frozen mammalian cochleae are filled with proteinaceous (or fibrillar) material(s), as reported by A. Flock. Mammalian sensory hairs are unique in their arrangement and in the loss of kinocilia as the organ of Corti matures, in contrast to the sensory hairs of other animal classes, which are strikingly similar to the mammalian vestibular sensory hairs. The mammalian outer hair cell sensory hairs are firmly attached to the tectorial membrane, but it is controversial whether the inner hair cell sensory hairs are likewise attached. The physiological significance of this arrangement and the cyto-archi-tecture of the mammalian organ of Corti are discussed. In addition, the stria vascularis, the spiral limbus, and Reissner's membrane, which are implicated in the production and/or maintenance of endolymph, are discussed.
Review of Sound Propagation in a Randomly Inhomogeneous Medium: Theory and Laboratory Experiments
Authors: Mintzer D.
Published: May 2012

A critical review is given of the theoretical analyses developed to describe the fluctuations in acoustic waves traversing a medium whose refractive index varies randomly as a function of space and time. Emphasis is on the physical and mathematical nature of the approximations used, their necessity for the analysis, and their effects on the solutions. The relation between these results and the data obtained from laboratory experiments is discussed. Comparison is made with theoretical and experimental work in other fields of fluctuation research. Suggestions for future lines of research is made.
A Technique for Investigating the Sensitivity of Ray Theory to Small Changes in Environmental Data
Authors: Solomon Louis P. , Merx William C.
Published: May 2012

In order to effectively use a ray tracing model it is advisable to determine its sensitivity to small perturbations in the velocity of sound. A model to compute transmission loss based on ray theory and using cubic splines for the sound velocity profile is presented and its sensitivity is examined. The sound velocity profile is perturbed randomly and the mean and standard deviation of the transmission loss is computed.
Noise Ordinance Enforcement in Boulder, Colorado
Authors: Adams James V. , Chanaud Robert C. , Simmons Robert A.
Published: May 2012

The City of Boulder, Colorado, has had an active noise control program for three years. The levels set for vehicles are more stringent than those of California and the enforcement statistics have shown that these lower levels can be reasonably applied at the present time-even to motorcycles. Enforcement is accomplished primarily outside the Police Department using the “soft fuzz” approach. The techniques used to maximize compliance with minimum personnel will be described. The educational program for civic groups and students, an important part of the enforcement program, are discussed. The City is currently spending about 23¢ per capita per year on noise control and may be second only to Inglewood, California. The results of a survey of citizenry taken two years after the passage of the ordinance are given. The experience has resulted in the writing of a more comprehensive ordinance, which is described. Agreements among city departments for noise prevention planning are described.
Effects of Discontinuation of Nocturnal Aircraft Noise
Authors: Fidell S. , Jones H.
Published: May 2012

A telephone survey was conducted to assess the effects of cessation of late-night overflights on communities to the east of Los Angeles International Airport. Approximately 1400 interviews were conducted before, immediately after, and a month after the cessation of flights. No appreciable effects were observed in terms of reduction of annoyance, or lessened speech, or sleep interference. Large, consistent, and statistically significant differences were observed, however, in response patterns as a function of level of noise exposure both before and after cessation of late-night flights.
Introduction to Workshop Session on Reverberation Room Qualification
Authors: Holmer C. I.
Published: May 2012

This workshop, sponsored by the Noise Technical Committee of The Acoustical Society, is intended to provide a summary of current state-of-the-art in reverberation room qualification for ANSI S1.21—1972. This standard prescribes evaluation procedures for the qualification of a reverberation room measurement system for the measurement of broad-band noise and discrete frequency sound. In this introduction, the evaluation procedures are reviewed and the performance requirements are discussed.
Historical Evolution of the Performance Requirements of ANSI S1.21-1972
Authors: Baade Peter K.
Published: May 2012

ANSI Standard SI.21-1972, “Methods for the Determination of Sound Power Levels of Small Sources in Reverberation Rooms,“ represents a significant departure from its predecessor S1.2-1962 in that it requires a performance evaluation to demonstrate the qualification of a reverberation room measurement system for measurement of discrete frequency sound. Experience in preparing this type of performance requirement was provided to many members of the working group through their association with ASHRAE and ISO writing groups who prepared or were in the process of preparing similar types of standards. Data on a number of facilities were available from round-robin evaluations sponsored by ISO. A forthcoming paper by Ebbing and Maling [“Reverberation Room Qualification for Determination of Sound Power of Sources of Discrete-Frequency Sound,” J. Acoust. Soc. Am. 54, No. 4 (1973)] provides an extensive discussion of the theoretical basis for the standard and presents some of the round-robin data. In this presentation, the data available to the writing group at the time of preparation of the standard are reviewed. As might be expected, the performance requirements represent a compromise between desirable measurement accuracy, and achievable measurement conditions in reasonable size rooms. The selected performance requirements of S1.21-1972 are discussed in the context of this compromise, and the data available on existing rooms. Finally, some estimates of the achievable accuracy of power level measurement of an arbitrary source are related to the performance requirements.
Distribution of Magnitude Estimation Judgment
Authors: Green David M. , Luce R. D.
Published: May 2012

Repeated judgments of the loudness of a 1000-Hz sinusoid were made by a number of observers in various experimental conditions. For all conditions, 20 different stimuli were used spaced 2.5 dB apart in intensity, and 300 to 600 judgments were made at each intensity. In most cases, the mean magnitude estimates were roughly power functions of stimulus intensity with the range of exponents for the individual subjects similar to those reported by earlier investigators. In one experimental condition, without a standard, the ratio of successive responses was compared to the ratio of the intensities of the successive stimuli. The mean ratio of successive responses are roughly power functions of the stimulus intensity ratio of the corresponding signals. The coefficient of variation (m/σ) of these judgments varies markedly as a function of the amount of stimulus change. It is lowest (∼0.1) for the small stimulus changes and reaches an asymptote (∼0.3) if the stimulus changes by 20 dB or more. A theoretical fit to the distribution of these judgments is considered.