bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Properties of Cochlear Combination Tones
Authors: Dallos Peter
Published: September 2005

The mechanisms of combination-tone generation in the cochlea are studied by recording microphonic potentials with the differential electrode technique. The results indicate that at moderate intensity levels the distortion components are most prominent in that region of the cochlea where the primaries create the greatest excitation and not at the location where a pure tone at the frequency of the distortion product would be located according to the place principle. Experiments with dc polarization of the cochlear partition show that these combination tones are most likely to originate in a nonlinearity that is in the transduction process as opposed to mechanical or hydraulic nonlinearities. It is probable, however, that at very high intensities a secondary (mechanohydraulic) nonlinear process becomes more prominent and as a consequence, the distortion components become redistributed according to their own frequencies. [Work supported by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]
Specification of a Digital Vocoder System
Authors: Anderson Walter M.
Published: September 2005

A recently proposed vocoder system that is suited to realization with digital hardware will be discussed. The analzer consists of 32 equal-bandwidth quadrature integrate and dump bandpass filters. The spectrum magnitude so measured is sampled, smoothed, and encoded for 2400 bits/sec transmission. Pitch detection is accomplished by processing the speech through two bandpass filters. Four identical detectors operate on the positive and negative peaks of the filtered waveforms and their outputs are coalesced by a majority logic into a final detected period. The synthesis is in two parts: First, truncated sinusoids of proper phase and, at the center, frequencies of the analysis filters are multiplied by the appropriate channel amplitudes and summed to form a symmetrical time function. Second, this time function, properly updated as the spectrum changes, is convolved with a voiced or unvoiced excitation pulse train to form the reconstructed speech. The vocoder system described can be economic in memory requirements, algebraic operations, world-length and control so that its digital hardware realization is relatively simple. Results of its stimulation will be demonstrated. [Operated with support from the U. S. Air Force.]
Speech Analysis-Synthesis System Based on Homomorphic Filtering
Authors: Oppenheim Alan V.
Published: September 2005

A digital speech analysis-synthesis system based on a recently proposed approach to the deconvolution of speech [A. V. Oppenheim and R. W. Schafer, Homomorphic Analysis of Speech, Conference on Speech Communication and Processing (1967)] will be discussed. The analyzer is based on a computation of the cepstrum considered as the inverse Fourier transform of the log magnitude of the Fourier transform. The transmitted parameters represent pitch and voiced-unvoiced information as measured from the cepstrum, and the low-time portion of the cepstrum representing an approximation to the cepstrum of the vocal-tract impulse response. In the synthesis, the low-time cepstral information is transformed to an impulse response function which is then convolved with a train of impulses during voiced portions or a noise waveform during unvoiced portions to reconstruct the speech. Since no phase information is retained in the analysis, phase must be regenerated during synthesis. Either a zero-phase or minimum-phase characteristic can be obtained by simple weighting of the cepstrum before transformation [Lincoln Lab. operated with support from the U. S. Air Force.]
Light Scattering from Shear Waves in Liquids
Authors: Stoicheff B. P. , Stegeman G. I.
Published: September 2005

In liquids with molecules having nonspherical polarizability, the spectrum of scattered light contains the usual central and Brillouin components and in addition, a depolarized component known as the Rayleigh “wing.” This depolarized component is centered at zero frequency, is often very broad (sometimes extending as far as 10 or even 100 cm−1), and arises from thermal fluctuations of anisotropy that are believed to originate from molecular rotational motions in liquids. We have studied the depolarized spectra from a number of liquids, under the high resolution available with a He-Ne laser and a pressure-scanned Fabry-Perot interferometer. In some liquids, this spectrum exhibits a doublet with an intensity minimum at the exciting frequency and with a peak separation of 1 to 5 Gc/sec, depending on the liquid. We shall discuss our observations of the polarization characteristics, line shape and intensity of the spectrum, along with measurements of the k-vector dependence of the doublet splitting. These results confirm in detail many of the features predicted in the theory of Rytov for light scattering by shear waves in liquids and thus lend strong support to the explanation that the depolarized doublet spectrum originates from scattering by thermally excited shear waves. It will also be shown that for those liquids for which the doublet splitting can be resolved, detailed analyses of the spectra yield values of the transverse sound velocity, the high-frequency shear modulus, and the shear relaxation time.
Rôle of the Cat Superior Olive S Segment in the Processing of Auditory Neurophysiological Data
Authors: Boudreau James C. , Tsuchitani Chiyeko
Published: September 2005

S-segment cells with CF's above about 1.0 kHz receive inputs from each ear with the ipsilateral input being excitatory and the contralateral inputs from each ear with the ipsilateral input being excitatory and the contralateral input being inhibitory. Measurements on excitatory and inhibitory tuning curves disclose that the tonal frequencies that are capable of exciting a cell when presented to the ipsilateral ear are nearly identical to the frequencies that inhibit the cell when presented to the contralateral ear. Measurements on excitatory and inhibitory intensity functions reveal that the contralateral input is about as effective in determining the output of the cell as is the ipsilateral input, although in an opposite manner. When the two inputs are equal, there is little or no discharge from S-segment cells. Appreciable discharge results only when the ipsilateral input is greater than the contralateral input. The rôle of the S-segment is to extract dissimilarities from the signals present in the two inputs. Signals common to the two inputs are not transmitted.
Spectral Component Coupling in Wind Instruments
Authors: Worman W. E.
Published: September 2005

The input impedance curves of wind instruments generally show a limited number of resonance peaks. These peaks disappear at a frequency set by the bell cutoff or by the high-pass filter action of a series of open tone holes. The playing frequency and spectrum of a wind instrument tone can be correlated with the input impedance at the harmonics of the playing frequency because the spectral components are primarily coupled to the pipe resonances by the nonlinearity of the valving action of the reed. The basic formalism, which has been reported earlier, will be used to explain the observed connection between “rigidity” of pitch in certain wind instruments and the placement of higher pipe resonances. Clarinet throat tones will also be discussed with reference to the number of associated pipe resonance peaks. There are only two of these for the throat tones, while the other notes of the chalumeau register have three or more.
Learnability of Melodies Generated by a Simple Markov Process
Authors: Smith Kirk H. , Mathews Max V.
Published: September 2005

Subjects without musical background were able to distinguish and remember melodies whose pitches were generated by a Markov process first described and investigated by G. Miller in a study of memory for letter strings. In a discrimination study, our subjects learned to classify successfully melodies as being the product of either the Markov generator or a completely random generator. In a recognition memory study, the final note of the melody was shown to be the most important feature affecting memorability. This result apparently reflects a property of the Miller generator, viz., that it always ends with the same pitch. A small change in the Markov process such that either of two pitches occurred with equal probability as the terminal note produced a decrement in the subjects' ability to discriminate. Increases in discriminability were obtained with Markov processes which tended to generate repeated notes or doublets. The subjects apparently learned special properties of the Markov process rather than its general structure.
Discrimination of F2 Transitions in Speech Context and in Isolation
Authors: Mattingly Ignatius G. , Liberman Alvin M. , Syrdal Ann K. , Halwes Terry
Published: September 2005

Parallel tests suggest that perception of a stop-consonant cue depends on whether the cue is presented in a speed]like context or in isolation. Subjects were asked to label as /bæ/, /dæ/, or /gæ/ two-formant synthetic speech stimuli differing only in the initial F2 transition, to discriminate between pairs of these stimuli, and to discriminate between corresponding pairs of isolated F2 transitions. A subject's discrimination function for transitions in speech context typically shows two sharp peaks, matching the crossover points of his three labeling functions; these peaks at phoneme boundaries exhibit little intersubject variation. For the isolated transitions, the two peaks that characterize the speech functions are absent; such peaks as do occur are generally lower and more variable, both in position and height. Evidently, the discrimination peaks that occur at the phoneme boundaries are not inherent in the perception of the F2 transition itself. [Support by ONR, NICHD, and VA is acknowledged.]
Catalytic Factors in Speech Perception
Authors: Thomas Ian B.
Published: September 2005

Speech from which all formant information except the second formant frequency has been removed by filtering and infinite clipping is still highly intelligible. Spectrograms of such speech exhibit a normal formant band and higher “harmonic” bands representing clipping distortion. This spectral configuration was approximated by use of a multivibrator whose period was controlled by the output of a second formant tracker. A voice operated gate was interposed between the multivibrator and the output terminals of the device. The resulting signal, although possessing a spectrogram closely comparable to that of the filtered-clipped speech already mentioned, is not at all speechlike and has zero intelligibility. Addition of random noise or a signal repetitive at typical glottal rates to the multivibrator control signal renders the signal speechlike and somewhat intelligible. It appears that the perturbations in individual multivibrator periods caused by the noise or repetitive signal are catalytic factors which enable this synethetic speech to be perceived as such. [Work supported by NASA.]
Fundamental Frequency Estimation by Harmonic Identification
Authors: Snow T. B. , Hughes G. W.
Published: September 2005

A novel method of fundamental frequency estimation is presented utilizing the inherent line spectrum characteristic of the speech signal. After finding the strongest harmonic in a limited frequency range, a computer program determines and examines the expected positions of lower and higher harmonics and assigns the proper harmonic number. An array of previously measured filter responses provides a frequency estimation of the identified harmonic. Two adjacent harmonics are necessary for proper identification, but the fundamental component need not be present in the limited filter bank range. The range of frequency estimation is limited only by hardware and is 75<fo<335 in this particular application. The effective bandwidth of the filter is greater than 12% of center frequency; however, the interpolation provides eighth-tone resolution (1.5%). Period-by-period measurements are compared to computer output for continuous speech sampled at a rate of 100 samples/sec. [This work was supported in part by the Air Force Cambridge Research Laboratories under contract.]
Experimental Study of the Scattering of Sound
Authors: Dill J. F. , Perez D. , Hunter J. L.
Published: September 2005

Measurements of ultrasonic absorption in critical binary mixtures have given rise to a controversy over the mechanism of attenuation. Measurements by Brown and Richardson indicate the presence of a scattering phenomenon, while those of D'Arrigo, Sette, Mistura, and Hunter can be interpreted as a thermal relaxation process. The latter failed to detect any significant scattered signal. To establish a criterion for signal strengths to be expected from scattering and to develop a workable method for detecting such signals, a fundamental scattering study at 2 MHz has been inaugurated. Patterns obtained with simple scattering structures will be presented—single slit, multiple slit, grating, etc.—and the variation of pattern with parameters—wavelength, slit dimensions, hydrophone dimensions, etc.—will be discussed. [Work sponsored by the Office of Naval Research.]
Accuracy Requirements for Damping Estimation in the Calculation of Resonant Response of Complex Structures
Authors: Himelblau Harry
Published: September 2005

Great progress has been made in the mathematical modeling of the stiffness and mass properties of complex structures using lumped-and distributed-parameter representations, permitting accurate prediction of natural frequencies and mode shapes for lower- and middle-order modes. However, in calculating the dynamic response to various types of applied loading, it is common practice to assume that energy dissipation occurs as viscous, complex, or simple frequency-dependent damping rather than realistic spatially distributed material, friction, viscoelastic, radiation, or hydrodynamic damping. Because the assumed damping cannot be adequately compared with the realistic damping, conservatism is used and overdesign results despite a sophisticated analysis. On the other hand, great progress has been made in the engineering description of realistic damping mechanisms and their applications in certain cases for simple structures, such as simple oscillators, beams, plates, and cylindrical shells. These are briefly reviewed and suggestions made for application to more complex structures. Special techniques are recommended for highly nonlinear mechanisms: substantial amounts of friction damping, and material damping above the endurance limit. The sensitivity of these mechanisms to fabrication processes and to the number of applied cycles is described, and suggestions made for future studies. Damping inadequacies are compared with other problems in predicting the dynamic response, such as the representation of the applied loading, the determination of possible failure locations, and the characterization of the failure mechanism. The rôle of damping in stability analysis is also reviewed.
Measuring Distances of English Phonemes Using Magnitude Estimation
Authors: Singh Sadanand , Brokaw Sonia P.
Published: September 2005

The dissimilarity between English phonemes was determined (separately for consonants and vowels) using a method of magnitude estimation. The stimuli were 23 consonants and 12 vowels of English. The consonants were presented before the vowel [a]; the vowels were presented in isolation. The auditors (18 female students of Speech) were presented 506 pairs of consonants and 132 pairs of vowels [n(n−1)] as recorded by a speaker of English. The auditors' task was to draw horizontal lines estimating the similar soundingness of each pair of stimuli. The results showed a direct relationship between the phonological account of dissimilarity and psychological estimates of magnitude of difference. The statistical models of Multidimensional Scaling (MDS) (Shepardd, Kruskal) and the Hierarchical Clustering Schemes (HCS) (Johnson) were used to indicate the appropriate number of dimensions needed to classify English phonemes and the differing degrees of weights on the different phonological features—i.e. the degree of intensity with which the phonemes relate to each other. [This work was partially supported by a grant from the Office of the Academic Vice-President, Howard University.]
Globe Valve as an Analog to the Speech Phonation Mechanism
Authors: Strumpf F. Michael
Published: September 2005

Dealing with the phonation mechanism involves various physiological activities. During speech, i.e., exhalation, pressure is built up and released at the larynx, different volumes of air flow through the glottis, and the resistance of the glottis is changed continuously. Different papers discuss the relations among pressure difference, volume flow, and resistance. The activities concerned are rather involved. However, dealing with an instantaneous condition, what relations are expected, having in mind the influence of pitch and intensity as additional parameters? The globe valve as an analog is a relatively simple device, the characteristics of which can easily be followed. It will be shown that intensity will increase with increasing pressure difference, and resistance while the flow is kept constant. This condition will represent low pitch. At high pitch, on the other hand, intensity will increase with growing pressure difference or volume velocity while the resistance is kept constant. The analog is meant mainly as a control technique to facilitate easier understanding of the complex existing conditions.
Equation of State of Water and Seawater
Authors: Fisher F. H. , Dial O. E.
Published: September 2005

Equations of state for both water and sea water have been evaluated making use of the recent highly accurate work by Kell and Whalley on pure water. It was found that fits of 5 ppm from 0°–150° and 1–1000 bar could be obtained using: (1) the Tumlirz equation (P+P0) (v—v0)=λ from 0° to 70° and the differential form of the Tait equation (dv/dP)=C/(B+P) from 40° to 150°. It is shown how Kell and Whalley data can be used to normalize other PVT data including sea water. The data of Wilson and Bradley on sea water can be represented with fits of 70 ppm by a modified Tumlirz equation, v=v0+k1S+λ(P0+k2S+P)−1, where the constants λ, P0 and v0 are the pure water values, S is salinity, and k1 and k2 are constants. The fact that the equation of state for pure water appears to change from one form to another around 50° is particularly interesting since this is the region of the compressibility minimum and suggests that if the two-state model of water is valid, then each state may have its own PVT equation. Evaluation of Vedam and Holton's data from 30°–80° on water to 10 000 bar reveals that the Tait differential equation provides three times better fits than the Tumlirz equation. [This paper represents results of research sponsored by the Office of Naval Research and the National Science Foundation.]
Relaxation Phenomena in Electrolytic Solutions
Authors: Fritsch K. , Hunter J. L. , DILL J. F. , Montrose C. J. , Litovitz T. A.
Published: September 2005

Sound-velocity and absorption measurements were made in a number of aqueous electrolytic solutions, principally the divalent sulfates. Ultrasonic pulse measurements were used between 30 and 900 MHz, and Brillouin scattering was employed for measurements between 6000 and 7000 MHz. In several of the solutions studied, the ultrasonic data indicate the existence of two relaxation processes with relaxation times between 5×10−9 and 2×10−10 sec. These two relaxations, considered together with the previously observed long relaxation-time process, can be interpreted in terms of the Diebler-Eigen model of ionic association that predicts three relaxation processes. The appropriate rate constants were calculated using data by other workers below 50 MHz and the present data above 50 MHz. Because, in this work, data as a function of concentration were not available, a calculation procedure was developed that allowed estimates of the rate constants to be made without the concentration dependence. Using this procedure, all the rate constants were calculated and compared with earlier results based on data taken below 200 MHz. [Work sponsored by the Office of Naval Research and the Office of Saline Water.]
Absolute Identification of Sound Intensity: Dependence of Observer Sensitivity on Range and Number of Stimuli
Authors: Braida L. D.
Published: September 2005

When an observer attempts to identify sounds differing only in intensity by comparing each sound with the context of sounds presented in the experiment, his accuracy is limited by his inability to determine the context precisely and by errors made in determining or representing the relation of the sound to the context. As a result, sensitivity to a given intensity increment depends on the range of stimulus intensities presented. Research has been conducted to examine this dependence in absolute identification experiments. Observer sensitivity was measured as a function of intensity range with 10 stimuli, and as a function of the number of stimuli for a fixed 54-dB range. For small ranges, cumulative sensitivity is essentially proportional to range. For large ranges, cumulative sensitivity is approximately independent of range. Cumulative sensitivity is nearly independent of the number of stimuli used when the range is fixed. [Work supported principally by the National Institutes of Health and in part by the Joint Services Electronics Program.]
Damping Nonlinearities and Transient Inputs
Authors: Reed R. R.
Published: September 2005

Damping is generally considered to be linear in the mathematical analysis of lumped parameter systems by their associated modal equations of motion. Considering all sources of damping, the damping force should be represented by both linear and nonlinear functions of the modal displacement and velocity and/or a hysteresis curve. One procedure for studying the various representations of damping is based on the energy loss per cycle for each representation. For transient systems, the energy loss per cycle includes an exponential decay factor. For both steady-state and transient systems, the energy loss is a function of the response amplitude to a power and frequency to a different power. To represent “gross” damping, an empirical equation with energy loss equal to a polynomial in modal amplitude and frequency is used. Coefficients of this polynomial are determined from a curve-fit program using experimental data. Applying the curve-fit program requires accurate experimental data. An alternate approach for studying various representations of damping is based on the amplitude versus frequency curve for steady-state response. The shape of this curve changes as the damping changes. To obtain an amplitude versus frequency curve from the modal equation of motion, the Ritz averaging method is used. Similarly for transient systems, differences occur in the amplitude-versus-time curves (ringout curves). The approximate analytical solution for a transient modal equation is obtained using the exponential series method. Finally, a discussion of what experimentation and research should be initiated to permit additional insight into nonlinear damping and transient systems is included.
Vibrations of Ring-and-Stringer-Stiffened Conical Shells
Authors: Crenwelge O. E. , Muster D.
Published: September 2005

Strain-displacement relations are developed for a thin truncated circular conical shell and its reinforcing rings and longitudinal stringers (an idealization of a spacecraft interstage adapter). Using these relations in an energy approach, methods are developed for determining the resonant frequencies of simply supported conical shells in unstiffened, ring-stiffened, and ring-and-stringer-stiffened configurations. These stiffeners may be widely separated or closely spaced. Results obtained by these methods are compared with the experimental data available in the literature for unstiffened and ring-stiffened shells and measurements made by the authors in tests of ring-stiffened and ring-and-stringer-stiffened conical shells.
Comparative Annoyance of “Approaching” versus “Receding” Sound Sources
Authors: Nixon Charles W. , von Gierke H. E. , Rosinger George
Published: September 2005

Sound sources that continuously increase in frequency and/or intensity over a period of several seconds may be perceived by observers as approaching entities, whereas the converse is true for sources with decreasing signal characteristics. The comparative annoyance of such sounds signaling “approaching” and “receding” sources was evaluated by means of paired-comparison judgments of several signals of 15 sec duration that continuously varied in both frequency (from 600 to 1200 or 1200 to 600 Hz) and intensity (from 70 to 100 or 100 to 70 dB). Findings clearly demonstrate that signals characterized as approaching entities were judged more annoying than all other signals assuming constant average intensity and frequency content over the signal duration. Increasing intensity influenced judgments of annoyance to a greater extent than did frequency changes. Rank order or annoyance corresponded to the hypothesis that the “approaching” characteristics of a sound source contribute significantly to its judged annoyance. The importance of these findings for the evaluation of aircraft flyover noises is discussed.
Adaption of Current Auditory Damage-Risk Criteria for use in Aerospace Operations
Authors: Gasaway Donald C. , Sutherland Harrell C.
Published: September 2005

The need for valid and realistic auditory-risk criteria for use in identifying and determining potentially hazardous noise encountered during ground and airborne areospace operations is discussed. The noises encountered during military operations are multifarious and complex. The set of criteria proposed by Working Group 46 of the National Research Council's Committee on Hearing, Bioacoustics and Biomechanics has been modified so that the criteria used in assessing wide-band and narrow-band continuous and intermittent-type noise can be more easily accomplished. The authors have devised an auditory-risk calculator that facilitates and simplifies the task of assessing wide-band and narrowband noise exposures. In addition, a simple chart has been prepared for use in evaluating intermittent-type noises. Examples of noise exposures encountered in ground and airborne aerospace operations are illustrated, and applications of the three basic types of auditory risk criteria are demonstrated. Desirable and undersirable features of older and newer types of criteria are discussed. The spectrum of criteria is reviewed and specific features of auditory risk criteria required in aerospace operations are identified and discussed.
Measurement of Sonic Booms Using Capacitive Transducers
Authors: Skode Frede
Published: September 2005

This paper discusses the techniques for detection of low-frequency signals, such as those encountered in sonic booms and thunderstorms, etc. The techniques for using a self-balancing carrier system having a choice of low-frequency limit going from 0.01 through 0.1 to 1 Hz and some additional features are discussed more thoroughly.
On the Performance of Small Sound Sources in Planar Arrays. Part I
Authors: Andrulis Marilyn W. , Gruber George J.
Published: September 2005

The gradual changes in the velocity distribution over an underwater sound array of acoustically small circular radiators (ka−0.71) mounted in an infinite, rigid baffle are traced from the initial distribution to the final distribution. The mechanism by which the velocity distribution is altered is explained by two iterative approaches: Green's function formalism and the governing network equations. Also, the steady-state velocity distribution is found directly by solving N simultaneous equations, the elements of the coefficient matrix being the mutual radiation impedances. The iterative and simultaneous equation approaches are shown to be equivalent.
Advantages and Disadvantages in Various Accelerometer Designs
Authors: Jensen Jens August
Published: September 2005

A discussion of various configurations used in accelerometer design. Advantages and disadvantages of different mechanical designs and different piezoelectrical materials. A rating is proposed, taking into consideration the electrical impedance, sensitivity, frequency range, and mass. Also, the influence of base bending, temperature, and other environmental effects is discussed.
Lateralizability and Detectability of a Low-Frequency Tone as a Function of Signal-Masker Phase
Authors: Robinson Donald E. , Yost William A.
Published: September 2005

Using a two-alternative temporal forced-choice technique, the detectability of a 250-Hz 128-msec, tonal signal masked by a gated 70-dB SPL tone of the same frequency and duration was measured as a function of the level of the signal, the phase angle at which the signal was added to the masker and the interaural phase difference of the signal. When the interaural phase difference is 0°, the detectability is found to follow a simple energy- or power-detection model. When the interaural phase difference is 180°, the task becomes one of lateralization. In this case, the signal level required for detecting the lateralized image is determined by the interaural phase and amplitude difference between the vector sum of the signal plus masker to one ear and the vector sum to the other ear. The data are discussed in terms of binaural masking-level differences and lateralization. The results are also compared to those reported by Wightman at the 74th meeting of ASA.
Some Aspects of the Theory of Diffusion and Diffusers
Authors: Doak P. E. , Dodd S. D.
Published: September 2005

Fundamental theoretical considerations strongly imply that the degree of diffusion of a sound field in a reverberation room can be satisfactorily defined only when the degree of averaging (over either space or frequency, or both), inherently present in whatever measurement is under consideration, is included explicitly in the definition. A relatively sophisticated computer program for generating analog sets of source/receiver response characterstics in a reverberation room has been devised. Results have been obtained relevant to the following situations and including the uniformity to be expected from different amounts of space or frequency averaging: fixed diffusers, moving diffusers, response characteristics for higher-order source distribution.
Testing of an Artificial Mastoid
Authors: Bruel V.
Published: September 2005

To be able to make exact comparison of the acoustical impedance between the human mastoid or forehead and an artificial mastoid such as described in the British standard 4009/1966 or the Beltone model, a small lightweight impedance head including a force transducer and an accelerometer has been developed. The real problem is that the mass of the human skin is in the order of 0.5 g/cm2, and consequently a mass much higher than 0.5 g between the force transducer and the contact surface of the skin cannot be tolerated. The impedance head should according to the IEC requirement of working group 11 have a contact surface of 1.75 cm2. A series of impedance measurements on different persons has been made with an automatic recording setup both with this small special impedance head and larger standard head.
Cavitation Measurements on Silicone Oils by Utilization of a Pumping Effect
Authors: Lierke Ernest G. , Wollny Heinz
Published: September 2005

Characteristic types of cavitation in silicone oils of different gas content and viscosities between 3 and 760 cP have been investigated microscopically and by utilization of a cavitation-pumping effect. The transducer was a 20-kHz stepped horn with a center hole 3 mm in diameter. At hydrostatic pressures between 30 and 760 Torr and transducer amplitudes between 0 and 24 μ, the static pumping pressure in the centerhole varied between 0 and 100 Torr, with “resonance peaks” up to 250 Torr. The dependency of the pumping pressure on the transducer amplitude shows characteristic and reproducible discontinuities that are related to microscopic observations.
Relation of Hearing Loss to Cochlear Histopathology Produced by Antibiotics in the Monkey
Authors: Stebbins W. C. , Johnsson L.-G. , Hawkins J. E.
Published: September 2005

A method is described for evaluating the effects of ototoxic drugs on hearing in monkeys by behavioral audiometry and phase contrast microscopy of Corti's organ. To date, four animals have been trained by operant conditioning procedures with food reinforcement, and pure-tone thresholds determined by the psychophysical method of constant stimuli. After the normal threshold curve was established (0.5–15 kHz), kanamycin or neomycin was administered daily (100 mg/kg i.m.), and the development of hearing impairment was followed. When a profound loss had appeared in one or more of the higher octaves, the animal was sacrificed and the temporal bones were fixed with osmic acid for microdissection and study of changes in the inner ear by stereo- and phase-contrast microscopy of surface preparations. Hearing impairment followed an orderly progression from the highest frequencies downward and was clearly correlated with the extent and pattern of destruction of Corti's organ found post mortem. [Research supported by PHS grants.]
Subminiature Inertial Reaction Transducer for Air-Conduction Hearing Aids
Authors: Sebesta G. J. , Mellen A. J. , Carlisle R. W.
Published: September 2005

A subminiature inertial reaction transducer has been adapted for use at the inner end of a complaint hearing aid eartip. Sound vibrations are imparted to the inner walls of the meatus and actuate the tympanum by air conduction. The structure of the transducer, preferred methods of mounting it, and experimental results will be presented. The sensitivity is greater than that of a conventional bone-conduction receiver. The frequency response has a characteristic that rises to the natural resonance frequency of the inertial diaphragm. Like a bone-conduction receiver, the device has the intrinsic advantage of freedom from occlusion of a sound passage by ear wax.
Method for Masking Audiometry
Authors: Tobias Jerry V.
Published: September 2005

Masking audiometry, the measurement across the acoustic spectrum of the masking effects of a signal, is usually done with test tones at discrete frequencies. The use of tonal probes for this purpose is sometimes unacceptable, as, for example, when tonal components exist within the signal. Then the test tone and the signal component will beat and otherwise interact to produce perceptual problems for the subject. A technique was devised to permit Békésy masking audiometry in which a narrow band of noise with a continuously increasing center frequency serves as the probe. The method permits the plotting of masking audiograms for any kind of signal, no matter what the components may be. An application of the technique to a problem in periodicity-pitch perception shows the method to be adequately precise and sensitive despite the inherent variabilities of the Békésy-audiometry method.
Fourier Analysis of Sound Fields Generated by Large Rocket Engines
Authors: Polly Robert C.
Published: September 2005

The sound field generated by a rocket engine is rotationally symmetric about the axis of the jet exhaust, and therefore the directional characteristics can be represented by a Fourier series. An expression is derived that shows that the acoustical power can be calculated directly from the Fourier coefficients. A method is presented by which the number of terms necessary to define the sound field within a given error can be determined. The acoustical characteristics of several large rocket engines are briefly examined in this paper.
Rotor/Propeller Rotational Noise Analysis Including Time-Varying Blade Forces
Authors: Healy Gerald J.
Published: September 2005

An analysis of the rotational sound field of a rotor/propeller has led to computational procedure using performance parameters for which values are readily available during the design phase of an aircraft. The procedure has been programmed for an IBM-360 computer. The equations developed are unique in that they incorporate separate radial and azimuthal blade-force distribution functions. They have also been formulated in terms of normalized rotor/propeller performance parameters and dimensions and normalized source-to-field-point distances. Also, a capability has been included for chordwise taper effects. Normalization of the equations facilitates the handling of a wide variety of rotor/propeller sizes by limiting the range of values of terms of the equations and thereby reducing the problem of maintaining sufficient precision during digital computation. In addition, the radial integration has been approximated for handling situations where limited accuracy can be accepted, where computer time is a premium, and where large numbers of field points and/or performance cases must be processed. Application of the new computational procedure has shown that use of time varying azimuthal blade forces results in a radically different radiation pattern than that predicted for steady blade forces (Gutin theory).
Theoretical Prediction of Aerodynamically Generated Noise in Fans and Compressors
Authors: Benzakein M. J. , Kazin S. B.
Published: September 2005

A prediction method for fan/compressor discrete-frequency tone generation and transmission is presented. The method is based on internal unsteady aerodynamics, coupled with an acoustic field described in terms of spinning modes. The sound-pressure levels generated by the rotor alone and the wake interaction between adjacent blade rows are calculated. The analysis of the sound propagation in the duct in the presence of axial and circumferential flows is described and incorporated in the prediction method. The analytical results are compared with experimental data and are shown to be in good agreement.
Measurements of Impulse Noise
Authors: Wahrmann C. G.
Published: September 2005

When measuring ac signals with an averaging instrument, there is always a problem of what is actually measured at the low end of the frequency range. Actually, it is not only the frequency content of the signal itself that is important, but rather the frequency content of the envelope of the signal. It is especially important to know the dynamic properties of the averaging when single short impulses, or repetitive pulses with low repetition rate are being measured. This paper first considers the theoretical behavior of an ideal mean-square circuit to single impulses. Then the behavior of a root-mean-square circuit is shown to be theoretically equivalent to the first, if the circuit has sufficient crest-factor capability. Finally, the results of some impulse sound-level measurements of practical impulse noises are shown. The conclusion is that a good impulse sound-level meter should have a crest factor capability of the order of 10–20, if short impulses are to be correctly evaluated.
Loudness Meter
Authors: Hackley R. A. , Olson H. F. , McCoy D. S.
Published: September 2005

A loudness meter is an instrument that measures and indicates the average person's loudness response to speech, music, and noise. The operation and design of a loudness meter is based on the subjective theories and information on the relation between the sound-pressure level and spectrum of the complex sound and the loudness. The loudness instrument which has been developed consists of the following basic elements: input network, octave filters, logarithmic converters, phon-to-sone converters, loudness compensators, summation logic, dynamical transient integrator, and a numerical indicator of loudness. Limited tests of the loudness meter employing various sound programs indicate that the performance of the meter agrees with subjective experience.
Digital Technique for Determining One-Third Octave Sound-Pressure Levels with More Uniform Confidence Level
Authors: Shipley John W. , Slusser Ronald A.
Published: September 2005

This paper describes a computer program that was written to analyze acoustical test data. It employs a fast Fourier subroutine to calculate the discrete Fourier coefficients that transform the time-domain data to the frequency domain. In order to achieve a more equal confidence level between the upper and lower 13 octaves, the digital data record is sampled at a high rate and the fast Fourier coefficients are calculated. Next the same digital data record is sampled at a much lower rate. This gives greater low frequency resolution to the lower 13 octaves. Consideration is given to digital windowing techniques for the purpose of comparison with analogous analysis methods and their effect on spectral representation.
Biomarker Evidence for Photosynthesis During Neoproterozoic Glaciation
Authors: Olcott Alison N. , Sessions Alex L. , Corsetti Frank A. , Kaufman Alan J. , de Oliviera Tolentino Flavio
Published: September 2005

Laterally extensive black shales were deposited on the São Francisco craton in southeastern Brazil during low-latitude Neoproterozoic glaciation ∼740 to 700 million years ago. These rocks contain up to 3.0 weight % organic carbon, which we interpret as representing the preserved record of abundant marine primary productivity from glacial times. Extractable biomarkers reflect a complex and productive microbial ecosystem, including both phototrophic bacteria and eukaryotes, living in a stratified ocean with thin or absent sea ice, oxic surface waters, and euxinic conditions within the photic zone. Such an environment provides important constraints for parts of the “Snowball Earth” hypothesis.
Fnr-, NarP- and NarL-Dependent Regulation of Transcription Initiation from the
Haemophilus influenzae
Rd
napF
(Periplasmic Nitrate Reductase) Promoter in
Escherichia coli
K-12
Authors: Stewart Valley , Bledsoe Peggy J.
Published: September 2005

Periplasmic nitrate reductase (
napFDAGHBC
operon product) functions in anaerobic respiration. Transcription initiation from the
Escherichia coli napF
operon control region is activated by the Fnr protein in response to anaerobiosis and by the NarQ-NarP two-component regulatory system in response to nitrate or nitrite. The binding sites for the Fnr and phospho-NarP proteins are centered at positions −64.5 and −44.5, respectively, with respect to the major transcription initiation point. The
E. coli napF
operon is a rare example of a class I Fnr-activated transcriptional control region, in which the Fnr protein binding site is located upstream of position −60. To broaden our understanding of
napF
operon transcriptional control, we studied the
Haemophilus influenzae
Rd
napF
operon control region, expressed as a
napF-lacZ
operon fusion in the surrogate host
E. coli
. Mutational analysis demonstrated that expression required binding sites for the Fnr and phospho-NarP proteins centered at positions −81.5 and −42.5, respectively. Transcription from the
E. coli napF
operon control region is activated by phospho-NarP but antagonized by the orthologous protein, phospho-NarL. By contrast, expression from the
H. influenzae napF-lacZ
operon fusion in
E. coli
was stimulated equally well by nitrate in both
narP
and
narL
null mutants, indicating that phospho-NarL and -NarP are equally effective regulators of this promoter. Overall, the
H. influenzae napF
operon control region provides a relatively simple model for studying synergistic transcription by the Fnr and phospho-NarP proteins acting from class I and class II locations, respectively.
Identification of GutQ from
Escherichia coli
as a
d
-Arabinose 5-Phosphate Isomerase
Authors: Meredith Timothy C. , Woodard Ronald W.
Published: September 2005

The glucitol operon (
gutAEBDMRQ
) of
Escherichia coli
encodes a phosphoenolpyruvate:sugar phosphotransferase system that metabolizes the hexitol
d
-glucitol (sorbitol). The functions for all but the last gene,
gutQ
, have been previously assigned. The high sequence similarity between GutQ and KdsD, a
d
-arabinose 5-phosphate isomerase (API) from the 3-deoxy-
d
-
manno
-octulosonate (KDO)-lipopolysaccharide (LPS) biosynthetic pathway, suggested a putative activity, but its role within the context of the
gut
operon remained unclear. Accordingly, the enzyme was cloned, overexpressed, and characterized. Recombinant GutQ was shown to indeed be a second copy of API from the
E. coli
K-12 genome with biochemical properties similar to those of KdsD, catalyzing the reversible aldol-ketol isomerization between
d
-ribulose 5-phosphate (Ru5P) and
d
-arabinose 5-phosphate (A5P). Genomic disruptions of each API gene were constructed in
E. coli
K-12. TCM11[(Δ
kdsD
)] was capable of sustaining essential LPS synthesis at wild-type levels, indicating that GutQ functions as an API inside the cell. The
gut
operon remained inducible in TCM7[(Δ
gutQ
)], suggesting that GutQ is not directly involved in
d
-glucitol catabolism. The conditional mutant TCM15[(Δ
gutQ
Δ
kdsD
)] was dependent on exogenous A5P both for LPS synthesis/growth and for upregulation of the
gut
operon. The phenotype was suppressed by complementation in
trans
with a plasmid encoding a functional copy of GutQ or by increasing the amount of A5P in the medium. As there is no obvious obligatory role for GutQ in the metabolism of
d
-glucitol and there is no readily apparent link between
d
-glucitol metabolism and LPS biosynthesis, it is suggested that A5P is not only a building block for KDO biosynthesis but also may be a regulatory molecule involved in expression of the
gut
operon.
Flavobacterium johnsoniaeGliding Motility Genes Identified bymarinerMutagenesis
Authors: Braun Timothy F. , Khubbar Manjeet K. , Saffarini Daad A. , McBride Mark J.
Published: September 2005

Cells ofFlavobacterium johnsoniaeglide rapidly over surfaces. The mechanism ofF. johnsoniaegliding motility is not known. Eightgldgenes required for gliding motility have been described. Disruption of any of these genes results in complete loss of gliding motility, deficiency in chitin utilization, and resistance to bacteriophages that infect wild-type cells. Two modifiedmarinertransposons,HimarEm1andHimarEm2, were constructed to allow the identification of additional motility genes.HimarEm1andHimarEm2each transposed inF. johnsoniae, and nonmotile mutants were identified and analyzed. Four novel motility genes,gldK, gldL, gldM, andgldN, were identified. GldK is similar in sequence to the lipoprotein GldJ, which is required for gliding. GldL, GldM, and GldN are not similar in sequence to proteins of known function. Cells with mutations ingldK, gldL, gldM, andgldNwere defective in motility and chitin utilization and were resistant to bacteriophages that infect wild-type cells. Introduction ofgldA, gldB, gldD, gldFG, gldH, gldI, andgldJand the region spanninggldK, gldL, gldM, andgldNindividually into 50 spontaneous and chemically induced nonmotile mutants restored motility to each of them, suggesting that few additionalF. johnsoniae gldgenes remain to be identified.