bluuebunny/crossref_metadata_2025 huggingface dataset:
Loudness Decrement: Monaural and Dichotic, Forwards and Backwards
Authors: Elmasian R. , Bernheim A. , Galambos R.
Published: May 2012

In a loudness decrement task subjects received a tone burst (Tc) separated at an interburst interval (ΔT) from a signal (S1) whose loudness they matched by adjusting the amplitude of another burst (S2) presented 1.5 sec later. All Signals were 5-kHz 20-msec tone bursts with ΔT set at plus or minus 100 msec. S1 was fixed at either 88 or 90 dB SPL and Tc was varied in 10-dB steps between 90 dB and threshold. When Tc was less intense than S1, the loudness of S1 was decremented by up to 5 dB. The function was U shaped, the decrement being largest with Tc at 50–60 dB and smallest with Tc at 90 dB and near threshold. Similar functions were obtained when Tc preceded (the forward case) and when Tc followed (backwards) S1 and with Tc presented to the same ear and to the ear contralateral to that receiving S1.
Perstimulatory Loudness Adaptation: The Effect of Comparison-Signal Duty Cycle
Authors: Ahaus W. H. , Stokinger T. E. , Vaughan R.
Published: May 2012

Using a double-staircase method, perstimulatory loudness adaptation was measured on a group of normal-hearing listeners for a variety of comparison-signal conditions. Signal on times ranging from 500 msec to 5 sec were employed in combination with duty cycles ranging from 10% to 8313%, resulting in a total of 22 different signal conditions. Adapting and comparison signals were 1-kHz pure tones, with the adapting tone always presented at 50 dB SPL. Mean data revealed that the duty cycle of the comparison signal had no systematic effect on adaptation in the test ear. This finding does not lend support to the previous assumption by Stokinger et al. [J. Acoust. Soc. Amer. 51, 602–607 (1972)] that there was a direct relationship between the duty cycle of the comparison signal and the amount of adaptation. [Work supported by the Research and Education Committee, Oklahoma City V. A. Hospital, under Project No. 20-69.]
Broad-Band Noise and Monaural Adaptation
Authors: Weiler Ernest M. , Agnello Joseph
Published: May 2012

The comparison stimulus used in the present experiment was white noise (20–20 000 Hz), with energy at 1000 Hz ± 50 Hz filtered out. The adapting tone was a 70-dB-SPL 1000-Hz tone. Both stimuli were presented simultaneously to the preferred ear. The adapting period was 7 min. Average adaptation was 6.5 dB for 11 Subjects. Adaptation values ranged from 0 to 1.58 dB (Wilcoxon T = l, p≤0.01). A small but significant amount of monaural adaptation is found with this technique, suggesting that auditory adaptation, at the least, is not entirely a phenomenon resulting from binaural interaction. The 6.5-dB value found is much less than the average 22.3-dB adaptation measured using a pure-tone comparison stimulus in another study run at approximately the same time. The report of subjects that there was difficulty in distinguishing the adapting tone from the white noise may account for the smaller amount of adaptation found in the present study.
Behavioral Measurement of Loudness Recruitment in the Monkey
Authors: Moody D. B.
Published: May 2012

When monkeys are trained to release a response key to the onset of a pure-tone stimulus, latency of key release is inversely related to tone intensity. Equal values of the behavioral measure (latency) can be said to reflect equal subjective intensities (loudness) and can be used to determine loudness matches. This technique was used to assess the extent of occurrence of loudness recruitment in the presence of noise-induced TTS and during tone-on-tone masking. Under these conditions, latencies measured at lower intensities are lengthened, while latencies at high intensities remain unchanged. When a conductive loss is produced, latencies at all intensities are increased such that the latency-intensity function appears to be shifted by a constant number of decibels. The data obtained are, in general, consistent with human data on loudness recruitment. Both TTS-producing exposures and tone-on-tone masking result in complete recruitment 20–30 dB above the shifted threshold. With both TTS and masking, overrecruitment is occasionally observed. [Research supported by grants from NIH.]
Sound Fluctuations at Sea: Dispersive Effects in the Upper Ocean
Authors: Medwin Herman
Published: May 2012

The temporal and spatial variations of the index of refraction, μ, cause fluctuations of sound phase and amplitude that can be understood only by defining μ in terms of the duration, location, and range of the acoustical experiment. A “universal” isotropic spatial correlation function of μ has been derived from a simplified form of the Kolmogorov-Batchelor spectrum of temperature fluctuations in a turbulent medium. However, such a correlation function, although more accurate than the popular Gaussian form, appears to be correct only for spatial lags less than 1 or 2 m at sea. Furthermore, in-situ experiments have confirmed that the common presence of ambient bubbles in the upper several meters of the ocean produces a microstruc-ture of the index in which the temperature is much less important than the bubble distribution. In this bubble-dominated region the average speed of sound, the variance, and the frequency spectrum of the fluctuations of the speed are all strong functions of the sound frequency, the ocean wave spectrum, and the depth of the experiment. The phase fluctuations due to propagation in the upper ocean volume are compared with those occuring during forward scatter from the surface itself. [Research support by Naval Ship Systems Command.]
Experimental Agreement of a Stochastic Say Theory for Underwater Sound Fluctuations
Authors: Neubert J. A.
Published: May 2012

The conventional undersea ray theory intensity relation was modified earlier [J. A. Neubert, J. Acoust. Soc. Am. 51, 310–322 (1972)] to allow consideration of the effects of ocean fluctuations. This study compares the earlier theoretical model with actual sea data. It investigates the theoretical relations for the standard deviation and the coefficient of intensity fluctuation in a real (variable and random) ocean. In all cases (plus an unexpected bonus, the kurtosis), good agreement is found to within the sampling limitations imposed by the sea data. The higher-order statistical quantities are remarkably well behaved (even beyond the predictions of the model). In fact, this seems to be the only theoretical model that correctly predicts higher statistical moments in the real ocean.
Fluctuation Statistics of Sound in Shallow Water
Authors: Smith P. W.
Published: May 2012

Many different stochastic measures, second-order in the pressure amplitude, can and have been made of sound fields in shallow water: variance of pure-tone amplitude and phase, spatial and frequency coherence intervals, impulse response, etc. The experimental literature is summarized, and a conceptually simple stochastic model is proposed based on the physical processes involved. The stochastic field is described as a superposition of locally plane waves, including a spatially variable “coherent” component and a statistically independent surface-scattered component, variable in space and time. Simple estimation formulas for stochastic measures are found in the canonical problem of constant sound speed. Comparisons of predictions with reported data show few contradictions. However, the experiments and their reports seldom provide a sufficient basis for a critical test of theory.
Line Array Performance When the Signal Coherence is Spatially Dependent
Authors: Cox Henry
Published: May 2012

The effects of a signal coherence which decreases exponentially with sensor separation are examined for a number of line array processors. For the conventional beamformer the limiting gain as the array is made infinitely long is simply (1 + ρ)/(l − ρ), where ρ is the signal coherence between adjacent sensors. The gain of the optimum processor is presented. A simple suboptimum processor which incoherently combines the outputs of a number of subarrays is found to provide near optimum performance. The performance of the split-beam multiplicative processor is shown to degrade rapidly as signal coherence decreases. [This work was done at the University of California, San Diego, Marine Physical Laboratory of the Scripps Institution of Oceanography, San Diego, California 92132.]
Coherence of Sea Surface Reflected Pulses
Authors: Reeves J. C. , Stern R.
Published: May 2012

Forward reflected undersea pulses are known to fluctuate and undergo severe distortion from arrival to arrival. The coherence of high-frequency surface reflected pulses has been measured by cross correlating the transmitted pulse with the reflected arrival. Both pulsed CW and linear FM pulses were utilized, with bandwidths ranging from 50 to 2000 Hz. Considerable care was taken to resolve the surface path from direct and bottom arrivals, thus enabling one to compute a normalized cross-correlation coefficient versus bandwidth. Data strongly shows that the normalized coefficient decreases with increasing bandwidth. Temporal elongation of the reflected pulse appears to be the major cause of decorrelation of the wider bandwidth signals. A statistical model of the sea surface is adopted based upon known properties such as the dependence of mean-square slopes and correlation lengths upon wind speed. Ray theory is used to compute the expected number of ray paths from facets and their attendant travel times. The problem is tractable, assuming Gaussian surface statistics. Woodward cross-ambiguity theory then allows one to predict signal coherence loss due to time spreading from the foregoing analysis, resulting in good agreement with experiment.
Vibration Signature Analysis for Electric Arc Furnaces
Authors: Higgs Roland W.
Published: May 2012

Electric arc furnaces have been used for many years to melt scrap iron and steel but operating practice and control still rely heavily on trial-and-error techniques. Some of the major operating problems encountered in the melting process are excessive refractory wear, electrode breakage, and electrical power control. These problems exist primarily because the status of the melt cannot be accurately determined for each heat. Vibration signature analysis is now being developed to determine the onset and termination of different phases of the melt. A vibration sensor, attached to the side wall, sends an analog vibration signal to a Fourier analyzer which provides the power spectrum of the vibration signature. The power spec-trums are correlated with condition of the scrap in the furnace. These signatures are different for each phase of the melt, and the features in the signatures which distinguish them from each other are utilized in an algorithm which is designed to indicate changes in the status of the melt. The electric arc furnace, its operation and problems, and the signature system are described.
A New Method for Flaw Characterization: Ultrasonic Frequency Analysis
Authors: Adler Laszlo
Published: May 2012

Reliable flaw characterization appears to be an important part of today's nondestructive testing technology. Flaw characterization refers to the determination of size, shape, orientation, etc., of a flaw. Ultrasonic amplitude-based techniques, such as pulse-echo through transmission techniques, can very well detect certain types of defects in metals, but they give very little or no information about the “character” of the flaw. It has been recognized for some time that, in addition to the amplitude, the frequency and phase measurements can give information about a “target.” We have used a broad-band ultrasonic pulse which is spectrum analyzed upon scattering from a flaw. The frequency distribution of the scattered pulse is related—by an analytic model—to the size and orientation of the flaw. The analytic model assumes interference between the wavelets scattered from various regions of the flaw. There is good agreement between actual flaw size and the size predicted from this method for artificially simulated flaws. Various applications of ultrasonic frequency analysis in NDT are discussed.
Dynamic Elastic Moduli of Socks and Their Use in the Petroleum Industry
Authors: Thompson Don D.
Published: May 2012

There is a recurring need in the petroleum industry to formulate the elastic moduli of various sedimentary rocks in terms of their mineralogy, fluid content, texture, and extrinsic variables such as temperature and pressure. Several existing theories and some evolving ones are currently being studied. They are used in all areas of petroleum technology, exploration, well logging, and production. Exploration geophysicists and geologists utilize velocity and attenuation data derived from surface seismic sources. Development geologists make use of the same information in evaluating reservoirs from subsurface sondes that are lowered into drilled holes. Producing engineers study the static moduli of geologic formations in order to better understand and control problems of subsidence in oil fields. We have formulated the problem of the acoustic response of rocks according to the basic principles first enumerated by Hashin and Shtrikman [J. Mech. Phys. Solids II, 127 (1963)] and then generalized by Korringa [J. Math. Phys. 14, 509 (1973)]. The basic assumptions are that the rock is isotropic and homogeneous and obeys Hooke's law. Calculations are shown for typical cases wherein the fluid-filled pores are permitted to have a variety of ellipsoidal shapes. Some data are shown for comparison.
In Vitro Visualization of Liver Metastases Using Ultrasonic Impediography
Authors: Jones Joie Pierce
Published: May 2012

A new technique suitable for medical diagnoses and nondestructive testing was recently introduced by the author [J. Acoust. Soc. Am. 52, 178–179(A) (1972); 53, 343(A) (1973)]. Termed impediography, this method employs time-domain deconvolution of appropriately shaped acoustic impulses and their echoes to produce a temporal waveform that can be related to physical parameters such as impedance. Thus, proper analysis of reflected pulses yields the specific acoustic impedance as a function of acoustic travel time. This acoustic “picture” is termed an impedogram. In this paper several impedograms of a human liver, obtained at postmortem, are presented. A number of metastatic deposits were identified by impediography and confirmed by autopsy. Standard diagnostic procedures failed to find the lesions located by impediography.
Lateral Resolution of a Broad-Band Dual-Element Ultrasonic Transducer
Authors: Jethwa C. P.
Published: May 2012

In the pulsed ultrasonic Doppler blood flowmeter, two types of resolution are of importance; these are the range resolution and the lateral resolution. A random signal correlation type of a pulsed ultrasonic system has been developed recently. In this system broad-band noise is used as the transmitted signal. Since the range resolution and the bandwidth of the transmitted signal are inversely related to each other, an improvement in range resolution is thus achieved. The lateral resolution of the system depends upon the dimensions of the ultrasonic transducer face. This may be improved by focusing the ultrasonic beam with lenses. However, this technique increases the complexity of the system and is associated with the risk of generating acoustic intensities harmful to living tissues. To obviate these difficulties, a broad-band dual-element ultrasonic transducer was developed. This paper describes the dual-element transducer and presents experimental results comparing the lateral resolution of the dual-element transducer with the existing single-element transducer. A tenfold improvement in the lateral resolution in the nearfield was achieved, while a fivefold improvement was achieved in the farfield.
Categorical Perception of Musical Intervals
Authors: Burns Edward M. , Ward W. D.
Published: May 2012

A body of evidence indicates that certain speech units are perceived in a special mode called “categorical perception,” the characteristics of which are (1) the existence of well-defined identification functions and (2) the ability to predict precisely the discrimination functions from the identification functions, based on the assumption that the subjects can discriminate two stimuli no better than they can differentially identify them. Categorical perception is usually assumed to be a unique property of speech and is part of the evidence supporting the idea that “speech is special.” A study of the perception of musical intervals by experienced musicians was performed using the procedures associated with categorical perception experiments; that is, identification and discrimination functions were obtained for points equally spaced along a physical continuum, in this case equal distances in cents along the logarithmic frequency scale defining musical pitch. The results show that the musicians exhibit categorical perception, some to a degree approaching that shown in the perception of stop consonants. The relation of these results to those of the relevant speech perception experiments and of other experiments in musical perception is discussed.
A Frequency Analysis Method for Adjusting Electronic Cello
Authors: Miller J. E. , Mathews M. V.
Published: May 2012

An electronic cello was constructed in a manner similar to previously described electronic violins [J. Acoust. Soc. Amer. 52, 147 (1972)]. The long-time-peak-spectra were measured for the electronic cello and for an acoustic cello. A chromatic scale passage of about 2-min duration was played on and spectrally analyzed for each instrument. The measurement technique is a modification of one described by E. Jansson and J. Sundberg [Progress Rep., Speech Transmission Lab., Royal Inst. Technol., Stockholm, Sweden (Jan. 1973)]. An adjustment network was designed for the electronic instrument to equate the two spectra. Listening tests showed that the network made the electronic instrument sound much more like the acoustic instrument.
Trumpet Acoustics: The Timing Effect of the Mouthpiece and Leaderpipe
Authors: Cardwell W. T.
Published: May 2012

The apparent acoustic length of the mouthpiece-leaderpipe combination increases with frequency through the normal playing frequency range. For example, the apparent length may increase from 23 cm at 165 Hz to 35 cm at 1100 Hz. At higher frequencies it declines. Theory indicates that, at frequencies low enough for losses to be neglected, the apparent acoustic length, l, should be related to the total internal volume of the mouthpiece-leaderpipe combination, V, the cross-sectional area of the main cylindrical tubing to which the leaderpipe is attached, S, the resonances and antiresonances of the mouthpiece-leaderpipe combination, Ω, and Ψn, by the equation: ctn(ωlc) = ScVΩ1[(Ω12−ω)Ψ12(Ω22−ω2)Ψ22(Ω32−ω2)Ψ32(Ω42−ω2)…ωΩ1(Ψ12−ω2)Ω22(Ψ22−ω2)Ω32(Ψ32−ω2)Ω42…]. Experiments show that the tuning behavior of the mouthpiece-leaderpipe combination can be quantitatively predicted with this equation in the frequency range from zero to 1000 Hz.
Input Impedance Curves for Reed Instruments
Authors: Backus John
Published: May 2012

Equipment previously described [J. Acoust. Soc. Am. 50, 128(A) (1971)] for determining resonance frequencies in musical instruments is used to give quantitative curves of the input impedance of the instrument as a function of frequency. The equipment also plots along with the impedance curve the frequencies of the harmonics of a chosen fundamental frequency. For the reed instruments, such as the clarinet, bassoon, and oboe, the resonance frequencies (at which the instrument can sound) are those for which the impedance is a maximum. A series of typical input impedance curves for selected notes on the above instruments has been prepared and will be discussed. The input impedance of the clarinet for the resonance used ranges from 500 to 1000 cgs acoustic ohms; that of the bassoon, from 400 to 1200 ohms; and that of the oboe, from 800 to 1700 ohms. For high notes the oboe plays as much as 300 cents flat as compared to the frequency of the resonance on which it operates. [This work was supported by the National Science Foundation.]
Transient Analyzer for Wind Instrument Tones
Authors: Finch T. L. , Benade A. H.
Published: May 2012

The starting or decay transient of a wind instrument tone may be written p(t) = Σfn(t) cos(2πvn + θn), where fn(t) is the time-varying amplitude of the nth component and vn and φn may vary slightly in time. To extract a particular fi(t), p(t) is multiplied by cos2πvt to give a heterodyne difference vλ = | vi − v0 | < 12 |vi  − vi ± 1 |. The produce enters three stages of second-order LP filtering (cutoff vc). A tap at the stage 3 input goes via a hard limiter to a similar LP stage, providing a “sinusoid” of constant amplitude with frequency and phase identical with that of the three-stage filter output. Multiplying these two synchronous signals together gives Fi(t) = fi (t)[1 + cos (4πvht+θi)]/2. For v1 >200 Hz, vc = 100 Hz, so that vλ≃50 Hz is useful. Careful design gives filter rise times near 6 msec with small distortion of fi(t). Tones recorded on tape loops are analyzed by photographing superposed traces from several repetitions, fi(t) appearing as an envelope. Since θi is random between repetitions, the envelope defines fi(t) better than does one trace. Results for clarinets, flutes, and organ pipes are presented, and compared with the work of others.
A Theory of Edgetone Production
Authors: Blocker Wade
Published: May 2012

Edgetone frequencies f in stages 1, 2, 3, 4, etc., are given by fT=0.500, 1.230, 2.239, 3.242, etc., where T is the transit time of a particle across the aperture-edge gap. Jet slowing must be taken into account. For a turbulent jet, T = T0{[1 + (X/x0)]1 −1} with T0 = 2x0/3x0 and x0 = 5.75b; b is the slit width, x0 is the initial jet velocity, and X is the gap width. Conversely, X = x0{[1 + (T/T0)1−1}. For stage 1, the phase velocity at any point is twice the jet particle velocity there; for higher stages these velocities are essentially equal. The common opinion that the phase velocity is a fraction of the jet velocity resulted from misinterpretation of experimental data, neglect of jet slowing, and acceptance of idealized calculations as valid for edgetones. The present description agrees with all experimental data, including those observations wherein the frequency decreased as the 32 power of the gap width instead of the usually seen first power. A theory based on a perturbation calculation of the jet motion explains these results, and the operation of recorders, flutes, and organ pipes.
Aplysia Statocyst Receptor Cell as a Model for Vertebrate Hair-Cell Physiology
Authors: Wiederhold M. L.
Published: May 2012

The Aplysia statocyst is a spherical organ, approximately 200 μm in diameter, filled with fluid and small (6–20 μm), dense statoconia. The wall of the statocyst consists mainly of 13 large receptor cells. Light, transmission- and scanning-electron microscopy have shown that each receptor cell bears many (500–1000) true cilia which project into the cyst lumen. The fine structure of the cilia and their associated basal bodies appear similar to those of vertebrate hair cells, suggesting that similar transduction mechanisms may be operative. The statocyst receptor cells were penetrated with micro-pipette electrodes in a preparation mounted on a table which allows a physiologic stimulus to be applied by tilting so that the statoconia roll to deflect cilia on the cell. Such a stimulus causes depolarizations from 0 to 15 mV and conductance increases from 0 to double the resting conductance. At rest, there are ongoing fluctuations in membrane potential from 2 to 15 mV peak-to-peak amplitude. These fluctuations increase as the recorded cell is tilted downward. Most of the energy in the baseline fluctuations lies at frequencies below 10 Hz.
The Differentiation of Hair Cells during Development
Authors: Flock Äke , J/rgensen M/rup
Published: May 2012

A series of experiments were devised to investigate the sequence of events that led to the differentiation of hair cells and their synapses. In particular, we inquired whether the presence of nerve fibers in the developing sense organ is necessary for induction of differentiation. Lateral line organs in the translucent tail of salamander tadpoles (Ambystoma mexicanum) were chosen for this study because here cellular structures can be observed in considerable detail in vivo with interference contrast optics. Furthermore, during degeneration of a new tail after amputation, new neuromasts develop and can be taken for electron microscopy at desired stages of development. At the first identified stage, nerve terminals are already present above the basement membrane. A cupula, afferent synapses, kinocilia, and stereocilia then appear. In another set of experiments, the tail was amputated and at the same time a segment of the lateral line nerve which innervates these organs was surgically removed behind the front limb. The nerve was prevented from invading the growing tail by repeated sectioning. New organs were now looked for and were also found. The ultrastructure of such organs is described and discussed in relation to the development of the inner ear.
A Reexamination of Cochlear Sensitivity to Cooling
Authors: Meikle M. B. , Vernon J. A.
Published: May 2012

Several reports in the literature have represented the sensitivity of the alternating cochlear potential as being easily degraded by cooling. Our attempts to replicate these findings in the guinea pig failed to confirm them; hence we have conducted a thorough investigation in which careful attention was given to (1) optimal physiological condition of the preparation, (2) accurate quantification of sound, and (3) precise measurement of intracochlear temperature. At low levels of cochlear output (1–10 μV) the sensitivity of the normal cochlea was found to be invariant down to at least 30° C. This invariance does not appear to hold for the cochlear output at higher levels, close to bendover. Possible theoretical implications of these findings are discussed.
Interaction between Agents Which Produce Temporary Hearing Threshold Shifts: Intense Sound and Sodium Salicylate
Authors: Mitchell C. , Brummett R. , Vernon J.
Published: May 2012

In previously reported experiments we have shown that an intense sound exposure can temporarily depress the cochlear nerve evoked potential (N1) while not affecting the alternating current cochlear potential [J. Acoust. Soc. Am. S3, 326 (1973)]. Sodium salicylate was likewise found to produce a temporary effect on N1 only. In this experiment it was found that when these agents are given together they produced a greater change in N1 than either agent alone, but not more than would be expected from a simple summation. This combined effect- of both agents on N1-was also temporary. The interaction of these agents did not affect the ac cochlear potential. This interaction—of intense sound and sodium salicylate-does not produce the permanent damaging interaction effects reported for other ototoxic drugs.
Slow-Played Speech with and without Time Restoration: A Phonemic Analysis
Authors: Picard M. , Bode D. L.
Published: May 2012

Intelligibility of speech divided by a frequency factor of two was explored in 12 young adults with normal hearing. Two conditions investigated were (1) 50% frequency division with 50% time expansion (FDTE), i.e., frequency halved and time doubled, and (2) 50% frequency division with 50% time-compression (FDTC), i.e., frequency halved and time restored. The latter condition was obtained by use of the time-compressor developed by Fairbanks el al. in 1953 and modified by Zemlin in 1970. Test stimuli were CVC words recorded by a male speaker and presented monaurally under phones. The response format was of the closed-set type. Test words were constructed so as to emphasize ten consonants in the initial word position, the same ten in final position, and ten vowels always in the medial portion. Results showed: (1) the initial consonants and the vowels were significantly more intelligible in the FDTE condition than in FDTC; (2) intelligibility of final consonants did not differ significantly in these conditions; (3) in the FDTE condition, the initial consonants were as intelligible as the final ones and both were significantly more intelligible than the vowels; (4) in the FDTC condition, the initial consonants did not differ significantly from the vowels and both were significantly less intelligible than the final consonants.
Binaural versus Monaural Speech Discrimination under Reverberation
Authors: Gelfand S. A. , Hochberg I.
Published: May 2012

The effects of reverberation time (RT) upon monaural and binaural speech discrimination were investigated for normal-hearing and hearing-impaired subjects. After preliminary tests, the Modified Rhyme Test was administered through headphones at RTs of 0, 1, 2 and 3 sec, monaurally and binaurally. For all conditions, the normals performed significantly better than the impaired group, although a similar trend was evident for both groups. Binaural scores were significantly higher at each RT for both groups (in spite of homophasic conditions). For both groups, monaural and binaural scores decreased with increasing RT. Monaural scores decreased at a faster rate with RT than binaural (this effect was more marked for normals). Increasing the monaural presentation levels to simulate binaural loudness gain did not result in higher scores. It was concluded that speech discrimination under reverberation is superior binaurally to monaurally for both normal and hearing-impaired persons. This is due, at least partly, to the ability of the binaural system to squelch the effects of reverberation. A theoretical model is suggested for the binaural squelch of reverberation.
Effects of Poles and Zeros of Linear Prediction Model on the Intelligibility of PB Words
Authors: Agrawal Arun , Lin Wen C.
Published: May 2012

Natural speech is modeled by linear prediction using Prony's formulation. An all-pole model is assumed for voiced segments while a poles and zeros model is considered more suitable for unvoiced segments. The relative magnitude in the short-time spectrum is also determined at the pole and zero frequencies. The effects of poles and zeros and their interaction (causing masking) on intelligibility were investigated by adaptively filtering them based on their frequency, bandwidth, and magnitude information. A recursive digital filter was used which suppresses real roots (corresponding to glottal source and vocal radiation) and/or complex roots (corresponding to vocal tract resonances). This approach was taken so that one or more roots can be removed at a time from the natural speech, without affecting anything else. A semiautomatic on-line intelligibility measurement system utilizing pattern recognition concepts has been developed for PB word listening tests. The preliminary results indicate that suppressing the real poles and the poles corresponding to third and fourth resonances does not degrade intelligibility. The effect of zeros and poles for the first and second resonances is discussed based on formal intelligibility test results. [The authors acknowledge Satish Chandra of CWRU for zeros estimation algorithm.]
On the Spectrum of Spoken English
Authors: Niemoeller A. F. , McCormick L. , Miller J. D.
Published: May 2012

The spectrum of spoken English was measured in 13-octave bands for men, women, and children. The speech produced by reading aloud newspaper text was recorded in an anechoic chamber for each member of groups of ten men, ten women, and six children. The combined output of each of the three groups was obtained by electronically mixing the member outputs with a 16-track tape recorder. After mixing, the resulting recordings were analyzed in 13-octave bands and converted to spectrum levels. The spectra exhibit peaks and valleys not revealed with wider-band analysis, but when the results of the 13-octave analysis are combined to simulate octave bands there is agreement with the previously published literature. Next these free-field spectra were converted to give the spectra at the eardrum of a typical listener, thus allowing for head diffraction and the resonance of the ear canal. The spectra so obtained have peaks appropriate to typical values of Fo, F1, and F3 for each of the groups. The region usually associated with F2 spans a dip between the F1 and F3 regions. At the eardrum, the frequency region from about 1.7–4 kHz, which is usually associated with F3 and many of the friction generated components in speech, lies only 5–10 dB below the maximum levels in the low-frequency region.
Some Results on Speaker Verification Using Amplitude Spectra
Authors: Doddington George , Hydrick Barbara , Beek Bruno
Published: May 2012

Verification is based upon the similarity of six spectral/time matrices located within a test phrase with corresponding matrices defined during training. Each matrix is 0.1 sec long and is precisely located by scanning the test phrase for a best match with the reference matrix. Evaluation was performed over a data set including 50 “known” speakers and 70 “casual impostors.” Twenty percent female speakers were used. Five different phrases (including “We were away a year ago”) were collected in each session. Known speakers gave 100 sessions; impostors, 20. Data collection spanned 3.5 months. The first 50 sessions of each known speaker's data were used for training, the last 50 for test; 0.6% of the phrases yielded unusable data. When this happened, a substitute phrase from that session was used (two substitutions allowed, maximum). All impostor acceptance rates were determined for 2% true speaker rejection. A single fixed threshold was used for all speakers. Impostor acceptance rates were 2.5% for one phrase, 0.25% for two phrases, and 0.08% for three phrases. Five percent of known speaker data was labeled by the speakers as “not normal” because of respiratory ailments, etc. This data yielded a 4.5% reject rate for one phrase. Two professional mimics were employed to attempt to defeat the system. Each chose the five subjects he thought he could most easily mimic. Interactive trials with immediate feedback were of no apparent aid. Successful impersonation of about 5.5% for one phrase was achieved. No successful attempts for three phrases could be constructed from the mimic data. Reject rate for known speakers was plotted versus session number, at a nominal reject rate of 10%. Initial and final reject rates of 5% and 15%, respectively, indicate the necessity of adaptation in a practical system. [This work is supported by Rome Air Development Center.]
Some Techniques for Assessment of Community Noise Environments
Authors: Sutherland Louis C. , Braden Marcia , Colman Richard
Published: May 2012

Several measurement techniques were evaluated for assessment of community noise environments. These included some new social survey techniques and methods for assessing noise exposure of individuals. Both of these are covered in companion papers. This paper considers some of the techniques and models for assessment of outdoor noise environments. Particular emphasis is placed on evaluation of the variances in levels in time and space. [The study was supported by the Department of Transportation and the Environmental Protection Agency.]
Application of Some New Survey Techniques for Assessing Exposure to Noise and Human Reaction
Authors: Braden Marcia , Colman Richard , Sutherland Louis C.
Published: May 2012

The components of human reaction to noise have been studied extensively in the laboratory, but have been less assessed in the real world. This paper describes a theoretical framework and practical application of some novel techniques for assessing human reaction under field conditions. Data collection techniques never before applied in this context included (1) 24-hour diary (recall), and (2) paired-comparison method to determine an individual's relative value of noise/ quiet. These techniques were utilized as part of a survey instrument, or questionnaire, which was administered to a small group of subjects in a preliminary test. The survey was tested in four different residential sites in conjunction with a pilot test of a system for assessing community noise and individual noise exposure and reaction to this exposure. [The study was supported jointly by the Department of Transportation and the Environmental Protection Agency.]
A Technique for Individual Noise Exposure Assessment
Authors: Colman Richard , Sutherland Louis C. , Braden Marcia
Published: May 2012

Instrumentation and methodologies were developed in a feasibility study to measure noise exposure, at the ear, of a person as he went about his usual daily activities. Two physiological parameters, heart rate, and peripheral vasoconstriction at the earlobe, were also monitored during the same measurement period. The instrumentation consisted of a small, portable package consisting of (1) a subminiature electret microphone worn on the ear, (2) standard EKG chest leads for measuring heart rate, (3) a photoplethysmo-graph sensor mounted on the earlobe for measuring peripheral vasoconstriction, (4) circuitry to convert the microphone signal into a dc voltage proportional to the A -weighted noise level, and (5) a subminiature four-channel cassette tape recorder. Each of the five persons who participated in the experiment were instrumented early in the morning, wore the device for the entire day, and removed it at night (leaving it in the bedroom until it was picked up the next morning). Each person also kept a log of location and activity during the day. Representative results of the pilot study are illustrated by synchronized time history records of the noise levels and physiological responses. The technique could be adapted to allow the measurement of noise exposure and physiological response under a wide variety of circumstances in the field. [The study was supported by the Department of Transportation and the Environmental Protection Agency.]
A Consultant's View of the U. S. Department of Housing and Urban Development's Noise Standards (HDD Circular 1390.2)
Authors: Garrelick J. M. , Kleinschmidt Klaus
Published: May 2012

A number of federal agencies in dealing with environmental noise specify criteria and by so doing imply a procedure by which one may assess the acceptability of a given noise environment. Based on consulting experience, a practical evaluation of the U. S. Department of Housing and Urban Development's policy in this area (HUD Circular 1390.2) is presented. In particular, the desirability of specifying a 24-h sample time is discussed. Alternate schemes are suggested. Also, diurnal variations in noise data have been compiled and are used to compare HUD's criteria with the Federal Highway Administration's standard (PPM 90-2).
New Approaches in Developing Regulations for Land Development near a Major Airport
Authors: Bishop Dwight E. , Randorff Jack E.
Published: May 2012

The construction of a a new major airport, the Dallas-Fort Worth Airport, in a relatively undeveloped area is stimulating community development for many miles around the airport. Unless land use can be controlled, the familiar patterns of encroachment and airport-community conflicts will appear. Both technical and political problems abound in developing land use regulations which take into account the potential aircraft noise environment. Among other factors, the regulations, to be successful, must be voluntarily adopted by a number of cities which vary greatly in size, resources, and community interests. Major steps in developing a draft model code that encompasses land use controls and sets minimum noise level reduction requirements for some buildings are reviewed. The technical approach adopted for the code involves the definition of five noise zones around the airport, established in terms of projected noise exposure. Permitted activities and/or land uses are specified for each zone. For sensitive land uses, buildings must meet minimum noise level reduction requirements. These requirements can be met by either incorporating specific building design details and materials or by submitting plans which have been certified by an acoustician as meeting the noise level reduction requirements.
Measuring Procedure for Urban Noise in the Center of Mexico City
Authors: Groenewold F. , Merino E.
Published: May 2012

The objective of measurements -is to give equal-noise contours in a dense traffic commercial zone in Mexico City, which is in the process of archaeological and architectural remodeling, and to obtain the relationship between noise and the various parameters involved so that the future noise conditions can be predicted. A continuous and a direct measurement schedule was choosed. For the continuous measurement, an observation station was designed which has a bridge with four microphones over the street. Data are tape-recorded in a semicontinuous way, and a correspondent register of weather conditions is taken. The recorded data are processed afterwards in laboratory by an A -weighted curve and by 1/3-octave bands. For the direct measurement, a hexagonal grid of 0.25 km sides is placed all over the zone. A series of ten measurements of 15 sec each is taken in each point. A correlation between direct and continuous measurements is done in order to trace the equal-noise contours.
Discharge Rate as a Function of Stimulus Level for Tones or Noise in Cat Auditory-Nerve Fibers
Authors: Sachs M. B. , Abbas P. J. , Bevan M. F.
Published: May 2012

Discharge rate in response to noise bursts and tone bursts was measured for single fibers in the auditory nerve of anesthetized cats. Rate was plotted as a function of stimulus level (in decibels). In each experimental run, various levels of tone bursts at fiber characteristic frequency (CF) were presented in a random sequence with the same number of levels of noise bursts or tone bursts at an off-CF frequency. In this way, rate versus level functions for noise or off-CF tones could be compared with functions for CF tones measured during the same time period. In general, rate versus level functions for noise were less steep than those for CF tones; maximum rates evoked by noise were less than those evoked by tones at the CF. The slopes of rate versus level functions for tone bursts at frequencies greater than CF were generally a decreasing function of frequency. For frequencies less than the CF, slopes were approximately equal to those at CF. [Supported by the National Institutes of Neurological Diseases and Stroke and General Medical Sciences and the U. S. Air Force Office of Scientific Research.]
Average Phase Angle of Discharges of Neurons in the Anteroventral Cochlear Nucleus of the Cat
Authors: Gibson Marv Morton , Kitzes Leonard M. , Rose Jerzy E. , Hind Joseph E.
Published: May 2012

Phase information transmitted by auditory nerve fibers is preserved by some cells in the anteroventral cochlear nucleus. The responses of these cells to low-frequency sinusoids presented at a number of sound pressure levels were collected in the form of period histograms. The average discharge phase angle relative to a fixed point on the input sinusoid was subsequently calculated. Phase locking occurs to about 4 kHz. At a fixed SPL the average phase angle is approximately a linear function of stimulus frequency. Intensity effects are much more subtle. In general, with increasing SPL there is a phase lag at frequencies below the best frequency and a phase lead at frequencies above the best frequency. The results are similar to and extend previous observations on auditory nerve fibers. Two factors could account for these data: (1) a delay due to mechanical travel time along the basilar membrane, and (2) an intensity dependent nonlinearity of the cochlear partition. A model incorporating these two factors has been proposed recently by Duck on Kim [“A Nonlinear Model for Basilar Membrane Motion and Related Phenomena of Single Cochlear Nerve Fibers,” Ph.D. Dissertation, The Washington University (1972)]. [Supported by NINDS Grants 5326, 6225, and 30897.]
Neural Information Processing in the Medial Superior Olive
Authors: Barrett T. W.
Published: May 2012

The neural response of neurons in the medial superior olive was recorded to electrical stimulation of nervous processes in the osseous spiral laminae and also to antidromic stimulation from the inferior colliculi. The osseous spiral laminae were stimulated at the first, second, and third turns. Time of signal arrival differences (Δτ) at the two spiral laminae and also intensity differences (Δi) were varied. It was found that (1) electrical stimulation gives a regular neural response; (2) the neural response to changes in Δτ and Δi is nonlinear; (3) fine latency changes in the neural response can signal changes in Δr and Δi; (4) stimulations of different turns of the osseous spiral laminae (i.e., with different current flows) give different neural responses reflecting the anatomical tonotopic arrangement of the medial superior olive; and (5) changes in Δτ and Δimay be registered by the ratio of the spike count in a short period following the stimulus to the spike count in a longer total period.
Response of Single Units in Inferior Colliculus to Temporal Auditory Patterns
Authors: Winfield J. A. , Clopton B. M.
Published: May 2012

Spikes from single units in the inferior colliculi of naive, albino rats were acutely recorded while tone-noise patterns were presented contra-laterally. Three patterns were used, an up pattern consisting of repeated alternations of a 1-sec tone sweep from 6 to 9 kHz and a 1-sec noise burst, a down pattern with the tone component being a sweep from 9 to 6 kHz, and a control pattern with the tone component deleted. A sample of 50 units revealed that the majority of units differentiated between the up and down patterns with great certainty. The greatest resolution in neural responses occurred for spikes during the first 250 msec of the noise-burst component, but a high degree of resolution characterized many units throughout all pattern components. The selectivity of a unit for the up or down pattern was dependent on the characteristic frequency (CF) of the unit, units with CFs within or above the tone-sweep range being biased toward the down pattern. Relative to the control pattern, the up and down stimulus patterns both increased and decreased spike counts, suggesting possibly mixed facilitory and inhibitory mechanisms underlying the temporal-pattern selectivities of these units. These findings support at least a partial analysis of temporal auditory patterns at subcortical stations. [Supported in part by NINDS Grant NS09551 and a General Research Grant, U. C. Academic Senate.]
Propagation through an Anisotropic Random Medium. II. The Multiple Scatter Region
Authors: Beran M. J. , McCoy J. J.
Published: May 2012

Using the results of the single scatter study discussed in Part I, a valid multiple scatter solution was developed for the coherence function for an initial horizontal time-harmonic plane wave incident on a random medium with horizontal correlation lengths that are orders of magnitude larger than vertical correlation lengths. Using this solution, we construct a qualitative description of the loss of spatial coherence due to the scattering of low-frequency acoustic signals by the temperature microstructure. Simple algebraic expressions are presented for a characteristic coherence length, which can be used to estimate the maximum useful array size for the coherent summing of signals, for a horizontal temperature fluctuations spectrum that may be described by a single power law. In this way, the most significant environmental parameters are clearly identified.
A Test of the Born and Rytov Approximations Using the Epstein Problem
Authors: Hadden W. James , Mintzer D.
Published: May 2012

The Born and Rytov approximations for the pressure field, amplitude, and phase were compared with exact solutions for two test problems involving propagation of a plane wave through a medium with continuously varying index of refraction. The comparisons are discussed in terms of limiting values of a parameter which describes the spatial extent of the inhomogeneous region, using as a secondary parameter the magnitude of the variation of the index of refraction. The extension of these results to other problems is discussed.