bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency selectivity in pure-tone forward masking
Authors: Wightman F. L.
Published: October 2005

In two pure-tone forward-masking experiments, modeled after classical simultaneous masking experiments, we have attempted to verify some of the commonly accepted features of auditory frequency selectivity. In both experiments the signal was a 20-msec pure tone, presented 10 msec after termination of a 200-msec pure-tone masker. An adaptive 2IFC paradigm was used to measure the threshold of detectability of the signal. In the first experiment the masker's intensity and frequency were fixed, and signal threshold was measured at several signal frequencies. The masking patterns thus obtained were similar to classical ones if masker intensity is low. With moderate- to high-level maskers (70–90 dB SPL), nonmonotonic patterns were obtained. For example, with an 80-dB masker at 1 kHz, signal threshold was the same as 1 kHz and 1.5 kHz, but 15 dB lower at 1.3 kHz and 1.8 kHz. This anomolous effect was both frequency and subject dependent. In the second experiment, the signal's level and frequency were fixed, and the masker was varied. The tuning curves thus obtained were quite similar to those from earlier psychophysical and physiological experiments.
Potentiation of cochlear injury by noise and ototoxic antibiotics in guinea pigs
Authors: Marques D. M. , Clark C. S. , Hawkins J. E.
Published: October 2005

Guinea pigs were exposed to 8-kHz octave band noise, eight hours daily for one week, while receiving kanamycin 200 mg/kg daily. Other groups of animals received kanamycin alone, noise exposure alone, or both treatments separated in time. Two weeks after kanamycin treatment, injury to the cochlea was assessed in terms of reduction in the microphonic potential (CM) recorded at the round window and hair cell loss as evaluated in surface preparations. Pathological changes were greatest when noise exposure was concurrent with kanamycin treatment or preceded it by only one week. Noise exposure alone and other sequences, with and without an intervening week of rest, produced lesser degrees of injury. The results are compatible with the hypothesis that noise exposure affects the hemato-labyrinthine barrier, causing a more rapid accumulation of the antibiotic in the inner-ear fluids and tissues or a reduced rate of clearance from them. [Supported by NIH-NIEHS contract NO 1-ES-2-2110 and NIH Program Project Grant 05785.]
Neomycin effects on cochlear microphonics and phospholipid metabolism
Authors: Nuttall A. L. , Marques D. M. , Stockhorst E. , Schacht J.
Published: October 2005

Neomycin (10−4 to 10−2M) in artificial perilymph was continuously perfused through the guinea pig cochlea by means of tubes sealed in the scalae vestibuli and tympani of the basal turn. The ac potential (CM) in response to a 4-kHz tone was recorded via an electrode in the basal turn. Neomycin brought about a rapid reduction in the magnitude of the CM during the first 5 min of perfusion. Within 15 min of perfusion with 10−2M neomycin, the CM stabilized at a loss of at least 50% of the initial magnitude. Some return of CM occurred with neomycin-free artifical perilymph. [32P] orthophosphate was added to the perfusion fluid to label cochlear phospholipids in the presence and absence of neomycin. With neomycin, labeling of phosphatidylinositol diphosphate [see J. Schacht, J. Acoust. Soc. Am. 56, S20 (1974)] decreased with the decrease in CM. [Supported by NIH Grant NS 11731-01, NIH-NIEHS Contract NO 1-ES-2-2110, and NIH Program Project Grant 05785.]
Recovery of middle components of human auditory averaged electroencephalic responses
Authors: Vivion Michael C.
Published: October 2005

Recovery functions of peak-to-peak amplitudes were derived for middle components (latencies approximately 8–80 msec) of auditory AERs recorded from 10 normal-hearing adults. Click stimuli were presented monotically at 50 dB SL in sets of three for 256 repetitions per AER. Interclick interval between the first two clicks of set (delta) was varied between 4 and 256 msec. Third click always followed second click by 256 msec. Amplitudes of responses to second clicks were compared to those of responses to third clicks in stimulus sequence through the use of special computerized scoring procedures. Full recovery of amplitude of the different peaks occurred for delta intervals of 45.6–64 msec and longer. No response was seen for second click of sequence when delta interval was between 4 and 16–22.4 msec. Recovery of amplitude was graded for intermediate delta interval values. Preliminary results of nonlinear curve fits to data suggest that recovery of amplitude is a power function of delta interval. For the middle components, delta interval required for full recovery appears to be less than that for late components and slightly longer than that for early (brainstem) components. No significant shifts of peak latencies occurred as a function of delta interval.
Brainstem evoked responses obtained from hearing-aided adults
Authors: Hecox K. , Breuninger C. , Krebs D.
Published: October 2005

Traditionally, the evaluation of auditory functioning in the hearing-aided patient has been limited to subjective response measures. This report demonstrates that brainstem evoked responses can provide an objective and reliable measure of auditory performance in such individuals. Moderate-output body-level aids were worn by three normal-hearing adults, on whom unaided responses had previously been obtained. Highly reliable responses to clicks, tone, and noise bursts were obtained from all subjects. Increases in the gain of the aid, and thus signal loudness, produced shorter latency and larger amplitude responses, as expected on the basis of unaided input-output functions. The number of decibels above physiological threshold required to generate a 6.0-msec latency response was smaller in the aided when compared to the unaided condition, thus mimicking the electrophysiological finding in “recruiting” patients. Variations in the low-frequency portion of the aid's frequency-response curve produced little change in the evoked response, while increases in its high-frequency cutoff produced shorter latencies. The reliable and systematic relation between subjective sensation, hearing-aid characteristics, and neuro-electrical response appears to warrant the continued investigation of the use of brainstem evoked responses for hearing aid fitting in hearing-impaired populations.
Shallow-water propagation under downward-refraction conditions. II
Authors: Cole B. F. , Cohen J. S.
Published: October 2005

In a previous paper [B. F. Cole and E. M. Podeszwa, “Shallow-Water Propagation under Downward-Refraction Conditions,” J. Acoust. Soc. Am. 41, 1479–1484 (1967)], some 3.5-kHz propagation data were analyzed based on the hypothesis that the time-variant parameters (i. e., velocity-profile-related effects) could be correctly separated from the time-invariant (i.e., bottom loss) parameters affecting shallow water propagation. A bottom-loss value of 1.3 dB per bounce was inferred from the measurements and was shown to compare favorably with theoretical loss values generated using sediment information for the test area. To further verify this bottom-loss measurement and further establish the validity of the parameter separation hypothesis, some additional tests were conducted in the same test area during May 1967. This paper presents the propagation-loss results collected during the May 1967 tests and compares these results with the values predicted by a propagation-loss model developed from the earlier set of measurements.
Underwater sound propagation described by range-dependent normal modes
Authors: Graves R. , Nagl A. , Überall H. , Zarur G.
Published: October 2005

A gradual range dependence of velocity profiles may be incorporated into normal-mode theory of underwater sound propagation, as shown by A. D. Pierce [J. Acoust. Soc. Am. 37, 19 (1965)] and by D. M. Milder [J. Acoust, Soc. Am. 46, 1259 (1969)], by using an adiabatic approximation for separating variables. We have extended this approach to include range variation of the boundaries, obtaining the modal range functions which replace the stratified propagators H0(1)(knr) as the solutions of a coupled set of range equations. Closed integral expressions were found for range-flattening parabolic profiles, or for isovelocity water above a linearly sloping bottom, and were evaluated by numerical integration. A numerical method for solving the coupled range equations is now being developed, which will be combined with the numerical depth functions used by us earlier [I.M. Blatstein, A. V. Newman, and H. Überall, J. Acoust. Soc. Am. 54, 271(A) (1973)] in order to obtain the total propagation loss. [Supported by Office of Naval Research, Code 486.]
Propagation of beamed signals through inhomogeneous media—a diffraction theory
Authors: McCoy J. J. , Beran M. J.
Published: October 2005

A theory, suitable for making estimates of the intensity distribution in beamed signals and of the spatial coherence of signals emanating from partially coherent sources, is presented. The limits of applicability of the formalism are considered and the range limitations required are shown to be considerably weaker than those of the geometric theory. A solution algorithm is developed, which is subsequently shown to be an extended ray trace algorithm. Applying the algorithm to a completely coherent, beamed signal in a medium with a quadratically varying sound-speed profile, an analytic expression is presented for the intensity distribution over the beam cross section. This expression is shown to approach the geometric theory solution in the appropriate limiting case. Removed from the limit, the expression exhibits beam spreading due to diffraction, beam focusing due to refraction, and beam bending due to refraction. Incorporation of volume scattering by a randomly varying refraction index field is accomplished, but at the expense of obtaining a much more complex formalism. It is shown that the solution algorithm that was developed for the nonscatter problem ceases to be valid when volume scatter is included. This suggests that attempts to incorporate volume scatter effects in ray trace programs by the addition of “side calculations” will not prove fruitful. A potentially useful numerical approach to the formalism that includes volume scatter is outlined.
Project ANZUS Eddy—Phase One: acoustic modeling of an ocean eddy
Authors: Browning David G. , Scully-Power Paul D. , Bannister Richard W. , Vastano Andrew C.
Published: October 2005

Project ANZUS Eddy is a joint program by scientists in Australia, New Zealand, and the United States to study ocean eddies. In support of a forthcoming experiment, acoustic modeling was done for the type of eddy commonly found off the east coast of Australia. These eddies are basically a large (200-km diameter) mass of warm isothermal surface water, resulting in a “dishpan” shape with a depth of 300 m in the center and rising to the surface at the edges. Propagation through the corresponding velocity profile structure is modelled by a ray tracing program. This analysis shows that for a shallow source and receiver (less than 300 m) the effect of the eddy is to redistribute acoustic energy between the convergence zones. [This work was supported in part by the Office of Naval Research under Contract N00014-75-WR50209.]
Axisymmetric forced vibration and acoustic power radiation response of a pipeline transporting oscillating fluids
Authors: Singh Rajendra , Soedel Werner
Published: October 2005

In power and process plants, a large number of piping systems are often encountered in which flow oscillations prevail. As the role of these fluid fluctuations in piping vibrations, structural problems, and noise radiation is vital, it is desirable to predict the dynamic and acoustic responses of the pipelines. In the present investigation, the pipeline has been modeled to be a thin, finite, elastic, and simply supported cylindrical shell Green's function technique along with the modal expansion has been utilized to predict the axisymmetric response of the shell due to a forcing function, which is assumed to be a linear combination of positive- and negative-direction travelling plane waves. The transverse displacement calculation of the structure and wave equation in cylindrical coordinates are used to predict the acoustic field and radiated power outside the pipeline. In the analysis, the back reaction of the shell on inner fluids and the effect of radiated noise on the vibrating structure are assumed to be very small. The results and conclusions are presented in the generalized parameters form.
Effect of crack size on acoustic emission
Authors: Ying S. P.
Published: October 2005

Acoustic emissions from the vicinities of cracks were monitored by a multichannel acoustic emission system, The experiment was performed on a flawed carbon steel vessel under hydraulic pressure providing a nearly uniform external stress in the vessel wall, However, the stress fields near the cracks were nonuniform. The numbers of acoustic wave packets generated from the individual cracked regions were analyzed by an on-line minicomputer, The correlation between the number of the wave packets and the size of crack at low stress levels was found experimentally and is consistent with a theory of non-uniformly distributed moving dislocations in the vicinity of crack, Further calculations by utilizing the theory and by analyzing available experimental data of acoustic emissions from other types of flawed specimens of various crack sizes also show agreement between the theory and the experimental data.
Ultrasonic identification of plastic worked zone on railroad railheads
Authors: Bray Don E. , Egle D. M.
Published: October 2005

Ultrasonic surface waves have been propagated longitudinally on the roiling surface along the length of 11 samples of new and used railroad rail. Excitation frequencies were from 0.5 to 2 MHz. Besides the expected surface wave, a strong wave analogous to Stoneley waves was also seen. This wave appears only in heavily worked surfaces, and most strongly at the higher frequencies. It is postulated that this wave might be useful in identifying rail sections that have experienced heavy working before shelling occurs.
Acoustic fuel vapor monitor
Authors: Losey R. E.
Published: October 2005

The speed of sound as a function of the average molecular weight in a gaseous mixture has been used to determine the concentration level of fuel vapor in air, in the range from 1.0% to 8.0% by volume. This method of measurement yields an error due to a 1°C change in temperature of only 0.18% and can be applied to many different types of fuel. The range can be extended to wider limits, but our interest included only the explosive region for gasoline fuel vapor, i.e., 1.6% to 7.8% by volume. Using this device, fuel vapor levels can be continuously monitored without altering the system in any way. Thus, error introduced by sampling, temperature change, and time delay are virtually eliminated. Sensitivity of the system to changes in fuel vapor levels is proportional to the ratio of the molecular weight of air. This method of measurement is applicable down to ratios of 1.51 and has been typically applied with a ratio of 3.9 with total success. Instrumentation has been developed to indicate fuel vapor levels by either meter movement or digital readout.
Real-time reverberation generator
Authors: Princehouse David
Published: October 2005

Since the performance of an active sonar is often limited by reverberation, an instrument which could produce accurate reverberation in real time would be valuable to sonar designers, users, and evaluators. An instrument is proposed which can satisfy their needs. It is equivalent to a digital matched-filter processor run backwards, and divides naturally into a hardware portion and a software portion. The complexity of the hardware portion depends only on the transmitter pulse length, receiver bandwidth, and the number of acoustic beams to be produced simultaneously. It employs the fast Fourier transform (FFT) algorithm, for which very fast computer processors. have been developed. The hardware portion of the reverberation generator is developed to the point where it will produce accurate reverberation if provided with the proper input information. The required input information is generated by the software portion of the instrument. It resembles the range-Doppler map produced by a matched-filter processor, except that the smearing caused by the ambiguity function of the pulse must be removed. The software portion is being developed by experimental and theoretical techniques.
Effects of vowel identity and fundamental frequency on the relationships of vocal intensity to physiological parameters associated with production of sustained vowels
Authors: Klich R. J.
Published: October 2005

The relationships of subglottal air pressure, airflow rate, glottal resistance, and physiological work to the SPL of vowels produced at three different pitch levels were investigated. The vowels /a/ and /i/ were produced at pitch levels corresponding to the 25%, 50%, and 75% points of the subjects' pitch ranges; the highest pitch level was in the falsetto register for all subjects. At each pitch level, the slopes of the functions relating SPL to the physiological parameters were greater for /a/ than for /i/. The magnitudes of the physiological parameters for /i/ were greater than those for /a/ at the two lower pitch levels, but there was little difference between the vowels at the high pitch level. The magnitudes of the physiological parameters tended to increase for /a/ as pitch level increased, but tended to decrease for /i/ as pitch level increased. The intervowel differences observed at a given pitch level probably are associated with differences in the relative sizes of the oral cavity for the vowels. Intravowel differences between pitch levels can be accounted for by differences in the acoustic coupling between the glottal generator and the oral cavity, particularly at frequencies near the first formant.
Spectral harmonic and nonharmonic levels and roughness severity ratings for normal and abnormally rough vowels
Authors: Whitehead R. L. , Jones K. O.
Published: October 2005

The purpose of this study was to investigate the relationship between spectral harmonic level (SHL)—spectral nonharmonic (noise) level (SNL) differences and degree of perceived vocal roughness. Other investigators [Sansone and Emanuel, J. Speech Hearing Res. 13, 489 (1970)] have postulated that a trading relationship exists between harmonic and nonharmonic spectral energy as voices vary in degree of vocal roughness. In the present study, 15 normal-speaking adult males phonated the vowels /u/, /i/, /a/, and /æ/, first normally and then with simulated abnormal vocal roughness at one intensity. Tape loops were constructed from each vowel recording and individually played into a narrow-band graphic wave analyzer to plot (a) the intensities of the first five harmonics, and (b) the intensities of the spectral nonharmonic energy. The differences between the mean SHL and mean SNL for each normal and abnormally rough vowel phonation was correlated with judges' median ratings of the degree of perceived vocal roughness. Significant (p <0.01) correlation coefficients were obtained.
Stop cognate production in cerebral palsied speakers
Authors: Farmer A.
Published: October 2005

Stop cognate production was analyzed for five predominantly athetotic and five predominantly spastic cerebral-palsied speakers. Tape recordings from a spontaneous naming task were analyzed phonetically and spectrographically. Voice onset time (VOT) analysis indicated that these subjects attempted to use distinct categorical voiced and voiceless bilabial, apical, and velar stops. Voicing errors were primarily of the lead for lag, or voiced for voiceless nature. Further, the athetoids as a group produced longer and more variable VOTs than the spastics. This difference was statistically significant for (p,t,k). The results are discussed in reference to the natures of the neuromuscular disorders.
Binaural interaction of backward and forward masking
Authors: Lynn G. K. , Small A. M.
Published: October 2005

As an initial step in investigating the binaural, interactive characteristics of backward and forward masking, the SPL of a signal required for equal detectability was determined in a paradigm that combined ipsilateral forward and contralateral backward masking. Paradigms involving only an ipsilateral forward masker and only a contralateral backward masker were used as a basis of comparison. The signal was a 10-msec 2000-Hz sinusoid; the masker(s) 80-dB overall SPL narrow-band noise with half-power points at 1600 and 2400 Hz. In the combination paradigm, three separations of the maskers were chosen: 15, 25, and 45 msec. Within these intermasker intervals, signal SPLs for equal detectability were determined for different temporal placements of the signal. The results indicated that when a contralateral backward masker is added to a forward masking paradigm, regardless of the temporal placement of the signal within the intermasker interval, the signal must be increased by a constant amount to remain equally detectable. This constant increase is greater for the 15-msec masker separation than either the 25- or 45-msec separations. To account for these interactions would appear to necessitate neural activity above the peripheral level.
Temporal summation as a function of signal definition and psychophysical method
Authors: Stiegel M. S. , Bilger R. C.
Published: October 2005

Temporal summation at masked threshold for three normally hearing subjects was investigated for two types of signals (pure tones and narrow bands of noise) with two experimental procedures (constant 2AFC and adaptive) at 250, 1000, and 4000 Hz. The narrow-band noise signal had a bandwidth less than the critical band of its center frequency. The spectrum level of the masking noise was 31 dB SPL. The data obtained were fitted by two models: hyperbolic and exponential, both of which accounted for more than 95% of the variance. By using the latter model, the time constants we obtained varied inversely with frequency and were of a larger magnitude (580, 500, 200 msec for 250, 1000, 4000 Hz, respectively) than those previously reported. This finding was independent of the experimental procedure or signal used. The hyperbolic model yielded slopes of the temporal integration function which varied inversely with frequency, with the difference between the 250- and 1000-Hz function being minimal. We also fitted these models to data by three other authors and found the Plomp and Bouman model [J. Acoust. Soc. Am. 31, 749–758 (1959)] to be clearly superior to the hyperbolic model for only one of those sets of data, that of Watson and Gengel [J. Acoust. Soc. Am. 46, 989–997 (1969)].
Quantal configurations for vowels
Authors: Stevens Kenneth N.
Published: October 2005

Examination of the vocal-tract configurations that are available for the production of vowels, and of the properties of the sounds produced by these configurations, suggests that certain configurations are preferred in the sense that they give rise to sound outputs that are distinctive and whose properties are relatively insensitive to perturbations in the articulatory representation. It is shown that anterior-posterior movement of the tongue body leads to two such preferred configurations independent of tongue height-configurations corresponding to the traditional phonetic feature [± back]. Variation in tongue height is postulated to produce three distinctive positions achieved through movements of the tongue and the mandible: tongue maximally raised toward the hard or soft palate, tongue lowered but with some palate contact maintained with the edges of the tongue, and severed contact of the tongue with the palate. Shifts from one of these positions to another produces well-defined contrasts in the acoustic output. Quantal adjustments leading to distinctive acoustic contrasts can also be made in the lips and tongue root, Implications of this point of view in the formulation of systems for the classification of vowels are discussed. [Supported in part by an NIH Grant.]
EMG—aerodynamic measures for intervocalic /p/ production
Authors: Putnam Anne H. B. , Shipp Thomas
Published: October 2005

Simultaneous EMG and aerodynamic recordings were obtained to study the temporal relationships of lip and larynx activity during production of intervocalic /p/. Hooked-wire electrodes were used to sample activity in the following muscles: posterior cricoarytenoid, interarytenoid, quadratus labii inferior, and orbicularis oris inferior, Subglottic and intraoral pressures were sampled via tracheal and intraoral catheters, In the repeated utterances of an adult subject under normal talking conditions, it was found that although muscle activity in the posterior cricoarytenoid, quadratus labii inferior, and orbicularis oris inferior varied in onset and offset times relative to the production of /p/, the peak intraoral pressure developed for the stop was consistent from utterance to utterance: i.e., ±1 cm of water for all utterances. EMG and aerodynamic records were also made under two other conditions: the subject produced the same utterances with a fixed mandible, and then with a transoral pressure-release device. Despite limitations on jaw movement or the ability to impound oral air, the lip/larynx system was still able to achieve an intraoral pressure for /p/ that was consistent from utterance to utterance within each condition: i,e., ±1.25 cm of water for all utterances.
Temporal control of voicing during occlusion in plosives
Authors: Smith B. L. , Westbury J. R.
Published: October 2005

A study was made of duration of vocal-fold vibration prior to release of occlusion (prevoicing during initial voiced bilabial stops and of duration of voice continuation after occlusion (glottal leak) in intervocalic voiceless bilabial and velar stops. There were six female and five male English-speaking subjects. Prevoicing duration in CVC syllables spoken in isolation was greater before front vowels than before back vowels and greater preceding high vowels than preceding low vowels. Females showed longer prevoicing durations than males. Glottal leak duration in voiceless intervocalic plosives in bisyllabic English words spoken in isolation was longer for bilabials than for velars, longer following than preceding stressed vowels, and longer for bilabials in the environment of [ɪ] than in the environment of [a]. Duration in velars was similarly affected by quality of the preceding but not of the following vowel. Glottal leak durations were less for females than males. Results are discussed in terms of the relative roles of learned adjustments and obligatory aerodynamic constraints arising from upper cavity configurations.
New kind of headphone receiver
Authors: Wallace R. L.
Published: October 2005

This talk describes the design of a special-purpose headphone receiver which uses the Western Electric 640AA condenser microphone as the motor element. The acoustic circuit between the 640AA and the ear canal is so chosen that the frequency response at the eardrum is essentially flat from below 20 Hz to about 25 000 Hz.
Validation of ear simulators
Authors: Burkhard M. D.
Published: October 2005

Earphone calibration couplers that more closely reproduce the median human ear are being evaluated in a number of laboratories as new standards to replace simple volume couplers such as the 2-cc coupler for insert earphones and the 6-cc couplers for supra-aural earphones. The new couplers [e.g., J. Zwislocki. J. Acoust. Soc. Am. 50. 110(A) (1971): or H. G. Diestel, 8th Int. Congr. Acoust. (1974)] use multiple acoustic elements that must be controlled during manufacture and that must be checked during the life of the coupler to verify accuracy as a calibrating standard. Methods of measurement, with standard electronic laboratory instruments, of transfer impedance magnitude are described and criteria given for checking out a coupler. The methods depend on, but are not restricted to, the use of a high-stiffness-impedance acoustic source and use of the coupler microphone to detect sound pressure. Examples of defects and their correction are given. [This paper uses material from Industrial Research Products Rep. No. 20022-1, “Zwislocki Coupler Evaluation with Insert Earphones,” for Knowles Electronics, Inc., by R. M. Sachs and M. D. Burkhard.]
Eardrum impedance and ear canal geometry
Authors: Shaw E. A. G.
Published: October 2005

A consistent description of the human external ear must take into account a diversity of data concerning (a) the transformation of sound-pressure level from the free field to the eardrum, (b) the transfer functions from the ear-canal entrance and insert positions to the eardrum, (c) the pressure distributions in the ear canal and concha, (d) eardrum impedance, (e) insert earphone response. (f) ear-canal length and volume (directly measured), and (g) sex differences. A cylindrical canal 23 mm in length and 7.5 mm in diameter satisfies most of the data fairly well but places the primary resonance frequency of the complete external ear at a frequency 5%–7% higher than the observed value. The discrepancy is probably associated with the connection between the canal and the concha.
Modeling the eardrum as a doubly curved shell using the finite-element method
Authors: Funnell W. R. J. , Laszlo Charles A.
Published: October 2005

The eardrum was earlier modeled as a plane membrane under tension using the finite-element method [J. Acoust. Soc. Am. 56, S3 (1974)]. It has now been modeled as a curved shell, taking into account the actual three-dimensional shape. The effects of the embedded malleus, and of the stiffness of the ossicular suspension, are included. The model is strictly static, or low-frequency. Calculations have been done for the cat, guinea pig, and human, and the results were compared with recent experimental data on eardrum vibration. The model is able to match measurements of peak drum displacement and of manubrial-tip displacement. We have studied the effects of variations of several parameters, including the curvature of the sides of the eardrum. We have also calculated the effect of the type of anisotropy assumed by Helmholtz. [Supported by the Medical Research Council of Canada, The Québec Department of Education, and the McConnell Foundation.]
Tympanic membrane shape determined by moiré topography
Authors: Khanna S. M. , Tonndorf J.
Published: October 2005

Calculations of the modes of tympanic membrane (TM vibrations require knowledge of its shape. Moiré topography may be employed for determining such shapes. A parallel beam of light produces shadows of a Ronchi ruling on the object under study. When the object is then viewed (or photographed) through the ruling, contour lines are observed, each line representing one given height. The spacing between these lines depends on the number of lines/mm of the ruling, on the angle at which the object is being viewed with respect to the incident beam, and on the shape of the object. Contour lines of high contrast require the object to be placed very close to the ruling. Since this was impossible with the TM, silastic casts were made of the TM of cat and guinea pig. Their weight was less than 0.05 g and, therefore, did not appreciably alter the shape of the TM. The method of calibration and results of the measurements are discussed. [Supported by NIH grants.]
Transfer functions of hearing-aid earmolds: empirically and computer-generated data
Authors: Franks John R. , Egolf David P.
Published: October 2005

Acoustic transfer functions for two different configuration hearing-aid earmolds (solid, side-branch vented) were measured empirically and the transfer functions for the earmolds were generated by computer programming techniques using classical acoustic transmission line theory. In the empirical phase of the study a special signal source designed to provide a constant sound pressure to the earmold over a wide frequency range was used. The earmolds were loaded by a Zwislocki coupler mounted in the head of KEMAR. The physical dimensions of the two earmolds were used as the bases for generating the analogous computer transfer functions. The empirical data and the computer curves were in good agreement. The data indicate that, by the use of a constant pressure source, acoustic characteristics of earmolds are amenable to investigation and modeling, providing information as to the role of the earmold as part of the overall amplification system.
Progress in development of a multichannel acoustic nerve stimulation prosthesis for the totally deaf
Authors: Merzenich M. M. , White M. , Schindler R. A. , Schindler D. N. , Michelson R. P. , Bjorkroth B.
Published: October 2005

Neurophysiological and anatomical studies in cats have been directed toward determining the feasibility of development of a multichannel acoustic nerve stimulation prosthesis with potential application as an aid for profoundly deaf individuals with surviving acoustic nerve. From recording experiments taking advantage of the binaural frequency response characteristics of neurons within the central nucleus of the inferior colliculus, the pattern of excitation across the acoustic nerve array can be defined for any intracochlear electrode array. These single-unit studies reveal that it is possible to excite a series of restricted sectors of the acoustic nerve array from within the scala tympani, with appropriately positioned electrodes mounted in silastic carriers that fill the scala (displace perilymph). Precisely constructed electrode arrays in carriers molded to fill the scala can be fabricated using dies of the scala made from soft-metal cochlear casts. Implantation of these multichannel electrode arrays does not lead to significant direct destruction of the acoustic nerve in prior normal or prior neomycin-deafened ears, over a time course of many months. [Supported by NIH Grant NS-11804.]
Effect of activating-signal bandwidth on acoustic-reflex thresholds
Authors: Popelka G. R. , Margolis R. H. , Wiley T. L.
Published: October 2005

Acoustic-reflex thresholds were determined as a function of activating-signal bandwidth in 10 subjects with normal hearing sensitivity and eight subjects with noise-induced sensorineural hearing loss. Acoustic-reflex thresholds were measured by monitoring the acoustic impedance at the tympanic membrane for multicomponent activating stimuli centered logarithmically around 250, 500, 1000, 2000, and 4000 Hz. Normal listeners displayed monotonically decreasing acoustic-reflex thresholds as bandwidth was increased by adding additional components to the complex activating signals. A knee in the functions occurred at values of bandwidth similar to previously reported critical bandwidths for the acoustic reflex. Sensorineural hearing loss altered the functions such that acoustic-reflex thresholds tended to be elevated when the spectral content of the activating signal extended into the hearing-loss region. This resulted in flatter functions relating acoustic-reflex thresholds to activating-signal bandwidth.
Clinical procedure for selecting the frequency response and level of amplification for hearing-impaired adults: a progress report
Authors: Asp C. W. , Berry J. S.
Published: October 2005

This procedure includes: (1) conventional audiometry (pure-tone, SRT, and PB tests); (2) a filtered nonsense syllable test for detection thresholds; (3) a nonfiltered word test where the test words are divided into five separate categories based on the frequency regions thought to be important for the perception of each word, and scored according to the percent correct in each category; and (4) an articulation curve for the percent correct as function of the presentation level (dB). Some of these tests are based on the principles of the verbo-tonal method. A multifilter system is used to select a frequency response with the highest discrimination score; it usually emphasizes where the patient has the most hearing. The patient receives approximately 18 hours of auditory training. Then, a hearing aid is selected with a frequency response that corresponds to one used in training. The results are encouraging; however, these tests need further research.
Simple rating of hearing-protector effectiveness
Authors: Tobias Jerry V.
Published: October 2005

Although hearing protectors should ideally be rated according to how much attenuation they provide in the actual noise in which they are worn, testing them that way is impractical. Compromises have been suggested; all are based on the ANSI “Measurement of the Real-Ear Attenuation of Ear Protectors at Threshold” (Z24.22-1957, R1971). In general, the effectiveness in noise of an ear protector is calculated from the Standard measurement of attenuation and from the spectrum of the noise. If the noise spectrum is unknown, the protector's average response in a number of typical noises is used. Such estimated attenuation values may be calculated to show the likely effectiveness for the worst case in any proportion of the population of users. Thus, a rating number might refer to the ear protector's performance with 50% of the population or any other preselected percentage. This paper describes two- and three-digit figures-of-merit for rating the effectiveness of ear protectors in most noise environments and for a range of percentages of users. Each digit is selected to represent the performance of the device-under-test relative to the performance of a large number of similar devices. Although the procedure for computing the number is complex, its meaning is simple and should be easy for most prospective users to understand.
Difference frequency generation by forced-air bubbles
Authors: Lockwood J. C. , Smith D. P.
Published: October 2005

An increase of 30 dB in the sound-pressure level at a 10-kHz difference frequency, measured at a range of 1.83 m, was obtained by introducing bubbles into the region of interaction of a parametric projector. The bubbles, produced by forcing air through a microporous filter, formed a thin screen that was situated perpendicular to the acoustic axis of the source transducer. The primary frequencies were 45 and 55 kHz. The difference frequency beam pattern was measured and appeared to be governed by the broadside directivity of the insonified region of the bubble screen. A theoretical model was derived that demonstrates the effects of bubble size and primary frequency on the difference frequency level. It was shown that the maximum difference frequency level is obtained from bubbles resonant at the primary frequencies. The results of this investigation are consistent with those of Clynch and Rolleigh [J. Acoust. Soc. Am. 55, S51(A) (1974)], who reported difference frequency level enhancement due to a small volume of bubbles produced by cavitation. [This work was supported by ARPA and the Naval Sea Systems Command.]
Parametric acoustic receiving array. I. Theory
Authors: Truchard James J.
Published: October 2005

In this paper closed-form solutions for several configurations of the parametric receiving array are found. First, the solution for the interaction of a high-frequency spherical wave from a point source and a low-frequency plane wave is obtained theoretically using a two-dimensional stationary phase solution of Westervelt's scattering integral. The point source solution is in turn used to generate the solution for parametric receiving arrays with various pump transducers, including a truncated line source transducer, a rectangular piston transducer, and a circular piston transducer. In each case, the observer is assumed to be in the farfield of the pump transducer. However, the result includes the effects of interaction in the nearfield of the pump transducer. The solution of the parametric receiving array with a point source pump and truncated line receiver is also found. The theoretical solutions also include the effects of misalignment of either the pump or receiving transducer.
Parametric acoustic receiving array. II. Experiment
Authors: Truchard James J.
Published: October 2005

A series of experiments was conducted with a 48-ft parametric receiving array with a pump frequency of 90 kHz. In the experiments, an omnidirectional transducer was used with either a rectangular piston transducer or a square piston transducer. Each transducer could be used as either the pump transducer or the receiver so that a variety of parametric receiving array configurations could be realized. A small rotator was used to allow independent rotation of the piston transducer for measurement of the effects of misalignment of the piston transducer. Theoretical and experimental results are compared for the parametric receiving array with several transducer arrangements. With either the pump transducer or the receiver misaligned, the difference frequency beam pattern is an asymmetrical beam pattern and is the mirror image of the sum frequency beam pattern. The agreement between the theory and the experiment was excellent.
Fundamental frequency of plates with boundaries deviating slightly from circular
Authors: Eastep F. E.
Published: October 2005

An exact solution for the fundamental frequency of a thin uniform plate can be obtained when the boundary is circular, rectangular, triangular, or elliptical or when the inner and outer boundaries are concentric circles or confocal ellipses. If either boundary has some other shape, approximate methods must be used. This paper presents a simplified approximate method for determining the fundamental frequency of thin plates whose boundaries deviate only slightly from circular. This method was initially used by Rayleigh in his investigation of the free vibration of irregular-shaped membranes. The radii of both bounding curves are approximated by a truncated Fourier series. The plate transverse motion and the normal derivative of motion, which are written as superpositions of the modes of a circular plate, are forced to vanish on the approximated boundaries. An approximate characteristic equation is obtained from which the approximate fundamental frequency may be found. This technique is used to determine the fundamental frequency of the following: (1) clamped elliptical plate, (2) eccentric annulus plate, (3) a square plate with a circular cutout, and (4) a square plate with a square cutout. Comparisons with exact solutions, when known, are given.
Sound radiation from multilayered structures
Authors: Kutschale Henry W.
Published: October 2005

The exact integral solution of the wave equation is derived from a vertical harmonic point force within a solid layer of a laminated structure of interbedded fluid and solid layers resting between two fluid half-spaces. Structural damping is included in the theory by introducing complex compressional and shear velocities in each solid layer and a complex compressional velocity in each fluid layer. The farfield radiation pattern is rapidly computed from the integral solution by application of the principle of stationary phase. Sample computations illustrate coincidence effects associated with flexural and extensional waves traveling in the layered structure. For a single solid layer resting on a fluid, the radiation patterns over a wide frequency range are generally in good agreement with results derived by Feit [J. Acoust. Soc. Am. 40, 1489–1494 (1966)] from the Timoshenko-Mindlin theory of flexural motions on thick plates. Exceptions to this agreement are noted for coincidence effects associated with extensional waves traveling in the structure. The present theory is applied to problems of sound radiation from floating pack ice of the central Arctic Ocean.
Vibrations and noise of textile loom picking sticks
Authors: Pierce Allan D.
Published: October 2005

Recent experimental work suggests that picking-stick vibrations are a dominant source of noise from fly-shuttle-type textile looms. A picking stick is modeled as a beam with internal damping. Impacts from the incoming shuttle are modeled by assuming the shuttle to be a rigid body with mass M and initial velocity V0 just prior to impact. The energy transfer during impact to higher-frequency vibrations of the beam is treated approximately by ignoring wave reflections from the far end of the beam, and a correspondingly simple expression is derived for the net energy transferred within any frequency band during a single impact. This energy is subsequently assumed to be distributed among the vibrational modes within the corresponding frequency band but to be relatively quickly dissipated by transmission out of the beam to other parts of the beam and by internal damping. However, during the time the energy is present, the beam is vibrating and radiating sound. The resulting sound radiation is computed based on a modification of the theory of sound generation by transversely oscillating slender bodies.
Auditory filter shape by subthreshold summation
Authors: Taylor M. M. , Smith S. M. , Tytla M. E.
Published: October 2005

The shape of the primary auditory filter has been calculated from masking measurements [R.D. Patterson, J. Acoust. Soc. Am. 56, S36 (1974)], It may also be determined using subthreshold summation, as Kulikowski and Kingsmith [Vision Research, 13, 1455–1478 (1973)] have done for visual feature detectors. The masked signal is a combination of 500 Hz with another frequency (e.g., 515 Hz) of equal or lower intensity. The threshold intensity of 500 Hz is plotted in linear coordinates as a function of the intensity of the other component, and the resulting curve determines two points on the filter characteristic. The relative gain of the 500-Hz filter at 515 Hz is given by the negative slope of the function at low intensities of 515 Hz, and that of the 507.5-Hz filter at 500 or 515 Hz is independently determined from the threshold when the two components are equal. Preliminary results using a noise level of 0 dB/Hz suggest a Gaussian filter of about 25-Hz bandwidth, whereas masking measurements suggest about 65 Hz. For visual orientation detectors, Kulikowski et al. [Visual Research, 13, 1479–1486 (1973)] found bandwidths a factor of 4 narrower when using subthreshold summation than those found by masking.
Some parameters of successive backward-forward masking of gated signals by gated noise
Authors: Creelman C. Douglas
Published: October 2005

An experimental paradigm to investigate “lateral inhibition” in hearing introduced by Houtgast involves detecting gated bursts of sinusoidal signals which are rapidly alternated with gated noise. The noise is low-pass filtered, and thresholds for the sinusoids are measured at frequencies in the vicinity of the noise cutoff frequency. Houtgast's experiments used an adjustment procedure to measure thresholds. We attempted to obtain two-alternative forced-choice psychometric functions, varying both signal amplitude and noise power, to obtain more precise measures of whatever changes in detectability might be introduced by proximity of the noise cutoff frequency to the frequency of the alternating signal. Although some evidence of changes in detectability were found, effects were swamped in these preliminary data by the apparent fact that a small change in signal amplitude can produce very large changes in detectability, while large changes in noise power can have rather small effects on detectability. This implies that the size of an apparent threshold shift at a particular frequency will depend strongly on both the signal level used, and the noise background chosen. [Supported by Canadian National Research Council.]
Equal-loudness judgments as modified by adaptation
Authors: Weiler E. M. , Hood J. D. , Poole J. P.
Published: October 2005

Binaural judgments of equal loudness were studied as altered by 2 min of adaptation at four base level intensities (20, 40, 60, and 80 dB). Comparison and adapting stimuli were presented to 21 subjects at 1000 Hz, and judgments made by the method of adjustment. Adaptation at base intensity values ranged from 5.5 to 14.8 dB as intensity increased. Test values 10 dB above base levels showed a sharp drop in measured adaptation and test values at 20 dB above showed virtually no adaptation. An approximate rule of the effect of adaptation on loudness judgments is discussed based on sound-pressure levels of stimuli.