bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Responses from the Cat's Auditory Nervous System to Certain Repetitive Stimuli
Authors: Goldstein Moise H. , Kiang Nelson Yuan-sheng
Published: September 2005

A mathematical technique for the representation of repetitive stimuli has been outlined elsewhere [M. H. Goldstein, Jr., J. Acoust. Soc. Am. 28, 153 (1955)]. This technique characterizes signals in a bi-frequency plane by coordinates that correspond to periodicity and to Fourier frequency. We are reporting here certain electrophysiological experiments in which anesthetized cats were stimulated by amplitude-modulated wide-band noise. These stimuli have maximal structure along the periodicity dimension and minimal structure along the Fourier frequency dimension. The electrical responses were recorded by means of gross electrodes located near the round window of the cochlea and at various points of the auditory cortex. The following parameters of the repeated bursts of noise were varied: repetition rate, rise time, and duty cycle. Responses were analyzed with respect to amplitude and wave form as a function of the aforementioned stimulus parameters. Responses to clicks and bursts of tone were also obtained at these same electrode locations. A tentative neurophysiological interpretation of the reported findings is suggested. [This work was supported in part by the Signal Corps, Air Research and Development Command, and the Office of Naval Research.]
Physiological Evidence for the Masking of Low Frequencies by High
Authors: Deatherage Bruce H. , Davis Hallowell , Eldredge Donald H.
Published: September 2005

In guinea pigs with intracochlear electrodes, successive sound waves at 500 cps set off easily detectable, well-synchronized volleys of action potential (AP) and also the familiar cochlear microphonic (CM). At low levels of stimulation, a high-frequency band of noise centering around 7000 cps and having no appreciable acoustic energy in the 500-cps region will not mask these responses, but as the intensity of the high-frequency band is raised to moderately high levels, two results are seen. First, the 500-cps CM in the first turn is, as we might expect, overlaid with the high frequency. Unexpectedly, however, the AP is reduced and blurred. This is best explained as the elimination of that part of the AP to 500 cps that originates in the first turn. Second, at still higher intensities, the AP and CM in the third turn to a 500-cps pip are masked just as they would be by a lower level low-frequency band. A random, low-frequency CM now appears in the apical region. Apparently the ear responds, nonlinearly to the high-level noise and “detects” its envelope as random low frequencies of random amplitude. This anomalous masking is produced by noise but not by pure tones. [This work was supported under Contract N6onr-272 with the Office of Naval Research.]
Reducing Noise in a Sugar Refinery
Authors: Raes Auguste C.
Published: September 2005

During a certain phase of sugar refining, low-pressure steam is allowed to flow from boilers into vacuum pipes. The flow is controlled by straightway valves which are normally only very slightly opened. Flow velocity in the pipes is of the order of 165 to 290 ft per second. A very shrill, painful, and permanent hissing noise was produced, accompanied by complaints from everybody in the factory. Investigations showed the valves to be the noise generators, and the pipes to be the radiators. The obvious solution was to use valves with smaller diameters and combine them with Venturi tubes. This could not be done for sugar technique reasons. The solution adopted was to place functional sound absorbers along and around the vacuum pipes. The results were that the over-all sound pressure level dropped only from 99 to 97 db. One-third octave band analysis showed marked improvements above 1000 cps. The workers unanimously declare that the noise “has disappeared” and that they do not suffer any more. It is not always necessary to reduce the over-all sound pressure level. Reducing the level in a few disturbing bands is easier and satisfactory.
Measurements of Noise from Cooling Towers
Authors: Miller Laymon , Dyer Ira
Published: September 2005

During the past few years, noise measurements have been made on a number of water-spray cooling towers used with air conditioning systems or in conjunction with industrial processes. For these particular cooling towers, the water flow rate has been in the range of 300 to 1500 gallons per minute and the power rating of the air circulating fan in the range of approximately 712 to 40 hp. The over-all acoustic power level of these cooling towers has been computed from the measurements and found to lie in the range of approximately 115 to 120 db re 10−13 watt. The peak band power level falls in either the first (20–75 cps) or second (75–150 cps) octave frequency band, and the band power level appears to decrease at a rate of approximately 4 db per octave for the higher frequency bands. Data are presented to indicate the approximate proportion of noise contributed by the various noise sources in a typical cooling tower.
Differential Sensitivity to Synthetic Speech Sounds within and between Phoneme Categories
Authors: Harris K. S. , Liberman A. M. , Hoffman H. , Griffith B. C.
Published: September 2005

The use of synthesizers provides an opportunity to vary speech-like sounds in small steps along a single acoustic continuum. We find that at some points on such a continuum large changes in the acoustic stimulus have no effect on phoneme identification, while at other points small changes cause the listener's identification to shift abruptly from one phoneme to another. Casual observation led us to suspect that there might be related discontinuities in the discriminability of these sounds—that is, that discrimination would be less sharp, other things equal, between sounds in the same phoneme category than between sounds which lie on opposite sides of a phoneme boundary. This effect might be related to the difficulties that linguists often experience in hearing certain differences among the sounds of an exotic language. Discrimination and identification functions were obtained for a series of stimuli which differed in the second-formant transition. In one part of the experiment these stimuli were presented singly to listeners for identification as b, d, or g; in another part, the discriminability of the stimuli was measured by an ABX technique. It was found that discrimination was, indeed, better in the vicinity of phoneme boundaries than it was near the middle of a category. The obtained discrimination function was quite close to a function predictable from the identification judgments on the extreme assumption that the listeners were able to discriminate the sounds only to the extent that they could differentially identify them as b, d, and g. [This work was supported in part by the Carnegie Corporation of New York, and in part by the Department of Defense in connection with Contract DA49-170-SC-1642.]
On Stop Consonants
Authors: Halle Morris , Hughes George W. , Radley Jean-Pierre A.
Published: September 2005

Short-time energy vs frequency spectra of stop bursts, and formant transitions in the adjacent vowel have been studied. Sound segments consisting of burst or transition alone were submitted to listeners for identification. Results are discussed with the aim of developing possible identifying criteria utilizing cues in the burst spectra and in the transitions. [This work was supported in part by the Signal Corps, the Office of Scientific Research (Air Research and Development Command), the Office of Naval Research, and the National Science Foundation.]
Automatic Voice Equalizer
Authors: Smith Caldwell P.
Published: September 2005

Instrumentation for measurement of voice pitch, for automatic segmentation of voice signals, and for voice pattern-matching, tends to be rather sensitive to the equalization of an input voice signal. A system for automatically compensating for various fixed equalizations of an input voice signal has been devised. The automatic equalizer uses a set of contiguous-band filters. The input voice signals first pass through a fixed equalizer designed to create a relatively uniform distribution of levels among the filter channels. The output signal from each filter is rectified, and the resulting dc voltages are integrated over an interval of many seconds. In each filter channel the average dc voltage is compared with the longtime average of the mean of the voltages in the various channels, and a dc error voltage signifies the amount by which the average level in any channel deviates from the mean level. The dc error voltage in each channel is fed back to automatically control the gain of that channel. Output signals from the various filter channels are also summed before rectification to recover the ac voice signal.
Propagation of Sound into a Wind-Created Shadow Zone
Authors: Pridmore-Brown David C.
Published: September 2005

A solution is given to an approximate form of the wave equation corresponding to a sound source located above ground in a wind gradient. Owing to the effective refraction of sound rays in the presence of a wind gradient, the sound field on the upwind side of such a source will exhibit a shadow provided the wind velocity increases with height. The behavior of the sound field diffracted into this region is found to be similar to that in a temperature-created shadow. Within the normal region the solution reduces to ray acoustics in the high frequency limit. [Supported by Contract NAw-6463 with the National Advisory Committee for Aeronautics.]
Reflection and Transmission of Sound by a Moving Medium: A Simple Aerodynamic Interpretation
Authors: Ribner Herbert S.
Published: September 2005

Significant reflection and refraction occur for sound waves incident at an interface between moving streams. An analysis is made for plane waves (not necessarily periodic) impinging on a plane interface. The analysis and the physical interpretation are both simplified by using axes moving with the speed of the ripple that must develop in the interface. The acoustic problem is thus changed into the aerodynamic problem of the flows above and below a wavy wall (the rippled interface). In this view the angles of incidence and refraction are regarded as the respective Mach angles in two supersonic streams. The velocity difference between these streams is identical with that of the original two streams. The known angle of incidence thereby leads immediately to an equal angle of reflection and a simply related angle of refraction. The angle of refraction is imaginary when the associated velocity, calculated by the velocity-difference rule, is subsonic; this is a condition of total reflection. Strengths of the reflected and refracted waves are evaluated in simple form by application of compatibility conditions at the interface; these are believed to correct an error found in Keller's work. In particular, a region of strong amplification of the reflected waves is predicted.
Measurement of Sound Propagation through the Atmosphere near the Earth's Surface
Authors: Richards R. L. , Williams L. D. , Benson R. W.
Published: September 2005

The facilities for the measurement of sound propagation from air to ground for altitudes up to 5000 feet and for distances up to two miles will be described. Propagation has been studied for various angles from 15 to 90 degrees with the earth's surface. In addition to the measurement of sound, various measures of atmospheric meteorological conditions are obtained. The sound source is a Consolidated Vultee B-13 airplane which is flown in prescribed patterns above the recording installation. Instrumentation for recording and analyzing data will be described and illustrations of specific flight data will be presented. Results of this study will be presented in the following paper. [This research was supported by U. S. Air Force Contract AF33(616)-2470.]
Report on Sound Propagation Measurements over Ground
Authors: Oleson Stanley K. , Ingard Uno
Published: September 2005

Results of measurements carried out with the field equipment described at the last Acoustical Society Meeting [J. Acoust. Soc. Am. 28, 158 (H5) (1956)] are reported. Particular attention is given to the effect of ground in making the sound pressure decrease with the inverse second power of distance. Studies of this effect for various heights of the receivers and the sources are presented, together with other field data demonstrating the effect of wind and temperature gradients on sound propagation, A comparison is also made between propagation over an open field and through a wooded area. [Supported by Contract NAw-6463 with the National Advisory Committee for Aeronautics.]
Instrumentation for the Study of the Propagation of Speech over Ground
Authors: Goff Kenneth W. , Keast David N. , Wiener Francis M.
Published: September 2005

The instrumentation described in this paper was designed to facilitate a study of the propagation of speech over ground for distances of the order of one mile. The state of the atmosphere near the ground plays an important part in determining the propagation of the speech signal. Therefore, attention was directed to specialized micrometeorological instrumentation for determining the state of the atmosphere and relating it to the measured sound attenuation. An array of precision cup anemometers and thermocouples on a 30 foot tower are scanned automatically to provide a measure of the vertical wind velocity and temperature gradients. A high-speed vane and thermistor are used to give a measure of atmospheric turbulence. The cup anemometers were calibrated in a wind tunnel and a gust calibration was made for the turbulence measuring devices. The electrical signals obtained from these systems are fed into a mobile laboratory for analysis and magnetic recording. The recording maintains the original time relationship with the acoustic signals picked up along two test courses. The mobile laboratory also contains a power amplifier with tape recorder input for driving the loudspeakers and equipment for automatically scanning the seven microphones on each course. This system was successfully used during a four-week measurement program near DeBlois, Maine, during the fall of 1955. [This work was supported by the U. S. Signal Corps under Contract No. DA-36-039 SC-64503.]
Measurements and Computation of the Loudness of Noises
Authors: Quietzsch Gerhard
Published: September 2005

Computing the total loudness of noises by summing the loudness of octave bands, according to the method used by Mintz and Tyzzer, still gives results that deviate from subjective measurements. Apparently, part of this deviation is caused by masking in the lower octaves. There are two possible ways of taking account of masking, either by correcting the loudness of the single octave bands before summation—the corrections depend on the distribution of energy in the whole spectrum—or by dividing the spectrum into bands of such width that the contribution of the computed loudness of each band corresponds to the real effective magnitude. The two possibilities are investigated empirically; only the second is suitable as the basis for constructing an objective loudness meter. Using six bands for the summation of loudness proves most favorable. The upper five bands are nearly equal in width on the “mel”-scale, whereas the lowest band is of greater width. The results of subjective and objective measurements of different noises are discussed and compared with the results of loudness computations.
Masking as a Function of Duration for Various Interaural Phase Combinations
Authors: Blodgett H. C. , Feddersen W. E. , Jeffress L. A.
Published: September 2005

Earlier studies have related the masked threshold for a tonal signal to its duration, where the signal and the noise are both in phase at the two ears. The present study is concerned with the cases where either the signal or the noise (or both) is reversed in interaural phase. Five combinations were used: noise and signal both in phase; both reversed in phase; noise in phase, tone reversed; tone in phase, noise reversed; and monaural. Durations of the 500-cps tonal signal ranged from 800 msec to 10 msec. The data agree with earlier studies for the in-phase condition and exhibit the same values for the monaural case and for the case where both the noise and tone are reversed in phase. The other two conditions show a somewhat different curve for masking vs duration, exhibiting substantially larger differences in masking level for the short durations than for the long. The data support a conclusion, tentatively proposed in an earlier paper, that interaural detection of a signal is less adversely affected by shortening the duration than is monaural detection.
Interaural Intensity Ratios and Sound Localization
Authors: Feddersen W. E. , Sandel T. T. , Teas D. C. , Jeffress L. A.
Published: September 2005

In an earlier study the writers measured the interaural time differences and interaural intensity differences for various azimuth positions of a sound source. The present experiment is an attempt to correlate the findings of that study with subjects' actual responses in a sound localization problem. The technique used was that of matching the position of a noise having an interaural time difference with that of a tone having an interaural intensity difference. The noise and tone were presented alternately via earphones, using a 100-msec rise and decay time to avoid cues from the envelope. Interaural time differences for the noise were chosen to correspond to azimuth positions of 0°, 23°, 45°, and 60°, and the subjects were asked to adjust the interaural intensity difference until the tone seemed to be in the same place (in the head) as the noise. This proved to be a possible judgment, although the match was not satisfactory to the subject for frequencies below 1500 cps. The nine frequencies employed ranged from 500 to 6000 cps. The results exhibited the expected increase of interaural intensity difference with azimuth angle and with frequency above about 1500 cps, but they were generally larger than the corresponding interaural differences from probe measurements. The subjects required a larger interaural intensity difference for a particular azimuth position and frequency than would actually be provided by a tone at that azimuth position and of that frequency. We must therefore, infer that subjects will localize actual high-frequency sources nearer to the median plane than they are. This agrees with earlier results on the localization of airborne sound reported by the present writers.
Objective Allocation of Sound Image from Binaural Stimulation
Authors: Kikuchi Yoshimitsu
Published: September 2005

As is well known, in the case of a sensation stimulated with binaural earphones, the location of the sound image inside one's head is done by subjective judgment. Now I would propose a new conception, i.e., an “objective position” of sound image. In order to realize this “objective allocation,” I have inaugurated two methods as follows: (1) The “Null Method”: If the binaural earphone circuit is momentarily reversed—thus interchanging right and left sides—, the subject then perceives the image rapidly moving to a new position. The closer the physical position of the sound source is to the exact center, the less will be the image movement. The sensation of this image movement is so very sharp that a minute movement can be perceived. The image position at the “adjustment of no-movement” or at “nullity,” is determined with much smaller individual and group errors than by the well-known subjective-center method. Accordingly, the image position at which there is no movement can be considered an “objective center.” (2) The “Comparative Sensation Method”: This consists of a comparison of the image-position of the sound being tested with that of a pilot-signal—with a controllable phase-difference—introduced into each ear. This sensation is also very sharp, and the image position coinciding with the pilot signal image can be considered an “objective position.”
Acoustics of Large Offices
Authors: Lang William W.
Published: September 2005

Noise control is of paramount importance in a large area divided by partial-height partitions into offices for scientists and engineers who require an optimum acoustic environment for creative work. A study has been made of noise conditions in a room 420×66×10 ft which has been partitioned into 220 offices for technical and stenographic personnel. Measurements were made of the noise levels attributable to each of the sources present in the room. Subjective reactions to noise conditions were obtained from a cross section of the occupants before and after measures were taken to improve environmental conditions. The effectiveness of each of these measures is discussed with particular emphasis on those designed to reduce “verbal” noise.
Sound Isolation Requirements for Public School Classrooms
Authors: Lane Richard N. , Mikeska Eugene E.
Published: September 2005

Acoustical measurements are presented showing transmission loss achieved between classrooms in several public schools of very recent design in the Southwest U.S.A. Several types of ventilating systems employing natural air circulation only were measured and their effectiveness evaluated. Minimum isolation requirements for public school classrooms are discussed.
Reactive Components in Sound-Absorber Construction
Authors: Becker Carl
Published: September 2005

Nonuniformity of sound-absorber construction is currently applied to improve absorption characteristics. However, realization of optimum effects has been hindered by difficulties in determining suitable critical combinations of numerous parameters. A fruitful approach is to treat first the preponderantly reactive components, and later the complex combinations. Provision of more than one reactive pair widens the high absorption range. Such combinations are described, in general, by ξ the frequency interval between successive zeros and poles in terms of the fundamental frequency, and Ω a function related to construction thickness and fundamental frequency. When circuits are realized, it is found that optimum values of ξ lie between 0.7 and 1.5, for increasing absorption band width below 500 cycles per second. Ω varies inversely with number of reactive component pairs, and, in this range, may be reduced below 1.0. For fundamental frequencies below 100 cycles per second, increased band width is obtained when ξ exceeds 2.0. Besides providing shunt resistances in the form of tank fillings, porous materials can be applied to the primary surfaces for widening the high-frequency absorption range. Tank fillings have flow resistances 5 to 20 times greater than facings. Low-frequency absorption levels for complex constructions are similar to levels for single panel absorbers of the same over-all thickness, but the absorption band can be extended over 4 octaves by incorporation of 6 and more reactive pairs.
Electronic Binary-Selection System for Phoneme Classification
Authors: Wiren J. , Stubbs H. L.
Published: September 2005

A successive binary-selection system for automatic classification of spoken English into several groups of phonemes is described. The first step separates voiced from unvoiced by measuring the filtered output in the range of the pitch frequency. The next step separates turbulent (noise-like) from nonturbulent by two alternative methods, one by measuring the density of zero crossings, the other by measuring the filtered output in the range of the first formant. Nonturbulent sounds are classified into six groups of two or three phonemes each in successive selections based on spectrum measurements. For each of the two groups of phonemes being separated in a given step, a frequency band is chosen where phonemes of that group have large amounts of energy compared to those of the other group. The polarity of the weighted difference of the corresponding band-pass filter outputs determines the classification. Unvoiced turbulent sounds are separated into stops and fricatives by means of the information contained in the onsets of these sounds. Two of the fricatives, s (see) and ∫ (she), are separated by means of their zero-crossing density levels. Results obtained from working models of the classification devices above will be presented in various forms. The system is adaptable for future extension to obtain more complete phoneme identification. [The research in this paper has been made possible through support and sponsorship of the Electronics Research Directorate, Air Force Cambridge Research Center, under Contract No. AF 19(604)-1039, Item I.]
Technique for Coding Speech Signals for Transmission over a Reduced Capacity Digital Channel
Authors: David Edward E. , McDonald Henry S.
Published: September 2005

The process of transmitting speech signals over digital channels requires sampling and quantizing the signals into a discrete number of levels occurring at discrete times. Speech signals quantized into 128 levels and sampled 8000 times a second are considered good quality for communications purposes and require a transmission rate of 56 000 binary pulses per second. It is the purpose of this paper to describe a coding technique that allows comparable quality speech to be sent over digital channels at pulse rates of from 20 000 to 40 000 binary pulses per second. The coding scheme consists of filtering the speech into two frequency bands and digitalizing the bands separately. The high-frequency band can be quantized into fewer amplitude levels and the low-frequency band requires fewer samples. The speech is remade at the receiving terminal by adding the outputs of the two channels. Because the average spectrum of speech signals falls off at high frequencies, the use of few levels in the high-frequency band introduces only a small relative error in the total signal. A typical system might use a 1000-cps dividing frequency and 64 and 4 levels and 2000 and 8000 samples, respectively, to produce a pulse rate of 28 000 binary pulses per second.
Theory of Ultrasonic Thermal Relaxation in Liquids
Authors: Litovitz Theodore A.
Published: September 2005

The mechanism of energy transfer in the thermal relaxation process in liquids is considered theoretically as being due to a binary collision phenomena. The theory of Schwartz and Herzfeld, which has been successful in explaining the energy transfer process in the gas state, is applied to the liquid state. The main difficulty in application of the Schwartz-Herzfeld theory is in the evaluation of the mean free path of the molecule in the liquid. This problem is considered in terms of several different free volume theories of the liquid state. It is shown that by the use of the cubic cell model for liquid CS2 very good agreement is obtained between the Schwartz-Herzfeld theory and the experimental results for the pressure dependence of the relaxation time, the probability of transfer of energy per collision, and the temperature dependence of this probability. These results indicate that the mechanism of the thermal relaxation process is the same in the gas and liquid states.
Differential Method of Measuring Ultrasonic Absorption in Liquids
Authors: Mikhailov I. G.
Published: September 2005

We give a new method of measuring the difference of ultrasonic absorption of two liquids. Two pulse generators excite two ultrasonic quartz transducers in two vessels. Having passed through the two vessels, the pulses are reflected from the opposite walls of the vessels and are received by the same quartz transducers. The received signals are amplified, detected, and then amplified again by a differential dc amplifier at the output of which there is a milliammeter. The milliammeter readings are proportional to the difference of two liquids absorption coefficients. The sensibility of the apparatus is evaluated by the value xΔα giving a current 1 ma (x—the double width of the vessel, Δα—the difference between absorption coefficients). For example, at x = 9 cm the sensibility equals Δα = 0.01 cm−1 per 1 ma. The accuracy of Δα measurement is nearly 3–5%. By means of the apparatus described in the foregoing, one can measure the absorption of ultrasonic diluted solutions, the temperature absorption coefficients of ultrasonic waves in liquids, coefficients of reflections from solid-liquid, liquid-liquid boundaries, and other applications.
Absorption of Sound in Humid Air at Low Frequencies
Authors: Horiuchi Isaburo
Published: September 2005

The reverberation technique of Knudsen has been applied to the measurement of the absorption of sound over the frequencies 300 to 3000 cps in air with mole ratio concentrations of water vapor ranging from 0 to 0.02. Pressures from 5 cm Hg to atmospheric and temperatures from 0°C to 65°C were employed in the study. With the use of a 66-in. spherical resonator and dry nitrogen gas as reference, following the method of Delsasso and Leonard, it has been possible to observe the anomalous absorption of humid air down to 300 cps. Pertinent graphs for the gases studied and detailed description of the experimental apparatus will be presented. [Support of this work by subcontract with the University of Michigan Signal Corps Contract No. DA-36-039-SC-52654 is acknowledged.]
Effect of Heat Radiation on Sound Propagation in Gases
Authors: Smith P. W.
Published: September 2005

The classical analysis of the effect of heat radiation assumes that the radiation is only slightly absorbed in the space of one acoustic wavelength; these results are sometimes then extrapolated to very low frequencies. This paper presents a re-examination of the effect. Account is taken of the fact that a gas radiates energy of given electromagnetic wavelength in proportion to its corresponding coefficient of absorption. Since the peak absorption coefficient (nepers per meter) may be rather large in some gases, no restriction is placed upon the value of the absorption per acoustic wavelength. The result indicates that the increase of acoustic absorption per wavelength with decreasing frequency is markedly reduced when the maximum radiation absorption per wavelength approaches unity.
Sound Absorption in Wide and Capillary Tubes at Audible Frequencies
Authors: Mariens P.
Published: September 2005

The attenuation constant in air of acoustic amplitudes has been measured for pressures from 2.3 to 0.18 atmos in a cylindrical tube of 5.16-cm diameter and in cylindrical capillary tubes of 0.10-cm and 0.15-cm diameter. In the first series of measurements the amplitude of stationary waves in the wide tube is measured as a function of the distance to the end, and the attenuation constant calculated. In the second series of measurements the measuring tube is closed by a sample of capillary tubes; the absorption coefficient and the phase difference at the input of the samples are measured and from that the attenuation in the capillary tubes is calculated. In both cases it is found that the theoretical values of Kirchhoff-Helmholtz are about 13% lower than the mean experimental ones.
Experimental Determination of Threshold Reliabilities for Four Methods of Automatic, Self-Testing, Pulse-Tone Audiometry
Authors: Voots Richard J. , Reger Scott N.
Published: September 2005

The development of a satisfactory, automatic, self-testing audiometric system (based on the pulse-tone techniques suggested by Gardner, Harris, Reger and Newby et al.) reveals the need for an investigation of the psychophysical procedures that might be used in such a system. Preliminary studies led to selection of four practical methods of threshold determination suitable for this project. Final choice of a single method requires a determination of statistical reliability as well as operational suitability of the method. Experimental apparatus was constructed to permit automatic testing by the four methods. Young adult subjects were tested with one of the four methods (randomly assigned) at three frequencies. A three-dimensional experimental design, permitting the use of analysis of variance, furnished an estimation of variance to be assigned to factors in the design, and also measures of reliability for comparison of the four methods. The results contribute data needed for selection of the method to be used in a final practical version of an automatic, self-testing system. [This work was supported by the U. S. Air Force School of Aviation Medicine.]
Contribution to the Study of Specifications for Audiometers
Authors: Chavasse Pierre , Lehmann René
Published: September 2005

Since 1936, the problem of specifications of audiometers has been faced in many countries and since then various national standards have been adopted which differ from one another principally in the definition and the values of “absolute zero” for different frequencies. The aim of the present work is to show the cause and the nature of the differences noted above and to present the results of three series of experiments that have been conducted in France, beginning in 1942, in order to establish the normal threshold of hearing by air conduction. The authors describe briefly the methods and apparatus used, as well as the technique that was employed to correlate the values obtained for human ears with values measurable for an artificial ear. They compare the results thus obtained with those of previous investigations and conclude by proposing values that should be acceptable to all countries.
A Further Study of the Influence of Sounds on the Endocrine System
Authors: Romani J. D. , Bugard P.
Published: September 2005

(1) Guinea pigs seem to sustain less well the stress caused by sound than do dogs or rabbits. The hyperactivity of the anterior lobe of the hypophysis, of the thyroid, and the adrenals remains within physiological bounds in the dog and the rabbit, and disappears after prolonged exposures (200 hr) to intense noises (1 to 4 kc at 130 to 140 db). (2) Two-thirds of our guinea pigs submitted to sounds of 100 to 125 db died spontaneously after 12 to 18 hr. Their pituitary glands showed congestion, with degranulation of the acidophile cells; the thyroid was inhibited and unable to react to over-stimulation. The adrenals showed a decrease of lipoids, though less than after stimulation by ACTH. (3) Including the results of former work, we may state the facts that we were able to demonstrate in the following order: (a) Ultrasonics of 22.5 kc at 160 to 165 db for 1 to 4 min induces a destruction of the medullar adrenal area, with the cortical area intact; death appears in a few minutes, with an increase of the body temperature. (b) Sounds of 100 to 125 db for 15 to 25 min induce in the guinea pig an alarm reaction at the stage of exhaustion; death appears in 12 to 48 hr. (c) Sounds of 1 to 4 kc at 130 to 140 db for 1 to 4 hr induce a well-compensated alarm reaction in the dog and the rabbit. If continued during 200 hr, these subjects show adaptation, with recuperation of normal functions of the endocrine system.
Semantic Value of French and American Crow Calls Tested Reciprocally
Authors: Busnel R.-G. , Giban J. , Gramet Ph. , Frings H. , Frings M. , Jumber J.
Published: September 2005

In France, we have studied the reactions of certain crows to the recorded assembly call and alarm call of the American eastern crow, and the reactions of certain gulls to the recorded food-finding call and alarm call of the American herring gull. For the French gull L. argentatus, the same species as the American form, neither of the calls provoked observable reactions when broadcast from distances of 50 to 1200 m. In the United States the food-finding call is strikingly attractive and the alarm call repellent. With roosting French crows, the alarm call of the American species had no effect. The assembly call, in 52 tests near Paris, provoked several reactions similar to the reactions evoked in American crows by this call. In the United States a few recorded calls of French crows were tested by broadcasting to the Eastern Crow, including cries of nestling C. frugilegus and distress calls of adult C. monedula and C. corone. The former elicited no observable reactions in Maine during the summer, but proved slightly attractive in Pennsylvania during the winter; the distress calls produced no observable reactions. Unfortunately, no attractive calls (such as the assembly call) of French crows have been received to date for testing in the United States. These preliminary experiments have some interesting implications so far as ideas of animal pseudo-language are concerned. It is curious that calls of the same gull species may not have generalized meaning; the alarm or distress calls of the crows, likewise, seem to lack general significance. On the other hand, the assembly call of the American eastern crow releases in three different species of French crows the same reaction as in the American species, thus apparently having a similar semantic value for all. The reactions of American crows to the cries of French nestlings suggest a generalized semantic value with some specific overtones.
Evaluation of Ear Protective Devices
Authors: Blackstock David T. , Hansen Ronald G.
Published: September 2005

Ear protective devices have been evaluated according to the procedures recently proposed by the American Standards Association (pure tone, binaural, free field, threshold shift method). To obtain an estimate of subject variability, attenuation values for the V-51R ear plug were determined for twenty subjects, with five replications for each subject. The results both of this study and of an extensive program for the evaluation of protective devices will be reported.
Noise Canceling Headset—an Active Ear Defender
Authors: Simshauser E. D. , Meeker W. F. , Balakrishnan A. V.
Published: September 2005

This paper is of the nature of a progress report on a device discussed at a previous meeting of the Acoustical Society [J. Acoust. Soc. Am. 27, 207 (1955)]. Two headset systems for reducing noise by acoustic interference are under study. Before working models can be made, the transfer characteristics (amplitude and phase) of the various components must be determined. Noise reduction is critically dependent on the phase and amplitude of the interfering sound and so sources of variation in the transfer characteristics must be located and minimized. This requires high accuracy in the measurements, and special techniques are used. Data will be presented for several headsets, including one designed to minimize variations in the transfer characteristics. [Work supported by U. S. Air Force and U. S. Army Signal Corps.]
Underwater Hearing Thresholds
Authors: Hamilton Paul M.
Published: September 2005

Underwater hearing thresholds were measured at frequencies of 250, 500, 1000, 2000, and 4000 cps on four Aqualung equipped divers known to have normal hearing in air. In the frequency range investigated, the hearing threshold underwater is from 44 to 60 db greater than the minimum audible fields in air, and the shape of the threshold vs frequency curve is different. Mechanisms based upon the changed impedance relationships between the ear and the medium are invoked to explain the loss of sensitivity at 250 and 500 cps. It is suggested that the greater loss at 1000, 2000, and 4000 cps is caused by a shift in the resonant frequencies of the external meatus when it is filled with a medium having a different characteristic impedance. Evidence is presented that indicates that hearing underwater is at or near the bone conduction threshold, and this is considered as an alternate explanation for the change in shape of the threshold curve.
Determining Acoustic Quality from Reverberation Curves
Authors: Brüel Per V.
Published: September 2005

A series of reverberation curves are recorded with small frequency intervals and, because of the technique used, the curves are placed close together in a manner similar to the well-known “pulse glide method.” No pulse or white noise is used, but normal warble tone, with a small band width and modulation frequency about 10 per sec is applied. By using a selective microphone amplifier, tuned synchronously to the BFO, a slope of more than 50 db can be recorded. From the points where the decay curves start to bend and the slope of the latter part of the decay curves, compared with the initial slope, a quality factor for the room is determined. It will, by some practical measurements from rooms with good and bad acoustics, be shown that the quality factor gives good correlation with the subjective impression.
Empirical Acoustic Criterion
Authors: Somerville T. , Head J. W.
Published: September 2005

A tentative criterion has already appeared in Acustica, but since then further objective and subjective investigations have been carried out to test the validity of an empirical acoustic criterion. By this means, it has been possible to establish for large enclosures an improved version of the original criterion and a new criterion, taking account of volume. A nomogram for the new criterion is described. For small enclosures, such as talks studios, it has been impossible to obtain satisfactory criteria, and a further investigation is therefore in progress.
Design, Construction, and Testing of the M. I. T. Kresge Auditorium
Authors: Newman Robert B.
Published: September 2005

The several acoustical problems presented by the unique structural form of this building are discussed, and the measures taken to assure good hearing conditions in the auditorium itself and to provide adequate transmission loss within the building for simultaneous use of the various spaces will be considered. Solutions to unexpected problems that were encountered during actual construction are discussed. Following completion of the building, physical measurements and listening tests have been made to evaluate the final result. Music critics have expressed differing opinions on the acoustics vigorously—the majority being favorably impressed.
Acoustics of the Rochester (New York) War Memorial Auditorium
Authors: Olney Benjamin , Anderson Roy S.
Published: September 2005

This arena-type auditorium with a stage at one end has a volume of 3.24 million cu ft, seats 5774 persons in stationary chairs and a total of 9852 with additional portable chairs. Both the stationary and the portable chairs have upholstered seats. The acoustical hazard of concave rear wall and opposite wall containing the proscenium opening was ameliorated by special treatment. A combination structural-acoustical ceiling was used. The design objective of a reverberation time of about two seconds at 500 cps was attained without adjustment. The results of reverberation-time measurements are shown and discussed. The public-address system is described and the subjective assessment of the auditorium is mentioned.
Noise Transmission from the Turbulent Boundary Layer
Authors: Kraichnan Robert H.
Published: September 2005

A theoretical study is made of noise spectra radiated by vibration of thin, stiff, flat plates under the action of turbulent boundary layer pressure fluctuations. The transmitted radiation investigated arises from the streamwise convection of quasi-static pressure fluctuations by the mean flow, and is critically influenced by the dispersive character of wave propagation in the plates. At moderate subsonic Mach numbers the total transmitted power for sufficiently thin boundary layers varies approximately as a power of Mach number between five and six, rising more steeply as transonic velocities are approached and more gradually at sufficiently low Mach numbers. The dominant transmitted frequencies shift up with Mach number, in some typical cases varying as Mach number squared. Plate parameters which importantly influence sound transmission include mass/unit area, size of independent plate sections, frequency of lowest vibrational mode of the independent sections, and damping factors for the various vibrational modes. For sufficiently thin boundary layers, the transmitted spectrum shape is essentially independent of boundary layer thickness, but the spectrum level varies as approximately the fourth power of thickness. For thicker boundary layers, the dependence is flatter, and the Mach number dependence is also flattened. The anticipated effectiveness of transmission reducing procedures including damping and stiffening of the plate sections, and boundary layer suction are discussed. [This work was supported by the Air Force, Wright Air Development Center.]
Measurements of Turbulence in a Subsonic Air Jet
Authors: Laurence James C.
Published: September 2005

Hot-wire anemometer measurements of the turbulence parameters were made in a 3.5-in. diameter free jet at exit Mach numbers between 0.2 and 0.7 and Reynolds numbers (based on jet rad.) between 192 000 and 725 000. The results of these measurements show that (1) the intensity of turbulence is a maximum at a distance of approximately 1 jet rad. from the jet center line and decreases with increasing Mach and/or Reynolds number, and (2) the lateral and longitudinal scales of turbulence are nearly independent of Mach and/or Reynolds number and vary proportionally with distance from the jet nozzle. The lateral scale is much smaller than the longitudinal and does not vary with distance from the center line, while the longitudinal scale is a maximum at a distance from the center line of about 0.7 to 0.8 of the jet rad.
Determination of Ultrasonic Dosage Relations for the Central Nervous System
Authors: Dunn Floyd , Fry William J.
Published: September 2005

High-level ultrasound, when properly controlled, produces quantitatively selective alterations in the central nervous system. The physical mechanism of this selective action of the sound on tissue is not presently understood. This paper describes a biological preparation and precision technique which are appropriate for accurately determining ultrasonic dosage relations. A knowledge of these relations will facilitate the understanding of the physical mechanism involved in the sonic action. Specific quantitative results obtained are reported.
Acoustic Mapping within the Heart
Authors: Wallace John D. , Brown James R. , Lewis David H. , Deitz George W.
Published: September 2005

A cylindrical barium titanate element has been placed at the distal end of a specially designed catheter and used in studies of heart sounds of dogs and humans. The heart sounds have been recorded with the sensitive catheter located directly in the heart and in the pulmonary artery. The location of the catheter at each mapping station has been monitored with x-ray photographs; simultaneous electrocardiogram and wide band sounds were recorded on a photographic galvanometer. The sounds were recorded on tape with several filter characteristics, and acoustic spectrographs were made. These studies indicate that much may be learned from an analysis of the spectra and time characteristics of sounds picked up directly within the circulatory system. [Work supported in part by National Institutes of Health H-1425(c).]
Performance of Ceramic Ferrite Resonators as Transducers and Filter Elements
Authors: van der Burgt C. M.
Published: September 2005

In recent experiments the compositions and methods of preparation of various ferrites were varied with the aim of achieving optimum mechanical and piezomagnetic performance. Essential improvements could be obtained by small, highly effective variations in the chemical composition and by suitable modifications of the mechanical and thermal treatments. In CW operation, ferrites can excite radiation intensities up to about 10 w/cm2, with an electroacoustic efficiency of more than 75% up to 50 kc/sec. So they are highly promising for underwater transmission and processing, in spite of their brittle nature (ultimate tensile strength about 6 kg/mm2). Wide-band hydrophones with linear frequency response and high pressure-sensitivity can also be built from such ferrites having magnetomechanical coupling coefficients at remanence up to almost 0.25, like Permendur. The total variation of the mechanical resonant and antiresonant frequencies of ferrite filter elements in the temperature range from +20 to +50°C, being 0.1 to 0.25% for existing commercial ferrites, could be lowered to 0.03% and less. Since the mechanical quality factors are usually much better than 2000, such ferrites can be profitably applied to the construction of electrical and electromechanical band filters.