bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Loud Contralateral Stimulation on the Threshold and Perceived Loudness of Low-Frequency Tones
Authors: Loeb M. , Riopelle A. J. 
Published: September 2005

Two experiments, employing different psychophysical procedures, were performed to measure the attenuation at intensities near the threshold due to the acoustic reflex. In both, a contralateral tone was introduced to activate a reflex and the resultant threshold shift for a test tone noted. Shifts observed were small and apparently inconsistent with findings of past experiments. Possible significance of the results was discussed.
The hypothesis was advanced that the reflex, once activated, attenuated loud sounds more than faint ones. Two additional experiments employing a loudness-matching technique were devised as a test of this hypothesis. In both of these the apparent loudness of different test tones was noted in the presence and absence of a contralateral activating tone. Results were in accord with the prediction. Applications and further tests of the hypothesis are discussed.
Effects of Response Complexity upon Listening to Competing Messages
Authors: Webster J. C. , Solomon L. N. 
Published: September 2005

Three groups of twelve men listened to sequences of two, three, or four competing messages. They listened under four different conditions, two conditions of filtering (filters in—filters out) and two conditions of spatial separation (channels split—channels together). They responded on certain occasions to one message of the set and at other times to two messages. The first group wrote down, in simple symbols, the content of the message (s) whose address(es) they were to guard. The second group spoke the content of the assigned messages to a partner who wrote it down. The third group transposed (decoded) the message content before writing it down.
The results show that (1) more than twice as many errors occurred when responding to two instead of one message, (2) whether responding to one or two messages, transposing or talking produced an increase frequency of errors of 10% over writing, and (3) errors increased as the listening condition changed from Filtered-Split to Unfiltered-Split to Filtered-Together to Unfiltered-Together.
Binaural Interactions of Impulsive Stimuli and Pure Tones
Authors: Harris Gerard G. 
Published: September 2005

The time-vs-intensity trade (ΔT/ΔI) in binaural lateralization was measured for pure tones and impulsive stimuli by the null method for high-pass and low-pass clicks at a repetition rate of 20 pps and pure tones of 200, 500, and 700 cps. Mean sensation levels (SL) of 20, 30, and 40 db and interaural intensity differences of 0, 4, and 6 db were used. The data on four subjects indicate a difference between high-pass and low-pass clicks: for instance, ΔT/ΔI≈0.025 msec/db for low-pass clicks below 1000 cps and I = 30 db SL, whereas at the same intensity ΔT/ΔI≈0.060 msec/db for high-pass clicks above 4000 cps.
It is concluded that the time vs-intensity trade is important for the localization of high-frequency impulsive stimuli. The interaural intensity difference also affects the ability to liberalize since the error of lateralization is least when both the interaural intensity difference and interaural time difference are zero. From the foregoing and from experiments with two liberalized images, it is concluded that the timing information used in binaural lateralization travels along frequency-dependent neural pathways. Any physiological timing signal must be able to explain this phenomenon.
Acoustic and Other Physical Properties of Shallow-Water Sediments off San Diego
Authors: Hamilton E. L. , Shumway George , Menard H. W. , Shipek C. J. 
Published: September 2005

This paper reports on a continuing study of the mass physical properties of surficial, shallow-water marine sediments off San Diego, California. Sound velocity measurements in situ at 100 kc were made by pulsing between small transducers inserted into the bottom by diver. Density, porosity, and size analyses were determined on relatively undisturbed samples taken by diver. The following averaged representative values have been obtained:
Velocity in
sediment at Impedance
Density Porosity Med. diam 60°F (105 g/
Sediment type (g/cc) (%) (mm) (ft/sec) cm2 sec)
Fine sand 1.93 46.2 0.19 5520 3.25
Very fine sand 1.92 47.7 0.12 5435 3.18
Silty very fine sand 1.68 61.3 0.05 5075 2.60
Medium silt 1.69 60.9 0.03 4825 2.49
Clayey fine silt 1.60 65.6 0.02 4800 2.34
Laboratory measurements of velocity and attenuation 25 to 35 kc were made by a resonant-chamber method using diver-taken samples; average attenuation values of about 0.5 db/ft (silt) to about 5 db/ft (fine sand) were obtained. At three stations the sediment sound velocity was less than the velocity in the bottom water.
Shock Spectrum Computer for Frequencies up to 2000 cps
Authors: Morrow Charles T. , Riesen Donald E. 
Published: September 2005

The shock spectrum for an acceleration impulse applied to an electronic equipment or other component is a measure of severity of mechanical shock in terms of possible peak response at each frequency within the component structure. It is commonly measured by a reed gauge, which is intended to simulate the possible resonant characteristics of the internal structure. The reed gauge is bulky, however, and provides data at a limited number of frequencies.
The shock spectrum computer operates on an accelerometer signal, either direct or recorded, and permits measurement of as many points in the spectrum as desired. It is a device which solves the differential equation of a simple undamped resonant mechanical appendage for any applied impulse of acceleration to yield the response. In the present version, the response is made available as an output signal which is applied to a commercial cathode-ray oscilloscope. Peak accelerations and their time of occurance may be obtained readily from the oscilloscope display. The computer can be tuned to any frequency up to 2000 cps. Control circuitry is used to damp the computer shortly after each impulse and to undamp it immediately before the next so that the impulse under study can be applied repeatedly from a recirculating loop of magnetic tape. Shock spectra obtained from the computer and oscilloscope display are used as a measure of the severity of shocks experienced by electronic apparatus and as a basis for deriving shock specifications for use in design approval tests.
Shallow Water Under-Ice Acoustics in Barrow Strait
Authors: Milne Allen R. 
Published: September 2005

During April and May 1959, some underwater acoustic measurements were made in Barrow Strait in the Canadian Arctic Archipelago. The water in the experimental area was covered with 7 ft of young, shore-fast ice and depths ranged between 380 and 815 ft.
Recordings of ambient noise were made at one location to include frequencies between 3 cps and 10 kc. These exhibited several harmonically related spectrum lines and, in particular, a prominent line near 7 cps which appeared to have a wind-induced excitation. The frequencies of the spectrum lines are apparently related to a set of standing waves between the surface and the bottom of the water. No relation between the frequency of the air-coupled flexural wave in the ice (17.5 cps) and the ambient noise spectrum was detected.
The velocity of sound vs depth in the water had a mean positive gradient of 0.04 sec−1, caused primarily by a positive temperature gradient. The velocity of sound vs depth in the sedimentary column, obtained by seismic refraction methods, can be expressed as 9025–4300 exp (−z/300) ft/sec with z in feet.
Additional work included a sound transmission run to a range of 10 nautical miles (hereafter abbreviated-nm) using explosive charges as sources. At distant ranges the transmission loss was essentially that to be expected from cylindrical spreading but exceeded this by 1 db per nm in the 9.6 to 19.0 kc band.
An Approximate Solution to the Acoustic Radiation of a Finite Cylinder
Authors: Brigham G. A. , Borg M. F. 
Published: September 2005

Utilizing the assumption of an omni-directional point source and varying degrees of acoustical transparency associated with a finite cylindrical shell with rigid end caps, the authors have derived two separate approaches to the problem of far-field sound radiation emanating from a normal mode of vibration. In addition, a third approach is obtained by expanding the expressions of Laird and Cohen and applying them to a shell-band source on an infinite cylinder. Several different environments are considered for each approach and for one of these environments, the results are compared to the experiment.
The comparison of these theories indicates that for acoustic wavelengths considerably greater than structural wavelengths and dimensions, the assumption of omni-directional point sources and acoustical transparency is reasonable even though the source is curved and “unbaffled.” At higher frequencies, the pressure levels and directivity in the far field are approximately independent of the transparency or opaqueness of the source, thus indicating that an “equivalent” transparent cylinder of infinitesimal spherical sources could give, at most, only three- or four-db cancellation effects when a single mode excitation basis is assumed.
Propagation of Longitudinal Waves and Shear Waves in Cylindrical Rods at High Frequencies
Authors: McSkimin H. J. 
Published: September 2005

Exact steady-state solutions for both longitudinal waves and shear waves traveling in isotropic rods of circular cross section are analyzed. Numerical examples are described for rods of large diameter to wavelength ratio.
The effect of mode conversion on the propagation of short duration longitudinal wave trains is considered; and an approximate expression for the resulting loss is developed.
Experimental results for 10–25 Mc/sec longitudinal and shear waves in fused silica rods of 1.13 cm radius are described.
On the Transmission and Confirmation of Messages in Noise
Authors: Egan James P. , Clarke Frank R. , Carterette Edward C. 
Published: September 2005

In several experiments, the restrictions imposed upon the communication process by an articulation test were relaxed by increasing the number of events in the communication sequence. A communication event is the transmission of a message from the source to the receiver followed by the return of a message (correct or incorrect) from receiver to source for confirmation. Although both source and receiver serve as talker and listener, the relation between them is asymmetric. Since the source knows the original message, he must accept or reject the message sent back to him according to some criterion.
Various types of communication events arise depending upon (1) whether or not the receiver correctly hears the message, and (2) whether or not the source confirms the message returned by the receiver. The various probabilities associated with these events are investigated as a function of speech-to-noise ratio. The behavior of the source is examined in terms of the relation between the two conditional probabilities associated with a correct and with an incorrect confirmation.
If each message is sent repeatedly until all are confirmed, a sequence of communication events is generated. A simple mathematical model accurately describes this process.
Base Pressure Fluctuations
Authors: Eldred Kenneth McK. 
Published: September 2005

The intense vibration accompanying the extension of dive brakes and other high-drag devices on aircraft and missiles has been observed for many years. Recently, considerable vibration has been experienced at the fundamental longitudinal mode and at other internal resonance frequencies of a vehicle which had a blunt base during the maximum dynamic pressure phase of flight. In both cases the vibration is believed to result from the turbulent fluctuations in the wake of the base or drag device.
The base pressure fluctuations have been measured at two base positions on a small body of revolution at eleven points in the velocity range of 68 to 352 ft/sec. The results show that: (a) The ratio of (〈p2〉nv/q2)12 varies between 0.007 at the center of the base to 0.015 at 65% radius; (b) The spectrum of the pressure fluctuations is a function of the body Strouhal number; (c) The variation of observed vibration response with flight parameters can be predicted from the base pressure fluctuation data.
Response of Nonlinear Shock Mountings to Transient Foundation Displacements
Authors: Snowdon J. C. 
Published: September 2005

The transient behavior of shock mountings disturbed by steplike displacements that invoke large departures of mount stiffness from linearity is described theoretically and compared with the behavior of an ideally linear mounting. The influence of mount damping upon the transient motion of the mounted item is discussed in detail.
For the majority of step rise times considered, a mount that softens upon compression and is not heavily damped is shown to reduce both the acceleration and displacement experienced by the mounted item below the values observed for a linear mounting or, as is normally the case in practice, a mount that stiffens upon compression. The reduction in acceleration can be comparable with 10 db for quite a wide range of step rise times. It is frequently the magnitude of the acceleration to which the likelihood of damage to the contents of the mounted item may be related.
Noise Bands versus Pure Tones as Stimuli in Measuring the Acoustic Attenuation of Ear Protective Devices
Authors: Webster J. C. , Thompson P. O. , Beitscher H. R. 
Published: September 2005

The sound-exclusion properties (acoustic attenuation) of various earphones and ear defenders and combinations thereof were determined by the binaural, free-field, absolute-threshold-shift technique with the psychophysical method of adjustment. The earphones included dynamic earphones in two different sockets and hearing-aid-type receivers with individually molded inserts. The ear defenders included certain conventional and newly developed earplugs and muffs, and a hard-shelled noise-exclusion helmet.
In a preliminary evaluation of a limited number of devices, both tones and noise bands were used as stimuli, and comparative results are shown. In evaluating the effectiveness of some of the newer devices, noise bands alone were used. For the exclusion of external sound, particularly that below 1200 cps, the order of merit for earphone combinations was: (l) large volume muffs with insert phones; (2) helmet with insert phones; (3) semiplastic sockets with dynamic phones; and (4) helmet with dynamic phones. The best combination provided the following amounts of attenuation in the seven octave bands from 75 to 9600 cps: 14, 22, 28, 33, 38, 44, and 40.
Acoustic Wattmeter
Authors: Schultz T. J. 
Published: September 2005

The author has constructed a device which gives pointer indications of acoustic intensity over a 50-db range at frequencies up to 10 000 c/sec.
The signals from a pair of pressure-sensitive condenser microphones, mounted back to back in a space roughly the size of a dime, are treated electronically to provide pressure and velocity signals which are then multiplied and averaged in a specially designed moving-coil dynamometer to give precise pointer readings.
The theory of operation of the apparatus is discussed and the paper concludes with a brief account of the test results of the acoustic wattmeter.
Nonlinear Response of a Simple Clamped Panel
Authors: Smith P. W. , Malme C. I. , Gogos C. M. 
Published: September 2005

Measurements are reported of some characteristics of the response of a simple panel to a steady periodic sound pressure intense enough to cause nonlinearity in the response. The panel is a 2-in. wide, thin aluminum strip, clamped at its ends with the clamp faces 12 in. apart, and left free on its edges. Attention is focused principally on the fundamental resonance point, which occurred at frequencies as large as twice the low-level resonance frequency.
Measurements of the frequency and strain at resonance, under various levels of excitation, are compared with predictions from a simple one-mode nonlinear dynamic equation. For good agreement it is found necessary to include not only a nonlinear stiffness but also a nonlinear damping term. Theoretical predictions of the nonlinear stiffness from the physical characteristics of the panel are in error by a factor of 4.7 when based on an assumed mode shape for transverse deflection which is identical with the linear characteristic function of a clamped-clamped beam.
Calculation of the Loudness of Complex Noise
Authors: Stevens S. S. 
Published: September 2005

Charts and formulas are presented for the calculation of the loudness of noises having approximately continuous spectra. By means of direct loudness matches it is shown that the loudnesses in octave bands can be combined according to the formula St = Sm+0.3(ΣS − Sm), where St is the loudness (in sones) of the total noise, Sm is the loudness of the loudest band, and ΣS is the sum of the loudnesses of all the bands. The loudnesses of the octave bands can be determined from measurements of their sound pressure levels by means of a chart based upon a new determination of the equal loudness contours for bands of noise. Other charts and formulas are presented for half- and third-octave band widths.
Measurements were also made of the dependence of loudness on such factors as (a) separation between noncontiguous bands, (b) width of very narrow bands, and (c) rate and level of square wave modulation.
Criteria for Office Quieting Based on Questionnaire Rating Studies
Authors: Beranek Leo L. 
Published: September 2005

In order to discover what are the maximum noise levels that office personnel find acceptable and what their reactions are to noisy offices, a survey was carried out at a large air base. A questionnaire composed of 15 rating scales was administered to 190 people scattered over 17 different locations on the base. The rating scales allowed the workers to assess such things as the “noisiness” of their environment and to appraise the effect of noise on various aspects of their work, such as their ability to converse or to use the telephone.
The results obtained with the rating scales were compared with various physical measures of the noise. A high correlation was found between perceived noisiness and the measure called “speech interference level” SIL, which is the average of the sound pressure levels measured in the three octave bands between 600 and 4800 cycles per second. An even higher correlation was found between the ratings of noisiness and a computed measure of loudness level. More than two-thirds of those questioned stated that speech communication was an essential part of their activities and that the more intense noises in their offices interfered with it. These correlations provide a basis for setting criteria for the maximum noise acceptable in terms of SIL and of loudness level. These results, plus those from a previous study, suggest that the maximum continuous noise levels acceptable for office spaces in which speech communication is important should not exceed an SIL of 40 db. Office employees are accustomed to a noise spectrum of a form that yields a loudness level of about 22 units higher than the SIL. Complaints are encountered when the loudness level exceeds the SIL by 30 or more units. Thus, with an SIL of 40 db the loudness level should preferably not exceed about 62 phons. Only under special conditions with this SIL would it be advisable to exceed a loudness level of 70 phons.
For intermittent noises, such as the noises produced by aircraft operations, evidence is presented to show that the mean (average) value of the SIL and loudness level should not exceed the numbers for steady noises if the work of office employees is not to be disturbed.
Onset and Growth of Aural Harmonics in the Overloaded Ear
Authors: Lawrence Merle , Yantis Phillip A. 
Published: September 2005

The threshold of overload and the growth in intensity of the aural harmonics are determined by the exploring tone method for frequencies of 100, 350, 1000, 2000, and 5000 cps. It is found that the level of a test tone at which it first overloads the ear can be quite accurately determined and that the range of beats between the second harmonic and the exploring tone, as the latter is changed in intensity, is considerably narrower at the overload threshold level than at higher levels. As the test tone is raised in intensity the loudness of the harmonic increases rapidly.
Overloading occurs at approximately the same sound pressure level for all frequencies so that the range of linear response is around 8 db at 100 cps, 30 db at 350 cps, and 50 db at 1000, 2000, and 5000 cps. All harmonics are detected when they reach a certain consistent level above threshold for that frequency. The exact level depends upon the subject.
These results are considered as additional evidence that distortion in the ear takes place within the sensory cells as part of the electromechanical process and is not due to any nonlinearity of the mechanical response of the ear.
Loudness Adaptation for Bands of Noise
Authors: Carterette Edward C. 
Published: September 2005

Loudness adaptation may be measured by a simultaneous loudness balance, or, as in the two experiments reported below, by a median plane localization of a dichotically presented acoustic stimulus. The loudness of a steady auditory stimulus generally decreases with time. That is, the intensity of a comparison stimulus in the rested ear is ordinarily set below the intensity in the stimulated ear.
Two experiments were done on loudness adaptation for bands of noise. In Experiment 1, using 36 subjects, loudness adaptation for a wide-band thermal noise of 100–5000 cps was studied as a function of five SPL's: 40, 70, 90, 100, and 105 db over all. The mean maximum loudness adaptation obtained was 2.3, 9.9, 11.4, 14.4, and 16.3 db, respectively. The mean standard deviation for all measures was 6.1 db, and the distributions of the sets of measures tended to be skewed toward greater adaptation.
In Experiment 2 (12 subjects), the loudness adaptation for a 1500-cps tone was compared with that for bands of noise whose centers (mel scale) were at 1500 cps, and whose over-all SPL's were equal to the SPL of the pure tone. The band limits in cycles per second were 1280–1120, 1075–1950, 720–2600, and 100–4900. For each band, adaptation was measured for 50, 70, and 90 db SPL over all. The essential results are: (1) Loudness adaptation for 1500 cps is about 8.5 db greater than the maximum adaptation for any noise band at any SPL; (2) Adaptation is small (4.5 db) at 50 db for all bands of noise; it is complete within one minute and is about equal for all band widths; (3) At 70 and 90 db, time taken for complete adaptation increases and the two widest bands give greater adaptation than the two narrowest bands. At 90 db a trend becomes clear: the wider the band, the greater the degree of adaptation and the longer the time required for maximum adaptation to be attained.
Successful Method of Attack on Plane Progressive Finite Waves
Authors: Fay R. D. 
Published: September 2005

The characteristic feature of the method is that at any point in the sound field the conservation criteria are expressed in terms of the instantaneous values of the speed of propagation, the particle velocity, the excess pressure, and excess density. These criteria, together with the adiabatic assumption, determine explicit relations between any two of these quantities. Excess pressure and excess densities are here defined as departures from the equilibrium values that exist at the instant when the particle velocity is zero.
For waves of finite amplitude these equilibrium values, as well as the speed of propagation, are found to depend on the intensity. The increment in the speed of propagation does not agree with that obtained by classical methods of analysis. The discrepancy found to be due to the omission in the classical forms of the continuity criterion of a term that specifies the effect of the rate of change in the speed of propagation.