bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mercury exposure during immune apheresis
Authors: Bauer Edith , Schaffer Andreas , Kramer Ludwig , Derfler Kurt 
Published: September 2005

Background: Immunoadsorption using protein A columns is increasingly used for selective extracorporeal removal of circulating antibodies and autoantibodies. Current apheresis systems employ reusable columns requiring long‐term storage (20–50 treatment sessions). To prevent microbial growth during storage, columns are primed with ethyl mercury thiosalicylic acid (thiomerosal, .01% solution) for storage and rinsed with phosphate buffer before use.Aims: To test the hypothesis of a substantial mercury exposure in protein A immunoadsorption and to investigate the effect of adding N‐acetylcysteine to the rinsing solution.Patients and Methods: Whole blood mercury levels were measured by atomic absorption spectroscopy (hydride method) before and after protein A immunoadsorption (11 patients, 26 treatments), anti‐IgG‐immunoadsorption (8 patients, 13 treatments) and LDL apheresis (DALI and Therasorb systems; 9 patients, 14 treatments).Results: Protein A immune apheresis treatment significantly increased blood mercury levels from a median of 5.4 µg/L (range, 1.4–37.6, normal, <5 µg/L) to 23.7 µg/L, (range 7.2–107, P < 0.001). Baseline mercury levels were normal in treatment‐naive patients but gradually increased on regular treatment. In a single patient with excessive mercury levels (107 µg/L), neurologic toxicity (intention tremor) occurred during immune apheresis. In the other groups blood mercury levels were not different from healthy controls. Adding N‐acetlycysteine to the rinsing solution lead to a significant decrease in mercury exposure during protein A apheresis treatment.Discussion: This preliminary report suggests that mercury toxicity may develop in patients on regular protein A immune apheresis treatment. Given impaired renal function in many patients, any effort should be undertaken to reduce systemic mercury exposure, either by adding chelators to the rinsing solution or ideally by replacement of thiomerosal. Adding N‐acetlycysteine significantly reduced mercury exposure, so that we now routinely rinse protein A columns with N‐acetylcysteine before use.
Acoustic Filter for Water-Filled Pipes
Authors: Hoover Robert M. , Laird Donald T. , Miller Laymon N. 
Published: September 2005

It is anticipated that some of the auxiliary equipment to be used in conjunction with the new water tunnel under construction at The Pennsylvania State College will be particularly noisy in the ultrasonic frequency region where certain low level acoustic measurements are to be made. This potentially noisy equipment includes such items as a deaerator, an energy dissipator and a pressure control system which are located in a water loop, external to the main tunnel section. To effectively isolate this loop acoustically from the remainder of the tunnel where the acoustic measurements will be made, it has been considered desirable to design an acoustic filter which can be inserted at the junctions of the loop with the tunnel. This filter should serve the multiple function of reducing the sound transmission through the pipe walls and through the water in the pipes while permitting the passage of relatively large volumes of water at small loss of pressure.
The problem of isolation in the pipe path is a fairly common one and essentially requires the use of sound attenuating gasket material. However, the isolation of the water path is more complex in that water must be allowed to flow while sound is attenuated. In this case a honeycombed structure of a pressure release material is used.
This paper discusses the hydraulic consideration of the problem and presents the results of acoustic transmission measurements on the filter components. The measurements include: 1. The frequency characteristics of the acoustic filter under free field conditions, 2. The transmission properties of the isolating gaskets mounted in the pipe flanges, and 3. The effective response of the filter and isolation gaskets combined.
The Masking of Pure Tones and of Speech by White Noise
Authors: Hawkins J. E. , Stevens S. S. 
Published: September 2005

This report presents the results of a study of the monaural masking of pure tones by white noise at eight sensation levels (SL) from 20 to 90 db. The observed values of masking were employed to determine two basic functions:
(a) The critical band width of a masking noise, i.e., the ratio, in decibels, between the level of a pure tone and the level per cycle of the noise that is just able to mask the tone.
(b) The function relating the amount of masking to the effective level of the masking noise.
With the aid of these two functions, a set of contours was constructed to represent the masked threshold for pure tones heard monaurally against background of white noise having an ideal flat spectrum at the ear of the listener.
A study was also made of the masking by white noise of speech in the form of continuous discourse. Measurements of the threshold of detectability and of the threshold of intelligibility were made at the same eight noise levels used to mask pure tones.
Loudness Patterns—a New Approach
Authors: Munson W. A. , Gardner Mark B. 
Published: September 2005

In the past loudness patterns have been based on the masking effect of one sound on another. For complex sounds having distributed energy spectrums this method appears to be valid. For sounds with single frequency components the method is thought to be in error due to the formation of beats and modulation products between the primary tone for which a pattern is desired and the probe tone which is used to determine the pattern details. To avoid these difficulties in the present tests, the probe tone was presented after the primary tone was turned off. The resulting residual masking patterns differ in a number of important respects from patterns based on the simultaneous masking procedure.
A comparison between the loudness of a primary tone, as evidenced by the magnitude of its residual masking pattern, with the results of loudness judgment tests was made. This was done by replacing the physical scales of pressure level and frequency by the subjective scales of loudness and position. A reasonably good check of computed and measured loudness values was obtained. Patterns for a 1000-cycle tone were measured to show how the loudness of the standard reference tone is distributed and how this distribution changes as the level of the tone is increased.
The Relation between Localization and Intelligibility
Authors: Hirsh Ira J. 
Published: September 2005

The binaural masked threshold for speech depends upon the relation between the interaural phase angles of the speech and those of the noise. When these phase angles are the same, the threshold is high, and both speech and noise appear to be in the same place. When the interaural phase angle of the speech is reversed relative to that of the noise, the threshold is low and the speech and noise appear to be in different places. These relations have been clearly demonstrated with earphones, and they suggest that in free-field listening the threshold of intelligibility might be affected by the relative locations of the sources of speech and of masking noise. It was found that when the azimuths of the sources of speech and of noise are changed relative to each other, the threshold of intelligibility changes by small but consistent amounts. When the sources are close together, the threshold is high; when the sources are far apart, the threshold is reduced.
Although this relation is partially confounded by the effect of azimuth on the sound pressure levels at the ears, the factor of localization appears to play a significant role, especially when two ears are used and when the head is allowed to move. In order that the hard-of-hearing may take advantage of these effects, they must have a hearing aid with two separate microphones mounted near the ears and connected each to a separate earphone.
Levels and Spectra of Transportation Vehicle Noise
Authors: Bonvallet G. L. 
Published: September 2005

In the recent past a program was initiated to survey vehicle, traffic, and industrial noise in the Chicago area. The phase on noise of vehicles has been completed. The investigation included street, elevated, and subway cars; diesel, steam, and electric trains; and motor buses, trucks, and automobiles.
Measurements were made of over-all and octave band levels. Inside of the vehicles, flat network over-all levels ranged from 85 db in a new “L” car to 95 db in subway cars. The readings in the 400–800 c.p.s. band ranged from 68 db in an automobile to 91 db in subway cars. Outside of and close to vehicles, the flat network over-all levels ranged from 78 db for automobiles to 94 db for subway trains. Observations in the 400–800 c.p.s. band ranged from 66 db for automobiles to 87 db for subway trains.
Variations in the over-all levels inside of vehicles ranged from ±1 to ±5 db. Variations the 400–800 c.p.s. band ranged from ±2 to ±5 db. Outside of the vehicles, variations ranged from ±2 to ±6 db in both the over-all and 400–800 c.p.s. band levels.
The Acoustical Impedance of Closed Rectangular Loudspeaker Housings
Authors: Meeker Willard F. , Slaymaker Frank H. , Merrill Lynn L. 
Published: September 2005

Direct-radiator loudspeakers are often mounted with the back of the diaphragm working into a completely enclosed space. Conventional theory states that when the maximum linear dimension of such an enclosure is small compared with the wave-length, the pressure is uniform throughout, and the acoustical impedance presented to the loudspeaker is -j/ω(V/ρc2), where V is the enclosed volume. Although it has not been clearly established how small an enclosure must be before it is “small compared with the wave-length,” the foregoing expression is generally used, at low audiofrequencies, to calculate the acoustical impedance of closed loudspeaker housings.
It is shown here that while the acoustical impedance of a closed rectangular housing is capacitive at very low frequencies, it passes through zero as the frequency increases and becomes that of an inertance as the frequency of the first normal mode is approached. For a typical housing 11 in. × 22 in. × 22 in., the frequency at which the impedance presented to a very small speaker passes through zero is in the vicinity of 70 c.p.s.; at this frequency, the maximum linear dimension of the enclosure is less than one-seventh of the wave-length.
These results are obtained by using the methods given by Morse for determining the pressure distribution in a room. A point-source loudspeaker is assumed and the pressure at the source is calculated as the summation of the pressures due to the normal modes of the enclosure, losses being neglected. Measurements of the pressure within the enclosure support this analysis.
From measurements of the pressure distribution over the surface of the loudspeaker diaphragm, it may be deduced that the magnitude of the acoustical impedance which the enclosure presents to the loudspeaker diaphragm and the frequency at which the impedance becomes zero depend upon the dimensions of the loudspeaker diaphragm as well as the dimensions of the enclosure.
Phase Distortion of Acoustic Pulses Obliquely Reflected from a Medium of Higher Sound Velocity
Authors: Arons A. B. , Yennie D. R. 
Published: September 2005

Theoretical analysis predicts the occurrence of phase shifts when harmonic waves are reflected from interfaces of higher sound velocity (such as the sea bed in underwater sound propagation) at angles exceeding the critical angle of total reflection. Since the phase shift depends only upon the acoustic parameters of the media forming the interface and upon the angle of incidence and is independent of the frequency of the incident wave train, one would expect pulses of arbitrary shape to be subjected to distortion upon reflection.
The expected shape of the pressure wave reflected from a semi-solid bottom is derived for the specific case of exponentially decaying shock waves produced in underwater explosions, and the theoretical predictions are found to agree well with the observed pressure-time curves of the first and successively higher order reflections. The theoretical analysis assumes acoustic plane waves incident upon an interface between two fluid media. Experimental records were obtained at relatively great distances from the charge so that finite amplitude effects were negligible and the radius of curvature of the wave front quite large.
Pulse Statistics Analysis of Room Acoustics
Authors: Bolt R. H. , Doak P. E. , Westervelt P. J. 
Published: September 2005

Many sounds of speech and music more nearly resemble pulsed wave trains than abruptly terminated continuous sounds as used in reverberation measurement. It is therefore not surprising to find that two rooms can differ markedly in acoustical quality even if they appear identical under reverberation analysis which ignores details of short transients.
This paper introduces a pulse statistics point of view which takes immediate account of the pulse-like nature of common sounds. Fundamentally, the method consists in examining the response of the room to a short pulse. The walls are replaced by an array of image sources (simple images if the walls are hard, or appropriately modified if there is absorption). These image arrays are then considered statistically.
From this approach one can derive such classical quantities as reverberation time and mean free path. One can also analyze the detailed nature of discrete reflections including interference effects, and thus obtain an average correlation between room geometry and the character of its pulse response.
Idealized experiments in a hard-walled rectangular room are employed to illustrate the essential features of this approach. A point source emits an exponential damped 3600-c.p.s. wave train of about 2 msec. duration. The received signals are recorded logarithmically on an oscillograph and the system is calibrated for quantitative results. Several dozen discrete reflections can be measured and correlated with calculation. The pulses merge into a more or less continuous background after a time that is calculated and confirmed experimentally. Detailed differences arise according to the positions of the source and microphone in the room.
A Continuously Variable Filter
Authors: Fant C. Gunnar M. 
Published: September 2005

A heterodyne filter for the speech frequency range is described. It can be used as a band pass filter of continuously variable low and high frequency cut-offs adaptable for any desired transmission band in the frequency range 40–4000 c.p.s. and with more than 60-db attenuation and with cut-offs of a maximal slope of 1 db per c.p.s.
Band width and low frequency cut off are varied by two separate controls. Band elimination filtering can also be obtained with continuously variable mid-frequency but with band width restricted to either 300 or 800 c.p.s.
The variable filtering is performed by single sideband transmission with successive filtering in two modulation units and demodulation in a third unit. Distortion products from impurities in transmission and modulation are kept at a −60-db level and random noise at a −85-db level, relative to a single test tone.
The filter was designed for articulation tests and general speech research purposes and also as a wave analyzer of continuously variable band width, 45–4000 c.p.s. in the frequency range 40–2000 c.p.s. The maximum permissible speed in analysis of sustained sounds, governed by the inverse square of band width law, is discussed with regard to the quality of the analyzing band pass filter.
Individual Differences in Noise Masked Thresholds
Authors: Webster J. C. , Lichtenstein Malcolm , Gales Robert S. 
Published: September 2005

Absolute thresholds and thresholds of pure tones masked by thermal noise were obtained for 3666 persons attending the 1948 San Diego County Fair. The masked hearing losses as well as the absolute hearing losses (1) increased with an individual's age, (2) were positively correlated with his awareness of hearing difficulty, and (3) were inversely related to his musical training. Masked losses, however, were less dependent upon one's sex and upon one's past noise environment than were absolute losses.
When groups of individuals were equated as to their absolute losses on 880 c.p.s. and 3520 c.p.s. (the frequencies which were masked), that part of each group that had the lower absolute thresholds on 440 c.p.s. also had the lower masked thresholds.
The signal to noise ratio (noise expressed as spectrum level) at masked threshold for those with no absolute loss was 20 db at 880 c.p.s. and 21 db at 3520 c.p.s. This is equivalent to saying that the noise bands which were effective in masking these frequencies were 100 and 128 cycles wide, respectively.
Response Peaks in Finite Horns
Authors: Molloy C. T. 
Published: September 2005

In this paper the term hyperbolic horn is used to designate those horns whose area law is given by: S(x) = πR02[coshax+T sinhax]2. Where S(x) is the cross-sectional area of the horn at distance (x) from the throat, (a) is the flare constant; (T) is the shape parameter and (R0) is the throat radius.
The pressure on the axis due to a circular mouth, unbaffled horn loudspeaker is derived. In this calculation use is made of the recent results of Levine and Schwinger [Phys. Rev. 73, 383 (1948)] and some useful additional functions are computed from their data and presented here in graphical form.
It is shown how to calculate the frequencies at which peaks occur in hyperbolic horn type loudspeaker frequency response curves.
It is shown how to calculate the parameters of hyperbolic and exponential horn type loudspeakers having pre-determined peaks in their frequency response curves.
Some experimental confirmation of the theory is presented.
On the Masking Pattern of a Simple Auditory Stimulus
Authors: Egan James P. , Hake Harold W. 
Published: September 2005

The masking audiogram of a pure tone is complicated by phenomena that arise from the interaction of the test tone with the masking stimulus. The production of beats and of difference tones results in a masking audiogram that does not represent the pattern of activity in the cochlea or nerve due to a simple masking stimulus. In the present experiments a narrow band of noise was used to mask pure tones. The “beat” heard in the immediate vicinity of the masking noise is not prominent, and a test tone higher in frequency than the band of noise is detected in terms of the characteristic pitch of that tone rather than by means of a difference tone.
With a band of noise slightly wider than a critical band (Fletcher), the amount by which the test signal at the center of the band exceeds the level/cycle of the noise is less than that obtained with a considerably wider band of noise. This smaller signal-to-noise ratio obtained with the narrow band of noise is probably due to “beats,” since the test tone is heard as a “buzz” or “rattle.” For purposes of deriving excitation or loudness patterns, a better estimate of the maximum amount of masking is obtained by using a wide band of noise whose pressure spectrum level is the same as that of the narrow band.
An Apparatus for Speech Compression and Expansion and for Replaying Visible Speech Records
Authors: Vilbig F. 
Published: September 2005

In speechband compression or expansion all the frequencies of the band are divided or multiplied in a certain ratio, but without changing the time dimension. This last requirement makes the problem very difficult because, if we could neglect the time aspect, we could record speech and simply play it back at slower or faster speeds.
I have tried to solve this problem by three different methods: (1) by transformation of the speech frequencies into an optical spectrum and retransformation by light modulation disk and photo-tube; (2) by use of a string filter; and (3) by use of an ultrasonic cell as a storage device.
Binaural Localization and Masking
Authors: Kock W. E. 
Published: September 2005

Binaural experiments are described which indicate that the ability of the brain to localize a desired sound and to suppress undesired sounds coming from other directions can be traced in part to the different times of arrival of a sound at the two ears. It is suggested that the brain inserts a time delay in one of the two nerve paths associated with the ears so as to be able to compare, and thus concentrate on, those sounds arriving at the ears with this particular time of arrival distance.
The ability to perceive weak sounds binaurally in the presence of noise is shown to be a simple function of the direction of the desired sound and noise. An explanation is given for the effect reported by Koenig that front and rear confusion is avoided by head movements.
Improved Methods for Measuring Ultrasonic Velocity
Authors: Willard G. W. 
Published: September 2005

Some improved sound wave interference methods for measuring the longitudinal and transverse ultrasonic velocity in opaque as well as transparent solids may be simply carried out by using the ultrasonic light-diffraction system (as arranged for making sound beams visible on a screen). The sonic unit of the system is arranged to produce two individual traveling-wave sound beams, by use of two generators by splitting a single beam. Three simple arrangements are described in detail. In Case A one beam travels entirely in a reference liquid, while the other beam travels a parallel path in an immersed transparent test specimen. In Case B one beam travels entirely in a reference liquid, while the other beam travels an adjacent course through an immersed, transparent or opaque test prism, and on into the liquid at an angle to the first beam. In Case C the two beams are generated at the equal edge faces of a transparent or opaque isosceles test prism (only the base edge face contacting the liquid). The two beams traverse the prism to the base, where they are refracted into the test liquid as confluent beams.
In Cases A and B, simulated interference (by optical integration), and in Case C true interference, each give a light and dark band interference pattern on the screen, whose band spacing is used in calculating the velocity of sound in the test solid. The other required factors are the optical image magnification, the frequency of the sound, the angular disposition of the one or more acoustic surfaces of the test solid relative to the incident sound beams, and in Cases A and B the velocity of sound in the reference medium. Other variations of arrangement are suggested.
Advantages of the improved methods are simple preparation of test specimen, directness and simplicity of measurement and calculation, good accuracy, low sonic power requirements. A table of measured velocities (and attenuations) in two metals and in numerous plastics and polymers show the wide range of materials that may be measured by the new interference methods.
Variable Resonant Frequency Crystal Systems
Authors: Fry William J. , Baumann Fry Ruth , Hall Wayne 
Published: September 2005

A general analysis of variable resonant frequency crystal systems which utilize liquid media as backing is presented. Formulas are obtained for evaluating the effect of different geometries of backing on the resonant frequencies of the system. The various loss factors associated with such a system are related to the measurable quantity, the quality factor.
The observed operating characteristics of a variable resonant system which covers a two-to-one frequency band (40 kc to 80 kc) are presented. The results of an experimental comparison of such a system with fixed resonant frequency systems for generation of ultrasound in liquid media are given. The theory is used to correlate the experimental observations.