摘要:

Following acoustic trauma in the guinea pig the changes in “threshold” and maximum voltages which can be measured for action potentials (AP) and for cochlear microphonics (CM) in different turns of the cochlea and for different test frequencies differ quantitatively. Acoustic trauma was produced by exposure to 500‐cps tones. Duration and SPL of the exposures were varied inversely and approximated exposures of equal energy. All changes in electrophysiological potentials were significantly correlated, some very highly. The anatomical ratings of cochlear injury were less well correlated. A factor analysis of all variables, including measures of the traumatic exposures, showed (1) changes in CM depend on the place of measurement, (2) changes in CM do not depend on the frequency of test signal, (3) changes in AP relate best to changes in CM measured in the basal turn regardless of frequency of test signal, and (4) the scale used for rating anatomical injury in these and prior experiments does not predict changes of CM when duration and SPL of traumatic exposure are varied widely. [Supported in part by Contract No. AF 33(616)‐3637, Bio‐Acoustic Branch of the Aero Medical Laboratory, Wright Air Development Center.]

ISSN:0001-4966    

DOI:10.1121/1.1930171

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Particle motion within the fluids of cochlear models occurs in elliptical orbits which are essentially Lissajou figures caused by interaction between the (forced) stapedial motion and the (induced) motion of the cochlear partition [J. Acoust. Soc. Am.29, 558 (1957)]. In response to beats these orbits were found to wax and wane synchronously with the beat frequency. However, the alternating waxing and waning was not symmetrically centered about the orbital midpoints. In scala vestibuli, the orbits invariably expanded farther in the apical than in the fenestral direction. In scala tympani, the directions were reversed. Thus a partial rectification occurred within the cochlear fluids which, being synchronized with the beat rate, was of opposite direction in both perilymphatic scalae. This manifestation of energy at the beat frequency had to be due to some nonlinear property of the model, since no energy occurs at this frequency in linear systems. The nonlinear property was finally identified as the stiffness gradient of the cochlear partition. The resulting beat amplitude (reparticle amplitude of a given set of primaries) was directly related to the steepness of the stiffness gradient. Furthermore, the beat amplitude reflected upon the shape of the gradient at various locations along the partition when beats (of a constant rate) were produced by different sets of primaries. [This research was supported in full by the U. S. Air Force under contract number AF 41 (657)‐148, monitored by the School of Aviation Medicine, U. S. Air Force, Randolph Air Force Base, Texas.]

ISSN:0001-4966    

DOI:10.1121/1.1930177

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

If the criterion is adopted that a schematic diagram of a system must give a complete representation of all the physical or engineering principles involved including a specification of the characteristics of each part and how the various parts are joined to form the system, it follows that perfect couplers must be included in the list of items available to anyone creating schematic diagrams. It is shown by examples that perfect couplers produce their action by the imposition of constraints and that the set of constraints for a given coupler imposes the condition of no power loss or gain. Conversely, if a conceptual device is known to be a perfect coupler and some constraints are known, then the remaining ones can be deduced. It is shown that perfect couplers may be of two types and that examples of each type are common. It is further pointed out that perfect couplers present no problem if an investigator is always aware of their possible existence. The discussion closes by showing that couplers can be dealt with mathematically in a systematic manner.

ISSN:0001-4966    

DOI:10.1121/1.1930181

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

This paper discusses the perception of resonant frequency shifts in damped sine waves as a function of the time and magnitude of the shifts. The relation between the perception of the changes in frequency and damping of the wave form is also investigated. The interest in this study stems from the fact that changes in formant frequency (transitions) constitute an important class of cues in speech. The equipment producing the proper stimuli has been built and perceptual tests have been run testing a number of possible hypotheses.

ISSN:0001-4966    

DOI:10.1121/1.1930190

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Studies of binaural signal selection for various contextual stimuli have been reported by a number of investigators. It is necessary to know, in an eventual complete analysis of the auditory system, whether binaural selection mechanisms operate differently on noncontextual signals. As a first approach, two broad‐band noises (N1andN2) were presented binaurally such that one‐second segments ofN2were immersed inN1, which was much longer.N1was identical at the two ears.N2, however, could be presented in several ways: in phase at the two ears, 180° out of phase, with an interaural time disparity of 500 μsec, or heterophasic. Subjects responded when they heard any change in the character of the signal, and from these responses, masked thresholds ofN2were plotted as a function ofN1/N2. Results for the in‐phase condition compare predictably with the monaural results reported by Miller (1947). Selection ability for all the various conditions of noncontextual signals is compared with that for spondees under similar conditions. (Part of this research was supported by funds from the National Science Foundation.)

ISSN:0001-4966    

DOI:10.1121/1.1930195

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

A headset microphone is described which will give a calculated 84% word articulation in a noise field of 140 db, such as may be found during trimming operations on jet engines and at missile test stands and launching sites. The M‐87/AIC microphone and H‐143/AIC earphone described at the May, 1958 meeting are employed with a noise shield and a specially designed ear cushion is a hard shell, circumaural type with a grease‐filled sealing pad. The internal volume is divided by a flexible plastic sheath which lays loosely against the auricle and couples the earphone to the ear with a cavity of approximately 10 cc. The sheath is perforated with a few small holes which couple the larger volume of the shell to the ear in order to obtain increased attenuation below 500 cps. The acoustic isolation of the sheath above 500 cps also minimizes the effect of standing waves in the larger cavity upon the response and attenuation characteristic of the headset. The articulation performance cited above is estimated assuming 200‐mw power available with 10‐db peak clipping. This can be obtained from the AN/AIC‐17 interphone system used by Air Force ground crews. Indicative articulation scores for jet noise fields up to 160 db, and tolerable exposure times based upon WADC damage risk criteria, are reported. [The work was supported by Contract AF 33(600)‐33172 from WADC Communication and Navigation Laboratories under the direction of T. P. Mountz.]

ISSN:0001-4966    

DOI:10.1121/1.1930202

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The proposed ASA Standard “Method for the Measurement of The Real‐Ear Attenuation of Ear Protectors at Threshold”—Z24.22/406, which is currently being considered for adoption, specifies the use of threshold shift techniques. It has been observed in our laboratory during extensive evaluation of developmental ear protective devices over the past ten years that large differences in attenuation are obtained when using different attenuation measuring techniques. In addition, these differences vary for the different type of protector being studied. In this study four grossly different types of protectors are measured. These protectors differ in volume under the protector and in the principal sound transmission path at low frequencies. The protective devices included (1) HS‐33 headset using the MX‐41 muff, (2) H‐70C/AIC headset using the MX‐2088 muff, (3) RCA “Quiet‐Ear” protector, and (4) RCA experimental ear protector. The attenuation methods employed are (1) threshold shift using a Békésy type audiometer, (2) loudness balance at approximately 60‐phon level, and (3) objective method using a miniature microphone. The test subjects and room environment are the same for all types of measurements. A discussion of the differences in attenuation values obtained from the three methods will be given. [Supported in part by the U. S. Air Force under Contract AF 33 (600)‐33172.]

ISSN:0001-4966    

DOI:10.1121/1.1930206

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Tests reported at the Fifty‐First Meeting of the Acoustical Society of America on the characteristics of cornet tones have been extended to other instruments which use a cup mouthpiece. The trends indicated by the cornet tone quality studies are shown to be followed by the other instruments also. The instruments are found to have formant‐like characteristics which exercise control over the harmonic content of the tones produced and help the listener in identifying the instrument producing the tones. Tape recordings and a tone analyzer will be used in presenting the paper.

ISSN:0001-4966    

DOI:10.1121/1.1930209

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Formulas are presented, which were derived from Kuwahara's tables. These formulas when programed on the Datatron have speeded up computations. The equations are in terms of temperature, depth, salinity, latitude, and the interaction of the temperature, salinity, and depth. Some recent long‐path measurements were made with excellent supporting oceanography for the purpose of determining how well the long‐path sound velocity can be computed with the equations. The long‐path measurements have a precision of slightly better than one part in a thousand. This is roughly the uncertainty of the computed long‐path sound velocity because the oceanographic parameters vary along the path and are never known in complete detail. There is fair agreement between the measured and the computed velocities.

ISSN:0001-4966    

DOI:10.1121/1.1930216

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP