摘要:

An analytical and experimental study was conducted to examine the interaction between a standing transverse resonant acoustic field and viscous fluid. The objective was to obtain flow‐behavior information related to combustion instability phenomena. Reduced governing equations were obtained in a form that separated the time‐dependent motion from the time‐mean motion through the use of a rigorous order‐of‐magnitude analysis. Solutions of these equations predict the existence of standing vortices (acoustic streaming) in the cross section of the cylindrical enclosure. The number of vortices and their circulation velocities are proportional to the resonant mode. The results extend and lend greater clarity to work of other authors. Pressure measurements confirmed that the experimental system satisfied the constraints of the mathematical analysis. Photographs of the streaming flow, using tobacco smoke as a tracer, substaniated the mathematical results. [Research supported by NASA.]

ISSN:0001-4966    

DOI:10.1121/1.1972393

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Recent studies of the acquisition of discriminative and productive speech capacities raise the possibility that certain aspects of human language are specifically innate. (1) In 1–3‐month olds, the relative amount of orientation to vowel‐vowel transitions suggest that /a/ is the most basic vowel, /u/ the next most basic, and /i/ the least basic. (2) In 1–2‐year olds, the notion of actor‐action‐object is present. There is no obvious explanation for the development of these universal features of adult language to be found either in the child's nonlinguistic behavior or in his experience.

ISSN:0001-4966    

DOI:10.1121/1.1972414

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A complex exponential algorithm developed for the representation and analysis of time‐limited signals is defined, and its evaluation with respect to conventional discrete Fourier techniques is discussed. It is shown that for a given length of a signal containing discrete frequency information, sampled at least to the Nyquist criterion, the complex exponential algorithm can often provide increased frequency resolution over standard Fourier techniques. It will also be shown that the complex exponential algorithm provides an improved mechanism over Fourier techniques for interpolation between points in a sampled signal containing discrete frequency components in the presence of broad‐band noise. The effects of noise on the complex exponential technique and the computational difficulties associated with the present complex exponential algorithm will be discussed. At the present time, the major difficulty associated with the complex exponential technique is that the algorithm requires more computational time than the fast Fourier transform.

ISSN:0001-4966    

DOI:10.1121/1.1972432

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Techniques used in the area of pattern recognition, particularly the methods of unsupervised learning, are beginning to appear useful in the area of analyzing underwater acoustic signal spectra. A problem encountered in the use of these techniques for varied situations is that of an unlimited memory requirement when uncertain parameters are present in either the signal or noise process. The problem considered here is the design of a limited‐memory receiver for the unsupervised detection of signals in noise. Limited memory is achieved using quantization of a sufficient statistic, and the optimum‐likelihood receiver is developed under this constraint. The limited‐memory receiver is shown to retain adaptive or learning characteristics, and its performance is shown to converge to that of the unlimited‐memory receiver with increasing time. The primary intent of this work indicates the effect of increasing memory—in other words, increasingly finer quantization—on the performance of the limited‐memory receiver and compares this with the performance of the unlimited‐memory receiver.

ISSN:0001-4966    

DOI:10.1121/1.1972442

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A brief review of simple resonator theory is given leading to a discussion of the motivation for the thin‐film composite resonator. A simplified analysis of a CdS‐quartz composite resonator is presented and the complications associated with a more exact analysis are indicated.

ISSN:0001-4966    

DOI:10.1121/1.1972456

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Single‐unit activity of the vestibular nerve of the squirrel monkey was recorded with 3MNaCl‐filled ultrapipets. Barbiturate‐anesthetized animals were fixed on a rotating device controlled by a velocity servo. The plane of any semicircular canal could be made to coincide with the plane of rotation. (1) Most fibers are characterized by a regular and high resting discharge (mean, 80 spikes/sec). (2) The response to angular accelerations is consistent with the established morphological polarization of hair cells. The discharge of all fibers innervating a given canal is increased by accelerations, which bend the hairs towards the kinocillium, and decreased by accelerations in the opposite direction. (3) In their dynamic properties, the fibers may be approximated by a first‐order, low‐pass linear system with a time constant of about 5 sec. (4) The dc sensitivity of the fibers averages about 2.3 spikes⋅sec−1/deg⋅sec−2but may vary considerably from one unit to another. [Supported by three NIH grants and an Air Force contract.]

ISSN:0001-4966    

DOI:10.1121/1.1972480

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Glass micropipets were inserted through the round windows of anesthetized cats. During penetration from scala tympani to scala vestibuli, we continusuly recorded (1) dc potential, (2) magnitude and phase of the fundamental component of responses to tones, (3) resistance of the electrode, (4) position of the electrode drive, and (5) responses from stationary electrodes. At the end of the experiment, electrodes were cemented to the temporal bones where they remained during preparation of the tissue for histological examination. From examination of the sectioned cochlea, we attempted to determine the structures that had been penetrated by the electrode. In 64 cochleas, the average potential of scala media is 100 mV and of scala vestibuli 0 mVrescala tympani. Large negative potentials frequently encountered between scala tympani and scala media were generally held for less than 60 sec. Hence, we find no evidence for an extracellular “Corti potential.” We are not able with this technique to associate recorded electric events with structures as small as individual cells. [Supported by NIH and the Joint Services Electronics Program.]

ISSN:0001-4966    

DOI:10.1121/1.1972486

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The gerbil ear is not mature at birth. The sound‐conducting apparatus as well as inner‐ear structures continue to develop over a period of at least 16 to 20 days postparturition. This circumstance allows a unique opportunity to examine relationships between morphology and function in the auditory apparatus. Mongolian gerbils were vitally perfused at various ages ranging from 20 min to more than 23 days. Serial sections were done and observations made on the developmental status of the external, middle, and inner parts of the ear. Cochlear potentials were recorded from some animals. The presence of reflex activity to sound was noted. Our observations indicate that the earliest reflex response to sound (whole body) occurred at 16 days. Electrical activity could be recorded from the round window niche by day 14. Maturation of the organ of Corti was questionable by day 10, and thelimbusandspiral sulciwere not well differentiated. By day 16, all parts of the organ of Corti appeared well developed. Ossicular ossification was almost complete by day 16, but mesenchyme was still present in the region of theincudomalleolarjoint. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.1972494

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This paper presents the results of an experimental research program to develop a novel type of assembly‐level vibration test. The design of a multimodal test fixture, which simulates the high‐frequency (100–2000 Hz) dynamic characteristics of aMARINERspacecraft structure, is described. Data obtained in research vibration tests with an electronic assembly mounted in the multimodal fixture indicate that the novel testing technique results in a more realistic and more uniform high‐frequency vibration environment than conventional tests utilizing rigid fixtures. The paper presents guidelines for designing multimodal fixtures and discusses means of utilizing these fixtures in future spacecraft assembly‐level vibration test programs.

ISSN:0001-4966    

DOI:10.1121/1.1972510

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

In a space vehicle or a missile system, two sections are sometimes connected together in such a way that a pyrotechnic device is incorporated, either continuously along a circumference or at several discrete locations. At a specific and controlled instant, the pyrotechnic charge is fired and the vehicular sections are separated. The initial forces of separation are explosive in nature. Because the time interval is extremely short, being microseconds in duration, a shock phenomenon is invariably created. The magnitude of this shock is usually quite difficult to measure. Often times, accelerometers are located near the interfaces to serve as transducers for the observation of the same phenomenon. The accelerometer outputs are, however, not always congruent with the original pressure rise. Even though the results are transformed in shock‐spectrum terms, the true shock‐impulse history is seldom reproduced accurately. However, an illustration is given that utilizes the accelerometer outputs at many monitor stations along with the characteristics in the transmitted responses to deduce the initial shock intensity. It is further demonstrated that in complex structures such as space‐system components, the specification based on rigid‐body dynamics of shock may be rendered equally applicable if the transmitted shock is so identified at a selected location.

ISSN:0001-4966    

DOI:10.1121/1.1972520

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP