摘要:

Directivity characteristics of the ocean noise field, including the effects of surface activity of the wind, were investigated. The results of this investigation suggest that the noise field in the ocean due to over all surface activity is primarily anisotropic. A comparison of experimental with theoretical covariance curves indicates directivity function of the formS(θ) = cosnθ(in which the angle θ is measured from the vertical), characterizing the radiative processes at the surface withnlargely in the neighborhood of two or three, except for low wind speed, wherenapproaches unity.

ISSN:0001-4966    

DOI:10.1121/1.1919277

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The results of a quantitative approach to the elucidation of the structure of the limbic system of the brain are presented. Total neuron populations and anatomically significant subpopulations of the medial and lateral mammillary nuclei of cat brain are determined. The subpopulations are measured by placing ultrasonic lesion arrays in efferent and afferent tracts and in associated nuclei, waiting for degeneration to occur, and then determining the residual populations in each case. The total neuron populations of a number of structures related directly to the mammillary nuclei are determined also. In addition, the size distribution of the nucleoli of the neurons is measured for each of the structures of interest in the population determinations. The methods and techniques that have been developed to obtain the necessary accuracy in the determination of the cellular populations are described. These include lesion placement, histologic preparation of the tissue, nuclear‐boundary determination, and neuron mapping. The data presented in this paper constitute the type of information upon which a complete quantitative description of the neural circuitry of brain structures can be deduced, as will be demonstrated in subsequent papers.

ISSN:0001-4966    

DOI:10.1121/1.1919278

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Direct measurements were made of the displacement of the guinea‐pig eardrum when acted upon by acoustic pressures (200–6000 cps). The mechanical nonlinearities of the ear were studied by introducing a static pressure (0 to ±3000 dyn/cm2) in the middle‐ear cavity. Below 1000 cps, the ratio of the tympanum displacement to the sound pressure was frequency‐independent, with a value of about 4×10−7cm3/dyn. Above 1000 cps, this ratio exhibited a series of maxima and minima. A static‐pressure difference across the tympanum changed the frequency at which the maximum occurred and generally decreased the displacement/pressure ratio. It was concluded (1) for low frequencies, the lumped‐parameter description of the ear as a cavity was valid; (2) the tympanum acts as a flexible, conical plate under slight tension; (3) the measurements were best explained in terms of two nonlinearities: hysteresis and a nonlinearity of the elastic properties of the ear.

ISSN:0001-4966    

DOI:10.1121/1.1919279

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Resection of the direct efferent cochlear bundle in the guinea pig causes greater reduction in the cochlear microphonic potential than is caused by resection of the crossed efferent cochlear bundle. The findings of the present series of studies are thought to constitute physiological proof of the existence, in the guinea pig, of another component of direct efferent cochlear fibers, other than the direct olivo‐cochlear fibers, which arises in cells of the reticular formation of the medulla.

ISSN:0001-4966    

DOI:10.1121/1.1919280

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Temporal integration of acoustic power was investigated 250, 1000, and 4000 cps over a range of signal durations from 1 or 2 cps to 256 msec. Signals were presented in a background of low‐level broad‐band white noise. Breaks in the function relating performance to signal duration (assuming that bandwidth equals 1/t) were used to infer critical bandwidth and difference limen for frequency. The critical‐bandwidth estimates are in agreement with most other data for the smaller set of critical‐bandwidth values sometimes called critical ratios. The difference‐limen estimates are in agreement with Shower and Biddulph's values obtained at a low sensation level.

ISSN:0001-4966    

DOI:10.1121/1.1919281

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The principles of electrokinetic phenomena are well‐documented in classical electrochemistry. This paper discusses a low‐frequency, electrokinetic, acoustic pressure transducer, suitable for both airborne‐ and underwater‐sound applications, that uses the principle of electrokinetic transduction. A broad frequency response has been obtained, which extends from 0.001 to 100 cps. A pressure sensitivity of 3.8 μV/dyn/cm2(266 mV/psi) is illustrated.

ISSN:0001-4966    

DOI:10.1121/1.1919282

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

For many types of data‐transfer systems, it is desirable that the data be delayed long enough so that the system is ready for the data. In the present Space Surveillance system, it is desirable to delay data until the recorder is up to speed. The requirement for delaying the composite Inter‐Range Instrumentation Group (IRIG) FM telemetering signals from a space surveillance site by12 secwas fulfilled by converting the phone line frequencies into sound, which is then transmitted through a pipe long enough to provide the desired delay and then reconverted into electrical signals. The delayed output is essentially distortionless.

ISSN:0001-4966    

DOI:10.1121/1.1919283

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Probe microphones are now in such common use and obtainable in so many different forms that it seems appropriate that a description of the various forms and a comparison of their salient features be set down. This paper discusses (1) the simple probe microphone, which consists of a tube terminating in the diaphragm of a pressure‐sensitive transducer; (2) the terminated probe microphone, which consists of a tube terminated in the diaphragm of a pressure‐sensitive transducer in parallel with which has been placed the characteristic impedance of the probe tube; and (3) the resistively tipped microphone, in which the damping resistor is placed at the tip of the probe and the probe tube is terminated in a pressure‐sensitive diaphragm. In addition to comments on the three types of probes, a suggestion for a figure of merit for probe‐tube microphones is also set down. Much of the work done on probe microphones is not original with this author, and proper credit is made to all sources known to the author.

ISSN:0001-4966    

DOI:10.1121/1.1919284

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An electrical analog of a piezoelectric transducer has been built and used to demonstrate the generation and detection of acoustic waves and the electrical characteristics of a piezoelectric resonator. The circuit uses an artificial transmission line to represent the distributed‐constant mechanical properties of the transducer, and is therefore capable of reproducing the behavior of a transducer under both transient‐ and continuous‐wave conditions. The theory of the equivalent circuit of a transducer is first extended to facilitate interpretation of the physical processes of generation and detection. This is done by developing an “impulse sequence” that takes into account waves generated at both faces of a transducer, and the delay in time and reflections that they undergo in passing through the transducer. This analysis is used to discuss examples of waveforms obtained with the analog in the following situations (with various simulated combinations of backing and load impedance): (1) as a generator of acoustic waves when excited by an electrical signal in the form of (a) a short impulse, (b) a step, (c) short trains of sinusoidal oscillations of various lengths; (2) as a detector of acoustic waves when excited by an acoustic signal in the form of (a) a step, (b) a train of sinusoidal oscillations. In detection, the effect of terminating the transducer with high and low resistances is also demonstrated. Experiments concerning the continuous‐wave response of the analog are also described.

ISSN:0001-4966    

DOI:10.1121/1.1919285

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A clarinet blown with an artificial embouchure was connected to one end of a large pipe with absorbing material at the other end so that the sound usually radiated was absorbed instead. Under these conditions, the sound radiated from the vibrating body was measured and found to be 48 dB below the sound normally produced by the instrument at the same location. Acceleration levels measured on the body with a vibration meter were correlated with the sound radiated by the body, both for the artificially blown clarinet and for clarinets set into vibration with an attachment energized by a complex signal. The figures obtained were used to check other woodwind instruments. Results showed that the body sound should be at least 37 dB below the normal sound for all instruments measured. The effect of nonrigid walls was checked by comparing tubes of brass and soft TYGONplastic blown on the embouchure, measuring the harmonic structure of the internal standing wave produced and the frequencies andQ's of the resonance modes. The differences were small. It is concluded that the vibrations of the walls of a woodwind instrument do not affect its steady tone either by radiating sound themselves or by affecting the harmonic structure of the internal standing wave.

ISSN:0001-4966    

DOI:10.1121/1.1919286

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP