摘要:

Circumferential waves have been detected in a thin‐walled air‐filled brass cylinder having an air gap in the wall. The cylinder is 11.94 cm in diameter, 24.13 cm long, and has a wall thickness of 2.62 mm. The air gap, 1.57 mm wide, extends the thickness of the wall and almost the length of the cylinder. The cylinder was immersed in water for all acoustic measurements. Two circumferential wave modes, flexural and compressional, were detected and measured over the frequency ranges 125–150 kHz and 275–300 kHz, respectively. Under the assumption that the circumferential wave is reflected at the air gap, ray theory is used to derive equations predicting the location in time, relative to the specular echo, of the circumferential waves in the cylinder. Experimental evidence establishing the validity of these equations for both the compressional and flexural modes is presented.

ISSN:0001-4966    

DOI:10.1121/1.1910719

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

In Expt. 1, six women were given 12 separate tests of short‐duration auditory adaptation. Correlations among subjects showed that two subgroups existed, one pair differing from the others in exhibiting an interaction between stimulus strength/duration and slope of recovery. A battery of four tests is tentatively recommended that would sample the effects on different subjects of stimulus frequency, intensity, and duration, and of slope of recovery. In Expt. 2, 15 adults were given 47 tests of true auditory fatigue with pure tones. Previous data on temporary threshold shift (TTS) growth rates, equinoxious contours, recovery slopes, etc., were confirmed. An obverse factor analysis was performed, upon a correlation matrix not among tests but among subjects. A general‐susceptibility grouping emerged; three individuals defined rather poorly a grouping with reduced high‐frequency and increased low‐frequency susceptibility; three other individuals showed recognizable specific patterns of susceptibility. Three specific tests can be shown to sample these groupings, and are recommended tentatively as an auditory fatigue battery for pure tones. Using a supplementary battery of 15 noise tests, a subgroup of three was sufficient to predict whole battery performance (r=0.81), as against a prediction (r=0.65) between any pure‐tone combination versus the whole‐battery noise data. Experiments 3, 4, and 5, used this information to study the prediction of susceptibility to noise‐induced permanent threshold shift in man, rat, and monkey, respectively. A rather low level of success was achieved.

ISSN:0001-4966    

DOI:10.1121/1.1910720

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

A modified energy detector is proposed as a predictor of human frequency‐ and amplitude‐discrimination performance. The model consists of an initial bandpass filter followed by a square‐law device and an integrator. The center frequency of the initial filter is assumed to be a random variable distributed over time. The predictions of the model for performance in two‐alternative forced‐choice frequency‐ and amplitude‐discrimination experiments are presented, together with data from human observers. While the model is able to predict the frequency and amplitude data very well, it is less successful with detection data.

ISSN:0001-4966    

DOI:10.1121/1.1910721

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

The perception of temporal gaps within periodic pulse patterns was examined in a forced‐choice test. The task of the listener was to identify which one of four pulse patterns contained a temporal gap. Extremely acute gap detection (in the region of 1–10 μsec) may be obtained with high pulse frequencies. Gap detection with high pulse frequencies is critically dependent upon the number of pulses; gap detection with low pulse frequencies is relatively independent of the pulse number. This result is consistent with the generalization, obtained in related studies, that extremely acute temporal discrimination is achieved at high pulse frequencies only with a large number of temporal samples, whereas the relatively poor temporal discrimination at low pulse frequencies is substantially less dependent upon the number of temporal samples. The temporal precision of the auditory system, in contrast with its precision of spectral analysis, appears to be insufficient to account for minimal gap thresholds.

ISSN:0001-4966    

DOI:10.1121/1.1910722

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

When threshold for single auditory‐nerve fibers are plotted in terms of stapes displacement, the tuning curves rise monotonically on both sides of the characteristic frequency.

ISSN:0001-4966    

DOI:10.1121/1.1910723

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

In deriving an equation to test the independence of sensory processing systems, Brown and Hopkins (1967) appear to have built in an assumption of response patterns lacking generality. In addition, the performance of their subjects is in excess of predictions from alternatively derived independence models, as well as one derived from signal detection variables. These data can be accounted for only by assuming a high level of “internal noise.”

ISSN:0001-4966    

DOI:10.1121/1.1910724

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

A table of formulas is presented for interrelating the coefficient systems of an isotropic solid: Young's modulus and Poisson's ratio; the Lamé constants; and tensor and matrix stiffness, compliance, and planar stiffness.

ISSN:0001-4966    

DOI:10.1121/1.1910725

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

This letter reports some results of an analysis, based on a wave‐optical formulation, of the farfield Bragg diffraction from a cylindrical line source light beam by a line‐source acoustic wave. The properties of the diffracted light that are relevant to the problem of optically viewing or imaging the acoustic fields of plane or cylindrical transducers are discussed. The most important of these properties are as follows: (1) A line light source exists for the diffracted light and is either real or virtual depending upon the location of the acoustic source relative to the light source; (2) the location of this line source for the diffracted light has a geometrical correspondence to the acoustic source location; and (3) the phase and amplitude of the acoustic source is preserved in the diffracted line source. As the field of a plane or cylindrical transducer can be represented as a superposition of a set of line‐source waves, it follows that the total diffracted field is either a real or virtual image of the acoustic field. In either case, a real, enlarged image can be formed by the used of proper lenses. A description and examples of results are given for an experiment in imaging the transverse section of two parallel but physically separated 923 MHz microwave acoustic beams in a rutile crystal. The image resolution obtainable is discussed and compared for the experimental conditions with that obtained using a finely focused, mechanically scanned light probe.

ISSN:0001-4966    

DOI:10.1121/1.1910726

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1910728

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP

摘要:

A sonic test system has been developed by North American Aviation, Inc., for nondestructively evaluating composite structures throughout their entire depth while requiring access to only one surface. Applications include adhesive‐bonded, diffusion‐bonded, and brazed honeycomb structures. Also, the system has been successfully utilized for testing laminated and corrugated‐core composites. Structural defects such as unbonds, core crushing, and core rupturing are detectable.

ISSN:0001-4966    

DOI:10.1121/1.1910729

出版商:Acoustical Society of America    

年代:1967

数据来源: AIP