摘要:

The logistic distribution yields an approximation to the normal probability function that is satisfactory for most psychophysical work. Probability is an explicit function ofxord′ and is easy to compute.

ISSN:0001-4966    

DOI:10.1121/1.1913467

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Normal listeners were exposed on separate occasions to nonreverberant impulses presented at various peak levels. During each exposure the total energy presented to the ear remained constant. The resulting temporary threshold shifts indicated that longer exposures to this type of impulse noise can be tolerated for a given decrease in peak level than is predicted by either the equal‐energy concept (which permits only a 10‐dB decrease in intensity per tenfold increase in the number of impulsesN) or recent proposals which require even greater reductions in level. The 1968 CHABA proposal (5‐dB decrease per tenfold increase inN) is found to be in reasonable agreement with the present data. These results and those from studies involving more reverberant impact noise suggest that the correct trading relation for exposures involving noise of impulsive character will be a function of the degree of reverberation associated with the exposure. The absurdity of damage‐risk criteria that are expressed only in terms of pulse peak level is emphasized.

ISSN:0001-4966    

DOI:10.1121/1.1913468

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A modification is proposed in Hirsch's equation for determining the range of a sound source of unknown strength [H. R. Hirsch, J. Acoust. Soc. Am.43, 373–374 (1968)]. The modified formula applies to the case where the direction of the sound source is known. Greene's comments on Hirsch's letter are investigated for their ability to predict the limitations on the resolution obtainable in human auditory ranging [D. C. Greene, J. Acoust. Soc. Am.44, 634 (1968)]. In a brief experiment, two subjects were unable to make distance judgments for sustained pure‐tone sources over ranges of 3 to 48 ft.

ISSN:0001-4966    

DOI:10.1121/1.1913469

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

In an earlier study [I. V. Nábělek, A. K. Nábělek, and I. J. Hirsh, J. Acoust. Soc. Am.48, 536–553 (1970)] of the pitch of a sound burst with two frequencies connected by a linear frequency change (a glide), it was found that the pair of frequencies, initial and final, are sometimes perceptually fused and sometimes perceptually separated. In the present study, the pitch of the same kind of bursts is compared with the pitch bursts in which the glide is supplanted by a pause. The method of adjustment was used. Some differences in the pitch perception of bursts with glides and those with pauses were found. Prolongation of the glide made separation more difficult and fusion easier, while prolongation of the pause made separation easier and fusion more difficult. Prolongation of either the glide or the final frequency of the burst casued the pitch to be shifted toward the final frequency, while the prolongation of the pause (0–40 msec) did not change the pitch. For an explanation of this discrepancy it seems to be necessary to take central processing into consideration.

ISSN:0001-4966    

DOI:10.1121/1.1913470

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Combined forward and backward masking of a click by preceding and following noise bursts was investigated for the region of gaps (between the two noise bursts) of 50 msec or less in duration. An interaction between the two modes of masking was found and was qualitatively explained in terms of the hypothesis of the temporal integrating period, or running average.

ISSN:0001-4966    

DOI:10.1121/1.1913471

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The computed attenuation afforded by an infinitely long barrier wall between a point source and a distant receiver has been extended to a source of finite size by considering it as a rectangular array of small equal closely spaced incoherent sub‐sources. While one axis of the array is assumed to be vertical, it may have any angular orientation relative to the receiver and to the axis of the wall. If the source and wall are parallel, the high‐frequency attenuation drops by 3 Db when the source‐to‐barrier spacing is doubled, and varies as 10 log (1 −h/H), wherehis the source height andHis the height of the barrier.

ISSN:0001-4966    

DOI:10.1121/1.1913472

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

We estimate the amount of time taken by listeners to perceive artificial stop consonants to be in the vicinity of 120 msec. The duration of the formant transitions in the syllables we employ, on the other hand, is 50 msec (followed by a nondistinctive vowel). Processing thus outlasts relevant input by some 70 msec. Moreover, forward masking develops as consonant processing takes place, which could lead to masking within a single syllable and block further‐input. These results suggest that, for a significant fraction of the time, normal speech perception takes place in the absence of input. A view of speech perception compatible with such a limitation ascribes most of the perceptual structure of speech to largely autonomous internal processes, rather than to the acoustic structure of the speech signal. This signal serves primarily to trigger the process of speech perception in this view.

ISSN:0001-4966    

DOI:10.1121/1.1913473

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Gas‐bubble behavior in a liquid flowing inside a circular tube subjected to an acoustic pressure field is studied analytically and experimentally. Consideration is given to both viscous fluids and whole blood, with the effects of acoustic radiation and viscosity taken into account. Slug flow and laminar parabolic flow cases are treated. Analytical solutions are obtained which predict the trajectory of bubble motion and the location where the bubble can be brought to a standstill on the tube wall by the acoustic force. It is disclosed that the trajectory is strongly dependent upon the acoustic pressure amplitude, flow velocity, and liquid viscosity. By either increasing the acoustic pressure amplitude or decreasing the flow velocity or liquid viscosity, the bubble can be brought to a standstill in the first half‐wavelength from the tube entrance, at the node or antinode depending upon its size. The theory is in good agreement with experiments performed in water and SEPARAN AP30 polymer solutions. The latter fluids resemble whole blood in rheological properties.

ISSN:0001-4966    

DOI:10.1121/1.1913474

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A method is presented for measuring ultrasonic attenuation as a function of frequency by spectrum analysis of broad‐band echoes in a buffer/specimen system. Also presented is a new technique for diffraction corrections in this configuration. The buffer rod/spectrum analysis method with diffraction corrections is applied to three experiments to demonstrate its accuracy and versatility in measuring attenuation and defining transducer radiation/reception efficiency.

ISSN:0001-4966    

DOI:10.1121/1.1913475

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The “Shouldered‐specimen pulse echo technique” has been used to study the temperature dependence of ultrasonic attenuation α at 5 MHz, in a 1% carbon steel. The attenuation‐versus‐temperature curve shows abrupt changes in its slope at 750 ° and 900 °C, respectively, after which the attenuation rises rapidly for temperatures up to 985 °C. A qualitative explanation of the experimental curve is sought on the basis of Bhatia's theory of scattering by the grains. The present work is first of its kind to provide evidence for the growth of the austenitic grains with increasing values of temperature in the austenitic range.

ISSN:0001-4966    

DOI:10.1121/1.1913476

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP