摘要:

Spontaneous speech differs from read speech in several ways, especially in hesitation phenomena. This paper reports results on hesitation pauses (filled and unfilled) and restarts. For comparison purposes, the acoustic correlates of (unintended) hesitation pauses are compared to those for intentional pauses. A distinction is made between grammatical pauses (at major syntactic boundaries) and ungrammatical ones. Such pause types cannot be separated based on silence or prepausal duration, but rather in the pitch of the prepausal word. Ungrammatical pauses tended to have fewF0continuation rises, whereas virtually all grammatical pauses were accompanied by a priorF0rise of at least 10 Hz. While silent pauses are easy to locate in speech recognition applications, filled pauses (e.g., “err,” “umm”) resemble words in continuous speech. Filled pauses at major syntactic boundaries were about 300–450 ms, whereas those within syntactic units were shorter. Filled pauses had falling or flat and lowF0patterns. Ones at syntactic boundaries tended to start higher inF0and then fall, whereas filled pauses internal to a syntactic unit had lowerF0patterns. Concerning restarts in spontaneous speech, when a work was completely repeated, it had virtually the same prosodics in both its instances. When a word was changed in the restart, its second instance was more stressed. [Work supported by Canadian government.]

ISSN:0001-4966    

DOI:10.1121/1.2029891

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Bubble‐producing capillary waves can be easily generated in a laboratory tank (8 cm × 22 cm × 150 cm) by blowing air over the water. The lowest wind speed required for the occurrence of this process is measured. The generation of the capillary waves depends solely on the surface tension, which can be changed by adding surfactants and other chemicals to the tank water. The effect of surface tension on the windspeed threshold for bubble production is discussed. Using a coincidence detector, the bubble production rates per unit area can be measured. Lowering the surface tension, surprisingly, increases the rate of bubble production. The dependence of the bubble production rate on wind speed and wind fetch is also discussed. The underwater acoustic emissions from these bubbles are measured. Average power spectrum for several wind speeds are obtained that exhibit a broad range of radiated frequencies (i.e., bubble sizes) and a weak dependence on the wind speed. [Work supported by ONR, ONT, and AEAS.]

ISSN:0001-4966    

DOI:10.1121/1.2029896

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

It is well known that entrapment of air bubbles near the sea surface contributes substantially to the underwater noise levels. The collapse of air pockets created by steep capillary waves is a possible mechanism of bubble formation. A boundary integral formulation is employed to simulate the bubble behavior after detachment from these air pockets. The initial profile of the trapped bubble, approximated from the form of the capillary waves, suggests a high elongated bubble relatively far from the sea surface. A sequence of initial bubble shapes is generated from successively closer approximations to the bubble shape. Depending on the initial curvature of the detachment point the bubble may break up into two or oscillate as a single bubble in a rather violent manner. Volume oscillations that are responsible for the radiation of sound are found to be affected by the shape oscillations. It is found that a traveling capillary wave on the bubble surface can cause a pressure pulse upon reaching the axis. As a result, the pressure signal may deviate substantially from the simple damped sinusoid of a spherical bubble. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2029904

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

The motion of spheres (bubbles) in an incompressible liquid undergoing a small‐amplitude oscillatory motion is calculated by a multipole expansion method. In the limit of small viscosity, the Stokes layer is confined to the vicinity of the surface of the bubbles, which therefore interact approximately only through the pressure field. The motion of the spheres is parametrized in terms of added mass, Basset, and drag forces; the coefficients of which are obtained from the simulation. To obtain results useful for the study of pressure wave propagation in bubbly liquids, several bubble configurations are studied for different (finite) volume fractions and the results then averaged. The effects of surface tension and bubble density are also considered. [Work supported by DOE.]

ISSN:0001-4966    

DOI:10.1121/1.2029905

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP