摘要:

Peak magnitudes of supraglottal air pressure, under a variety of conditions, were obtained during stop productions from three normal adult speakers of Hindi. The stops were produced in CVCVC nonsense utterances which were embedded in the carrier phrase, “ye—hae.” Significant differences in peak magnitudes were found as a function of the place of articulation of a stop and its position in an utterance. Peak magnitudes were always significantly higher for unvoiced stops than for voiced stops. Aspirated stops, in general, showed higher peak magnitudes than unaspirated stops, but a significant level of difference in peak magnitudes was reached only under voiced conditions. Differences in peak magnitudes as a function of stress were significant under voiced conditions; under unvoiced conditions the differences were less pronounced.

ISSN:0001-4966    

DOI:10.1121/1.2015565

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Theoretical models of airway constriction for sibilants make assumptions which may or may not be justified and which are difficult to extend to pathological cases such as malocclusion. In an attempt to determine the exact shape of the constriction, fast‐setting dental impression material was placed in the mouths of normal English speaking adults, who then attained and held articulatory positions for /s/ and /æ/. The impressions thus formed were then sectioned to obtain successive cross‐sectional areas. There is wide variability among normal speakers in the observed cross‐sectional area patterns, and an attempt will be made to relate these differences to variations in air flow and pressure and the resulting acoustic signal. [Supported by NIH Grant No. 1 R01 DE04267.]

ISSN:0001-4966    

DOI:10.1121/1.2015570

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Utilizing a digital acquisition system and minicomputer, two promising techniques for accurate determination of reverberation times have been studied in detail from the viewpoint of standard reverberation room tests. The first is Schroeder's “integrated impulse method”; special attention was given to the question of repeatability and the influence of signal‐to‐noise ratio on the successful application of the method. The second technique involves taking an ensemble average of a large number of the logarithmic decay curves. It was found that even for nonuniform decays, the averaged decay curves obtained by the second method compared well with those determined by the “integrated impulse method.” Some of the advantages and disadvantages of both methods will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2015583

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The normal procedure in acoustical designs usually emphasizes audience acceptance. This approach often results in unfavorable acoustical conditions for performing artists, both instrumental and vocal. The imbalance occurs from neglect of the musician's need for mutual communication, and too great an emphasis on achieving “optimum” reverberation conditions. There have been notable examples of halls meeting accepted reverberation criteria which have nevertheless proved to be unsatisfactory, and many of these gave trouble because of performance difficulties as transmitted to the audience. Conversely, reverberation conditions can differ considerably from the norm, and still provide a satisfactory hall if the stage properly designed. Study of a variety of halls strongly suggests that an essential requirement for music is that conditions should be suitable for performers. Architectural designs that provide ample sound reflecting and diffusing structures on stage to enable artists to hear each other well, blend the sound, and achieve favorable “local reverberation” are usually judged to be excellent by both performers and audience. This essential result can be achieved even in rooms which depart appreciably from standard reverberation time criteria. Several specific examples will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2015592

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

An optional, one‐unit laboratory course to accompany a three‐unit general‐education course in descriptive acoustics has been designed to utilize some fairly sophisticated equipment available in our electronics laboratory. In the very first experiment, students become familiar with the use of the oscilloscope by following a literal cookbook to get a stable display on the screen, then systematically varying the individual controls to observe their effects on the instrument's operation. In later experiments they get to use stroboscopes, frequency counters, digital multimeters and tuneable filters to investigate pitch intervals, sound spectra, resonance, standing waves and other important concepts that they are studying in the lecture course. Typically about half the students taking the lecture will also take this lab; currently we are filling two lab sections to their enrollment limits of 24 students each. The experiments are quite demanding for the students (and the instructor!), but morale and performance are noticeably stronger than is typical for more traditional laboratory classes.

ISSN:0001-4966    

DOI:10.1121/1.2015599

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The sound radiation from an elastically supported circular plate in an infinite baffle, which is excited by a concentric voice coil, was discussed taking account of the reaction of the acoustical fluid. Eigenvalue, elgenfunction, and volume velocity of each mode of the plate with different edge stiffness were calculated. It was found that the effect of elasticity was smaller for higher order of modes. There was a remarkable difference between the frequency response curves for light and heavy loading. For light loading(air), the peaks and dips were the results of resonances between the mass of the voice coil and the reactance of the mechanical impedance of the plate. On the other hand, for heavy loading(water), peaks and dips occurred when the reactance of mechanical impedance of the plate and radiation impedance canceled each other. The effect of several factors such as the loss factor of the plate, the mass and the radius of the voice coil on the frequency response curves were also discussed.

ISSN:0001-4966    

DOI:10.1121/1.2015608

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A frequency‐dependent mechanism for theoretically scattering sound into the deep sound channel is presented. For points sources of sound in the oceanic thermocline, theeffectiveindex of refraction has periodic ripples that are a function of source depth and acoustic frequency. These ripples induce scattering. For sufficiently large ripples, it is sufficient to consider only direct paths and refracted paths with a single vertex in order to ensonify the entire deep sound channel. All profiles considered were assumed to ice depth dependent only.

ISSN:0001-4966    

DOI:10.1121/1.2015612

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

During October 1976, reverberation measurements using wide‐band bionic signals were made in shallow coastal waters (30 m) off Oahu, Hawaii. These measurements were made to help assess the acoustical environment in which porpoises are known to perform effectively. The areas of these experiments were selected to provide a range of bottom types which included sandy, rocky, and a combination of the two. The projector and receiver bandwidths and wide‐band transmitted signal permitted the estimation of bottom backscattering strength over a range of grazing angles (5–40°) and frequencies (20–80 kHz). [Work supported by Naval Sea Systems Command.]

ISSN:0001-4966    

DOI:10.1121/1.2015615

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

An early study with synthetic speech suggested that vowel identification includes a normalization stage, such that the listener calibrates his perceptual apparatus for each talker's vowel space [Peter Ladefoged and D. E. Broadbent, J. Acoust. Soc. Am.29, 1 (1957)]. In the present study, no evidence for such a perceptual mechanism was obtained using natural speech. Each of a set of b‐vowel‐t test; words, spoken rapidly within a sentence carrier by an adult male was presented for recognition within the carrier in which It was uttered, appropriately embedded within an identical carrier produced by a second adult male with substantially different vocal tract dimensions, and excised from sentence context. The two talkers achieved the same pitch levels and speaking rate, with the result that mixed‐talker sentences were perceived as if uttered by one talker. Errors in recognition were typically found only for isolated test words. Preliminary data from a replication of this design with more widely divergent vocal tracts (i.e., adult male and nine‐year‐old male) are similar. Apparently, some factors beyond the syllable shape the acoustic specification of vowels, though not in the sense in which normalization is traditionally defined.

ISSN:0001-4966    

DOI:10.1121/1.2015624

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

As an introduction to the session on construction noise at University Park, PA, the state of the art in construction equipment and site noise prediction, measurement and control will be reviewed. Typical construction equipment and site noise levels will be indicated. Standard procedures to measure equipment noise levels, particuarly SAE J88 and J88a, will be reviewed. Construction‐site noise levels predicted by adding worst‐case equipment noise levels, result in conservative site levels, since not all equipment operate simultaneously. Alternative techniques to predict either maximum likely, equivalent (Leq) or statistical (Ln) noise levels instead of maximum noise levels will be described. The existing state of the art in construction noise control will be illustrated in terms of noise control for portable air compressors and pile drivers.

ISSN:0001-4966    

DOI:10.1121/1.2015664

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP