摘要:

The purpose of this investigation was to explore the possibility of using ultrasonics to produce a drier filter cake in vacuum filtration. The research was divided in two phases: (1) use of airborne ultrasonics near the filter cake surface and (2) use of ultrasonics to vibrate the filtration membrane. The ultrasonics frequency of 20 kHz was used with intensities varying from 0 to 12 W cm2. The filter thicknesses used varied from 2 to 5 mm, the vacuum applied varied from 260 to 510 mm Hg. The airborne ultrasonics was applied at distance of 1/4 to 13/4 wavelength which were equivalent to 4–52 mm away from the filter cake surface. Filtration time was varied from 1 to 5 min. From the data obtained, the effect of ultrasonics on dryness of the filter cakes, was calculated using the various conditions described above. It was found that ultrasonics could be effective in reducing the moisture content of cakes produced by vacuum filtration.

ISSN:0001-4966    

DOI:10.1121/1.2002639

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The function of the violin and the guitar are being investigated. Plate vibrations are recorded by hologram interferometry in cooperation with the Institute of Optical Research, KTH, and a qualitative understanding of eigenmodes and their excitation have been obtained. Properties of the enclosed air volume have been investigated by means of the STL‐Ionophone, which has proved that higher air volume resonances can be used as sound radiators. Played scales recorded in reverberation chamber are analyzed by long‐time‐average‐spectra (LTAS). Such analysis has proved that different instruments may be separated by LTAS. Work is in progress trying to correlate LTAS with function and tonal qualities. Listening tests have been started in cooperation with A. Gabrielsson (Department of Psychology, University of Uppsala). Findings from the present investigations will be reported on. [Work supported by the Swedish Natural Science Research Council and the Swedish Humanistic Research Council.]

ISSN:0001-4966    

DOI:10.1121/1.2002646

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

For some time it has been apparent that the finding reported previously—namely, that a good sounding instrument of the violin family results when the “tap tone” frequency of the free back plate is a semitone to a tone higher than that of the free top plate—is not the only criterion to be respected in the optimum tuning of violin plates. Ten conventional violas were constructed using mode No. 5, the tap tone of free top and back plates, to determine whether frequency or so‐called damping of this mode in the two plates is the more important for good tone production in the finished instrument. Findings will be discussed and illustrated with Chladni patterns and frequency amplitude curves—and compared to comments of professional violists on the tone and playing qualities of the 10 finished violas.

ISSN:0001-4966    

DOI:10.1121/1.2002647

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Damping materials dissipate mechanical energy when cyclically strained by converting it to heat. For sinusoidal strain the amount of energy dissipated per cycle depends on temperature, frequency, and amplitude. Each of these should be measured and reported. If the energy dissipated is proportional to the square of the amplitude, the damping mechanism is called linear and the damping may be reported as energy per cycle loss as a function of amplitude, storage, and loss modulus, or storage modulus and loss ratio. The measurement of system energy loss may be made by direct measurement of force, deflection, and the phase angle between them. The energy loss may also be inferred from the rate of decay in free vibration, the electrical impedance of or the energy input to a vibrating electromechanical system of which the specimen is a part. Regardless of the method used, it is impossible to distinguish between the energy dissipation in the specimen and that dissipated elsewhere in the system. This latter must either be accurately known or negligibly small. In order properly to interpret the data, the state and distribution of strain must be known though the volume of the specimen. Methods for measuring and controlling each of these parameters will be discussed and illustrated.

ISSN:0001-4966    

DOI:10.1121/1.2002652

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Vibration damping materials play an increasing role in environmental protection and mechanical design. Specially developed resins with optimized properties for noise abatement applications are used with success. As most metals have low internal losses, large amplitudes may be obtained in resonance modes when they are vibrated. The application of coatings of damping material with large internal damping in single layer or sandwich constructions has proved very effective in “deadening” noisy structures. A direct consequence of these developments is a great need for an objective damping measuring technique. The intersting viscoelastic properties are the density and the complex modulus of elasticity of the materialsĒ = E′ + jE″ (j =−1)and the complex shear modulusḠ = G′ + jG″. AsĒandḠare closely related through the Poisson ratio, the measurement of the complex modulus of elasticity will do. The real partE′ represents the dynamic stiffness which is the storage modulus representing the energy stored in the material during oscillation, the normally used term is dynamic modulus of elasticity. The imaginary partE″ is a measure of the loss modulus representing the energy losses. The loss factor isd=E″/E′. The viscoelastic properties may be measured through an experimental setup using standardized samples mounted in a well defined fashion and brought into oscillatory motion. The dependency on temperature and frequency may be determined in this experimental setup which is standardized in DIN 53440, pp. 1–3. Considerable experience with this method has been gained over twenty years. The method was pioneered by the late Dr. Hermann Oberst.

ISSN:0001-4966    

DOI:10.1121/1.2002660

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Working group chairpersons will present reports of their recent progress on writing and processing letter ballots on various shock and vibration standards. In addition, there will be a report on the interface of S2 activities with those of ISO/TC 108.

ISSN:0001-4966    

DOI:10.1121/1.2002662

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The ear is an extremely sensitive detector of acoustic energy. Its dynamic range at 1 kHz is at least 120 dB, although some harmonic distortion occurs at 70 to 80 dB SPL. The range of sensitivity is from about 20 to 20 000 Hz, although sensitivity decreases on both sides of an 800–7000 Hz band. There is an absolute limit above which the ear is likely to suffer direct physical damage: rupture of the eardrum occurs at about 140–160 dB SPL and, more importantly, destruction of the sensory elements of the inner ear at about 140–150 dB SPL. Much below these levels, i.e., starting at about 80–90 dB SPL, the sensory elements are gradually worn out, where there is some reciprocal relationship between exposure level and duration. There are some built‐in protective mechanisms, but their effectiveness at industrial noise levels is rather low. After a brief outline of the ear's anatomy, some examples of noise‐damaged ear tissues obtained in experimental animals and/or accidentally found in man will be demonstrated. [Supported by several NIH grants.]

ISSN:0001-4966    

DOI:10.1121/1.2002663

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Segments of the burst portions of stop‐consonant CV's, increasing in duration in 10‐msec steps from the burst onset, were identified by 18 listeners. The responses were analyzed for the correct identification of vowel features. Coarticulatory effects of the vowel on the burst were found to (1) occur early in the burst, (2) vary with consonant and vowel, and (3) vary with vowel feature. In general, however, front versus back tongue placement for the vowel was perceived correctly most often, tongue height next most often, and the tense versus lax feature least often. For some CV's, sufficient cues for above chance level of identification of a feature were contained during the shortest segments of the burst. The results lend support to the point of view, in the case of unvoiced stops, that listeners can narrow the choice of the following vowel to a small number of alternatives prior to the beginning of the formant transitions or voicing.

ISSN:0001-4966    

DOI:10.1121/1.2002670

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Rating scales were used to examine the role of burst intensity and burst position in the perception of the stop consonants [d] and [g]. Bursts and formant transitions were combined to form synthetic CV syllables with conflicting (e.g., d‐burst with g‐transitions) and nonconflicting (e.g., d‐burst with d‐transitions) sets of cues. In separate experiments, burst intensity and burst position relative to voicing onset were varied. Subjects were asked to identify and to rate the adequacy of the stimuli with conflicting cues; stimuli with nonconflicting cues were presented in pairs, and subjects rated the adequacy of the consonant of the second syllable relative to that of the first. Within a limited range of burst intensities or positions relative to the following vowel, the nonconflicting burst and transition integrated to form an optimal [d] or [g]. There were substantial individual differences in the way in which subjects responded to a conflicting set of cues. However, results suggest that the conflicting burst is most likely to influence perception when it falls within its optimal range as determined above. [Work supported by NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2002681

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Certain properties of a feature detector system sensitive to VOT were investigated with a binaural adaptation‐dichotic testing paradigm. On each dichotic test trial, a nonboundary voiced stop was paired with one of a set of voiceless stops. The voiceless stops varied in VOT, from values close to the phonetic boundary to values well within the voiceless category. The relative effectiveness of each of the voiceless stimuli in competing for processing with the voiced stimulus was assessed before adaptation and after adaptation with voiceless stops with a range of VOT values. During both pre‐ and postadaptation, the number of correct voicing responses when targeting for the voiceless stop, and the number of voicing intrusions when targeting for the voiced stop, systematically varied as a function of the VOT value of the voiceless stimulus. In addition, the VOT value of the adapting stimulus determined the amount of adaptation obtained. These results indicate first, that the output of the detector is a graded signal, and second, that the magnitude of decrease in detector sensitivity during adaptation is a function of the VOT value of the adapting stimulus. [Supported by NIH grants.]

ISSN:0001-4966    

DOI:10.1121/1.2002686

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP