摘要:

This paper considers some basic problems inherent in the instrumental analysis of intonation. The problems are illustrated by a detailed analysis of one intonation contour in American English. The material studied consisted of two sets of data. The first set involved sentences recorded by one speaker with determined stress and pitch patterns. These sentences consisted of 1263 CNC words produced in an identical frame, with primary stress and the peak of the intonation contour occurring on the CNC word in the frame. The second set of frame sentences involved 70 minimally different words, uttered by five different speakers of the same general dialect. The fundamental frequency values for the various levels of the intonation contours of the sentences were measured from narrow‐band sound spectrograms, and the measurements were correlated with the segmental phonetic structure of the utterances in which the intonation contours were produced. The intrinsic fundamental frequencies of the various syllable nuclei of the words from both sets of data, and the influence of preceding and following consonants on these frequencies, are described. The relationships among successive intonation levels within the sentences also are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1936362

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

The diameter of cylindrical transducers employing the radial mode of operation can be extended to permit resonant operation to much lower frequency. Heretofore the techniques for assembly of bars into cylinders have limited the practical physical size because of the dimensions of available ceramic bars. This paper describes an assembly method whereby available barium titanate bars can be oriented to provide cylinder wall thicknesses up to 12 in. A 200‐in. diameter transducer will have an operational depth of 10 000 ft without pressure compensation and will resonate at 160 cycles per sec. This cylinder can supply 2 megawatts of acoustic power, essentially nondirectional. The same construction technique can be employed on units for frequencies up to 2000 cycles per sec. The paper also will indicate the power capability as a function of size, and stacking procedures are shown to realize the optimum source levels. Cylindrical transducers of nickel ferrite employing the conventional technique with permanent magnets installed have measured efficiencies of 69%. Properly associated windings permit a very low electrical impedance. Comparable transducers employing the barrel stave and the brick wall techniques have been evaluated.

ISSN:0001-4966    

DOI:10.1121/1.1936370

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

In many recent sound system installations, the results have been so poor as to make the rooms where they are installed unusable. In redesigning the sound systems we have applied the concept of sound reinforcement rather than the usual philosophy of the P. A. salesman. In many cases in school, church, conference room, and theater sound systems, excellent amplifiers are used in conjunction with high quality but suitable microphones and loudspeakers. In some cases basic errors in equipment location or the use of an unnecessary low‐level system have caused system failure. Case histories illustrate the failure of a number of sound systems to meet the needs for sound reinforcement (dead spots, low intelligibility, intermittent ringing, mechanical or tinny quality) and the simple solutions to provide complete satisfaction for the owner.

ISSN:0001-4966    

DOI:10.1121/1.1936377

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

A theoretical analysis of the nonlinear suspension and the nonlinear compliance of the air in the cabinet has been carried out. The results of the analysis have been applied to the development of a back enclosed, direct radiator loudspeaker with low distortion.

ISSN:0001-4966    

DOI:10.1121/1.1936378

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

Digital computers have proven themselves to be a useful tool in the solution of many scientific and engineering problems. To date, however, its use in the solution of electroacoustic problems has been very limited. A mathematical treatment of the equivalent electroacoustic networks often produces large systems of complex simultaneous equations which are time‐consuming to solve by hand‐calculations. As a result, the average electroacoustical engineer has developed a “feel” for the analog approach in preference to the classical methods. The ready facility of digital computers to perform innumerable arithmetic operations at high speed and without mistakes makes it now feasible to revive classical methods as a useful engineering tool. In this paper we will discuss the use of a computer to (1) calculate the gain‐frequency characteristic of a transistorized audio amplifier, (2) to predict the low‐frequency response and sensitivity of proposed loudspeaker designs. and (3) as an aid to predict the acoustic load characteristic of proposed loudspeaker locations.

ISSN:0001-4966    

DOI:10.1121/1.2142337

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

Data on the threshold of audibility of underwater sound have been published, but virtually no data are available on the upper threshold of tolerance to underwater sound of high intensity. The present experiment was undertaken to obtain such data. Twenty‐three listeners, UDT (Underwater Demolition Team) and scientific personnel, were given audiometric tests preceding and immediately following exposure in a high‐intensity underwater sound field. The stimulus was a 1500‐cps tone of 1‐sec duration that was increased in 1‐db steps from 161 db (re0.0002 d/cm2) to 180 db. Masking from breathing noise of the open circuit SCUBA (Self Contained Underwater Breathing Apparatus) was eliminated by having the listener breathe during the 2‐sec interval between steps. The listeners indicated to the experimenter their “tolerance” limits by means of an electrical signaling device. Tests were run with and without foam neoprene hoods. The data indicate that the threshold of discomfort to underwater sound at 1500 cps is approximately 173 db for divers without hoods. A comparison is made with similar data for airborne sound. A shift in the visual field which occurred at the onset of the sound is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1936395

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

Adequate description of noise environment, as related to human exposure and hearing conservation, requires detailed information not only on spectrum and SPL, but also on temporal duration of SPL above hazardous levels with due regard for spectrum. Continuous magnetic tape recordings were made at six different microphone positions, four on the flight deck and two on the hangar deck, approximately 6 continuous hours per microphone position, totaling 35.7 hr. These recordings include all of the noise occurring during the time sampled, regardless of the type of ship's operation. The ship was under fully operational conditions, and the time samples were taken during the normal working day which included air operations. The recordings were analyzed in the laboratory by a Noise Cumulator to yield the time in minutes that the noise exceeded 7–11 pre‐set sound pressure levels above 80 db in each of three frequency bands; i.e., 30–17 500 cps, 300–1200 cps, and 1200–17 500 cps. The results of these analyses were plotted as a function of percent of accumulated time. Other analyses, employing more limited time samples were made but with greater frequency‐intensity detail.

ISSN:0001-4966    

DOI:10.1121/1.1936400

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

In order to evaluate the feasibility of conducting a hearing testing program under various conditions of an operational cruise aboard a CVA type aircraft carrier, an audiometric test room (modified 1AC Model 1203) was installed aboard theUSS Saratoga. The audiometric test equipment that was placed in the test room consisted of one individual and two group audiometers—namely, (a) the Rudmose ARJ‐3, (b) the Maico Group Audiometer R‐4 (a pure tone pulse test with single descent feature in 10‐db intensity steps), and (c) the Ampex Group Audiometer Model S‐3510 (reported as the NMRL Group Monitoring and Screening Audiometer). Two groups of subjects were tested to obtain hearing levels as determined by each audiometer during three conditions—namely, (1) in port, (2) underway, and (3) during catapult operations. The general effectiveness of the test room will be discussed in terms of ambient noise in the room and the measured noise reduction. The hearing data will be presented so as to show comparisons among the three audiometers as well as among the three conditions of testing.

ISSN:0001-4966    

DOI:10.1121/1.1936401

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP

摘要:

Measurements have been made of the nonlinear steady‐state response of a 2‐in. by 12‐in. strip of 2024 T3 aluminum,116 in.thick, which was clamped on the short side and free on the long side. Vibrations were excited by the sound of a siren at the end of a duct in whose side the strip was mounted. Measurements were made in a broad range of frequencies around the fundamental resonance and at sound pressure levels up to 150 db,re0.0002 microbar. Skewed response curves typical of a hard‐spring oscillator were obtained. The data can be reasonably interpreted by means of a theory which includes the effects of in‐plane tension generated by large amplitudes of bending displacements. when allowance is made for a number of interesting experimental complications. (Supported by Wright Air Development Division.)

ISSN:0001-4966    

DOI:10.1121/1.1936412

出版商:Acoustical Society of America    

年代:1960

数据来源: AIP