摘要:

The Louisiana Superdome, an enclosed stadium with a seating capacity of 95 000 people, was designed for a variety of uses ranging from sports events through entertainment to large conventions. The presentation describes the acoustical treatments included in the stadium to control reverberation and intrusive noise. Also, the loudspeaker systems employed are described as well as the functional and electrical arrangement of components, and some observations on the performance of the system.

ISSN:0001-4966    

DOI:10.1121/1.2015483

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

The authors have, over the past fifteen years, been involved in the design of over 30 arena‐type buildings, seating from 3500 to 22 000 people. A new arena, called a Special Events Center, under construction in Austin, TX, will approximate what the authors consider to be the state of the art in acoustics and audio, based on experience gained in previous spaces. Among the items to be covered will be the sound reinforcing system, which will accomodate all events from opera to rock concerts, and which will be operated by a professional operating company to avoid pitfalls of union soundmen. Salient features of other arenas will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2015485

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

A computer program has been developed for the prediction of sound pressure levels in large, irregular rooms utilizing a geometric acoustics approach. Experiments indicated that the program gave good predictive accuracy when receiver positions were in the line of sight of the sound source. However, the accuracy was poor when the receiver was out of the line of sight. The present discussion reports on the further development of the program to include diffraction effects using an extension of Maekawa's approach for thin screens and right‐angle wedges. The program is capable of finding all valid diffracted rays which undergo three or fewer reflections before diffraction and three or fewer reflections after diffraction. Limited experimental work indicates good predictive accuracy.

ISSN:0001-4966    

DOI:10.1121/1.2015492

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

During the Haswell Experiment sponsored by NOAA's WPL in March 1974, sound propagating from a source on a 150‐m tower was received on the ground at slant range of 188 and 333 m. Recordings were made using a tetrahedral array 1 m on a side at frequencies of 500 and 1000 Hz. Using time delays between three pairs of microphones, direction cosines were computed for a plane wave arriving at the array. The cosines indicate that the direction of the sound reaching the array fluctuates several degrees in direction during medium turbulence at 188‐m distance. Computed sound source direction misses the actual source direction by about 12° in the vertical and 5° horizontal at 188 m for both 500 and 1000 Hz. At 333 m, noise and loss of signal prevented computing reliable source direction.

ISSN:0001-4966    

DOI:10.1121/1.2015498

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Computer‐assisted synchronous hot wire, or “CASH,” method was developed to permit computer averaging of hot wire data when sampling oscillating velocity profiles. Using emitted sound pressure as phase reference, computer separates periodic component of hot wire signal from turbulent background by averaging over large number of acoustic cycles. So far technique has been utilized in two investigations: (1) interface oscillations of flow‐excited cavities, and (2) growth of instability waves in laminar jets. Accuracy depends on the ability to match closely the reference source frequency. Any mismatch produces systematic error. For given amount of mismatch, however, error is minimized by dividing sample into subsets and performing the averaging at two levels. In the cavity resonator problem, random deviations from periodicity in the reference itself make frequency‐matching difficult. Measured standard deviations show a predicted periodicity, with greatest amplitude discrepancy occurring 90° after signal maximum. To assure amplitude error of no more than 3% requires that frequency mismatch be kept to less than 0.1%. [Work sponsored by Naval Ship System Command, GHR program, administered by Naval Ship Research and Development Center.]

ISSN:0001-4966    

DOI:10.1121/1.2015501

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Previously we reported [J. G. McCormick, R. M. Clayton, and I. L. Holleman, J. Acoust. Soc. Am.52, 193 (1972)] that round window cochlear potentials of old pigeons that developed spontaneous carotid atherosclerotic plaques were poorer in sensitivity than younger birds of the same breed with little or no evidence of plaques. We also noted that a high cholesterol diet fed to these birds was correlated with a reduction of cochlear potentials. This initial work, which included studies on birds genetically resistant to atherosclerosis was a pilot project on 75 birds. In our present paper we will report further findings from a one year study of over 220 additional atheroselerotic pigeons. The age relationship to cochlear potential loss is substantiated, and correlative sophisticated blood coagulation tests will be discussed. [Work supported by NIH Grant No. NS‐12013 and Bowman Gray School of Medicine, Venture Capital Grant No. 2‐156‐801‐2507.]

ISSN:0001-4966    

DOI:10.1121/1.2015509

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

To study how cortical neurons express directional information about a stationary echo source, responses of single neurons were recorded from the Doppler‐shifted—CF‐processing area of the mustache bat (Pteronotus parnellii rubiginosus). All cortical neurons studied were excited by contralateral stimuli and were either excited or inhibited by ipsilateral stimuli. They are called E‐E and I‐E neurons, respectively. Each penetration orthogonal to the cortex was characterized by either E‐E neurons. I‐E neurons, or neurons exhibiting binaural interaction, which varied with depth. Thus the cortex consists of three types of binaural columns. E‐E neurons were poorly directional and showed maximum responses to tone bursts directed at the front of the head. I‐E neurons were sharply directional. E‐E neurons (or columns) were mainly located ventrally in the Doppler‐shifted—CF‐processing area, while I‐E neurons were mainly distributed dorsally. E‐E neurons, which were more sensitive to weaker echoes, are suited for integrating signals from both ears for echo‐detection. I‐E neurons, which were more sensitive to stronger echoes, are best suited for processing echo direction. [Work supported by NSE.]

ISSN:0001-4966    

DOI:10.1121/1.2015513

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Frequency discriminability of pure tones was measured in a variety of background noise conditions. Difference limens were estimated at 4 kHz using a method of constant stimulus differences, Maskers included wide‐band white noise, low‐pass noise at 1 kHz, high‐pass noise at 6 kHz, and a 500‐kHz tone. In all cases the test signal was held at 15 dB SLrequite or masked threshold. Initially measures were obtained with 20 dB of masking for each condition, Frequency DL's in wide‐band and in high‐pass noise were comparable to those in quite. In low‐pass noise and in the low‐frequency tonal masker, DL's were significantly greater than in quiet. When the amount of masking was changed (SL of signal held constant). DL wide‐band noise was approximately constant while DL in low‐pass noise increased with noise level. These results are discussed in relation to single nerve‐fiber tuning curves in noise and also in relation to data on two‐tone suppression effects.

ISSN:0001-4966    

DOI:10.1121/1.2015517

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

Our laboratory's recent work on the nature of masking has revealed that stimulus change can cause both forward and backward maskinglike effects. In these previous demonstrations, a decrease or shift in the noise contained in the signal channel constituted the stimulus change. To demonstrate that these masking effects were attributable to stimulus change and not the interaction of off‐frequency transients, we designed the present experiment in which the stimulus change occurred in the nonsignal ear. In this case, stimulus change consisted of a shift in correlation of the noise between the two ears by inverting the contralateral noise at various times (4<Δt<200 msec) prior to the onset of the potential signal. Relative to the unchanging (+1 or −1) contralateral noise control conditions, the detectability of the signal was significantly decreased independent of the direction of change in correlation (+1 to −1, or −1 to +1). Effects of differing rise‐fall times (1, 2.5, and 5 msec) of noise change were also examined. The results are discussed in terms of current masking theory. [This research was supported by a grant from NINDS.]

ISSN:0001-4966    

DOI:10.1121/1.2015543

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP

摘要:

In a single‐interval (yes‐no) detection paradigm identical to that employed previously [J. S. Puleo and R. E. Pastore, J. Acoust. Soc. Am.60, S49 (A) (1976)], we investigated the extent to which contralateral cues of various spectral complexity could improve signal detectability during monotic backward masking in the presence of a second, continuous masking noise. We used a 20‐msec segment of a 500 Hz sinusoid as the signal and a burst of band‐limited noise (100 to 800 Hz wide) centered at the signal frequency as the cue. Results showed that, relative to the noncued condition, significant reductions in backward masking occurred regardless of the type of cues employed. Although the narrower‐band cues were somewhat more effective in reducing backward masking than the wider‐band cues, these differences were not behaviorally significant. None of the cues were very effective in reducing simultaneous masking. These results are discussed in terms of their theoretical implications regarding the nature of backward masking. [This research was supported by a grant from NINDS.]

ISSN:0001-4966    

DOI:10.1121/1.2015556

出版商:Acoustical Society of America    

年代:1977

数据来源: AIP