摘要:

The technique from fuzzy set theory was used in combining the values of several parameters to determine the overall evaluation of concert halls. The factor set was tentatively defined as F = {RT (or EDT), LE, [EDT′(f)],Vmax(10 log LE)}, where LE is lateral efficiency, EDT′(f)} = 1/3 [EDT (2000‐Hz octave) − EDT (250‐Hz octave)], andVmax(10 log LE) denotes the maximum difference among 10 log LE values in a hall [V. L. Jordan, Apppl. Acoust.14, 253–266 (1981)]. The evaluation set was defined as E = {excellent, good, acceptable, no good} and the test set was defined as T = {measurement under full condition, measurement under empty condition}. Weight assignation for the factor set and test set was made asWF= (Wf,,Wf,,Wf,,Wf,) = (0.4, 0.3, 0.15, 0.15) andWT= (Wt,Wt) = (0.6, 0.4). The membership function values matrixR, in which the entryrijrepresents the impact ofith factor uponjth evaluation rank, was constructed. Last, the overall evaluation vectorS, in which the value ofith element denotes the possibility with which the hall would be evaluated toith rank, was calculated byS = WF⋅R. As examples, ten halls quoted in Jordan's paper were evaluated by using this method.

ISSN:0001-4966    

DOI:10.1121/1.2028824

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In order to determine how to accurately predict the reverberation time and sound propagation (the variation of steady‐state level with distance from a source) in rooms, predictions have been compared with measurements for an empty scale‐model room and in various nominally empty factories. In the case of rooms with disproportionate dimensions, predictions by the method of images, which accounts for room shape but assumes specular surface reflection, were found to deviate in a consistent way from experiment. The reverberation time is always too high; the short‐distance sound propagation tends to be slightly low and the large‐distance sound propagation is always too high. This result suggests that diffuse surface reflections were occurring. To test this hypothesis, further predictions were mad.e using a ray‐tracing model that accounts for diffuse surface reflections. It is found that excellent prediction accuracy is obtained as follows: (a) scale model—if all surfaces are 10%–10% diffusely reflecting; (b) real factories—if the ceiling and walls are 70%–90% diffusely reflecting.

ISSN:0001-4966    

DOI:10.1121/1.2028828

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In the design of noise‐critical spaces such as music and theatre performance and rehearsal spaces, low background noise levels are essential. Therefore, noise emanating from the supply and return air terminals of the HVAC system must be kept to a minimum. This requirement often dictates the need for many large terminals. This approach can be a very expensive alternative. In addition to the expense, the large area of duct terminals can have a negative impact on the room acoustics, particularly in a concert hall where sound absorptive materials/openings must be kept to a minimum. A number of different supply and return air terminals that create a minimum amount of noise at relatively high outlet velocities (up to 600 fpm) have been designed and tested. The results of these tests and guidelines for the design of low noise terminals will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2028831

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Intonation and stability of clarinet tones are influenced by the resonance frequencies of the instrument that are influenced in turn by the placement and size of its tone holes. Dimensions of an instrument of moderate quality were measured and served as the starting point for the optimization procedure. Input impedances were calculated for 47 different fingerings of the instrument. Minimization of the frequency differences between four resonance frequencies—modes 1 and 2 in the chalumeau register, mode 2 in the clarion register, and mode 3 in the altissimo register—and four reference frequencies served as the optimization criteria. The reference frequencies were arbitrarily chosen from an equal tempered chromatic scale tuned to A4 = 440 Hz. Tone‐hole position, diameter, and height were the optimization parameters. In one method, these parameters were modified one at a time, while in a second method all three were modified together. Both methods produced similar results with average reductions in “frequency error” of 9 cents for chalumeau mode 1, 28 cents for chalumeau mode 2, and 16 cents for modes 2 and 3 of the combined clarion and altissimo registers. Optimization procedures and results will be discussed.

ISSN:0001-4966    

DOI:10.1121/1.2028836

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

In an attempt to simulate guitar sounds, a discrete model was developed that consisted of real strings with stiffness and internal damping, the player's finger, the resonance box, and the modelization of the sound pressure. The vibrating string equation was solved in the time domain using the finite‐difference method. The player's figure was modeled as a force density term in the string equation, which accounted for the initial plucking conditions. The resonance box was modeled as impedancelike boundary conditions at one end of the string. These end conditions were obtained under the assumption that the driving force exerted by the string at its ends excites a set of second‐order resonances in parallel, the first resonance of the plate being coupled with the air resonance of the box. Finally, the sound pressure was modeled as the contribution of a set of monopoles, where each monopole corresponds to one given resonance. The radiation efficiency of each monopole was derived from a curve fitting on a guitar sound‐pressure spectrum measured in an anechoic chamber. The waveforms obtained are in good agreement with experimental waveforms measured on real guitars. Sound examples will be presented high‐lighting the realism of the simulation.

ISSN:0001-4966    

DOI:10.1121/1.2028843

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Since the advent of the interdigital transduction for efficient transducer of surface acoustic waves (SAW), SAW devices have provided a key technology for communication and signal processing systems. In order to obtain the required electrical terminal characteristics, a diverse number of SAW components have evolved. Some of these components include bidirectional and unidirectional transducers, couplers, beam compressors, waveguides, and reflectors. The various SAW components are monolithically integrated, using processors similar to those for integrated circuits, on a piezoelectric substrate to produce dispersive filters, linear phase filters, resonators, convolvers, and correlators. These devices are manufactured for a wide variety of applications which include TV‐IF, cable TV, VCRs, fiber optic repeaters, radar, spread spectrum receivers, cellular radio, sensors, and a variety of communication receiver applications. The technological innovations and operation of the primary SAW components will be discussed. The presentation will focus on component implementations, their operation, and their most significant parameters. A review of some of the key developments of SAW technology and their applications will also be presented.

ISSN:0001-4966    

DOI:10.1121/1.2028847

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Acoustic tomography is a promising method for monitoring atmospheric wind and temperature fields. It may be possible to achieve better spatial and temporal resolution than offered by existing technologies. In this paper, three different schemes, all based upon travel‐time measurements, are proposed and analyzed: a horizontal array for determining structure of boundary‐layer thermals and gravity waves; a vertical array for high‐resolution monitoring of the mean surface‐layer profiles; and a long baseline array for studying the evolution of stable boundary layers. The schemes are evaluated in terms of resolution capability, practicality, and interest in atmospheric science. Some preliminary results from experimental and numerical studies of the horizontal array are given. The numerical studies use wind and temperature fields generated by a large‐eddy simulation (LES) model.

ISSN:0001-4966    

DOI:10.1121/1.2028854

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

This paper will present the results of a 3‐yr study (1986–1989) comparing the effect of two tactile devices on communication skills of deaf‐blind children—a 2‐channel vibrotactile (Tactaid II) and a 16‐channel electrotactile aid (Tacticon). A total of three communicative behaviors were selected for each child. A single‐subject alternating treatment design was used and data from each of three substudies were analyzed using three combined Wilcoxin tests. In the first substudy, subjects displayed significanfly more of the desired behaviors when wearing the Tactaid than the Tacticon (0.05 level). In the second and third substudies, and in the replication‐across‐settings study, no differences were found in any of the conditions. In the replication‐across‐change agents study, both tactile devices produced significantly more of the desired behaviors than no device (0.05 level). One of the most important findings was that the children accepted both devices despite the tactile defensiveness often exhibited by so many of them. A second study to replicate the research using only the Tactaid II + device with deaf‐blind infants and preschoolers is underway (1989–1992), and the results of the first year of this study will also be presented. [Work supported by OSERS, U.S. Dept. of Educ.]

ISSN:0001-4966    

DOI:10.1121/1.2028861

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Acoustic parameters were measured for vowels spoken in /hVd/ context by three postlingually deafened cochlear implant recipients. Two female subjects became deaf in adulthood; the male subject, in childhood. Recordings were made before and at intervals following processor activation. The measured parameters included formant frequencies,F0, SPL, duration, and amplitude difference between the first two harmonic peaks in the log magnitude spectrum (H1–H2). A number of changes were observed from pre‐ to post‐implant, with intersubject differences. The male subject showed changes inF1, vowel durations, andF0. These changes were consistent with one another; however, they were not necessarily in the direction of normalcy. On the other hand, the female subjects showed changes inF2, vowel durations,F0, and SPL, which were in the direction of normal values and, for some parameters, tended to enhance phonemic contrasts. For all three subjects, H1–H2 changed in a direction that was consistent with previously made flow measurements. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2028864

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP

摘要:

Extracellular events of single units were studied in response to acoustical and electrical stimuli in the barbiturate anaesthetized cat. The electrical stimuli were biphasic current pulses, 100–200 μs/phase, delivered at 100–400 pulses per second (pps) via a bipolar electrode implanted into the scala tympani. The first group of units, group 1, generated action potentials 1.6–2.4 ms following an electrical pulse, while the latency for group 2 was 2.4–4.8 ms. In both groups, the spontaneous activity and the response to a pure tone was commonly suppressed between 2.5–3.75 ms following an electrical pulse. It is possible that groups 1 and 2 received mono‐ and di‐synaptically mediated excitatory inputs, respectively, and a disynaptically mediated inhibitory input. Both groups commonly generated action potentials at a second latency between 3.75–10 ms, which may have been due to long latency monosynaptically mediated or disynaptically mediated excitatory inputs. There was a difference in discharge rate between acoustic noise stimulation and electrical stimulation at high current levels for group 2, but not for group 1, suggesting temporal interaction between excitatory and inhibitory drives.

ISSN:0001-4966    

DOI:10.1121/1.2028868

出版商:Acoustical Society of America    

年代:1990

数据来源: AIP