摘要:

This paper reports on acoustical measurements made with Vatican permission in several large churches, including St. Peter's Basilica and the other three Patriarchal Basilicas in Rome: S. Giovanni in Laterano, S. Paolo fuori le Mura, and S. Maria Maggiore. The observed reverberation times for these large churches are unusually short. This is because of the acoustical coupling of the air volumes making up the structures and also the profusion of architectural detail and decoration, especially sculpture, that produces a very considerable amount of sound diffusion. The measured reverberation times are consistent with standard reverberation theory when the coupled nature of the air volumes is considered.

ISSN:0001-4966    

DOI:10.1121/1.1912648

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

Acoustic signals received in the northeast coastal regions of the United States from rockets launched at Cape Kennedy show strong seasonal effects. For the Saturn V rockets, strong signals are received in winter, very weak signals in summer, and weak signals in the transitional months of early fall and spring. These seasonal effects are attributed to the winds in the stratosphere (around an altitude of 50 km). In winter, when strong signals are received, the stratospheric winds have strong components in the direction of propagation of the signals. These components are weak during the transitional months, and during summer the stratospheric winds have components in the direction opposite to that of the signal propagation. It is shown that calculations of horizontal trace velocities provide an indirect method of estimating upper atmospheric winds.

ISSN:0001-4966    

DOI:10.1121/1.1912649

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This paper is a survey and a progress report on present and potential instrumentation to measure loudness levels of sounds. The development of the sound‐level meter (SLM) in the 1930's, its technological and psychoacoustical evolution, and its evaluation as a measurement device are discussed. A loudness‐level monitor, designed to measure the relative loudness level of broadcast programs directly on an indicating instrument, and the development of a new set of equal‐loudness contours are described, together with a new law of loudness‐level addition for combined bands of noise which was discovered during the research. An experimental loudness level meter, devised by adapting CBS Laboratories' loudness level monitor and the potential development of an accurate and practical loudness‐level indicating device are discussed. The results of psychoacoustic evaluations of the loudness level meter versus sound‐level meter are given.

ISSN:0001-4966    

DOI:10.1121/1.1912650

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The frequency response of a multilayer semiconducting piezoelectric transducer is obtained algorithmically. The multilayer transducer is first reduced to a conventional three‐port structure by defining recursively the mechanical impedance loading each face of the piezoelectric layer. Electromechanical power conversion theory is then used to obtain the transducer loss. Computed results for the performance of multilayer transducers composed of a 1.5‐μ‐thick ZnO film and other metallic layers illustrate the use of this theory in the design of microwave ultrasonic transducers. The effects of finite resistivity, contact resistance, and different tuning conditions are described. The possibility of frequency‐response shaping by using a multilayer is demonstrated by showing that an unusually broad‐bandwidth transducer is obtained for an Au‐ZnO‐Au‐Al structure.

ISSN:0001-4966    

DOI:10.1121/1.1912651

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The acoustic signal velocities for pressure modes in an infinite rectangular hard‐walled duct with a steady flow are investigated for the purpose of clarifying the degeneration of wave propagation which occurs with a low‐frequency sinusoidal excitation. It is found that all pressure modes propagate both upstream and downstream at a speed governed by the Doppler effect. All modes other than the plane wave are dispersive and leave a lingering disturbance after passage. In steady sinusoidal excitation, this lingering disturbance gives rise to cancellations and reinforcements which can cause nearly complete attenuation in the cutoff condition or can cause waves with negative phase velocities in the downstream section of the duct even without end reflections.

ISSN:0001-4966    

DOI:10.1121/1.1912652

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This study concerns the question of whether or not the relation between intelligibility test scores and the Articulation Index (AI) established for steady‐state noise can be used to predict speech intelligibility in the presence of time‐varying aircraft noise. For various aircraft flyovers, intelligibility scores and several noise measures were obtained as functions of time. In addition, intelligibility scores and measures of AI were obtained for steady‐state simulated aircraft noise. The relation between speech intelligibility and AI for time‐varying noise was different from the relation obtained for steady‐state noise. The various noise measures were almost equally effective in predicting speech intelligibility in the presence of time‐varying aircraft noise. There is an appreciable disruption of contextual speech when the peak level of a flyover exceeds 88 PNdB, a speech‐interference level of 68 dB, or anA‐weighted sound‐pressure level of 76 dB.

ISSN:0001-4966    

DOI:10.1121/1.1912653

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The termresonant frequencyembodies both technical and grammatical errors and its use should be deplored and deprecated. The proper form isresonance frequency.

ISSN:0001-4966    

DOI:10.1121/1.1912654

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912655

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912658

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912661

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP