摘要:

Several fish with swimbladders have been shown to detect the angular location of a source of low‐frequency pure tones, e.g., 75 Hz, if it is situated in the “horizontal” plane of the fish. Moreover cod possess truly three‐dimensional directional hearing. Two variables are pertinent: particle acceleration a(t) and acoustic pressure p(t) at the position of the fish. Directional information in a(t) might be obtained through differently oriented acceleration detectors such as the otolith organs. Electrophysiological evidence supports this. Time of arrival differences appear irrelevant. Bony fish with swimbladders (cod, ide) show a 180° reversal in directional response if a sinusoidal sound field with a(t), p(t) is replaced by a(t), −p(t). This suggests a phase analysis to overcome the 180° directional ambiguity when inferring propagation direction from a(t). Pressure is transformed by the swimbladder into accelerations along a line of action characteristic for the recording site in the labyrinths. Sharks, which lack swimbladders, show acoustic attraction from afar. It is unknown how they are able to localize the source if the detection is also based on a phase comparison system.

ISSN:0001-4966    

DOI:10.1121/1.2004090

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The amphibian auditory periphery is traditionally viewed from one of two perspectives: (1) that it is degenerate and by implication derived from the amniote condition or (2) that it represents, at least in most frogs, a simple intermediate condition between the ears of rhipidistian fishes and reptiles. These two perspectives, or various hybrids, guide modern workers in the design of their investigations and the interpretation of the data resulting from these studies. The development and diversity of the amphibian auditory periphery is reviewed and compared to that of amniotes. The otic region in key fossil tetrapods is reviewed. Our current concepts of otic homology are reviewed and some alternative homologies are suggested. This review indicates that the most parsimonius perspective on the amphibian auditory periphery is that it represents a unique experiment in aerial hearing unrelated to that found in modern amniotes. The implications of this perspective for modern morphological and experimental work are discussed. [Work supported by NSF.]

ISSN:0001-4966    

DOI:10.1121/1.2004142

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The structures of the avian outer and middle ears are furnished by the most extensive adaptive variations according to different ecological requirements. The cochlea with lagena is almost straight and cell arrangement in the cochlear duct is distinguished from the mammalian: Two types of hair cells lie in one continuous row, the cilia are inserted firmly into the tectorial membrane, the pattern of nerve innervation is quite different from that of the mammalian corti, and the orderly seqence of innervation on the basilar membrane is reserved obviously in tonotopical organization of the cochlear nuclei. Songbirds can hear most of the frequencies in their vocalization, while their ears are not the kind of specialization for communication seen in orthopterans and frogs: Recognition of conspecific songs involves in processing in the higher CNS rather than in the range of frequency alone. The behavioral relation of vocalization and hearing may light on tentative approaching the problem of pattern recognition in auditory CNS.

ISSN:0001-4966    

DOI:10.1121/1.2004193

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The ability of an animal to localize sound is correlated with its ethological niche. Birds face a particularly difficult task in sound localization, since they must localize well in both azimuth and elevation: The azimuth of a target is of no use to an airborne predator unless it can also determine the target's elevation. Furthermore birds must perform sound localization with access to only a limited range of low sound frequencies (<12 kHz), with heads that provide little sound shadow, and with ears that have no pinnae and are close together. However behavioral, physiological, and anatomical data suggest that the auditory systems of birds are capable of extremely fine time resolution. Also, birds have elaborated a large, patent air canal connecting their two middle ears that might improve the directional properties of their ears. Finally, some birds have developed asymmetrical ears that cause interaural time and interaural intensity cues to assume different axes of symmetry. It is proposed that these adaptations permit birds to achieve a high level of sound localization ability, the best of which rivals, and may exceed that of man. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2004239

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

Various acoustic researches for telecommunication are performed in the Electrical Communication Laboratory, NTT. Among these, researches on acoustic standard apparatus, acoustic measurements, electroacoustic transducers, vibrating systems, acoustic materials, room acoustics, and telephone networks are included. A new12‐in.standard condenser microphone has been developed for precise sound measurement and sensitivity calibration of telephone sets. This new standard microphone, made of titanium alloy, has high sensitivity (−54 dBre1V/mgr;bar, high reliability, and wide frequency range (∼35 kHz). A precise calibration method using standard couplers, as well as a simplified calibration method using active coupler, are established. Research of room acoustics is important for telephone systems in the future, because the acoustic transmission characteristics of rooms may take an important place in the system. Transmission characteristics and the spatial correlation coefficients of various rooms are investigated. The results of these researches are especially useful in telephone loudspeaker design. Based on the results of various researches, several types of new telephone sets and systems are now being developed.

ISSN:0001-4966    

DOI:10.1121/1.2004334

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

This paper describes the signal generation and processing capabilities of an automated acoustical measurement system. The basic design goals for the signal generation and timing capabilities of the system were to provide the maximum flexibility for signal generation and reception while using sampling techniques that allow fast signal processing algorithms to be used in the data processing and analysis. The waveform and timing generator was designed to generate the conventional sinusoidal pulse waveforms used in many acoustical measurements along with special purpose arbitrary waveforms which can either be used directly as the transmit signal or to modulate the sinusoidal transmit pulses. The system timing technique allows a user to make simple single pulse measurements or to make multiple pulse measurements where data samples are summed either coherently or incoherently to maximize the signal‐to‐noise ratio. [Work sponsored by NAVSEA 06H4D.]

ISSN:0001-4966    

DOI:10.1121/1.2004383

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

An impulse technique for determining radiation impedance and radiation directivity of jet nozzles is discussed. Results for an unflanged pipe are compared with the theoretical results of Levine and Schwinger [Phys. Rev.73, 383–406 (1948)] for the purpose of justifying the technique. Data are then presented to show the effect of nozzle size and jet velocity on both nozzle transmission and radiation impedance and radiation directivity. Conical nozzles are used and the results for 2‐ and 1‐in. diameter nozzles are compared with those for the 4‐in. diameter straight unflanged pipe. Effects of jet exit velocity up to 1300 ft/s are displayed and discussed in the light of available theory. Spectral energy is determined for the incident and reflected wave signals in the pipe, and the transmitted wave in the farfield and energy conservation for the system is discussed. Finally, it is shown that the test method can be usefully applied at frequencies above the plane mode regime.

ISSN:0001-4966    

DOI:10.1121/1.2004441

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

A transmitting hydrophone which remotely senses both absolute pressure and changes in pressure has been developed using a surface‐acoustic‐wave (SAW) oscillator. This oscillator is formed by placing a SAW delay line or resonator in the feedback loop of an amplifier. The pressure applied to the hydrophone is converted to a flexural loading of the piezoelectric plate which alters the surface‐wave velocity on the plate, consequently shifting the oscillator frequency. This frequency modulated signal is easily transmitted to a remote location for signal recovery. The piezoelectric plate thickness and length can be chosen to optimize the sensitivity of the SAW hydrophone. The surface‐wave element of the oscillator is a planar structure; therefore, it is simple and inexpensive to manufacture. Furthermore, the size and power requirements of the SAW hydrophone are small, typically less than 50 cm3a and 300 mW. This paper presents performance data of a number of SAW hydrophones using SAW oscillators in the 40–100‐MHz range in conjunction with a versatile signal demodulation system. Extensive measurements of sensitivity and frequency response were made for both delay line and resonator hydrophones manufactured onLiNbO3and S‐T cut quartz substrates and compared with measurements obtained from conventional hydrophones in the identical setup. [Work supported by Naval Electronics Systems Command Contract No. N00039‐78‐C‐0042.]

ISSN:0001-4966    

DOI:10.1121/1.2004492

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

During the 1960's, round‐robin tests on the measurements of sound absorption coefficient in reverberation rooms had been carried out extending over four times in Japan. One of the main objectives of these investigations was to find a sensitive and useful measure of sound diffusion in reverberation room. Two kinds of indices, the ratio of horizontal to vertical mean energy during decay process and the directional distribution of spatial correlation coefficient, were adopted for the evaluation of the degree of diffuseness. Most of reverberation rooms in Japan have nonparallel walls in order to obtain diffuse sound field. Moreover, suspended diffusing plates are often used to improve the degree of diffuseness. Compared with the case of rectangular room, relatively small number of diffusers would be sufficient to obtain the same order of diffuseness. An essentially important factor would be the volume of the room, and for measurements at low frequencies, extremely large volume would become necessary. Thus, it would be desirable to use two or three reverberation rooms with different volumes in order to cover the whole frequency range. In parallel with these investigations, theoretical studies on the sound field in rectangular reverberation rooms have been carried out extensively.

ISSN:0001-4966    

DOI:10.1121/1.2003693

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP

摘要:

The directivity factor of small sound sources in the direction of the measurement microphone may be determined in a reverberant room by using a pressure gradient microphone to separate the direct and reverberant components of the sound field. Experimental verification of the theory, together with analysis of the advantages and limitations of the method compared to more conventional means will be presented.

ISSN:0001-4966    

DOI:10.1121/1.2003738

出版商:Acoustical Society of America    

年代:1978

数据来源: AIP