摘要:

The directional characteristics of the string instruments depend not only on the frequency, but on the kind of wood and the thickness of the plates. It is necessary, therefore, to measure several violins, violas, violoncellos, and contrabasses and to evaluate an average characteristic for each instrument group and many frequency ranges. The results of such investigations, made in an anechoic chamber, demonstrate the main directions of the sound radiation and the directions of less sound pressure in dependence on the frequency. These characteristics make it possible to discuss the influence of different seating arrangements of the orchestra on the loudness, the harmonic content and the clearness of the transients in a concert hall. The interaction between the room acoustics and the main directions of the instruments is very important for the ratio between direct and slightly delayed sound and reverberation. It is interesting, too, for the construction of reflectors on the walls near the orchestra and under the ceiling.

ISSN:0001-4966    

DOI:10.1121/1.1973368

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The general purposes of these experiments were to: (1) replicate earlier findings that release from masking could not be obtained using a pure‐tone masker, (2) determine whether the release from masking could be obtained for remote masking of low‐frequency tones by higher‐frequency noise, and (3) determine if there was a relation between the amount of masking and the release from masking. Results indicated that, in confirmation of earlier work, release from masking could not be obtained using a pure‐tone masker. Also, the use of high‐frequency noise to mask lower‐frequency tones did not result in release from masking. Research on the possible relation of the amount of masking to the amount of release from masking is still in progress.

ISSN:0001-4966    

DOI:10.1121/1.1973406

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A theoretical procedure is developed in an effort to solve the acoustic propagation problem in the ocean in the presence of stochastic boundaries. This theory is believed to be an improvement over past efforts that treated the surface as a separate problem. My result for the mean or mean‐squared potential function can be used to calculate the effects of a stochastic surface including mode coupling, attenuation, scattering into a shadow region, etc., without recourse to the approximations of past theoretical efforts. While this theory is complex in structure, it is my opinion that the difficulties are justified in that less is neglected. The usual plane‐wave surface scattering theories may suffice in certain applications; however, it is evident that they must be used in conjunction with ray tracing. A mode theory is a step in the right direction in that the limitations of the ray theory are overcome.

ISSN:0001-4966    

DOI:10.1121/1.1973416

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Harmonic analyses of several violin tones have been performed by computer. Each sound is represented by a finite series of harmonic‐amplitude and phase‐spectrum components varying with time. Graphical representations of spectra being explored are: (1) individual plots of fundamental‐frequency harmonic amplitudes (both linear and dB), and relative phases as functions of time; (2) line‐spectra movies with harmonic amplitude changes slowed 20:1; (3) spectrograms with vertical frequency scale, horizontal time scale, and darkness indicating amplitude. Spectrum analysis can be performed synchronously with the fundamental or asynchronously at a base frequency much lower than the fundamental, with advantages for each method. Completeness of harmonic analysis is demonstrated by examples of tones resynthesized using smoothed versions of harmonic‐amplitude and pitch curves. For storage purposes, synthetic tones typically require 500 to 800 parameter‐time coordinates per 1 sec of sound. Over all, the violin tones analyzed are characterized by strong resonances in regions 500–700 Hz and 1800–2500 Hz, a strong antiresonance at 1100–1500 Hz, and many peaks and valleys above 2000 Hz. Features of attack, steady‐state, and decay will be discussed in terms of spectrum graphs.

ISSN:0001-4966    

DOI:10.1121/1.1973428

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Selected pure‐tone pulses (1 to 13.7 kHz) were directed toward a methyl methacrylate replica of the left external ear from a large albino rabbit. Sound‐pressure measurements were taken 4 msec after pulse‐envelope arrival through a14‐in.calibrated condenser microphone situated within the auditory canal. The signal was amplified, displayed on a CRO, and photographed for analysis. The 12‐cm pinna served to diffract directionally sounds of wavelengths smaller than its dimensions. Sensitivity in the horizontal plane 90° to 150° ipsilateral to the pinna opening produced amplifications of 20 dBre0.0002 dyn/cm2at the canal base for frequencies 2.2, 5, 8, and 10 kHz. Vertical and horizontal angles displayed marked frequency dependence. Sound‐pressure measurements at the base and opening of the auditory canal suggest that cavity resonance interacts with the pinna‐diffraction effects and is dependent upon the azimuth of the incident sound. [Supported by a National Science Foundation grant to R. A. Suthers.]

ISSN:0001-4966    

DOI:10.1121/1.1973436

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

When localizing sounds in a free‐field environment, listeners frequently confuse front and back. Careful study of these front‐back reversals reveals a dependence on factors other than the lack of a reverberant sound field. In the experiments described here, median‐plane localizations were produced by single and symmetrically disposed pairs of loudspeakers. Front‐back discrimination was examined as a function of source position, head movements, signal type, frequency, and bandwidth. Subjects differed in their sensitivity to each of these factors, but it was clear that source position and signal bandwidth had the most pronounced effects. Some subjects demonstrated front‐back localizations that were almost entirely dependent on source position; others exhibited localizations that altered as a function of signal bandwidth but that appeared to be substantially independent of source position. Experiments in which head movements were progressively restricted have shown that small involuntary head movements cannot be of more than slight importance in front‐back discrimination.

ISSN:0001-4966    

DOI:10.1121/1.1973442

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

At the last three meetings of the Society, we have described MDCC experiments with unmasked cues. When the signal (and therefore the cue) is a sinusoid of frequency below about 1100 Hz, the cue may either aid or detract from the detection of the monaural signal. The direction of effect depends on the phase difference between the signal and the cue. As the cue is made louder, performance at bad phase drops steadily; but over a wide range of cue intensities, performance at optimum phase is near that of the signal‐known‐exactly (SKE) observer. However, performance drops drastically for very loud cues whether the phase is good or bad. In this paper, we consider the effect of masking the cue. If the detrimental effect of the loud cue at all phases were due simply to “contralateral masking,” adding more noise should further reduce performance. If, on the other hand, the loud cue provides some sort of misinformation to the detector, cue masking should improve performance. The latter proves to be the case; the masked cue acts like a softer cue.

ISSN:0001-4966    

DOI:10.1121/1.1973452

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP