摘要:

Undergraduate students in audiology, speech pathology, and education of the deaf present two problems for the would‐be teacher of acoustics. First, they are typically deficient in basic mathematics and physics. As a result, they fall victim to “symbol shock,” a disorder characterized by glazed eyes and cortical dysfunction. Second, they require at least a modest understanding of acoustics for their later professional health. A reasonable treatment has been found in the form of the Keller Plan or the Personalized System of Instruction (PSI). This plan has been used successfully for four years in an undergraduate course designed to convey the rudiments of physical acoustics, bioacoustics, and psychoacoustics. PSI uses explicit performance criteria, unit mastery, self‐pacing, and individualized tutoring. Laboratory demonstrations are used for motivational purposes and to promote student discovery. Critical information is conveyed by the written word; lectures are given only upon student request. Details of the PSI method will be presented, as well as the results of a modest retrospective analysis of the course taught under traditional and PSI formats.

ISSN:0001-4966    

DOI:10.1121/1.2003094

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The measared of near‐surface and upper‐air temperature and humidity is required during flyover noise tests to adjust the noise data to reference‐weather conditions or to classify the data with respect to various criteria. Parallel advancements in equipment, test techniques, and noise data adjustments have occurred in the last several years at the Douglas Aircraft Company. Measurements of near‐surface temperature and humidity began with a psychrometer hand‐held at four feet above the ground and subsequently evolved through a series of instrument types mounted 33 feet above the ground on a trailered tower. Upper‐air (or sound‐path) weather data were initially acquired from local weather bureaus and later from various instrumented light aircraft. The more notable improvements are the use of dew‐point sensors for humidity measurements, increased data sample rates, and system performance monitoring. Current instruments, along with sufficient attention to time and space dependencies, appear to furnish an adequate definition of the test atmosphere. However, more data are required to quantify and evaluate the actual accuracy of the system.

ISSN:0001-4966    

DOI:10.1121/1.2003097

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Static tests of aircraft engines can exhibit greater than 10‐dB random unsteadiness of tone noise levels because flow disturbances that prevail near test site facilities are ingested. Presumably such changes are related to installation and test site features. This paper presents some properties of unsteady noise observed at a NASA—Lewis facility during tests of a Lycoming YF‐102 turbofan engine. Time and spacial variations in tone noise obtained from closely spaced farfield and inlet duct microphones are displayed. Long (0.5‐sec) to extremely short (0.001‐sec) intermittent tone bursts are observed. Unsteadiness of the tone, its harmonies, and the broadband noise show little similarity. In the farfield, identity of tone bursts is retained over a directivity angle of less than 10°. In the inlet duct, tone bursts appear to propagate axially but exhibit little circumferential similarity. They show only slight relationship to tone bursts observed in the farfield. The results imply an intermittent generation of random mixtures of propagating duct modes.

ISSN:0001-4966    

DOI:10.1121/1.2003106

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Natural infrasound of 5‐sec periods is generated continuously by ocean waves to the east of our location. The amplitude characteristics and horizontal phase velocity are functions of the acoustic reflection characteristics of the upper atmosphere. The monthly patterns of the observed acoustic parameters, culled from eight years of continuous observations, are reviewed and compared to the existing knowledge of 30–120‐km winds and temperatures. Included in the discussion are (1) the percentages of observed semidiurnal and diurnal amplitude oscillations for each month, related to the reliability of these tides in the upper atmosphere; (2) annually repeating oddities in each month such as a late March increase in semidiurnal tidal strength and varying meridional wind influences from summer to winter; and (3) the failure of current atmospheric models to correctfy predict the observed lower thermosphere sound velocity at 0400 which is much greater from the east then predicted.

ISSN:0001-4966    

DOI:10.1121/1.2003111

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Recent theoretical and experimental studies of acoustically induced axial oscillations of control valves are reviewed, and a mechanism for acoustically induced lateral oscillations is proposed. Possible methods of quenching the instabilities are also discussed. [Work supported by ONR.]

ISSN:0001-4966    

DOI:10.1121/1.2003115

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Prediction of the detectability of well‐defined signals in steady‐state background noises are based on considerable theory and much practical experience. Little information is presently available to support predictions of detectability of complex signals in time‐varying noise environments. The current study has temporal variability of background noise is long with respect to signal duration, observers' detection performance improves in more highly variable noise environments of constant average energy. Observers detecting a sinusoid embedded in one‐third‐octave band of Gaussian noise in a two alternative forced‐choice task produced psychometric functions characterized by higherd′ values for increasingly variable background noises, relative to performance in steady‐state noise.

ISSN:0001-4966    

DOI:10.1121/1.2003120

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

In a pulsation, threshold experiment the frequencies and intensities of the two tones in the “masker” were fixed and the frequency of the signal was varied. The plot of pulsation threshold versus signal frequency is called the pulsation‐threshold pattern of the “masker”. First the pulsation‐threshold pattern was measured when the “masker” contained only a 1000‐Hz tone. Then the patterns were measured for a 400‐Hz tone and for a 1500‐Hz tone. Finally, the pattern was measured when the masker contained both the 1000‐Hz tone and either the 400‐Hz tone or the 1500‐Hz tone. The 400‐Hz tone was able to reduce the pulsation thresholds around 1000‐Hz by 20 dB or more for each of the three subjects. The 1500‐Hz tone did not reduce the pulsation thresholds at 1000 Hz but did at 1100 Hz, i.e., on the high‐frequency tail of the 1000‐Hz pattern. Suppression is assumed to be the cause of these reductions. Thus one tone is able to suppress only part of the excitation pattern of another tone. Mutual suppression was also indicated for one subject. Relationships to partial masking will be discussed. [Work supported the NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2003125

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

One current view of the mechanism underlying the ear advantage in dichotic listening has two components. The first is the relative superiority of contraolateral over ipsilateral auditory pathways, the second, the supression of ipsilateral information. While the notion of superiority simply implies an advantage for contralateral information, supression suggests that the information is unavailable. Three commissurotomy patients were given dichotic tests using consonant—vowel syllables and digits, as well as a binaural fusion test, in order to evaluate their ability to use information presented to the ear ipsilateral to the language hemisphere. Consonant—vowel syllables produced complete or near complete extinction of left ear information, while the digits test revealed a substantial increase in the use of left ear information. The fusion task produced performance greater than what would be expected by probability summation of the performance of each ear alone. The data suggest that in the absence of the corpus callosum, information from contralateral and ipsilateral ears can be integrated. Furthermore, the inability of the subjects to use information presented to the ipsilateral ear appears to be a function of the degree to which the competing items are acoustically similar, rather than a general suptession mechanism.

ISSN:0001-4966    

DOI:10.1121/1.2003132

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

CV syllables (kindly provided by Kresge, LSU) were presented dichotically to a 13‐year‐old boy prior to and post surgical section of the majority of hiscorpus callosum. Pre‐operatively no ear advantage was observed; however, after callosal section a clear right ear superiority emerged. Correct performance approximately doubled for the right ear and fell to change for the left ear. Voiceless CV's were reported correct more often than voiced, both prior to and post surgery. In addition, alveolars were more often reported correctly than labials, which in turn are reported more correct than velars. His single correct response performance was highest when pairs shared voicing preoperative and lowest when pairs shared place. Postoperatively sharing place still resulted in the lowest percent correct; however, performance was highest when pairs shared neither place nor voice. An analysis of pairs resulting in errors revealed that for the (1) voiceless/voiceless condition 16.6% errors occurred pre; and postoperatively, (2) voiced/voiced condition 21.0% errors occurred preop and 25.0% postop.; (3) voiceless/voiced condition 64.4% errors occurred preop and 58.4% postop. Thus error pattern did not change after section. These data suggest that callosal section results in suppression of the ear countralateral to the speech processor by removing the interhemisphere relay route.

ISSN:0001-4966    

DOI:10.1121/1.2003133

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Some problems and possible solutions associated with teaching musical acoustics specifically to musicians are discussed, along with some typical questions encountered. The topics are considered from a dual viewpoint: the physicist knowledgeable in music and a musician knowledgeable in physics. Some of the subjects considered are vibrators, tuning, terminology, transposition and algebra, scales, translation between scientific and musical language, choice of instruments and personality, and problems in communication.

ISSN:0001-4966    

DOI:10.1121/1.2003146

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP