摘要:

A solution which is suitable for numerical computation is obtained for the classic problem of random flights in two dimensions with flights of unequal length. The solution is obtained by a development in series of the exact integral solution. The solution is applied to one aspect of the problem of the fluctuations present in the intensity of sound as it decays in a room. It is assumed that the room has reached a steady state of vibration under the excitation of a single frequency, and that the normal frequencies of the room are randomly distributed. The period of the decay is then broken into two sub‐periods, in the first of which there is some degree of coherence in the phases of the normal vibrations. The treatment presented in this communication applies to the second part of the decay, comprising all but the first π/kseconds, for which the phases as well as the frequencies of the normal vibrations may be considered as distributed at random. It is found that the relative extent of the fluctuations which may be traced to beats between normal modes of vibration, does not depend appreciably on the number of characteristic vibrations excited unless the number is so small that statistical considerations are not helpful, nor does it depend significantly on the size or shape of the room.

ISSN:0001-4966    

DOI:10.1121/1.1916042

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916043

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916044

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916045

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916046

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1916047

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

摘要:

During recent years several studies of vocal pitch in speech of various types have been made at the University of Iowa by means of measurement of the fundamental sound wave frequency from phonograph records.One investigation was concerned with the voices of well‐known actors and actresses, disclosing among other data median pitch levels of 140.7 and 233.2 c.p.s. for the respective groups, with total pitch ranges in the neighborhood of 12 tones.In a second experiment five actors simulated different emotions successfully in five readings of the same material. Simulation of contempt was found to be characterized by a range of 10.5 tones about a median of 124.3 c.p.s.; measurements of simulations of anger revealed a mean range of 10.3 tones about a median of 228.8 c.p.s., and a more rapid rate of pitch change [25.6 tones/sec.] than the other emotions studied: the highest median pitch level [254.4 c.p.s.]and widest range [11.2 tones] were found in fear; in grief the mean range was 9.0 tones with a median of 135.9 c.p.s., the mean extent of inflections [1.7 tones]was the narrowest and the rate of pitch change [15.6 tones/sec.] the slowest of the five emotions; the narrowest range [7.8 tones]and the lowest median pitch level [108.3 c.p.s.] were measured in simulations of indifference. Most of the subjects employed total pitch ranges of over 18 tones in the simulation of all five emotions. Another study investigated the pitch usage of carefully selected superior male speakers reading a 55‐word test passage, and found a mean total range of 10.5 tones about a median level of 132.1 c.p.s. In the latter measure individual subjects were grouped closely about this value. The pitch usage of these subjects in speech was related to their total singing ranges including falsetto, these ranges averaging 20.4 tones. It was found that the pitches used in the measured samples of speech lay within the lower fractions of the singing ranges, and that the ratio of the extent in tones between the lowest sung tones and the median pitch levels in speech to the total singing ranges averaged 0.25.In a fourth experiment the same trained subjects re‐read the test passage in response to instructions to read with more variability of pitch, with less variability of pitch, at a higher pitch level and at a lower pitch level. Extremes were avoided. Measurements revealed that the subjects followed instructions, and certain characteristic features of pitch variability were disclosed. Of interest was the finding that pitch level and pitch variability tended to vary concomitantly, i.e., increased variability was accompanied by a rising pitch level andvice versa.Another investigation made a preliminary exploration of the pitch aspects of voice change in the male. Ten‐year‐old, 14‐year‐old, 18‐year‐old and adult subjects were studied. The two younger groups were found to have median pitch levels in the neighborhood of the values reported for adult females, while the 18‐year‐old subjects used levels approximately equal to those of the adult male group. Wave‐to‐wave measurement of so‐called “voice breaks” revealed several interesting features. (1) Almost as many breaks were found at 10 years as at 14 years. (2) Downward breaks, although outnumbered by upward breaks, were frequent. (3) Breaks averaged approximately one octave in extent. (4) All breaks measured were made up to and down from the median pitch levels of speech or their vicinity; none were found above these levels. However, in two atypical cases of voice change, not included in the above groups, the breaks departed from this typical location below the median.These experiments are immediately suggestive of further researches, some of which are under way at present.

ISSN:0001-4966    

DOI:10.1121/1.1902146

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

摘要:

A review of the more significant work in this field, and an attempt to synthesize from the available material a picture of how the vocal apparatus works as a whole.

ISSN:0001-4966    

DOI:10.1121/1.1902147

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

摘要:

With the increasing use of acoustical materials for purposes of interior finish, a number of additional uses have been found for these products. Cases are cited where the acoustical treatment has been made an integral part of the air conditioning system. The adaptation to improved lighting methods is discussed. Certain materials have such inherent architectural value that they are used primarily as interior finishes, with the acoustical function secondary. In the summary, suggestions are made to assist the architectural profession in taking advantage of these various adaptations. Details and photographs will be included.

ISSN:0001-4966    

DOI:10.1121/1.1902154

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP

摘要:

By means of the articulation recordings and high‐fidelity reproducing system described in an earlier paper, and a large variety of frequency distortion networks, the selective amplification principle in hearing aids has been tested by extensive measurements on normal and typical hard‐of‐hearing persons. The criterion used for evaluating the effectiveness of each type of amplification has been the standard percent syllable articulation. For all ears tested, uniform amplification, free from nonlinear distortion and adventitious noise, has proved superior to amplification “peaked” at various frequencies to provide what is often falsely called selective amplification. Carefully prescribed selective amplification, even when first tried, has proved to be better than uniform in some instances. In other cases it does not give as good results. Some hard‐of‐hearing persons did not hear well witheitheruniform or selective amplification at first, because they never had heard some of the speech sounds before, or had become unfamiliar with them owing to their impairments. However, after practice with the prescribed amplification most of them became accustomed to it, and their percentage articulation rose with successive tests. The opinion of the listener has proved to be a very poor criterion for determining the correct amplification. Many of the hard‐of‐hearing listeners have chosen as sounding best the types which had frequency response curves of the same general shape as their threshold curves, and have criticized as sounding very unpleasant those with which they attained the highest articulations. It is not yet always possible to prescribe immediately the best type of amplification for a given hearing impairment, but a method of prescription based on the “most comfortable equal loudness curve” has proved highly satisfactory in several cases.

ISSN:0001-4966    

DOI:10.1121/1.1902156

出版商:Acoustical Society of America    

年代:1940

数据来源: AIP