摘要:

A typical single wall is characterized by a free flexural wave speed,cB, which increases withω12. WhencBapproachesc0(the speed of sound waves in the surrounding medium) the impedance of the wall to incident sound wave ceases to be mass‐like because of the coincidence effect and the transmission loss will be less than that given by mass law. SincecB = (B/M)12(ω)12for homogeneous walls, the deleterious effects of the coincidence of the flexural wave speed with the phase velocity of sound in the medium can be avoided for homogeneous walls by reducing the ratio ofB/M. (Bis the dynamic bending stiffness of the wall;Mis the mass per unit area of the wall.) Thus the problem of good acoustical performance in homogeneous walls is seen to be in essential conflict with the need for structural rigidity.A new wall design has been found in which the ratio of the static to the dynamic stiffness can be in excess of 1000:1 and where the stiffness changes from the static to the dynamic value in such a way that the acoustical behavior is nearly that of a perfectly limp wall. If desired, the loss tangent of the wall can be made large and nearly constant over a wide range of frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1907780

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

This paper deals with some measurements concerning the thresholdversusduration for tone pulses. A new hypothesis introduced: Switching on a tone pulse of intensityIresults in an effectssomewhere in the hearing pathway, that approaches its final value asymptotically according to an exponential function; this final value is proportional toI; perception occurs whensexceeds a critical values0. The experiments show that this hypothesis gives a better description than the hypotheses thus far used. The time constant varies fromca375 msec at 250 cps toca150 msec at 8000 cps. For short pulse durations the data deviate from the hypothesis. This deviation can be explained by the assumption that energy integration around each frequency is restricted to a fixed band width. A formula is derived which gives a correction to the mentioned relationship for short durations. In this way the band width at the different test frequencies could be determined. The general course of this band width as a function of frequency agrees with the “Kopplungsbreite” after Gässler.

ISSN:0001-4966    

DOI:10.1121/1.1907781

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

Whereas temporal intervals as short as a few milliseconds are sufficient to separate two brief sounds so that a listener will report that there are two (instead of only one) sounds, a longer separation time of between 15 and 20 msec is required for the listener to report correctly which of the two sounds preceded the other. This minimum temporal interval appears to be independent of the kinds of sounds used: whether short or long, of high or low frequency, of narrow or wide band width. There is some suggestion that rise‐time and duration may change this minimum interval, but these somewhat secondary relations are not investigated in detail here. The length of the required temporal interval suggests that the judgment of order requires other mechanisms than those associated with the peripheral auditory system.

ISSN:0001-4966    

DOI:10.1121/1.1907782

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

With the theory of signal detectability as a framework, two psychophysical experiments were conducted in which each observation interval was well defined for the listener. Each interval contained noise, and it either did or did not (p=0.5) contain a signal (1000 cps, 0.5 sec in duration). In separate sessions of the first experiment, either the listener gave a yes‐no decision or he responded with a rating (1–4) after each observation interval. Operating characteristics were obtained withE/N0equal to 15.8. It is clear from the data that the trained listener can perform as well when he adopts the multiple criteria necessary for the rating method as when he adopts the single criterion required by the binary‐decision procedure. In the second experiment, only the rating method was used to determine the relation betweend′andE/N0. The resulting function, ford′⩽ 3.0, approximates straight line which passes through the origin and which has nearly the same slope as that obtained in other laboratories.

ISSN:0001-4966    

DOI:10.1121/1.1907783

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

An experiment is described in which time and intensity differences of 2‐kc high‐pass clicks were mutually offset to produce sound images centered in the head. Binaurally correlated and uncorrelated clicks were used, and the trade was tested at 10–70 db SL. The results show that generally the two types of clicks behave similarly, and that up to 60 db SL, at least, as over‐all intensity increases, the time difference compensating a given intensity difference (in db) decreases. A function is derived describing what is interpreted as a physiological intensity‐to‐time conversion. The place of such a conversion in lateralization is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1907784

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The loudness of complex sounds was studied as a function of the number of components. Complexes of two, three, four, and eight tones, and a band of white noise were matched in loudness to a 1500‐cy tone. The over‐all spacing, ΔF, between the lowest and highest components of these stimuli was held constant at either 175, 1600, or 3400 cps. All the complexes were centered around 1500 cps when ΔFwas either 175 or 1600 cps. At each of the four levels tested (25, 50, 75, and 90 db SPL), loudness remained essentially unchanged when only the number of components within a complex was varied. This invariance of loudness occurs even though inhibition may be greater within the complexes that contain a larger number of components. It is suggested that the increased inhibition may be offset by greater loudness summation when the energy is more evenly distributed within the complexes.

ISSN:0001-4966    

DOI:10.1121/1.1907785

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

There is psychophysical evidence that both spectrum and periodicity of acoustic signals may be cues for pitch judgments. At the level of the auditory nerve, these stimulus characteristics seem to be coded in terms of place and time pattern. Very little is known of their representation higher levels of the nervous system. Tonotopic organization of the auditory cortex has been demonstrated in anesthetized cats by the evoked strychnine potential technique. In these demonstrations only tonal stimuli were used. We use similar physiological preparations but employ acoustic stimuli that permit independent manipulation of spectrum and periodicity. The results show that the previously reported tonotopic organization is based only upon spectral characteristics of the stimulus.

ISSN:0001-4966    

DOI:10.1121/1.1907786

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

The TTS at 4 kc was measured 2 and 17 min after successive 12‐min exposures to broad‐band noise at 106 db SPL separated by 18 min of silence. The results indicate that the TTS existing at the beginning of a particular exposure can be treated as additional time of exposure. Thus, if the residual TTS has a value that would be produced byRmin of exposure, then the total TTS at the end of anM‐min exposure will be given by solving the equation for growth of TTS with exposure time set equal toM+R.

ISSN:0001-4966    

DOI:10.1121/1.1907787

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

As part of an over‐all evaluation of the USNEL Flight Deck Communications System, an RCA modulated air‐flow loudspeaker (air speaker) was tried out as a speech and alarm signaling transducer on the flight deck of an aircraft carrier. Tests with 200‐ to 6000‐cps noise showed that the air speaker produced 130 db SPL at optimum points on the deck, as compared to 110 db for the present system. Speech intelligibility and alarm detection tests showed the air speaker to be usable with jet aircraft at idle (30%) power while the present loudspeakers could not be heard. Neither loudspeaker system was adequate with jets at full power.

ISSN:0001-4966    

DOI:10.1121/1.1907788

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP

摘要:

An apparatus is described that applies the frequency components of speech, as spoken into a microphone, to the fingers of one hand with the purpose of enabling a deaf person to comprehend speech. Frequency is indicated by position along the fingers. The sense of touch is not called upon to make any direct frequency discrimination by distinguishing vibrational sensations of different frequencies as in previous attempts of this nature [R. H. Gault, J. Franklin Institute204, 329–358 (1927)]. The frequency analysis is done partly electrically and partly mechanically. Small tuned steel reeds are used for the final frequency analysis. These steel reeds also serve as transducers by operating directly against the fingers.The results of a short series of experiments on a deaf person are promising but the recognition of individual consonants is difficult.

ISSN:0001-4966    

DOI:10.1121/1.1907789

出版商:Acoustical Society of America    

年代:1959

数据来源: AIP