摘要:

A laboratory facility is described as evolved for the measurement of sound transmission through suspended acoustical ceilings under field conditions of erection over part high partitions. The results of exploratory measurements are reviewed for a wide range of the dimensional and acoustical parameters of the ceiling‐plenum system. Consideration is extended to the ceiling‐partition system and to the importance of an accurate simulation of field conditions of erection for the testing of all elements, individually and interacting, in the ceiling‐plenum‐partition system. The compatibility of this approach with conventional test methods is suggested.

ISSN:0001-4966    

DOI:10.1121/1.1908488

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Field measurements of airborne sound‐transmission loss involve several practical difficulties and limitations as compared to the laboratory standard test procedures for such measurements. Data from field measurements are valuable to architects and acoustical consultants, in spite of these limitations. A workable procedure for field measurements is described, along with a discussion of the difficulties. Measured transmission loss data are presented for double plaster walls on cork isolation, double plaster walls on concrete slabs, double concrete block walls, double brick walls, single concrete block walls, and a floor slab with resiliently suspended plaster ceiling.

ISSN:0001-4966    

DOI:10.1121/1.1908490

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

An improved understanding of some stereophonic phenomena may be obtained by use of acoustical pressure phasors to portray sound pressure at the ears of the observer. With the help of phasors it is possible to expand and modify certain conclusions of previous observers, and to validate some previously unpublished observations; stereophonic “law of sines” is derived. The existence and location of “out‐of‐bounds” stereo‐phonic image is analyzed and verified. The “allowed maximum out‐of‐phase ratio” is derived, together with the observation that this maximum is exceeded by certain microphone arrays. The motion and elevation of the center image in stereophonic reproduction is observed and explained.

ISSN:0001-4966    

DOI:10.1121/1.1908492

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Thresholds of audibility are determined by the Békésy technique for four periodic trains of rectangular pulses. The pulses of a given train are uniform in amplitude and duration, and the trains differ in their periodic patterns of pulse polarity. The parameters considered are pulse rate, pulse duration, and polarity pattern. The stimuli are presented binaurally in quiet over headphones. Data for four subjects are reported. The results show the threshold amplitudes to be little dependent upon polarity pattern. For pulse rates less than about 100 pps the thresholds are also little dependent upon pulse rate. They approach constant values determined by pulse duration. Above 100 pps the thresholds diminish with increasing pulse rate. The experimental technique also provides an estimate of the intensity limen at threshold. An analytical specification of the stimulus is derived which provides an objective correlate of the threshold percept. An electrical circuit model of the threshold is developed which takes account of middle‐ear and basilar membrane transmission. The threshold model reflects a constancy of percept over a pulse‐rate range of 10 octaves and a pulse‐duration range of ten to one. Its application to the metering of subjective loudness is suggested.

ISSN:0001-4966    

DOI:10.1121/1.1908494

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

If a narrow bandpass filter is driven by a periodic train of narrow rectangular pulses, the resultant wave train elicits a strong pitch perception which varies monotonically with the pulse repetition rate. This periodic wave train can be used as a pitch reference to match against various stimuli. Consideration of double wave train stimuli with various delays establishes sharp dichotomy between the perception of pitch and timbre. Further evidence is adduced in support of the development of a partial model of psychoacoustic perception which is plausible in terms of the known physiologic mechanisms. In brief, the total acoustic stimulus undergoes a differential filtering action along the cochlear partition due to the resonant characteristic of the cochlear structure. The response characteristic of any particular segment of the partition exhibits a single broad peak and consequently has a relatively fast time response. The envelope of the response is assumed to be detected by a relaxation detector having a relatively wide dynamic range, and periodicity of the envelope is detected by a delay‐line detector. The second‐order time envelope of the cochlear‐partition response defines a function over the length of the partition. The shape of the envelope (along the partition) of the absolute value of this function elicits the perception of the timbre structure of the total stimulus. The total area under this envelope elicits the perception of the loudness of the total stimulus. This combination of broad‐band spectral filtering, envelope detection, and delay‐line periodicity detection provides both a mechanism for relatively sensitive pitch discrimination and for spectral discrimination with relatively fast time response.

ISSN:0001-4966    

DOI:10.1121/1.1908496

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The purpose of the experiment was twofold: to compare the effectiveness of narrow band noise and a train of clicks in eliciting the middle‐ear acoustic reflex, and to correlate two methods of estimating amount of reflex activation. One method involved measurement of increase in threshold in the contralateral ear, the other, measurement of reduction of TTS produced by a series of gun shots. Sixteen subjects were employed. Shifts produced by the clicks and noise were of the same order of magnitude (after correction for the direct masking effect by the clicks), but there was considerable reflex adaptation to the noise and none for the clicks. Correlations between contralateral threshold shift and reduction of TTS were small and not significant.

ISSN:0001-4966    

DOI:10.1121/1.1908498

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

In continuation of a previous paper, the relation between threshold, repetition time, and duration for periodically repeated tone pulses is treated. Experimental data at test frequencies of 250, 1000, and 4000 cps appeared to agree very well with a derived relation based on the following assumptions: Switching on a sinusoidal signal of intensityIresults in an effectssomewhere in the hearing pathway, that approaches its final value asymptotically according to an exponential function; switching off this signal gives a decay ofsalso according to an exponential function; perception occurs whensexceeds a critical values0. For the time constants of the growth and decay ofsthe same value could be chosen, being in agreement with the corresponding value for single tone pulses (0.2–0.3 sec). For very short repetition times, the data deviate from the predicted curves, which is explained by the assumption that energy integration is restricted to a fixed bandwidth. These critical bandwidths determined for the periodic tone pulses are also in harmony with the results for single pulses.

ISSN:0001-4966    

DOI:10.1121/1.1908501

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

If a 2200‐cps tone is pulsed 150 times/sec under appropriate conditions, a low pitch (periodicity pitch) will be heard corresponding to that of a 150‐cps pure tone. This experiment investigates the effectiveness of different bands of filtered noise in the masking of such pulses and in the masking of two pure tone stimuli, 150 and 2200 cps. Although the pulses and 2200‐cps pure tone yield quite different pitches, the present results indicate that the masking of each requires nearly identical frequency components and levels of noise. The 150‐cps tone, although yielding a pitch approximating that of the pulses, requires greatly different characteristics of noise to mask. Considering differences in apparatus and technique, reasonable agreement with other studies of pure tone masking by bands of noise is found. If masking is viewed as a neural phenomenon, these data provide additional evidence of the neural nature of periodicity pitch.

ISSN:0001-4966    

DOI:10.1121/1.1908503

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

In order to improve the procedure for calculating the loudness of a complex sound, two changes have been made. (1) The equal loudness contours for bands of noise in a diffuse field have been approximated by straight lines in a log‐log plot. (2) The spacing of the contours have been altered to reflect the nonlinear growth that takes place in the loudness level of bands of noise when their width exceeds the critical bandwidth. The basic formula for the addition of loudness across frequency remains the same: the total loudnessStis given bySt = Sm + F(Σ S − Sm), whereSmis the loudest band andFhas the values 0.3, 0.2, and 0.15 for octave, half‐octave, and third‐octave bands.The revised procedure has the advantages that it can be described more easily and it agrees better with the available measurements on loudness level.

ISSN:0001-4966    

DOI:10.1121/1.1908505

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

We raise again, in the framework of a very simple recognition task, the question of the relative efficacy of specifying the stimulus alternatives before and after the stimulus is presented. Our experiments show information given before the observation to facilitate recognition and information given after the observation to have little, if any, effect. We conclude that the facilitative effect of restricting alternatives, in the task studied, depends on a perceptual mechanism rather than on a response mechanism. These experiments are discussed in connection with two current psychological theories: the theory of signal detectability, which is essentially a perceptual theory, and the theory of individual choice behavior, which is essentially a response theory. The results of another experiment, the only other experiment discovered to date for which these two theories make different predictions, are also reported. In this experiment, too, the results are in agreement with the detection theory.

ISSN:0001-4966    

DOI:10.1121/1.1908507

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP