摘要:

The method of free response refers to the following listening situation. Against a background of noise, a weak signal is presented several times in a long (2‐min) observation interval. The temporal intervals between the presentations of the tones are randomly distributed; consequently, the listener does not know when a tone will occur, and he does not know how many tones will be presented. From one series of observation intervals to the next, the listener is instructed to adopt various criteria and to press the single response‐key each time he “hears a tone.” The problem consists in the determination of a procedure that allows the total number of yes responses to be partitioned meaningfully between “hits” and “false alarms.” A model is developed in which the measurable quantity, rate of response, is related to the “hit rate” and to the “false‐alarm rate.” Although the criterion adopted by the listener cannot be directly evaluated, the use of a wide range of criteria makes it possible to estimate the detectabilitydsof the signal. Two experiments are described, and the results support the model.

ISSN:0001-4966    

DOI:10.1121/1.1908935

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Listeners were required to detect an auditory signal against a background of “white noise.” The effects (1) of giving trial‐by‐trial information as to whether or not a signal was delivered, and (2) of giving the subject an opportunity to hear the signal before the test sequence began, were studied at two levels of signal energy. The results were analyzed within the context of the theory of signal detectability. Subjects who were given an opportunity to hear the signal before the test sequence began maintained a stable level of performance throughout the experimental session. On the other hand, subjects who were given no opportunity to hear the signal performed near chance level at the beginning of the session but showed gradual improvement as trials progressed. The effect of trial‐by‐trial feedback was surprisingly small in all groups. Near the end of the session, the signal was demonstrated to all subjects and the differences between the groups vanished.

ISSN:0001-4966    

DOI:10.1121/1.1908878

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Measurements are made of the masking of pure tones by various bands of noise. Curious masking spreads beyond upper frequency limits of noise are observed and these are expressed uniquely by means of the relative masking and the incremental bandwidth. Then the normalized representation of noise‐band masking in some restricted ranges is achieved and applied for the prediction of speech intelligibility. Predicted articulation scores agree fairly well with measured ones.

ISSN:0001-4966    

DOI:10.1121/1.1908880

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Pitch shifts with changes in sound level were investigated for two types of stimuli, one whose pitch was hypothesized to be analyzed on the basis of “place” and the other whose pitch was presumed to be related to “periodicity.” Eight subjects made alternate monaural pitch matches with four stimuli; pure‐tone, dc pulses (both with energy at the fundamental frequency‐place pitch), and two varieties of ac pulses (with little energy at the fundamental frequency‐periodicity pitch). The fundamental in all cases was approximately 100 cps. Generally, pitch shifts were small, although there were marked differences in the extent and in the variability of the pitch matches as a function of the type of stimulus. Partly because of large differences between subjects, statistically significant shifts were found for only two of the stimuli, one “place” and one “periodicity” stimulus. These shifts were similar in direction, with the pitch shifting downward as level is first increased, then upward with a further increase. Although there appears to be little in the data to support duality of pitch analysis, it is possible that all stimuli were perceived on the basis of periodicity. However, it seems difficult to handle pitch shifts with changes in level within the confines of “periodicity” analysis.

ISSN:0001-4966    

DOI:10.1121/1.1908882

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Widely divergent amounts of perstimulatory adaptation have been reported previously, possibly due to differences in technique of measurement. One method often used determines perstimulatory adaptation from a series of simultaneous binaural loudness balances between a continuous stimulus in the adapting ear and a stimulus intermittently presented to the test ear. The present study attempts to evaluate the effect of the characteristics of intermittency of the test stimulus upon the measured adaptation in the adapting ear. With a 4000‐cps adapting tone presented at 75‐db sensation level, 16 combinations of on‐ and off‐duration of the test tone were investigated using 11 listeners. For all experimental conditions the adapting curves showed the same general shape, with a rapid initial decline, followed by a more gradual decline reaching asymptote after 5 to 6 min. As the on‐time of the test stimulus increased, less adaptation was seen, except for off‐times of 30 sec or greater where on‐time no longer influenced adaptation. This is interpreted as indicating that greater amounts of adaptation took place in the test ear as on‐time was lengthened; but for the stimuli used, 30 sec was sufficient for recovery to occur. In general, however, variation in on‐time produced greater changes in measured adaptation than did similar changes in off‐time of the test stimulus.

ISSN:0001-4966    

DOI:10.1121/1.1908884

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The phenomenon of “contralateral remote masking” is described: the elevation of threshold sensitivity to a low‐frequency tone in one ear produced by a high‐frequency band of noise in the other. Evidence is presented indicating that this effect is mainly attenuation induced by reflex activation of the stapedius muscle, although probably some central masking is also involved. The strength of the activation (1) increases linearly with sound pressure level of the arousal noise beginning at about 85 db SPL, (2) decreases linearly with frequency level of the noise, and (3) gradually decreases with time (i.e., adapts), reaching an asymptote after about 3 min. Individual differences in reflex activity could not be explained in terms of differences in resting thresholds. The relation of this phenomenon to ipsilateral remote masking and loudness adaptation is studied, and its effect on temporary threshold shift and on loudness judgements at high intensities is discussed.

ISSN:0001-4966    

DOI:10.1121/1.1908886

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

This paper examines some sequential effects found in the behavior of observers in the signal‐detection situation. The Tanner‐Swets‐Green model treats the subject as a stable decision maker operating on information from a noisy but unbiased transducer. It is suggested that this model may be profitably replaced by one in which a bias is introduced by a simple finite‐state machine which makes the subjects' behavior a function not only of the present stimuli but also of past stimuli and responses.

ISSN:0001-4966    

DOI:10.1121/1.1908888

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

A correlator detector is considered which processes the outputs of two identical collinear arrays of uniformly spaced elements. When the input signal is sinusoidal, the mean system output is bounded by the product of the space factors of the arrays. Complex amplitude factors are introduced following each element, and it is shown how to choose them in order to optimize the main lobe‐width‐side‐lobe‐level relationship of the space‐factor product or envelope. In addition, it is proved that the use of amplitude factors for improving envelope resolution gives rise to a signal‐noise degradation relative to the corresponding uniform amplitude system. Various numerical results are given, including the fact that the optimum system provides an envelope main‐lobe‐width reduction of approximately thirty percent when twenty or fewer elements appear in each array.

ISSN:0001-4966    

DOI:10.1121/1.1908890

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

“Quasi stereophony” is defined as the reproduction over two or more loudspeakers (or binaural earphones) of different sound signals derived from a single audio signal. The purpose of quasi‐stereophony is to create (from a single audio signal) an illusion of spatially distributed sound sources. Quasi‐stereophonic reproduction does not permit correct localization but does share with true stereophony the properties of “depth” and “ambience” which are important attributes of stereophony (for the casual listener perhaps even more important than correct localization).This paper describes a new filtering method for producing quasi‐stereophony. In contrast to earlier proposals, the new filtering method leaves the amplitude spectrum of the sound intact. The same kind of filter has also been used for generating “colorless” artificial reverberation. Experimental results indicate that both quasi‐stereophony and artificial reverberation can be achieved without spectral distortion.

ISSN:0001-4966    

DOI:10.1121/1.1908892

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Measurements are presented of the noise produced by a 1.5 in. diameter air jet, with an exit Mach number of 0.66, impinging perpendicularly on a plane, rigid plate. The over‐all sound power output increased rapidly, as the nozzle‐to‐plate separation distance was decreased. The over‐all sound power generated, when the plate was 2 diam from the nozzle, was 10 db greater than that produced with the plate removed. For a 2‐diam plate separation the over‐all sound‐pressure levels (SPL's) (measured at a radius of 24 nozzle diameters from the center of the jet exit in the horizontal plane through the jet centerline) were 15 to 18 db greater than those produced at corresponding positions with the plate removed, while for a 20‐diam separation, the increase varied between 2 and 7 db. The spectrum of the noise changed as follows as the separation distance was increased: (a) the peak frequency decreased, (b) the pronounced peak changed to a broad one, and (c) the magnitude of the peak decreased.

ISSN:0001-4966    

DOI:10.1121/1.1908894

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP