摘要:

The fusion or blending of two or more spatially separated complex signals (such as speech or music) into an apparent single image requires that the common origin signals be alike in quality and follow each other in rather close sequence (within about 50 msec). If both the quality and arrival‐time conditions are fully met, complete fusion appears to occur and a single image is heard coming from a single location. If these conditions are only partially met, then only partial fusion or image broadening results. The degree of broadening may be relatively small, or it may be sufficient for the image to appear to fill the intervening space between the physical boundaries of the real sources. For certain combinations of parameters, the creation of a single image either inside or outside these boundaries (image displacement) may occur. The present paper describes a number of arrangements that may be used to achieve each of these effects. The techniques employed date from as early as the mid‐nineteenth century to the modern filter and computer techniques of recent years.

ISSN:0001-4966    

DOI:10.1121/1.1911695

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The responses of human observers while tracking 75%‐correct thresholds using a block up‐and‐down adaptive procedure has been examined. Three signals (wide‐band noise, narrow band noise, and a 2000‐Hz sinusoid) were used with a continuous or a gated wide‐band masking noise at various levels. A strong bias in favor of the “2” response in the two‐interval paradigm and the “NO” response in theYES NOparadigm was consistently observed. Subjects also tended to follow correct responses with correct responses and vice versa. These data suggest that, although the subjects were supposedly performing a two‐interval task, they were actually attending to only one interval, most frequently the first, on each trial.

ISSN:0001-4966    

DOI:10.1121/1.1911696

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Proper specification of the magnitude and purity of the sound stimulus is of utmost importance in studies dealing with distortion processes in the ear. It is shown that, in general, sound pressure level (SPL) measurements in rigid‐walled couplers do not provide adequate representation of sound levels observed at the experimental animal's eardrum. Similarly, the distortion generated by the experimental apparatus can be either over or underestimated if measured in couplers. It is shown that, in general, the absolute specification of tolerable distortion level created by the experimental apparatus is not possible, and that this level depends on various factors of the actual experiment. Finally, evidence is presented that favors the prosecution of studies on aural distortion with the auditory bulla closed.

ISSN:0001-4966    

DOI:10.1121/1.1911697

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

This study sought to examine the temporal relations of binaural masking as compared with monaural masking for conditions of forward, simultaneous, and backward masking. Five conditions of different signal‐masker configurations and a number of temporal relations were examined to determine the masking effects on a tone by a tonal masker. The results indicate that forward, simultaneous, and backward masking are all the result of time‐dependent properties of the neural mechanism, but the dependency for all three types of masking is wholly or in part mediated by the central nervous system. The concept of peripheral adaptation as an explanation for forward masking is not supported. A discussion of the various contralateral masking conditions is presented.

ISSN:0001-4966    

DOI:10.1121/1.1911698

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

An attempt is made to develop a quantitative theory of intensity resolution that is applicable to a wide variety of experiments on discrimination, identification, and scaling. The theory is composed of a Thurstonian decision model, which separates sensitivity from response bias, and an internal‐noise model, which separates sensory limitations from memory limitations. It is assumed that the subject has two memory operating modes, asensory‐trace modeand acontext‐coding mode, and that the use of these two modes is determined by the characteristics of the experiment. In one‐interval paradigms, it is assumed that the context‐coding mode is used, and the theory relates resolution to the total range of intensities in the stimulus set. In two‐interval paradigms, it is assumed that the two modes are combined, and the theory relates resolution to both the total intensity range and the duration between the two intervals. The theory provides, among other things, a new interpretation of the7 ± 2 phenomenon.

ISSN:0001-4966    

DOI:10.1121/1.1911699

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Thresholds of human hearing were obtained underwater for two conditions: (1) with the external auditory meatus completely water filled and (2) with a bubble of air trapped against the tympanic membrane. The first condition was accomplished by forcibly irrigating the external meatus underwater the second, by placing plugs in the ears in order to encapsulate air in the meatus until the head was underwater and the test with the plugs removed) initiated. Subjects were seven divers who were tested in DICORS at a depth of 12 ft; threshold SPLs were obtained free field by a modified Békésy technique for the frequencies 125 Hz, 250 Hz, and 1, 2, and 8 kHz. Threshold shifts (reair) for both conditions of underwater hearing were consistent with those previously reported. SPLs for the two experimental conditions were virtually identical for all frequencies except 250 Hz, where hearing was 6 dB better for the water‐filled meatus condition. Apparently, the presence or absence of air bubbles in the external meatus contributes little if anything to underwater hearing thresholds.

ISSN:0001-4966    

DOI:10.1121/1.1911700

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The resting potential of the scala media (EP) in the first turn of the guinea pig's cochlea was altered by the application of currents. The EP as well as the cochlear microphonics (CM) and the summating potential (SP) were enhanced when the source electrode was in the scala media, whether the sink electrode was in the scala tympani or scala vestibuli. Using the scala media electrode as the sink for the current caused decreases in these potentials. When the EP change was sufficient to reverse the dc gradient across the reticular lamina, the CM reversed their polarity. A linear relationship exists between the changes in CM and EP. These results support the electromechanical theory of the production of microphonics.

ISSN:0001-4966    

DOI:10.1121/1.1911701

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Remote masking in ears with cochlear impairment was investigated, According to one theory, remote masking results from unsymmetrical mechanical action in the inner ear that generates a broad‐band noise within the inner ear. The broad‐band noise is said to mask tones at frequencies remote from and below the narrow‐band masker. A second theory proposes that remote masking is the result of attenuation provided by the acoustic reflex. Two noise bands were presented at three levels to a group of listeners with normal hearing and two groups with high‐frequency hearing losses of presumed cochlear origin. From these results, it appears that, when a noise band is located at frequencies of hearing loss, listeners with presumed cochlear impairment require a higher level of noise for remote masking to occur than do normal‐hearing listeners; and their remote masked thresholds are at a lower SPL and there is less remote masking than for normal‐hearing listeners. It was observed that remote masking is not necessarily at a constant sensation level across frequency, with the greatest amount of remote masking occurring near 800 Hz. The similarities between results of this investigation and known parameters of the acoustic reflex lead us to the conclusion that a dual mechanism of middle‐ear plus inner‐ear activity is a more suitable explanation of remote masking than either theory alone.

ISSN:0001-4966    

DOI:10.1121/1.1911702

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The detection of a brief (40 msec) 1000‐Hz sinusoid in the presence of narrow‐band noise was investigated using a rating‐scale procedure. Signals were added either to noise alone (simpledetection) or to noise plus sinusoidal pedestal (pedestaldetection). In the simple‐detection experiment, the noise masker was presented in one condition as a steady background and in another as a gated burst for a duration equal to the observation interval. In the pedestal‐detection experiment, the masker, consisting of noise plus pedestal, was gated on only during the observation interval. Receiver operating characteristics (ROC curves) were determined utilizing both a one‐interval and a two‐interval observation period. A comparison of performance measures estimated from ROC's for one‐ and two‐interval paradigms showed that detectability was superior for the two‐interval paradigm. The slopes of the ROC's for two‐interval detection were slightly larger than unity and were greater than those obtained in comparable one‐interval experiments.

ISSN:0001-4966    

DOI:10.1121/1.1911703

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Eleven female subject, with normal hearing sensitivity were exposed to 90 dB SL 2000‐ and 4000‐Hz fatigue stimuli for 3 min; temporary threshold shifts (TTS) were measured one‐half octave above the fatigue frequency. Over several experimental sessions separated by at least 24 h, each subject performed each of the following tasks during the exposure time for each fatigue frequency: Reading a passage aloud (RA); Reading a passage silently (RS); Reading a passage silently while articulating the words without voicing or whispering (RSA); Reverie which involved no reading (REV). The RA task produced significantly greater TTS than the other task conditions when the fatigue frequency was 4000 Hz, implying that transmission of the fatigue stimulus was enhanced, perhaps owing to impedance changes resulting from contraction of the middle‐ear muscles during speech production. The RA‐task condition produced consistently, but not significantly, less TTS than the other task conditions when the fatigue stimulus was 2000 Hz, which might indicate that transmission of the fatigue stimulus was being slightly attenuated during speech production. The data are discussed in terms of a hypothesis indicating that speech production alters the impedance of the auditory system, hence altering the transmission of sound. A TTS paradigm incorporating speech activities may be an indirect but useful method for assessing the sound transmission properties of the human auditory system.

ISSN:0001-4966    

DOI:10.1121/1.1911704

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP