摘要:

Higher‐order Markov sequences were constructed by a digital computer, converted into electrical pulse trains, and transduced to a high‐speed auditory display by earphones. Under appropriate conditions, the depth of sequential information processing available to the auditory system is virtually without limit.

ISSN:0001-4966    

DOI:10.1121/1.1911815

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A study of intensity discrimination employing click stimuli revealed three unusual effects.First, clicks are difficult to differentiate with respect to intensity.Second, the Weber function differs from those usually obtained with stimuli of longer duration.Third, click‐intensity discrimination is, improved by the addition of a continuous background noise. Since click stimuli have virtually no energy variations, these results cannot be explained by stimulus‐oriented theories of detection and discrimination.

ISSN:0001-4966    

DOI:10.1121/1.1911816

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Round‐window potentials evoked by clicks were recorded from anesthetized guinea pigs. By comparingN1amplitudes on line, it was possible to computephysiological difference limensfor click intensity. The method requires no assumptions about the underlying distributions of neural effect. Weber functions were generated with and without a continuous masking noise. The effects of click intensity and of background noise paralleled those previously reported for human listeners. A neural model was described in which variability ofN1amplitude turned out to be the principal parameter.

ISSN:0001-4966    

DOI:10.1121/1.1911817

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Knowledge of the frequency of the stimulus and existing interaural intensity differences are inadequate for predictingS‐segment cell discharge rates. The stimulus level,rethreshold, of dichotically delivered tones must also be known. At low stimulus levels the most active population ofS‐segment cells consists of cells whose CFs are tuned to the frequency of the stimulus tone. As stimulus levels of dichotically delivered tones increase above threshold, cells with CFs not tuned to the stimulus frequency, tend to discharge at rates higher than these of the cells initially responsive at low levels. The higher the stimulus level, the greater the discrepancy in frequency between the CFs of the most active cell population and the stimulus. Thus, the locus of maximum activity within theS‐segment is dependent not only on the frequency of the dichotically delivered stimulus tone but also on its stimulus level.

ISSN:0001-4966    

DOI:10.1121/1.1911818

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Levels of monaural signals at behavioral threshold were determined by a psychophysical method of adjustment for seven highly trained listeners. Thresholds were studied as a function of signal frequency (octave steps, from 0.125 to 8 kHz) and of signal duration (logarithmic steps, from 16 to 1024 msec). Measurements were made in the presence of a contralateral broad‐band masking noise with a spectrum level of 30 dB SPL. The time constant, τ estimated from at least 12 replications of each measurement, was found to range systematically from values considerednormal(125–175 msec) by some earlier investigators, at low frequencies, to much lower values (30–70 msec) at high frequencies. Comparison between the performance of listeners with normal audiograms and those with high‐frequency hearing loss shows this interaction between frequency and the time constant to be similar for both samples. The data are also compared to the results of a second experiment that employed a two‐alternative forced‐choice psychophysical method.

ISSN:0001-4966    

DOI:10.1121/1.1911819

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The changes in masking for spondee words that result from varying both the level and the interruption rate of a white‐noise masker were studied with 14 normal hearing subjects and 14 subjects with sensorineural hearing loss diagnosed as resulting from cochlear otosclerosis. The masker was a white noise and was presented monaurally at either 90 dB sound‐pressure level (SPL) or 30 dB sensation level (SL). It was either continuous or was pulsed at rates of 1, 10, or 100/sec with 50% duty cycle. During the burst‐off half of each cycle, the noise was either dropped 14 dB in level or was fully interrupted. The masked speech reception threshold (SRT) was not improvedrethe masked SRT in continuous noise when the 30 dB SL masker was pulsed 100 times/sec. Reduction in masking was observed under all other circumstances of cycling the noise. This reduction was more pronounced when the noise was completely interrupted rather than only modulated by 14 dB, when the masker was at its higher level (90 dB SPL as opposed to 30 dB SL), and when the masker was interrupted at the slowest rate [1 interruption per second (ips)]. During equivalent conditions, the reduction in masking was greater for normal‐hearing subjects than for those with cochlear otosclerosis. Appreciable residual masking (reSRT in quiet) persisted across the range of all parameters of noise level, modulation depth, cycling rate, and type of subject encompassed during the present study. This last finding appears to be contradictory to some of the results from earlier studies but not to others. This discrepancy, along with other aspects of the present findings, are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1911820

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

When two equally loud tones of somewhat different frequency are simultaneously pulsed and presented, one to each ear, a single coherent tonal image can be heard lateralized toward the higher‐frequency side. When the higher‐frequency signal is delayed by an appropriate amount, the sound image is brought to the midline. According to place theory, the two different frequencies are now arriving simultaneously at their designated places on the cochlear partition. A number of such tonal pairs were used to determine traveling‐wave velocity along various short segments of cochlear partition. Averaged estimates from three trained listeners showed wave velocity decreasing from about 30 m/sec on the higher‐frequency portion of the partition to approximately 1.0 m/sec near the low‐frequency end. Our results are compared with some psychophysical and electrophysiological findings.

ISSN:0001-4966    

DOI:10.1121/1.1911792

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Coarticulation effects have been observed in the motion of the lateral pharyngeal wall (LPW) during speech. Pulsed ultrasound was used to measure the displacement of LPW during the trisyllables/aba/, /abi/, /iba/, /ibi/. The extent of vowel‐consonant (VC) and consonant vowel (CV) motion was different depending on the other vowel.

ISSN:0001-4966    

DOI:10.1121/1.1911793

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Statistical properties of spectral samples derived from the continuous speech of six talkers and summarized by means of covariance‐matrix eigenvectors are used to study the dimensionality of the data space. The importance of eliminating low‐level samples by means of a fixed threshold is emphasized, and criteria for selecting such a threshold are presented. Measurements of spectral correlations stabilize after about 30 sec of speech, suggesting that short‐term examination of a talker's output may prove sufficient to calculate parameters useful in recognition schemes. Some features of the correlation matrix, which are readily displayed via isocorrelation contours, appear to be related to talker characteristics, while others are talker independent. The results suggest that the separation of speech data into gross classes prior to the application of statistical procedures will enhance the performance of processing schemes.

ISSN:0001-4966    

DOI:10.1121/1.1911794

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Automatic speaker verification was accomplished in this study usingcepstralmeasurements to characterize short segments in each of the first two vowels of the standard test phrase “My code is .” The length of the word “my” and the speaker's pitch were used as additional parameters. The verification decision is treated as a two‐class problem, the speaker being either the authorized speaker or an impostor. Reference data is used only for the authorized speaker. The decision is based on the test sample's distance to the nearest reference sample. Data is presented to show that, if reference samples are collected over a period of many days, then verification is possible more than two months later, whereas, if reference data is collected at one sitting, verification is highly inaccurate as little as 1 h later. Four authorized speakers and 30 impostors were examined, with error rates obtained from 6% to 13%. Impostors attempting to mimic the authorized speaker could not improve their ability to deceive the system significantly.

ISSN:0001-4966    

DOI:10.1121/1.1911795

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP