摘要:

Many seal vocalizations consist of frequency swept tones. The signal detection thresholds of a harbor seal (Phocavitulina) and of human listeners were measured using ascending and descending frequency swept tones at 1/3‐ and 1‐oct bandwidths. The swept tones increased or decreased exponentially and traversed the same frequency range. The sweeps were centered on 2, 4, and 8 kHz for the seal study and 0.5, 1, and 2 kHz for the human listeners. The bandwidth of the sweep did not affect signal detection abilities of either the seal or human listeners. The seal had lower signal detection thresholds (1–5 dB) when presented with the descending frequency swept tones (F=32.04, df=(1,31),p≤0.000001). Human listeners also had lower detection thresholds for descending frequency swept tones (t=−4.78, df=52,p≤0.0001). Pinniped ascending frequency swept calls may not function as well as descending frequency sweeps for long‐distance communicative signals.

ISSN:0001-4966    

DOI:10.1121/1.411296

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

In this paper, a simple recurrent neural network (SRNN) is employed to model the prosody of continuous Mandarin speech to assist tone recognition. For each syllable in continuous speech, several acoustic features carrying prosodic information are extracted and taken as inputs to the SRNN. If proper linguistic features extracted from the context of the syllable are set as output targets, the SRNN can learn to represent the prosodic state of the utterance at the syllable using its hidden nodes. Outputs of the hidden nodes then serve as additional recognition features to assist recognition of the tone of the syllable. The performance of the proposed tone recognition approach was examined by simulation on a multilayer perception (MLP)‐based speaker‐dependent tone recognition task. The recognition rate was improved from 91.38% to 93.10%. The SRNN prosodic model is further analyzed to exploit the linguistic meaning of prosodic states. By vector quantizing the outputs of the hidden nodes of the SRNN, a finite‐state automata that roughly represents the mechanism of human prosody pronunciation can be obtained.

ISSN:0001-4966    

DOI:10.1121/1.411274

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Many of the characteristics and processes associated with adolescence are reasonably well understood; others are not. Still unanswered are questions about adolescent voice change. For example, when does the average child start the process; what changes result and what is their extent; when is it complete? Further, how closely do shifts in vocal level parallel, or even predict, the adolescent process? This project was carried out in order to obtain data which would complement available information on the subject and provide additional specificity about voice change and pubescence—at least for boys. To that end, a longitudinal study was conducted in which 48 males were tracked over a 5‐year period. Voice measurements were made—including speaking fundamental frequency (SFF) and phonational frequency range (PFR)—as were others relating to physical size (height, weight, and six body dimensions). It was found that (1) stable adolescent voice change (AVC) measurements could be obtained, (2) maturation patterns appeared predictable on the basis of AVC changes, and (3) both the onset and duration of voice change extended over a longer period of time than had been previously thought.

ISSN:0001-4966    

DOI:10.1121/1.411275

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

To test the conjecture that cochlear impairment and a masking noise in normal ears produce analogous effects on the growth of loudness, loudness was measured for 21 listeners, all with bilateral symmetrical high‐frequency cochlear losses. Beyond the normal‐hearing region, thresholds increased by 30–49 dB/octave for 10 listeners in group I and by 51–71+ dB/octave for 11 listeners in group II. Measured by absolute magnitude estimation and production at two frequencies where thresholds were normal, the dynamic range over which loudness grows was not altered by the adjacent hearing loss. This was not true however, for the slope. Whereas the overall shape and slope of the loudness functions were essentially the same for group I, the mid‐to‐high level slope for group II was noticeably flatter for a tone at the cutoff frequency than for a lower‐frequency tone. In contrast, markedly steeper loudness functions, characteristic of loudness recruitment, were obtained for both groups at a frequency in the region of impaired hearing. The reduced rate of loudness growth observed in the region of normal hearing for listeners with steep low‐pass losses, like the reduction usually found for a tone masked by an adjacent high‐frequency noise, is ascribed to the tone’s restricted excitation pattern. These results indicate that high‐frequency auditory cues are effectively eliminated by a steeply sloping high‐frequency hearing loss just as they are eliminated by the addition of an external noise.

ISSN:0001-4966    

DOI:10.1121/1.411445

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The percepts elicited by electrical stimulation of auditory neurons by trains of amplitude‐modulated current pulses were studied in a group of six cochlear implant users. Modulation frequencies of 100, 150, and 200 Hz were studied, with a range of carrier rates up to 1200 Hz. It was found that all but one subject could consistently rank 150‐ and 200‐Hz modulated stimuli by modulation frequency when the carrier rate was more than 800 Hz, but for lower carrier rates the ranking was greatly affected by the harmonic relationship between carrier and modulation frequency. Pitch matching experiments showed that the subjects generally considered the modulated stimuli to be equal in pitch to unmodulated stimuli with rates the same as, or somewhat higher than, the modulation frequency. The results showed that the ‘‘pitch’’ of pulsatile electrical stimulation resulting from periodicities in the time structure of the electrical stimulus has similarities to the ‘‘pitch’’ observed for temporal patterns in acoustic stimulation such as amplitude‐modulated noise. There were some differences, however, which may be attributable at least in part to the physiological response differences for electric and acoustic stimulation.

ISSN:0001-4966    

DOI:10.1121/1.411377

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Thresholds for the detection of a 1.0‐kHz pure tone were measured in modulated and unmodulated noise for a group of nine elderly listeners, aged 62–83, with normal or near‐normal audiograms, and a reference group of seven younger normal‐hearing listeners. The masker was either a band of noise 128 Hz wide [approximately one equivalent rectangular bandwidth (ERB) centered at 1.0 kHz], or a band of noise 1505 Hz wide (approximately five ERBs above and five ERBs below 1.0 kHz). The noise was either unmodulated or was square‐wave modulated at rates of 10, 20, 30, 40, and 50 Hz. A measure of comodulation masking release (CMR) was derived from the masking data. Because wider filters have been found to be associated with reduced CMR, auditory filter shapes were also estimated for the elderly listeners. The filters were found to be normal at the center frequencies of 800, 1000, and 2000 Hz ruling out possible confounding effects of impaired auditory filters on CMR. Masked detection thresholds were generally significantly higher for the elderly as compared to the younger listeners for both unmodulated and modulated noise. Thresholds were lower in modulated as compared to unmodulated noise masking for both elderly and young listeners. For both groups of listeners and for both narrow‐ and wideband masking, detection thresholds continued to increase as modulation rates were increased. CMR was not different for the elderly and young listeners and it was similarly decreased, for both groups, at higher rates of modulation.

ISSN:0001-4966    

DOI:10.1121/1.411446

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Weber fractions (ΔI/I) for gated 500‐ms tones at 0.3, 0.5, 1, 2, and 3 kHz, and at levels of the standard ranging from absolute threshold to 97 dB SPL, were measured in quiet and in high‐pass noise in five listeners with cochlear hearing loss and in three normal‐hearing listeners. In regions of hearing loss, the Weber fractions at a given SPL were sometimes normal. When the Weber fractions were normal or near‐normal, the addition of high‐pass noise elevated the Weber fraction, strongly suggesting the use of spread of excitation to higher frequencies. Inversely, when the Weber fractions were elevated, the addition of high‐pass noise produced no additional elevation, suggesting an inability to use spread of excitation. In general, the relative size of the Weber fractions, the effects of high‐pass noise, and to a lesser extent, the dependence of the Weber fraction on level, were consistent with expectations based upon the audiometric configuration and the use of excitation spread. There were several notable inconsistencies, however, in which normal Weber fractions were seen at a frequency on the edge of a steep high‐frequency loss, and in which elevated Weber fractions were observed in a flat audiometric configuration. Finally, when compared at the same SL, the Weber fraction was sometimes smaller in cochlear‐impaired than in normal hearing listeners. This was true even in high‐pass noise, where excitation spread was limited, and may reflect the unusually steep rate versus level functions seen in auditory nerve fibers that innervate regions of pathology.

ISSN:0001-4966    

DOI:10.1121/1.411276

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Experiments on young adults studied the effects of suddenness of onset or offset on the discrimination of the order of pitches of individual tones in a 1‐s, 4‐tone cluster of overlapping pure tones. In experiment 1, the tones, all within a critical band, went on asynchronously. Each rose and decayed linearly in amplitude. Faster onsets, within the range 10 to 640 ms as measured on the first tone, increased the accuracy of the discrimination of the order of onsets, but 10‐ms onsets were slightly worse than 40‐ms onsets in early sessions. Experiment 2 found similar effects for the abruptness of offsets of tones in clusters whose components came on synchronously but went off asynchronously. Onset order was very much easier to detect than offset order. The auditory system may use neural onset and offset responses to reset itself and carry out new analyses at frequency‐by‐amplitude points of sudden amplitude change, thereby contributing to auditory scene analysis.

ISSN:0001-4966    

DOI:10.1121/1.411277

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The methodology derived from the trace–context theory of intensity resolution (Durlach and Braida, 1969; Macmillanetal., 1988) was applied to resolution over an octave range along two continua: a sequential‐frequency‐ratio continuum for possessors of relative pitch (RP), and a pure‐tone frequency continuum for possessors of absolute pitch (AP). The performance of both RP and AP possessors was exceptional in that total identification sensitivity along both continua was much greater than identification sensitivity along unidimensional psychophysical continua characterized by the 7±2 rule. In addition, the performance of RP possessors was exceptional in that, on average, total sensitivity for identification resolution was greater than sensitivity for resolution in discrimination. Finally, identification sensitivity between category prototypes (chromatic semits) along both continua was approximately the same as identification sensitivity between phonemic category prototypes along speech continua, despite the fact that both the discrimination ranges and the total number of categories are much larger for the two pitch continua.

ISSN:0001-4966    

DOI:10.1121/1.411447

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

A two‐dimensional stimulus classification paradigm was used to assess the extent to which listeners’ processing of interaural delays at low frequencies is spectrally analytic or synthetic. Listeners were presented with a 753‐Hz target with an interaural delay that varied from trial to trial, taking on one of ten values, five leading to the left ear and five leading to the right. A 553‐Hz distractor component was simultaneously presented, with its interaural delay also presented at one of ten different values. During a block of 100 trials, each of the possible combinations of target and distractor delay was presented once, and only once, in a random order. Listeners were instructed to make left–right judgments based on the target delay. Each condition was repeated ten times, and the slopes of the best linear boundaries between left and right responses were used to derive the relative weights given to the target and distractor in judgments of laterality. Six of the nine listeners gave increasing weight to the target as the duration of the signals was increased from 25 or 50 to 400 ms. Three listeners showed little change with duration; one consistently gave equal weight to the target and distractor, two consistently gave greater weight to the target than to the distractor. The utility of classification paradigms in the study of multidimensional acoustic signals is discussed.

ISSN:0001-4966    

DOI:10.1121/1.411278

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP