摘要:

In evaluating a speech‐processing device, the result of applying a suitable fidelity criterion to its output and the tolerance within which the reduced signals must be represented to satisfy this criterion, as well as the corresponding band width, are important. These factors establish a measure of the efficiency of the particular representation achieved by the device. This quantity can be utilized to compare it with systems having known characteristics. An important constraint is that the systems being compared have equal fidelity according to the criterion being used. The quantitative result of this comparison depends markedly upon the criterion selected. It should be chosen with the contemplated application in mind and can be either objective or subjective in nature. Since speech‐processing devices operate on the basis of an objective criterion, it appears that as future research establishes relations between subjective impressions and physical measurements, better and perhaps even the ultimate speech‐processing devices will become realities.

ISSN:0001-4966    

DOI:10.1121/1.1908405

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908407

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1908409

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Computations of the band widths and signal‐to‐noise ratios necessary for the transmission of continuous data on the first three formants of speech are presented. The results indicate that, on the average, band widths of 7.1, 6.7, and 5.3 cps and signal‐to‐noise ratios of 33, 24, and 20 db are sufficient for the transmission of signals specifying the frequencies of the first, second, and third formants, respectively. The band‐width and signal‐to‐noise figures are computed on the basis that the error incurred in each formant signal is less than the just discriminable difference in formant frequency at least 65% of the time. The channel capacity necessary for the transmission of the three formant signals is, therefore, of the order of 200 bits per second.

ISSN:0001-4966    

DOI:10.1121/1.1908412

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Previous investigators have shown that speech waves can undergo any one of a number of severe forms of distortion in low ambient noise levels without serious reduction of word articulation. There are well‐known notable exceptions (e.g., center clipping). However, it is not enough to avoid these exceptional forms of distortion. In the study reported here it has been demonstrated that combinations of speech‐wave distortions, which individually are quite innocuous with regard to word articulation, can be devastating in their combined effect, even in the absence of serious noise. Four types of speech‐wave distortion were studied, individually and in combination, as follows: gross attenuation of high‐frequency components, multiple echo, random amplitude modulation, and gross irregularity of response‐frequency characteristic. Ambient noise was also a controlled environmental condition in some phases of the investigation.

ISSN:0001-4966    

DOI:10.1121/1.1908414

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Listeners responded to two simultaneous messages through dichotic headset circuits. Each message consisted of word groupings from the multiple‐choice intelligibility tests. The signal level of one of the messages remained constant while the level of the contralateral message was attenuated in five steps of three decibels each step. The variable under study was the effect of these attenuation levels upon the reception of the two messages. The simultaneous messages were received under conditions of noise and quiet. The findings were that the general effect of attenuating one of the simultaneous messages was that of decreasing the reception scores of the attenuated message and increasing the reception of the unattenuated message. The effect was more pronounced in noise than in quiet.

ISSN:0001-4966    

DOI:10.1121/1.1908416

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Previous investigations have shown that the masking capacity of a prolonged auditory stimulus remains constant over its duration in spite of its great diminution in loudness. The experiments which follow were designed to determine the relation between the masked threshold and the duration of the masked stimulus. The results show that (1) within limits, as the duration of a pure tone is increased less noise is required to mask the tone, (2) the magnitude of this effect increases as a function of frequency of the masked tone but appears to be independent of its SPL, and (3) in general, these effects diminish somewhat with practice.

ISSN:0001-4966    

DOI:10.1121/1.1908418

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Temporary threshold shift after auditory fatigue was measured in 178 subjects with normal hearing prior to their placement in an environment of high‐level noise. In addition, two audiograms were made: one, prior to the noise exposure period; the second, eight weeks after its termination. Results indicated that ears showing hearing losses at 3000 and 4000 cps eight weeks after the noise exposure tended to show longer recovery times on the prenoise exposure fatigue test than ears with no change. These findings are discussed in relation to the prediction of noise susceptibility.

ISSN:0001-4966    

DOI:10.1121/1.1908420

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

An experiment is described in which detection of the absence of signal remained high and relatively constant while detection of intermixed signals varied over the threshold region as a function of signal voltage. Statistical signal detection thresholds of observers with set to detect absence of signal were approximately 2 db lower than those of observers with set to detect signal.

ISSN:0001-4966    

DOI:10.1121/1.1908422

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

The observer's responses to aural signals in noise are compared to the output of an electronic detection system whose constants are intended to be close to those of the human auditory detection system.Of the four variations of an electronic detector tested, the best correlation between the detector and the observer occurred for signals of duration 0. 3 second, band pass 60 cps (single tuned RLC circuit), square law detector, output filter time constant, 0.15 second.The incomplete correlation between the signal responses of the observer and the detector can be explained by assuming that the observer's threshold fluctuates randomly about a mean value with a dispersion of about 20% of the mean, or alternatively that there is internal noise with this dispersion generated inside the observer's detection system.The observer's false alarms appear to be caused by noise fluctuations (as measured by the electronic detector) of the same average magnitude and dispersion as those calculated for a detector with the same threshold fluctuation. However, the observer's false alarm rate is about an order of magnitude lower than that calculated for the fluctuating threshold detector so it is clear that the model is deficient in some important respects.

ISSN:0001-4966    

DOI:10.1121/1.1908424

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP