摘要:

The numerous experiments on multichannel listening allow certain broad conclusions: that the listener has a limited capacity, that therefore much of the information presented to him is discarded, and that this discarding is made easier when the signals to be ignored share certain physical characteristics which the desired signals do not have. These conclusions suggest further lines of advance. The same speech signals may interfere with each other more when they are chosen from a larger ensemble. This implies that the information content must be considered. In addition, momentary peaks of information are handled by a curious form of immediate memory in the listener.

ISSN:0001-4966    

DOI:10.1121/1.1908385

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

In several experiments, the restrictions imposed upon the communication process by an articulation test were relaxed by increasing the number of events in the communication sequence. Acommunication eventis the transmission of a message from the source to the receiver followed by the return of a message (correct or incorrect) from receiver to source for confirmation. Although both source and receiver serve as talker and listener, the relation between them is asymmetric. Since the source knows the original message, he must accept or reject the message sent back to him according to some criterion.Various types of communication events arise depending upon (1) whether or not the receiver correctly hears the message, and (2) whether or not the source confirms the message returned by the receiver. The various probabilities associated with these events are investigated as a function of speech‐to‐noise ratio. The behavior of the source is examined in terms of the relation between the two conditional probabilities associated with a correct and with an incorrect confirmation.If each message is sent repeatedly until all are confirmed, a sequence of communication events is generated. A simple mathematical model accurately describes this process.

ISSN:0001-4966    

DOI:10.1121/1.1908387

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Each of four men spoke messages at predetermined times to a central operator over an independent communication channel. Each message consisted of an address, station identification, and three pieces of information. The operator identified relevant messages by the address and/or station identification and transcribed the information symbolically onto a plotting board. Message density varied from the overlapping of two or three messages to gaps of 20 seconds between single messages.The purpose of the study was to evaluate two message storage schemes. In one scheme the messages could be delayed by 9 seconds at the option of the operator (fixed‐delay), in the other every message was stored until the operator called for it (variable‐delay). The fixed‐delay and variable‐delay message storage schemes were compared to a no‐help (no‐delay) condition, where the operator had no control over the sequence of messages.The criteria used to evaluate the storage schemes were (1) the number of message repeats requested by the operator (and the associated time delays) and (2) the number of messages incorrectly transcribed (or not transcribed). The variable‐delay storage scheme was superior for all criteria, that is, fewer repeats were requested and fewer errors were made. The fixed‐delay scheme was difficult to use and was not always superior to the no‐help case.

ISSN:0001-4966    

DOI:10.1121/1.1908389

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

MAYDAY and S.O.S. were compared in the presence of noise and speech to determine their relative detectability values (audibility thresholds). Results of the tests indicated that S.O.S. had the lower audibility threshold and therefore the greater detectability value.

ISSN:0001-4966    

DOI:10.1121/1.1908391

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

To test several types of voice and code signals, communication was carried on over the conventional submarine underwater telephone between two submerged submarines. The signals included normal speech, differentiated and clipped speech, quarter‐speed speech, and multiple‐tone Morse code. It was found that normal speech was received at least as reliably as any of the more elaborate signals tried.

ISSN:0001-4966    

DOI:10.1121/1.1908393

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Two studies were made to assess the effects of high‐level noise (1) upon efficiency in speech reception and (2) in causing temporary hearing losses. Over 1400 observers made responses under various sound‐pressure levels for each of 13 different noise spectra. It was found that: (1) Increases in noise level always adversely affected speech reception, while changes in spectra did not always have an effect; time‐in‐noise did not progressively decrease scores. (2) Hearing threshold shifts of 4 to 5 db were found after a 2‐hr noise exposure; certain spectra caused greater threshold shifts than others.

ISSN:0001-4966    

DOI:10.1121/1.1908395

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

A comparison of the intelligibility of UHF and VHF communications was made between “plane to tower” and “tower to plane” at fifteen control towers. A specially equipped plane was flown in a circle with a 20‐mi radius for these tests. Voice Communication Laboratory multiple‐choice word lists were read by two talkers, one in the plane and the other in the tower. These messages were recorded on tape in both places.Five subjects listened to these recordings in the laboratory, and their responses were scored for accuracy against the original word lists. The percentage of words heard correctly from tower to plane varied from 90% to 38% with an average of 73.7% and was much higher than the corresponding percentage from plane to tower of 63% to 3% with an average of 44.4%. There was very little difference between the intelligibility of VHF and UHF. In general, those towers that had high plane‐to‐tower scores also had high tower‐to‐plane scores: the correlation among towers between hearing and being heard was fairly high.

ISSN:0001-4966    

DOI:10.1121/1.1908397

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Since the wave form of speech is apparently continuous and the phonemic entity is discrete, it is reasonable to expect that during the developmental stages of speech compression systems the process will gradually evolve from continuous to mixed discrete‐continuous and finally to a completely discrete type. Two plans for such systems are discussed. Plan I is an attempt to use two discrete features of speech together with continuous extractions of the formants, moments, and pitch of speech. Plan II is an attempt to identify phoneme‐like elements through a scheme of successive selection.

ISSN:0001-4966    

DOI:10.1121/1.1908399

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

Speech‐band compression aims to reduce the frequency band width without impairing the desired informational content. Physical compression systems are of two types: spectrum‐alteration systems and vocoder (voice coding) systems. Spectrum alteration is not restricted to speech, is relatively simple to perform, but achieves only a compression factor of 3 to 5. Considerably higher ratios (10 to 20) are obtainable by vocoder‐type systems. Here, by a spectrum analysis on the transmitter side, a “pitch” frequency is extracted and a system function is derived. Both are then transmitted to a receiver where speech is synthesized. At the A. F. Cambridge Research Center, the following vocoder‐type systems are being developed and investigated: the scan vocoder with envelope scanning, the pulse vocoder in which the envelope is coded, and the formant vocoder in which the envelope is represented by three formant frequencies. By means of alterations and additions, the scan vocoder can be transformed into a pulse or a formant vocoder.

ISSN:0001-4966    

DOI:10.1121/1.1908401

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP

摘要:

An electrical analog of the vocal tract is used to obtain experimental relations between certain idealized articulatory parameters and formant frequencies associated with the transitional and stop portions of vowel‐consonant syllables. The data are discussed in terms of the “locus hypothesis” proposed by Delattre, Liberman, and Cooper [J. Acoust. Soc. Am.21, 769 (1955)] and in terms of simple resonator theory. It is concluded that the results modify the hypothesis that assigns one second‐formant locus to all vowel‐consonant transitions involving a given class of stop consonants. In particular, the second‐formant loci for transitions to velar and bilabial stop consonants appear to vary over a range of frequencies depending on the vowel, while loci for post‐dental stop consonants are relatively invariant. Characteristics of first‐ and third‐formant loci are discussed briefly.

ISSN:0001-4966    

DOI:10.1121/1.1908403

出版商:Acoustical Society of America    

年代:1956

数据来源: AIP