摘要:

This paper will discuss the results obtained to date with a real‐time speaker‐verification system being developed by ARL's Speech Systems Research Department. A speaker wishing to have his identity verified supplies his identity to a computer via a teletype. Reference data previously obtained for that speaker are read into the computer memory from a disk storage unit. The speaker then repeats the test phrase, “My code is _____,” into a microphone whose output is A/D converted and entered into the computer. A comparison is made between the test phrase and the reference data. On the basis of the comparison, the computer either verifies or challenges the purported identity of the speaker. The discussion will describe the “cepstral” measurements made on the test phrase, the nearest‐neighbor decision procedure, and the problem of collecting adequate training samples. The system has been trained to recognize four speakers. When tested on new data for both the original speakers and 30 impostors, error rates of from 6% to 13% were obtained.

ISSN:0001-4966    

DOI:10.1121/1.1973646

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

In small rooms, the spatial variation of the sound pressure at low frequencies is very large. In order to reduce the time‐average spatial variations in a designated test section within the reverberant room, in the region below the frequency of modal overlap, a rotating vane diffuser is employed. Effects of the rotating vane, such as changing the character of the acoustical space from a time‐invariant into a time‐variant system, which in turn introduces new frequencies, is considered. Some experimental findings are presented. [This research was supported by the Naval Applied Science Laboratory, Brooklyn, N. Y.]

ISSN:0001-4966    

DOI:10.1121/1.1973660

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Hydrophones sensitive to particle velocity or pressure gradient are not yet available as off‐the‐shelf devices, although they have been studied quite thoroughly in the past. A new look at their possible application to underwater‐acoustic research shows that they hold promise in applications where low sensitivity can be tolerated, since reproducible performance can be bought at the expense of sensitivity. Nearfield studies of radiators can, for instance, make use of extremely insensitive transducers. The noise performance of the devices in the presence of turbulent flow is, on the other hand, a very severe restriction to their use in a free field.

ISSN:0001-4966    

DOI:10.1121/1.1973672

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

An experimental study of the directivity gain of underwater transducers with the attachment of horns was made, and factors influencing such directionality were established for exponential, tractrix, and conical horns. The influence of steel and aluminum for construction materials and the effects of polyurethane foam or air backings were determined. The directivity index was found to show sudden drops at discrete frequencies, and it was shown that this behavior was related to transverse modes of propagation inside the horn by the mouth of the horn for acoustic pressure and phase variations. The effect on directivity of various cell arrangements in a conical horn was studied. [This work is supported by the Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1973676

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Under the proper conditions, the response of two coupled, nonlinear oscillators driven by a sinusoidal input will contain a pair of subharmonic frequency components. The frequenciesf1andf2of these subharmonic components correspond approximately to the resonance frequencies of the linearized system, and their sumf1+f2is equal to the driving frequencyf. The occurrence of subharmonic pairs requires that the driving force exceed a threshold value. This threshold is determined by an analysis that relates the existence of the subharmonics to the properties of a pair of coupled Mathieu equations. Finally, results are presented of an experimental study of subharmonic‐pair generation in a nonlinear circuit that was constructed to illustrate this phenomenon.

ISSN:0001-4966    

DOI:10.1121/1.1973690

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

A series of auditory localization experiments has been performed with S's listening in a sound field. However, audiometric screening was done with headphones, implying a known relation between these two conditions. There is little in the literature concerning precise relationships between threshold measurements taken with headphones and suprathreshold tasks performed in a sound field. Using Békésy audiometry, we tested 10 college students listening both with headphones and with loud‐speakers in a partially balanced experimental design. Statistical analysis of the findings demonstrated significant differences between results produced under the two test conditions with respect both to threshold and to variances.

ISSN:0001-4966    

DOI:10.1121/1.1973699

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

In this study, a comparison is made between oral and nasal sound‐pressure levels for subjects with normal oral structures and complete velopharyngeal closure, for subjects who had undergone surgical repair of the palatal clefts and had complete velopharyngeal closure, and for subjects with repaired cleft palates but who lacked velopharyngeal closure as determined by cinefluorographic analysis. The study is also concerend with the relationship between SPL measures obtained for the right nostril as opposed to the SPL for the left nostril for all subjects. Statistically significant differences were found between the normal group and the cleft‐palate group that lacked velopharyngeal closure and between the normal subjects and the cleft‐palate group with no velopharyngeal gap. Other aspects of this study are presented.

ISSN:0001-4966    

DOI:10.1121/1.1973713

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The degree of stimulation of the research tool is determined by comparing the synthesized echograms with those recorded in real auditoriums. Thus, the similarity of physical occurrences during the growth and decay periods of the sound is taken as reasonable justification for using the tool as a research device to explore the preferences of musical subjects for auditorium sound.

ISSN:0001-4966    

DOI:10.1121/1.1973728

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

The sound produced by the trumpet is quite complex, being characterized by a highly peaked waveform having strong harmonic components near 1500 Hz. How this complex waveform is generated has hitherto not been satisfactorily explained. Highly nonlinear lip motion is not the cause, since it has been shown that the area of the lip opening varies nearly sinusoidally [J. Acoust. Soc. Amer.13, 305 (1942)]. Measurements in this laboratory now show that over a small fraction of the lip‐motion cycle, the impedance of the lip opening is much greater than the input impedance of the trumpet, while over the remainder of the cycle, the converse is true. A sinusoidal lip‐opening variation then produces a strongly nonsinusoidal air flow into the instrument; this accounts for the harmonic generation. Mouthpiece pressure waveforms have been calculated for a simple model based on this idea, using measured values of the impedance of a mechanical “lip” together with values of trumpet input impedance. The curves obtained closely resemble those observed with a blown trumpet. [Research supported by the National Science Foundation.]

ISSN:0001-4966    

DOI:10.1121/1.1973736

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP

摘要:

Noise radiated from a hermetic reciprocating compressor consists of harmonics of the rotational frequency. At low frequencies, the noise radiation is due to solid body motion and exhibits a dipole pattern. At higher frequencies, the noise radiation is due to shell deformations and the corresponding noise pattern is that of quadrupole or higher‐order radiation.

ISSN:0001-4966    

DOI:10.1121/1.1973752

出版商:Acoustical Society of America    

年代:1969

数据来源: AIP