摘要:

The existence of Doppler distortion in loudspeakers was demonstrated more than 30 years ago, but the question of whether or not such distortion is of significance in music reproduction has not been settled. In this study the audibility of Doppler distortion in simple direct radiators is investigated both theoretically and experimentally through (1) an analogy to tape‐machine flutter, (2) an analysis of the effect of normal listening‐room conditions on Doppler distortion (for a given low‐frequency power the radiation‐load and reverberant‐field correction factors typically reduce this distortion to 0.36 of its value on the axis of a speaker radiating into anechoic half‐space), and (3) double‐blind listening tests. An eight‐member jury compared music reproduced in two modes, one of which was essentially free of Doppler distortion. In one experiment, two recordings were made of the output of a speaker, one with a sharp bass‐attenuation filter in the speaker input circuit and the other with the same filter moved to the microphone circuit. In a second experiment, on‐axis and off‐axis speaker output were recorded in an anechoic chamber, the speaker input circuits being compensated to make the frequency responses in the two modes equal. The theoretical analysis indicates that for any practical cone velocity Doppler distortion will be less audible by an order of magnitude than the flutter of a 15‐ips tape machine that meets the NAB Standard. The experimental results provided confirming evidence that it is inaudible.

ISSN:0001-4966    

DOI:10.1121/1.385210

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

A new method of measuring the acoustic intensity of plane waves in a duct with flow is described. In this method, the acoustic transfer function between two locations in the duct is used to determine the acoustic intensity. In the case of no flow, the transfer‐function formulation reduces to a cross‐spectral relation similar to the relation used to measure acoustic intensity in three dimensions. In contrast to the relation in three dimensions, however, the cross‐spectral formulation for a duct is not limited in accuracy by the microphone spacing. The new method has been verified experimentally with a series of laboratory tests. Test results obtained by the transfer function method reveal that the net acoustic power transmitted along the pipe increases as the Mach number increases. The acoustic power radiated from the pipe opening, however, remains unchanged with increasing Mach number. This difference between the transmitted and the radiated power appears to be due to sound absorption caused by vorticity shedding at the pipe opening.

ISSN:0001-4966    

DOI:10.1121/1.385211

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

The influence of type 1 A‐weighted tolerances and frequency‐band limits on level measurements is investigated theoretically and is verified experimentally. Three A‐weighting circuits, each of which satisfied type 1 tolerances, were tested with pulse trains with various crest factors; depending on the frequency‐band limits of the measuring system, erroneous level readings could be obtained. For example, at a constant repetition rate of 10 kHz and a crest factor of three, the measured levels obtained with the A‐weighting circuits spanned a range of 4 dB when the frequency‐band limit was increased from 30 to 100 kHz.

ISSN:0001-4966    

DOI:10.1121/1.385212

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Behavioral audiograms were determined for four species of Glires: one lagomorph (domestic rabbit,Oryctolaguscuniculus) and three feral rodents (cotton rat,Sigmodonhispidus; house mouse,Musmusculus; and kangaroo rat,Dipodomysmerriami). Considerable variation in hearing ability was found among the four species with low‐frequency hearing limits ranging over 5‐1/2 octaves from 50 (kangaroo rat) to 2300 Hz (feral mouse) and high‐frequency hearing limits ranging from 49 (rabbit) to 90 kHz (feral mouse). Comparison of the characteristics of each audiogram with the audiograms of other animals of the same Order, Cohort, and Class provide further evidence for the validity of two relationships: (1) interaural distance is strongly and inversely correlated with high‐frequency hearing ability, and (2) good high‐frequency hearing is apparently incompatible with good low‐frequency hearing in most, if not all, land mammals. Furthermore, it is shown that cotton rats and feral mice possess the ability to perform frequency discriminations even at very high frequencies, indicating that there is probably no difference about the way in which they perceive high and low‐frequency sounds. Finally, it is shown that kangaroo rats are not unusual in their ability to localize brief sounds, indicating that these animals have not compromised this ability in their acquistion of their unusual low‐frequency sensitivity.

ISSN:0001-4966    

DOI:10.1121/1.385213

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Although handbells can vibrate in many different modes, only the two modes of lowest frequency are normally tuned by the bellcrafters. The frequency of the second mode is generally tuned to be three times that of the first. Each of these modes also radiates sound at twice the modal frequency, however, so that the radiated sound spectrum includes the second and sixth harmonics as well as the first and third. The amplitude of the second harmonic partial is proportional to the amplitude of the fundamental, and a similar relationship relates the sixth harmonic to the third. The first and third harmonics are radiated most strongly at right angles to the bell axis; the second and sixth harmonics are maximum along the axis. Small asymmetries in the bell often create warble due to beats between the two components of a split modal doublet. The tonal quality of a handbell depends upon the clapper strike point, the hardness of the clapper, and the force of the blow in addition to the design and construction of the bell itself.

ISSN:0001-4966    

DOI:10.1121/1.385214

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

In a heterogeneous group of ten hearing‐impaired adolescents, relations are studied between several psychophysical test results and speech reception thresholds in quiet and noise. To examine the results, data‐reduction techniques were used to extract the most relevant parameters. High correlations were found between the intelligibility of speech in noise on the one side, and vowel‐perception parameters resulting from INDSCAL analysis (frequency resolution parameters, critical bandwidth and critical ratio) and audiogram parameters on the other.

ISSN:0001-4966    

DOI:10.1121/1.385215

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

This article deals with the combined effects of noise and reverberation on the speech‐reception threshold for sentences. It is based on a series of current investigations on: (1) the modulation‐transfer function as a measure of speech intelligibility in rooms, (2) the applicability of this concept to hearing‐impaired persons, and (3) hearing loss for speech in quiet and in noise as a function of age. It is shown that, generally, in auditoria, classrooms, etc. the reverberation timeT, acceptable for normal‐hearing listeners, has to be reduced to (0.75)DTin order to be acceptable for elderly subjects with a hearing loss ofDdB for speech in noise; for listening conditions as in lounges, restaurants, etc. the corresponding value is (0.82)DT.

ISSN:0001-4966    

DOI:10.1121/1.385216

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Vowels produced in isolation by six speakers were identified less accurately than vowels coarticulated in /k/‐vowel‐/k/ syllables, whether tested by a key word task or by a rhyming task. Performance by naive listeners in the two tasks was highly correlated.

ISSN:0001-4966    

DOI:10.1121/1.385217

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Previous explanations of vowel perception held that the most definitive information for vowel identity is the relatively constant formant frequencies in the steady‐state portions of vowels. Perceptual studies indicate, however, that vowels spoken in syllables with labial stop consonants are identified more accurately than vowels spoken in isolation. The present study investigated the nature and scope of this consonantal context advantage in the perception of ten American English vowels spoken by adult male and female speakers. Vowels in /p/‐vowel‐/p/, /b/‐vowel‐/b/, /k/‐vowel‐/k/, /k/‐vowel, and vowel‐/k/ syllables were identified much more accurately than isolated vowels. This is consistent with the hypothesis that dynamic acoustic information due to the coarticulation in syllables is important for vowel identification. Identification of vowels in /g/‐vowel‐/g/, /g/‐vowel, and vowel‐/g/ syllables was not better than isolated vowels and was significantly poorer than for other consonantal contexts. Acoustical analyses were performed to determine whether poor production of vowels could account for perceptual errors. Misproduced vowel targets could not account for the overall pattern of identification performance. Phonological factors were also considered but were found to be inadequate to account fully for the results.

ISSN:0001-4966    

DOI:10.1121/1.385218

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP

摘要:

Strangeetal. [J. Acoust. Soc. Am. 60, 213–224 (1976)] report that naive listeners misidentified approximately three times as many tokens of vowels spoken in isolation as the corresponding vowels spoken in consonantal context. On the basis of these findings, they argue that the superior intelligibility of vowels in consonantal context is due to coarticulatory effects: ’’acoustic information distributed over the temporal course of the syllable is utilized regularly by the listener to identify vowels’’ (p. 213). The present study tested naive listeners’ identification of eleven American English vowels spoken in isolation and in consonantal context with an experimental design comparable to that used by Strangeetal. Here, however, listening tests were administered under high quality listening conditions, speakers and listeners were closely matched for regional dialect, and problems with the response alternatives for the vowels were minimized by having listeners identify the isolated vowels and /tVt/ syllables by rhyming them with English words. The results of the tests indicated that isolated vowels could be identified quite well; listeners misidentified only 2% of the vowels when tokens were blocked by speaker and only 8% when tokens were randomized across speakers. Further, the tests did not reveal any overall difference in identifiability between the isolated vowels and vowels in consonantal context.

ISSN:0001-4966    

DOI:10.1121/1.385219

出版商:Acoustical Society of America    

年代:1980

数据来源: AIP