摘要:

This study investigated attentional factors involved in two‐channel auditory signal detection. The brief 50 msec sinusoidal signals, masked by binaurally uncorrelated, band‐limited noise, were presented simultaneously to two separate earphone channels each with an independent probability of 0.5. The two‐channel detection tasks required observers to monitor one (selective attention condition) or both (divided attention condition) of the earphone channels. Compared to the single channel condition, observers showed a slight (1–3 dB), but consistent, decrement in detection performance in both the selective and divided attention conditions with signals separated in frequency by less than one critical band (Δf=65 Hz). With signals separated in frequency by more than one critical band (Δf=1565 Hz), observers again showed a slight performance decrement when dividing their attention between two earphone channels, but could effectively monitor one channel while attempting to ignore the other. [This work was supported by a grant from NINDS.]

ISSN:0001-4966    

DOI:10.1121/1.2002495

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Recent data on interaural time discrimination of high‐frequency complex stimuli are described by a model based on auditory‐nerve activity. This model is a simple extension of a model that was developed for detection and discrimination of low‐frequency stimuli and that includes an explicit description of the activity in the auditory‐nerve fibers. In the extension to high frequencies it is assumed, consistent with available physiological data, that the high‐frequency neurons have instantaneous firing rates that follow the envelope of the tuning‐curve filtered signal. Beyond the auditory nerve description, the model assumes a structure for processing timing information on high‐frequency fibers that is the same as the structure for low frequencies. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2002503

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Mechanisms for the coding of speech sounds may be suggested by a knowledge of factors not having cue value but affecting the discriminability of cues. Two experiments were run on adolescent listeners' identification of /bε, dε/ with near‐boundary values of syntheticF2andF3transitions; effectively, this measures discrimination. The trajectory ofF0over the duration of the formant transitions could be high falling or low rising but first‐pulse timing was controlled. Overall,F0had no effect; lowF0conditions gave intermediate performance, while highF0gave high performance for narrowF2bandwidths but low performance for broadF2bandwidths. These results are consistent with joint operation of peak‐picking and spectral‐shift modes of spectral analysis but not with periodicity analysis for theF2andF3region. Biasing effects indicating secondary cue value did emerge; for example both narrow bandwidths and highF0favored /bε/ responses. Such effects have to be explained partly as valid perceptual inferences to articulatory events and partly as byproducts of auditory transforms.

ISSN:0001-4966    

DOI:10.1121/1.2002508

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

American English liquids have been considered intermediate between stop consonants and vowels acoustically, articulatorily, phonologically, and perceptually. Liquids are unique among English phonemes in requiring different notation in phonetic transcription depending on syllable position. Cutting [Percep. Psychophys.16, 601–612 (1974)] found position‐dependent ear advantages for liquids in a dichotic listening task. The present study used a categorical perception paradigm to provide answers to three questions: (1) Does perception differ for liquids in syllable‐initial and syllable‐final position? (2) Are liquids perceived categorically in the context of the vowel /i/? (3) Does perception of the isolated third formant (F3), the only acoustic difference among the tokens, predict perception of the speech tokens? Fifteen subjects listened to two synthetic series‐/li/ to /ri/ and /il/ to /ir/‐in which stepwise variations of F3 parameters cued the difference in consonant identity. Results indicated that: (1) perception did not differ between syllable positions, (2) all liquids were perceived categorically, and (3) discrimination of the isolated F3 did not account for the perception of the speech sounds. [Work supported by NIMH, NICHD.]

ISSN:0001-4966    

DOI:10.1121/1.2002532

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

A convincing demonstration that a component of selective adaptation to speech is acoustic can be provided by inducing opposite direction boundary shifts on two acoustically different but phonetically identical stimulus continua. This was done by using a contingent adaptation procedure on two continua which differed only in amplitude. The “loud” stimulus continuum, which consisted of nine syllables ranging from /bow/ to /gow/, was synthesized digitally and presented to subjects at 85 dB SPL. The “quiet” continuum was made by attenuating the same syllables to 50 dB. Phoneme boundaries were measured for both continua before and after adaptation with an alternating sequence of loud /gow/'s and quiet /bow/'s. An amplitude contingent boundary shift was obtained. Adaptation shifted the “loud” continuum boundary toward /g/ and the “quiet” continuum boundary toward /b/. Since amplitude is not part of the linguistic description of speech sounds, this amplitude contingent adaptation effect must reflect changes in processing at an acoustical level of analysis.

ISSN:0001-4966    

DOI:10.1121/1.2002600

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The performance of a cylindrical line of array of radially, vibrating ceramic rings when liquid filled for pressure compensation is affected by the acoustic loading of the internal cavity. This internal loading may be varied by the use of a concentric baffle of compliant tubes. This paper presents experimental data showing variations in acoustic loading resulting from various sizes and numbers of tubes used in the baffle and an approximate method of calculating these effects.

ISSN:0001-4966    

DOI:10.1121/1.2002606

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The long‐term degradation of Corprene‐backed hydrophones has been investigated by the use of color microphotography using finegrain film with slide‐projected magnifications up to 500 × life size. Oil absorption is significant and visually obvious when compared to pure cork and non‐oil‐soaked Corprene. Variations in cork to neoprene ratio and grain of various samples of the same military specifications are visually apparent and their effect on oil absorption is discussed.

ISSN:0001-4966    

DOI:10.1121/1.2002609

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Psychophysical measurements of middle‐ear transmission change, 0.4 to 4 kHz, and physical measurements of eardrum acoustic admittance, 0.063 to 4 kHz, have been made on four normal‐hearing subjects during activation of the acoustic reflex via contralateral noise,LN′, 80–110 dB SPL. The psychophysical data have been obtained by exploiting the sensitivity of the phase of the aural combination tone 2f1−f2to primary tone level [W. M. Rabinowitz and J. L. Goldstein, J. Acoust. Soc. Am.54, 293(A) (1973)]. The admittance measurements have been obtained with a specially designed electroacoustic probe tip assembly coupled to an automated transfer function analyzer. The middle‐ear transmission, |H(f)|, changes monotonically withLN. For the maximal elicitor used,LN‐max, the average Δ|H(f)| is −10 dB (σ = 1.8 dB) forf⩽ 0.63 kHz, −2 dB atf= 1.25 kHz, and zero (±1 dB) forf⩾ 2 kHz. The observed admittance change, Δ|Yd(f)|, forLN‐maxis −2.5 dB (σ = 1.4 dB) forf⩽ 0.63 kHz, zero at 1 kHz, +1.5 dB at 1.25 kHz, and zero at 4 kHz. Together the Δ|H(f)| andYd(f) data provide constraints on possible middle‐ear models. [Work supported by NIH.]

ISSN:0001-4966    

DOI:10.1121/1.2002620

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Although the middle ear is often called an impedance matching device, published measurements of the load impedance presented by the cochlea are not extensive. In the experiments reported here, sound stimuli were applied directly to the stapes in anesthetized cats in which the malleus and incus had been removed. Measurements were made of sound pressures at the stapes (Ps) and in the vestibule (Pc) with calibrated probe‐tube transducers. Stapes velocityVswas determined with the Mössbauer technique. Magnitude and phase of the total acoustic impedanceZf=Ps/(AfpVs) and the cochlear impedanceZc=Pc/(AfpVs) were obtained at frequencies between 10 and 104Hz (Afp= footplate area).Ztis approximately characterized by a series circuit with compliance of 3 × 10−10cm5/dyne, resistance of 1 × 106dyne‐sec/cm5, and mass of 3 × 10 g/cm4.Zcis approximately equal toZtfrom 500 to 5000 Hz, hence for this frequency range force applied to the stapes is all transmitted to the cochlear fluid. At lower frequencies the annular ligament absorbs most of the applied force. [Supported by grants from NIH and the Research Fund of the American Otological Society.]

ISSN:0001-4966    

DOI:10.1121/1.2002625

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

When the received level of a transmitted acoustic wave reaches an upper limit that cannot be exceeded regardless of how much acoustic power is radiated by the source, the wave is said to have saturated. Experiments on saturation of plane waves in air are reported in this paper. The measured quantity is the pressure amplitudeP1of the fundamental. To obtain a theoretical prediction valid close to and including saturation, we assume the decay rate ofP1is the sum of the sawtooth and ordinary absorption decay rates (Rudnick's assumption). Solution of the assumed equation givesP1 = 2p10e−αx/[1 + (1−e−αx)/αx̄]wherep10is the source amplitude, α is the ordinary (small‐signal) attenuation coefficient, and x̄ is the shock formation distance. The experiments were done in a plane‐wave tube over a frequency range of 2–4 kHz at source levels up to 160 dB (re0.0002 μbar). The data confirm the theoretical prediction. Design curves to assess the importance of nonlinear propagation effects on spherical waves in the atmosphere are also given.

ISSN:0001-4966    

DOI:10.1121/1.2002632

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP