bluuebunny/crossref_metadata_2025 huggingface dataset:
Horn and horn driver two-port measurements
Authors: Hixson E. L.
Published: October 2005

Each installation of an electroacoustic aid to ship navigation has a unique requirement of sound pressure levels over geographical areas. To meet these requirements horn arrays. special horns, and baffles are required. Design is greatly aided by being able to predict the performances of horn-horn driver combinations. A design method and measurement technique are reported here that characterize a horn by its driving point impedance at the throat, its transfer function of SPL at one meter to-throat pressure, and its directivity characteristics. The driver is characterized by its electroacoustic two-port parameters. Examples will be given where the electrical potential and power requirements can be predicted from the far field acoustical requirements. [This work was sponsored by the Ocean Engineering Division of the U.S. Coast Guard.]
Aural harmonics: Some parameters of distortion
Authors: Ayres T. J. , Clack T. D.
Published: October 2005

Subjective-harmonic amplitudes between ears, listeners, and frequencies are basic data relevant to several clinical and theoretical issues. Monaural tone-on-tone masking measurements for the second and third harmonics of 250, 500, and 1000 Hz have been obtained at 75 dB SPL from each ear of 8 subjects with normal bilateral hearing. The estimates of the corresponding aural harmonic amplitudes tend to: (1) be lower at the third than second harmonics, (2) differ nearly as much between ears as subjects, (3) correlate with overall masking levels across but nol within frequencies, and (4) increase slightly with fundamental frequency. These latter two findings are particularly interesting: (3) because such a correlation implies a previously unsuspected nonindependence of the distortion and masking processes, and (4) because such increases are inconsistent with the simple power-series description of aural distortion. Sensation level of the fundamental may mediate these increases in both masking and distortion. [Work supported by NIH and the Department of Otorhinolaryngology, University of Michigan Medical School.]
Quadratic summation tone fn + f1: Differences in phase and growth rate for a three octave variation of f1
Authors: Erdreich John
Published: October 2005

Although the nonlinear amplitude characteristic of the ear has received much attention of late, the problem of whether this response is dependent only on the stimulus to the nonlinearity or, whether the nonlinearity is also frequency dependent is unresolved. In this study the level of the quadratic distortion product fh + f1 was estimated using the tone-on-tone masking paradigm under a 2AFC transformed UP-DOWN procedure. The higher frequency tone (fh was maintained at 1.2 times the lower (f1 = 250, 500, 1000, or 2000 Hz). Changes in the monaural phase effect (MPE) amplitude, in the aural distortion product phase, and in the growth of the combination tone amplitude were examined as functions of primary frequency and level. The results indicate that MPE amplitude is simply a function of S/N ratio between the combination tone and the masking at that frequency. Distortion product phase varies over 360° and is unrelated to primary frequency or intensity. Within listeners the range of distortion product phase is more narrow (70°–90°) at a single frequency. The absolute level of the summation tone does not correlate well with primary frequency. However, growth rate of the combination tone varies with frequency over a range of 1.1 dB/dB to 2.3 dB/dB. This change is not statistically significant. [Work supported in part by Faculty Research Council award and by U. S. Army Contract DAMD17-78-C-8074.]
The Lockheed-Georgia coannular jet research facility
Authors: Burrin R. H. , Tanna H. K.
Published: October 2005

The facility described in this paper comprises two essentially identical installations, very carefully designed, for the measurement of both the acoustic and the flow fields associated with coannular jet configurations. Both primary and secondary flows may be operated at temperatures up to 1500°F at pressure ratios as high as eight. The nozzle designs were carefully selected to provide the basis for systematic investigations. Acoustic measurements are made in the anechoic chamber in a free-field environment anechoic above 200 Hz, while corresponding flow measurements are made in the turbulent flow facility using a four-channel laser velocimeter (LV) system. A brief description of the anechoic chamber is given with a more detailed discussion of the turbulence facility, the laser velocimeter, and the modifications incorporated to include coannular configurations. Details of the performance tests of the complete facility are discussed. These include (i) exhaust muffler/collector attenuation measurements, (ii) inverse square law tests to determine the anechoic quality of the room, (iii) a systematic study to establish the lack of any significant internal (or upstream) noise levels for cold as well as hot operation, (iv) checks on the performance of the various inner and outer nozzles, and (v) qualification tests of the laser velocimeter as the primary flow measurement device.
Nonlinear effects in the generation of sound by internal-combustion engine exhausts
Authors: Brammer A. J.
Published: October 2005

The exhaust waveforms and spectra of single cylinder, two- and four-stroke engines have been studied under closely controlled operating conditions, to provide information on the nonlinear parameters to include in analytical treatments of mufflers. Typical waveforms at an open exhaust, obtained by signal averaging to remove cycle to cycle variations, consist of a large amplitude (2–6 psi), highly damped, sinusoidal pulse followed by a smaller amplitude (∼0.5 psi) oscillation after the port/valve closes. The amplitude of the radiated pulse is found to decrease progressively as the angle from the direction of the exhaust discharge is increased, leading to front-back differences in sound pressure level of ∼10 dB at low frequencies. it appears that the dominant source properties can be predicted by treating the cylinder and exhaust port as a Helmholtz resonator, with a pressure dependent orifice resistance of the type described by Ingard. Measurement of the peak velocity of efflux of the exhaust gases permits the observed radiation patterns to be predicted by including convection of the simple acoustic source by the flow.
Asymmetric distribution of SAW power flux emitted from LFM IDT
Authors: Shu-yi Zhang , Song-ru Fang
Published: October 2005

According to the prediction of theories, both acoustic power flux distribution between the right and left acoustic ports emitted from LFM IDT is asymmetric. By means of optical diffraction, we have detected the distribution of acoustic fields excited by the LFM IDT. Three unapodized LFM IDT which have different parameters are studied. These transducers with aluminum electrodes were deposited on the piezoelectric substrates of YZ-LiNbO3. The experimental results show that the SAW power run radiated from the high frequency port of LFM IDT is found to be stronger than that from the low frequency one. The asymmetry increases with the number of the finger pairs, but decreases with the band width. In general, the asymmetry increases with the excited frequency but the relation is not monotonic. Some theoretical models are taken for numerical evaluation of the asymmetric distribution. The comparison between the theoretical curves and the experimental results are presented and discussed briefly. However, in the theoretical calculations the mode-conversion from SAW into BAW induced by the interdigital electrodes, has not been taken into consideration.
Study of a SAW nonlinear FM dispersive line
Authors: Xiaorong Zhang , Chang-min Gan , Zhoug-nan Lu
Published: October 2005

Study of a SAW nonlinear FM dispersive delay line (NLFM-DDL) for generating and processing power series FM (PFM) signals with time bandwidth product of 160 and fractional bandwidth of 32% is reported. Firstly, it deals with the SAW NLFM single dispersive delay line (SDDL), with it's design, theoretical and experimental result of the frequency response and the self-correlation pulse. It has been shown that the DDL can be used to produce signals with a power series frequency modulation and the observed sidelobe level of the self-correlated pulse of this NLFM-DDL is smaller than that of the LFM-DDL with transducers having no weightings. Secondly, a double dispersive delay line (DDDL) is discussed and shown that a wider bandwidth is easier to obtain by using a DDDL than by a SDDL. It is also to be shown that by the combined action of a pair of dispersive transducers, the total pulse length which is the combined response of the two is found equivalent to the response of a PFM signal. This design has been performed by means of computer.
Ultrasonic absorption in UF6 and UF6 with N2 and Ar
Authors: Bass H. E. , Cravens Dennis , Shields F. Douglas , Breshears W. Dale
Published: October 2005

Ultrasonic attenuation has been measured in neat UF6 and in mixtures of 5% and 10% UF6 in Ar and in N2 at 273 of K and 323 of K for f/P values in the range of 10 kHz/atm to 2 Hz/atm. These attenuation measurements were analyzed to determine the relaxation time for vibrationally excited UF6. Isothermal relaxation times were in the range 4–15 × 10−9 atm-s. Argon and N2 were found to be slightly less efficient collision partners (by factors of ∼1.5–3) than UF6 itself.
Ultrasonic examination of mammalian tendon with acoustic microscopy in various media
Authors: Edwards C. A. , O'Brien W. D.
Published: October 2005

Fresh mammalian tendon threads (diameter ≃110 μm) were examined using the scanning laser acoustic microscope (Sonomicroscope 100R, Sonoscan, Inc., Bensonville, IL) at 100 MHz to make quantitative ultrasonic velocity and impedance measurements. Tendon is high in collagen (about 30% wet weight, 50%–90% dry weight), a structural protein which is believed to be important in the ultrasonic visualization of tissues. Ultrasonic velocity measurements are made by measuring a shift in the phase front of the sound as it propagates through the tissue as compared with the surrounding medium. Ultrasonic impedance measurements are made by comparing the acoustic contrast of the specimen with respect to that of the surrounding medium. The use of different media provides the opportunity to match velocity and impedance of the medium with that of the collagen threads thus yielding quantitative values of these ultrasonic characterization parameters. The use of different media also allows examination of the possibility that the medium itself is affecting the collagen thread. Two reference media at various concentrations were used, viz., aqueous solutions of sodium chloride or glycerine. Initial results using the different media indicate that the velocity of tendon is similar to that of pure glycerine (velocity ≃ 1926 m/s). This is almost 30% greater than the ultrasonic velocity of soft tissues. An impedance match has not been obtained using the reference media of the present study. This result suggests that the collagen thread may not be homogeneous with respect to its ultrasonic properties. This result when considered with the high velocity of the tendon, indicate that there is a marked difference in the ultrasonic characteristics of this tissue and other biological tissue. [This work was supported in part by grants from NIH and a Biomedical Research grant from University of Illinois, Urbana-Champaign.]
Attempts to determine uniform, objective criteria for assessing human perception and acoustic impact
Authors: Mantel J.
Published: October 2005

The questions of the acoustic impact on a section of the population and the intelligibility of speech in transmission systems or in room acoustics are being treated in terms of statistics without consideration of the scatter in human perceptiveness. Both the nuisance threshold and the threshold for other kinds of perception differ from person to person and have a relatively wide scatter. Different approaches therefore cannot be extended to other investigations conducted with other parameters. The fidelity index method for music transmission is discussed by analogy with the articulation index method for speech transmission. Because of the scatter in human requirements and sensitivity as regards noise, we discuss the indifference levels and the classification of sensitivity in the categories “sensitive,” “normal,” and “insensitive.” The correlation of the results with those obtained by means of information theory is pointed out.
Measurement of the quantity of sound energy returned to stage positions within a nominated period
Authors: Harkness E. L.
Published: October 2005

Further to a paper presented at the 96th Meeting of the ASA [J. Acoust. Soc. Am. 64, S171(A) (1978)], in which a method for measuring the attack sequences and the spread of attack of musicians playing in ensemble was presented, a method has been developed for measuring the quantity of sound energy returned to stage positions within a nominated period of time. Hence, if a spread of attack of 80 ms is considered to be a clean attack, a measure of sound energy returned to stage positions within a period of 80 ms might be of value in assessing the comparative ease with which musicians can play in ensemble in various halls. In measuring the quantity of sound energy returned to stage positions in five Australian auditoria, a gated signal was emitted from an isotropic sound source, the SPL of the signal was calibrated to be 100 dB linear SPL at a distance of 0.4 m from the sound source, signals emitted were pure tones of frequencies 250, 500, 1000, and 2000 Hz. The sound energy returned was displayed on a CRO screen which enabled the sound energy returned to each position on each stage, to be measured.
Power series for the reverberation time
Authors: Joyce W. B.
Published: October 2005

A power series is derived for 1/T, the reciprocal of the geometrical-acoustics reverberation time of an enclosure. The first term is Sabine's expression and the second term provides a correction to the Sabine value in many practical cases where his value is a good, but not quite good enough, estimate of T. The Eyring formula and other expressions which have been advanced as improvements on the Sabine formula are shown to contain only parts of the second term and hence to be unreliable, yielding in some enclosures a correction of even the wrong sign.
Acoustical design of a radio broadcast studio using wood-frame construction
Authors: Angevine Eric Neil
Published: October 2005

A major-market, adult-contemporary radio station renovated a turn-of-the-century carriage house into offices and studios. Constraints imposed by the existing building shell included floor-to-ceiling heights and wood-frame construction. Acoustical performance was given top priority by the owner, to assure the finest broadcast facility possible. Special design techniques were used to provide adequate room-to-room insulation as well as insulation from exterior noise. Conflicting requirements included the second-floor location of studios and a large window in the on-air studio, facing a major city street. Mechanical equipment noise was adequately controlled despite many constraints imposed by space limitations of the existing building.
Airborne-sound transmission loss of wooden- and metal-stud partitions with sound-absorptive faces
Authors: Brown Steven M. , Niedzielski Joseph , Spalding G. Robert
Published: October 2005

Laboratory measurements are reported of the effect of sound-absorptive faces on the airborne-sound transmission loss of wooden-and metal-stud partition constructions. Data are discussed for commonly employed structures with two gypsum-board leaves and for structures incorporating a sound-absorptive face in place of one gypsum-board leaf. Sound-insulation behavior is examined for structures both with and without sound-absorptive faces or internal sound-absorptive material. For certain constructions, the use of sound-absorptive partition faces can result in significant improvements in mid- and high-frequency transmission loss.
Hearing thresholds for two teleost fish species with different peripheral auditory systems
Authors: Coombs S. , Popper A. N.
Published: October 2005

Behavorial audiograms have been obtained from two different species of squirrelfishes (Family: Holocentridae). Lowest thresholds measured for Myripristis kuntee were −50 dB re dyn/cm2 for frequencies extending from 300 to 2000 Hz, whereas best sensitivity measured for Adioryx xantherythrus was −28 dB at 500 Hz. While the low frequency end of the auditory range was at least 100 Hz for both species, the high end extended up to 800 Hz for A. xantherythrus and to 3000 Hz for M. kuntee. The two species tested can be taxonomically distinguished by anatomical differences in their peripheral auditory system. The genus Myripristis is characterized by anterior projections of the swimbladder which abut against the inner ear cavity, whereas in the genus Adioryx, the swimbladder lacks projections and is situated some distance away from the inner ear cavity [E. M. Nelson, Fieldiana: Zool. 37, 121–130 (1955)]. It is hypothesized that these anatomical variations affect the way sound reaches the inner ear, resulting in the reported differences in thresholds and frequency range of hearing. [Supported by NIH grant NS-15090.]
Hearing in the elephant (Elephas maximus)
Authors: Heffner Rickye , Heffner Henry , Stichman Ned
Published: October 2005

The auditory sensitivity of a 7-year old female Indian elephant was determined using a two-choice procedure. The animal was trained to initiate a trial by pressing a “center” button and was rewarded with flavored sugar water for pressing a button to its left if a tone was presented or for pressing a button to its right if no tone was presented. The elephant proved to be quite sensitive to low-frequency tones and could hear as low as 16 kHz at 65 dB SPL. The frequency of best hearing was 1 kHz at which the animal's threshold was 8 dB. However, the elephant proved insensitive to high-frequency tones and was unable to hear above 12 kHz at which frequency its threshold was 72 dB. The high-frequency hearing ability of the elephant is the poorest of any mammal yet tested and the failure of the elephant to hear much above 10 kHz demonstrates that the inverse correlation between head size (i.e., interaural distance) and high-frequency hearing ability is valid even for the largest of terrestrial mammals. Furthermore, this finding indicates that humans can no longer be considered unique among mammals for their inability to hear above 20 kHz. Instead, it appears that the upper limit of human hearing is a consequence of our relatively large size and not the result of any special adaptation for the reception of speech sounds. [Work supported by NSF grant BNS 78-07391 and NIH grant HD 02528.]
The discrimination of species-specific vocalizations by monkeys: Evidence for perceptual specializations?
Authors: Petersen Michael R.
Published: October 2005

The study of animal acoustic communication systems has, until recently, been confined largely to characterizations of the vocal repertoires of different species with few attempts to test directly a species perception of its sounds. The present study was an initial attempt to identify possible perceptual strategies that the Japanese monkey (Macaca fuscata) uses to process different aspects of its conspecific vocalizations. To assess the species specificity of any strategy that might be identified, several other Old World monkey species were tested under the same conditions as the Japanese monkeys. All subjects were trained, using operant conditioning techniques, to discriminate between two classes of acoustic stimuli which were composed of Japanese macaque vocalizations. In one discrimination task the animals were required to discriminate between acoustic classes containing stimuli differentiated by their valence on an acoustic dimension of communicative relevance to the Japanese animals. In a second task the animals were forced to attend to an orthogonal, less communicatively prominent dimension of the same vocalizations. The Japanese animals had little difficulty with the discrimination involving the communicatively relevant distinction but had considerable difficulty with the discrimination involving the orthogonal feature. The results for the comparison animals showed the reverse trend: they had more difficulty with the communicatively relevant discrimination than with the orthogonal feature task. The data seem to suggest that the Japanese animals are in some sense perceptually predisposed to attend to the communicatively significant aspects of their sounds in a fashion reminiscent of the humans' predilection to attend to the linguistically relevant aspects of their vocalizations. [Work supported by NSF and NIMH.]
Contralateral-probe measurements of the amplitude suppression and phase shift of one tone caused by another
Authors: Zurek P. M. , Sachs R. M.
Published: October 2005

Observers are capable of adjusting, independently, the amplitude and phase of a probe tone at the frequency of a contralateral test tone so that the intracranial image is centered. This ability has been used to measure the amplitude suppression and phase shift of a test tone brought about by a suppressor tone. Suppression patterns are asymmetrical functions of frequency, with high-frequency tones causing greater amplitude reductions of lower-frequency tones than the reverse. With a low-frequency suppressor at a fixed sound-pressure level, the amount of suppression decreases rapidly as test-tone level is increased above masked threshold. A suppressor of higher frequency than the test tone produces a nearly constant amount of suppression over a large range of test-tone levels. Under all stimulus manipulations a phase lag of the suppressed tone is observed that co-varies with the magnitude of amplitude suppression. Some of the complexities of tone-on-tone masking may be understood as resulting from signal suppression prior to detection, the amount of suppression being dependent upon the frequency and intensity of the masker. [Work supported by NINCDS Grant NS03856.]
Frequency selectivity measured by a forward masking paradigm
Authors: Kidd G. , Feth L. L. , Burns E. M. , Mason C. R.
Published: October 2005

Comparisons between psychophysical tuning curves and masking patterns obtained via forward masking will be presented. Tuning curves were measured for probe frequencies from 250 to 3000 Hz at 10 dB S.L. and 20 dB S.L. In general it was observed that sharpness of tuning as reflected by Q10 dB increased with increasing probe frequency. Masking patterns from the same subjects were obtained at corresponding masker frequencies and at sensation levels from 10–90 dB. Again, increasing selectivity was evident for higher frequency maskers. In all experiments the nonlinearity of the underlying forward masking function, for both similar and dissimilar probe-masker frequency sets, was apparent. Discussion will center on the implications of these findings for the use of forward masking to estimate the spectral resolution of the auditory system, as well as for the mechanism(s) of very short term auditory fatigue. [This work supported by a grant from NIH.]
Temporal properties of loudness matching in a forward partial masking paradigm
Authors: Pavel M. , Iverson G.
Published: October 2005

Loudness recruitment phenomenon induced by partial masking of a tone by noise was shown to be consistent with an automatic gain control type of model [M. Pavel and G. Iverson, J. Acoust. Soc. Am. 63, S18(A) (1978)]. The present study was intended to examine the temporal properties of such an adaptation process. In particular, we were interested in the course of gain recovery following the cessation of a masker. A forward masking paradigm was employed for both the detection of a brief stimulus and for loudness growth determined by loudness matching. The signal was a narrow band click centered at 1 kHz lasting for 10 ms and the masker was a 400 ms rectangular burst of white noise. The 2IFC paradigm was used for both detection and loudness matching. Our analysis focused on two aspects of the data: (1) the relationship of signal level to the masker level—homogeneity (expressed by a “signal to noise” invariance), and (2) the decay of the effect as a function of delay. The homogeneity considerably constrains the possible types of interaction between the masker and signal levels. The temporal effects were characterized at each delay in terms of equivalent noise level i.e., the level of noise required to achieve the same effect in a simultaneous masking condition. The results indicate that the equivalent noise for detection decays faster than that for loudness matching.
Forward masker cueing effects on backward masking
Authors: Harris Laura B. , Pastore Richard E.
Published: October 2005

The interactions of monaural backward and forward masking were examined to determine if a weak forward masker could serve as a timing cue to counteract a more intense backward masker. Employing an adaptive up-down procedure, the duration and intensity of the forward masker were manipulated for two different interstimulus intervals. At forward masker durations of 200, 50, and 10 ms, masker intensity was varied in 10 dB steps from 40 to 80 dBA. The signal was a 10 ms segment of a 2000-Hz sinusoid. The backward masker duration was held constant at 500 ms. The data indicate substantial reductions in backward masking as a function of the duration and intensity of the forward masker. Independent of the backward masker parameters, the greatest reductions in backward masking occurred with low intensity, long duration forward maskers. For weaker intensity maskers in isolation, significantly more backward than forward masking was obtained; with these weakest maskers in combination, backward masking was nearly eliminated, with the total amount of masking approximately equal to that obtained for the forward masker alone. The implications of these findings are discussed. [Research supported by grant NS 10995 from NINCDS.]
The coding of intensity and the interaction of forward and backward masking
Authors: Penner M. J.
Published: October 2005

The only qualitative explanation describing the interaction of combined forward and backward masking involves the temporal positioning of an integrator [C. Robinson and I. Pollack, J. Acoust. Soc. Am. 53, 1313–1316 (1973)]. We ran two experiments to test this model. In both experiments, noise masker levels were adjusted so that the maskers were equivalent (i.e., singly, each masker produced the same amount of masking of a click). First suppose, as the model states, that two long maskers, one forward and one backward, position the integrator. If so, then the addition of two more maskers should not affect the signal level by more than 3 dB. In fact, all four maskers result in 12 dB more masking than is produced by the two long maskers only. Second, we compare the masking effect of two forward maskers with that produced by one forward and one backward masker and find the same signal threshold in the presence of either set of equivalent maskers. Since integrator movement seems unlikely in the combined forward masker conditions, the model does not capture the major factor causing the interaction. We introduce an alternative quantitative explanation relating the interaction to the nonlinear coding of intensity. This hypothesis is tested in a third experiment in which we predict the click threshold in the temporal center of a silent interval separating a forward and backward masker. [Work supported by NSF.]
Analysis of synthetic vowels by pulsation threshold techniques
Authors: Brandt John F. , Bacon Sid P.
Published: October 2005

Auditory analysis of synthetic vowels /a and æ/ was investigated by the pulsation threshold paradigm. Vowel maskers were alternated with sinusoids with 50% duty cycle and period of 250 ms. Listeners varied the level of the sinusoid to pulsation threshold or to detection threshold (simultaneous masking). The pulsation threshold data generally parallel the envelopes of the vowel spectra at moderate SPLs (50–60 dB). At high SPLs, the pulsation thresholds representing the formant regions shift upward for F2 and downward for F3. The troughs between formants are not as deep as those at lower SPLs. In some individuals they fill up so that formant regions are not evident. Increases in SPL then do not necessarily lead to increased suppression. Simultaneous masking (detection) fails to show anything but the first formant. It appears that “upward spread of masking” which has been used to explain simultaneous masking data of vowels is only a decrease in suppression effects.
Temporal integration of multiple-component signals
Authors: Wakefield Gregory H. , Viemeister Neal F.
Published: October 2005

Thresholds for ten-tone complexes masked by continuous wide-band noise were determined for simultaneous and for sequential presentation of the components. Five component durations (10, 20, 50, 100, 200 ms) and four component frequency spacings (3, 6, 50, 200 Hz) centered at 2.5 kHz were used. Thresholds generally increased with increasing frequency spacing. For total durations of 200 ms or less and for a fixed component spacing, signal energy at threshold was approximately constant regardless of whether the components were presented simultaneously or successively. For durations longer than 200 ms and for small component spacings, signal power at threshold was approximately constant, in agreement with the data on temporal integration of pure tones. However, for large component spacings, threshold signal power continued to decrease up to at least 2000 ms. The results suggest that temporal integration precedes combination of information over disparate frequency regions. [Research supported by NINCDS and the Graduate School of the University of Minnesota.]
Detection of tones in band-reject noise. II. Effect of notch depth
Authors: Dubno Judy R. , Margolis Robert H.
Published: October 2005

The detectability of long duration (0.5 s), 1000-Hz, 50 dB SPL tonal signals was measured under several simultaneous noise masking conditions. First, the depth of an 84-Hz spectral notch removed from a wide-band noise was varied from 0 dB (wide-band condition) to −35 dB. The detectability of the tone centered in the notch was then measured as a function of “notch depth.” Next, detectability of the tone centered in an 84-Hz narrow band of noise was measured as a function of noise-masker level. Narrow-band maskers were presented at previous spectrum levels equivalent to the “notch depths” used in the previous experiment. Increasing the depth of the notch centered on the tone resulted in decreased detectability relative to the wide-band (or O-dB notch depth) condition. However, reducing the level of a narrow band of noise surrounding the tone resulted in increased detectability until subjects performed without error. Thus, reducing the level of the noise within a narrow notch centered on the tonal signal has the opposite effect of reducing the level of a narrow-band masker centered on the tone. The results will be discussed in terms of auditory edge effects. [Work supported by NIH.]
Two-tone masking in normal-hearing listeners
Authors: Rabinowitz W. M. , Bilger R. C. , Trahiotis C. , Nuetzel J.
Published: October 2005

Psychophysical measurement of two-tone masking [E. Zwicker, Acustica 4, 415-420 (1954)] were obtained at signal frequencies of 0.25, 0.5, 1, 2, and 4 kHz with seven masker separations tested at each signal frequency while utilizing a masker level of 62 dB SPL/ tone. Fifty-eight subjects were tested using a single run of a 4I-4AFC adaptive procedure for each condition. Although there were large individual differences, the average data were quite systematic. An objective technique (based on fitting two line segments to the data) was used to estimate critical bandwidths and values similar to those reported by others were obtained. These data and those of others will be discussed in terms of the effects of signal type (narrow-band noise versus tone) and masker level. A substantial increase in critical-bandwidth estimates is observed at high masker levels and may be accounted for by (a) the masking patterns produced by the individual tones of the two-tone complex, and (b) the removal of cues produced by aural nonlinearities. [Work supported by NIH.]
Some stimulus conditions and observer characteristics which affect the form of auditory receiver operating characteristics
Authors: Emmerich David S. , Binder David L.
Published: October 2005

Emmerich, Gray, Watson, and Tanis [Percept. Psychophys. 11, 65–72 (1972)] discuss some anomalies in the forms of receiver operating characteristics (ROCs) obtained in auditory signal detection experiments. In order to investigate these anomalies further, ROCs have been determined for two stimulus conditions: a standard diotic signal detection condition, and an increment-detection (pedestal) condition. A comparison of data obtained in these two conditions shows, as expected, that the increment-detection task yields ROCs with overall slopes closer to 1.0 on normal-normal coordinates. However, anomalies in the forms of the ROCs for the increment-detection task remain. Evidence will be presented to show that subjects have certain response proclivities (for example, a tendency to avoid making the same response twice in a row) which may act to distort the forms of ROCs. In addition, the likelihood that short-term sensory changes also influence the data will be considered. Some consequences of such effects for inferences drawn from signal detection experiments, and the use of signal detection measures, will also be discussed.
Sinusoid intensity discrimination, with gated and continuous maskers
Authors: Green David M. , Nachmias Jacob
Published: October 2005

Detectability of sinusoidal signals 10 or 100 ms in duration was measured in the presence of sinusoidal maskers of the same frequency. Maskers were either continuous or gated on and off with the signal. For both signal durations and both types of masker, ΔI/I varied with I raised to the −0.1 power, approximately. Psychometric functions were two or three times steeper with continuous as compared to gated maskers, while duration had a smaller and less consistent effect. [Work supported in part by a grant to the first author from the National Institutes of Health. Public Health Service, U.S. Department of Health, Education, and Welfare.]
Auditory intensity discrimination in the blackbird and pigeon
Authors: Hienz R. D. , Sinnott J. M. , Sachs M. B.
Published: October 2005

Redwing blackbirds, brown-headed cowbirds, and pigeons were trained using operant conditioning techniques to respond to small increases in the intensity of pulsed tone trains at three frequencies: 0.5, 1.0, and 2.0 kHz. All three species produced similar intensity difference limens (DLs) at the frequencies tested. Intensity DLs decreased as sensation level increased at all three frequencies, with the slopes of these sensation level functions being greatest at 2 kHz. The minimal intensity DLs at 50 dB sensation level were 3.3, 2.7, and 2.8 dB at 0.5, 1.0. and 2.0 kHz, respectively, averaged over the three species. Some subjects who were required to detect decreases in intensity produced intensity DLs two to three times larger than the DLs obtained when these subjects were required to detect increases in intensity. Comparative aspects of intensity discrimination will be discussed, and the relations between intensity discrimination and other aspects of hearing will also be considered.
Post-partum survival of mice exposed in utero to ultrasound
Authors: Edmonds P. D. , Stolzenberg S. J. , Torbit C. A. , Madan S. M. , Pratt D. E.
Published: October 2005

On day 8 of pregnancy we exposed pregnant Swiss Webster CFW mice to continuous ultrasound at 2 MHz, 0.5(± 10%) W/cm2 spatial average intensity [in the vacant water bath (37°C)] for 60, 100, 140, and 180 s. Estimated intensity at the uterus was 0.45(±20%) W/ cm2. By comparison with sham treated controls we found the ultrasound had no effect on the survival of neonatal mice through day 25 of age (84 to 108 neonates per group). This result may be compared with Curto's (1976) report [K. A. Curto, Ultrasound in Medicine 2, 535-6 (1976)] of 13% to 26.7% reduction in neonatal survival after exposure of CFI mice on day 13 of pregnancy to 1 MHz, 0.125 to 0.5(±20%) W/cm2 spatial average intensity [in the vacant saline bath (30°C)] for 180 s. Curto sought enhancement of exposure and her conditions could have resulted in intensities at the uterus as great as 1.0(±20%) W/cm2. We conclude that the expression of this end-point at (0.5 W/cm2, 180 s) as cited in summaries is at least questionable and is possibly dependent on other conditions of exposure. [Research supported by NIH grant ♯GM 22684.]
Effect of presentation probability on intensity identification performance
Authors: Bugnacki P. , Chase S. M. , Braida L. D. , Durlach N. I.
Published: October 2005

Identification experiments using 13 tone pulse stimuli (1000 Hz, 500 ms) spaced by equal decibel increments from 48 to 90 dB SPL were conducted under three conditions: EQ (all intensities equally likely, MF (the middle intensity presented on 13 of the trials, and EF (the two extreme intensities presented on 15 of the trials). Experiments were performed both with and without feedback and were analyzed in terms of sensitivity and bias. Similar results were obtained with and without feedback, except that sensitivities were generally higher with feedback. Listeners generally shifted decision criteria for the MF and EF conditions so as to increase identification performance, but did not improve sensitivity, relative to the EQ condition. These results are consistent with the effects of payoff variation [R. P. Lippmann, L. D. Braida, and N. I. Durlach, J. Acoust. Soc. Am. 59, 129–134 (1976)], but differ from those on the effects of presentation probability for tone frequency identification [L. L. Cuddy, J. Pinn, and E. Simons, J. Exp. Psychol. 100, 218-220 (1973)]. [Work supported by NSF.]
Stability of individual loudness functions obtained by magnitude estimation and magnitude production
Authors: Hellman Rhona
Published: October 2005

A correlational analysis of individual magnitude estimation and production exponents at the same frequency has been performed as well as an analysis of individual exponents produced across frequency (250, 1000, and 3000 Hz). Results show, in agreement with those of Wanschura and Dawson [J. Exp. Psychol. 102, 806-812 (1974)], that a moderately positive but not significant correlation coefficient is obtained between individual magnitude estimation and production data. However, strong positive correlation coefficients are found when individual magnitude estimation and production data are combined and then, compared across frequency. These results imply that individual differences in exponents not only persist over time but also remain stable across changes in stimulus frequency. Further results disclose that the slope (exponent) of the equal-sensation function between two different stimuli can be predicted from individual magnitude estimation and production data. Examples are given showing that the stability of individual exponents can be used to predict the slope of the loudness-recruitment function produced by ears with cochlear pathology, i.e., transitivity can be achieved for individuals.
The growth of loudness in the presence of a masking noise
Authors: Atkinson William H.
Published: October 2005

Under conditions of quiet, the subjective loudness of a pure tone increases with the cube root of the sound pressure for levels less than approximately 70 dB SPL. At this point there is a discontinuity of slope and a second linear process appears. Under conditions of noise, the threshold for the low level process is increased but the function remains linear and the slope is invariant with the level of noise. For the high level process, subjective loudness (S) can be represented by the equation: S = k(Ps0.33 − P00.33) 10−cPu/Ps, where Pa, Pn, and P0 are the pressures of the signal, noise, and threshold; k and c are empirical constants. The results which will be reported are consistent with Stevens' power law of sensation; the exponent is invariant under conditions of masking.
Approximations to Dolph-Cbebyshev data windows
Authors: Burgess John C.
Published: October 2005

A family of optimum data windows was presented recently [J. C. Burgess, J. Acoust. Soc. Am. 62, S51(A) (1977)]. These windows are optimum in the sense that their spectral representations have the narrowest main lobes possible for a specified ratio of maximum side lobe amplitude to main lobe amplitude subject to the condition that the windows are described by Fourier series having very few nonzero coefficients. The process by which the Fourier coefficients are determined is equivalent to fixing the amplitude of one lobe in the spectral representation for each nonzero coefficient. A Fourier series having M + 1 coefficients thus controls the amplitudes of M side lobes. The Dolph-Chebyshev windows have the narrowest main lobes possible, and all side lobes for each window have the same level. The windows described by Burgess can thus be thought of as approximations to Dolph-Chebyshev windows. For M + 1 = 4 (i.e., four nonzero Fourier coefficients), the approximations have main lobe widths less than 5% wider than the corresponding Dolph-Chebyshev windows.
Effect of element failure and random errors in amplitude and phase on the sidelobe level attainable with a linear array
Authors: Ramsdale Dan J. , Howerton Roger A.
Published: October 2005

Low sidelobe levels may be a crucial factor in the success of achieving high gain using linear receiving arrays, since the level of the sidelobes determines the degree to which noisy nearby sources can be prohibited from interfering with the detection of a weak source on a different azimuth. In real world experiments at sea, one frequently operates with an array which has not only errors in amplitude and phase between channels but also dead elements. The effect of random errors in both amplitude and phase is to yield a sidelobe level of the average beam pattern which is the sum of the error-free pattern and an additional level due to the random errors. The sidelobe level due to the random errors depends upon the details of the amplitude shading function, the distribution function from which the random errors are drawn, and increases with the mean square value of the errors. Thus, given rms values of amplitude and phase errors, there is a practical limit to which the sidelobes can be reduced by amplitude shading the array. The effect of element failure on the sidelobe level can be drastic and depends on the sum of the amplitude weights of the dead elements. Thus, a failure of a highly-weighted element will have a greater effect on the sidelobe level than the failure of two or three whose combined weights are less. [Work supported by NAVMAT.]
Simultaneous estimation of target range and bearing
Authors: Skinner D. P.
Published: October 2005

Simultaneous estimation of the range and bearing of a point target from a moving platform is discussed. The proposed approach exploits the relation between Doppler and bearing by transmitting into a broad sector and separating targets in bearing on the basis of their Doppler. The design of large time bandwidth product signals for this purpose is examined and a comparison is made of the range-bearing ambiguity function for simple waveform types. This work concludes with a brief inspection of the effects of focusing error on the range-bearing ambiguity function.
Directivity index of partially random sonobuoy arrays
Authors: Thorn J. V. , Booth N. O. , Lockwood J. C.
Published: October 2005

The directivity index DI of the partially random sonobuoy array described in a previous paper [J. Acoust. Soc. Am. 64, S123(A) (1978)] is analyzed. The analysis is based on the definition of DI as the ratio in decibels of the power received by a single omnidirectional hydrophone of unity gain to the array power normalized to unity maximum gain. The array power is a random variable. Its expected value is used in the definition of DI to define the “nominal DI.” The variance of the array power provides a measure of the variability of the DI among the members of an ensemble. The type of partially random array analyzed consists of N elements arranged in vertical strings of M elements each. With N constant, the variance of the array power tends to increase as M is increased. The increase is the result of the increasingly large contribution to the array power of the side-lobes at the main lobe elevation, which have a relatively large variance. The effects of the number of elements per string on the nominal DI and on the variability of the DI are examined quantitatively.
Multipath induced corruption of bearing estimation by split ring hydrophones
Authors: Cater Jack E.
Published: October 2005

A single acoustic plane wave, insonifying a four piece, split ring hydrophone, produces voltages in orthogonal directions proportional to the cosine and sine of the bearing to the source with respect to some reference direction. In certain circumstances, e.g., shallow water, multipath conditions exist where comparable energy contributions are made from several paths along the same bearing. If the contributions are in phase or nearly in phase at the hydrophone, voltages similar to those of the single plane wave case are observed. In general, however, the phases are different and the voltages consist of series of products of Bessel functions related to phase difference, hydrophone radius and frequency, and sines and cosines of the fundamental frequency and harmonics of the source.
Excess attenuation or impedance of common ground surfaces characterized by flow resistance
Authors: Piercy J. E. , Embleton T. F. W.
Published: October 2005

The excess attenuation due to the presence of the ground has been measured at several different sites using two fixed configurations of point source and receiver. These were source height 1 ft, and receiver location either 1.5 ft high at 25 ft from the source, or 4 ft high at 50 ft. Assuming that the ground surfaces can be considered locally reacting and that their specific normal impedances can be adequately described by their specific flow resistance (Chessell's model, following Delany and Bazley) we have predicted the spectra of excess attenuation using flow resistance as parameter. Comparing a measured spectrum of excess attenuation with the set of predicted spectra enables one to ascribe an approximate value of specific flow resistance to the ground surface. In this way we find the following ranges of values from both our own and other people's measurements: snow (depends strongly on weather conditions and age), 2 to 20 cgs units; shaded ground in mature forest, 25 to 50; plowed and freshly disked sandy loam, about 50; many different grass sites in several countries, 150 to 300; settled earth with many weeds (but not as dense as “grass”), about 800 to 1000; limestone chips of 12 to 1-in. size with open voids, 800 to 2000; hard compacted quarry dust, 1000 to 2000; sandy silt well packed by passage of vehicles, about 1000; concrete or mature asphalt, about 20 000 and perhaps greater.