bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Experiments on Fan Noise and Their Implications
Authors: Lowson Martin V.
Published: October 2005

Noise output from an open rotor has been measured in an anechoic room. Simultaneously measurements of the aerodynamic input to the fan have been made. The aeroacoustic transfer function has thus been measured and compared to various theoretical models. Results suggest that the fan noise output is due to three sources, distorted inflow, turbulent inflow, and self-generated tip noise. The latter source is significant at higher frequencies and may dominante subjective noise levels for both ventilating fans and low-speed geared fans for aircraft use. It appears that this noise source can be successfully attacked via blade-tip modifications, which can give noise reductions of over 10 dB.
Frequency Discrimination for FM Chirps of Various Bandwidths
Authors: Ronken Don A.
Published: October 2005

Gated sinusoids with linearly changing frequency and essentially rectangular power spectra were used as signals in a frequency discrimination experiment. Signal bandwidths of 10, 50, 200, 500, and 1000 Hz were produced by changing the extent of frequency modulation for a fixed-duration chirp. The 100-msec FM chirps were generated digitally with 10-msec linear rise/fall times and presented at 70 dB SPL in a continuous wide-band noise of 0-dB spectrum level. One of the two observation intervals in a 2AFC experiment always contained a chirp that had a center frequency of 750 Hz. The other interval contained an identical chirp, except that its center frequency was 750+Δf Hz. The Δf required for 75% correct discrimination (Δf75) was estimated from individual psychometric functions for each of four experienced listeners. As the bandwidth of the chirp increased from 50 to 1000 Hz, the increase in Δf75 was almost proportional to the square root of the signal bandwidth. FM chirps with a bandwidth of 10 Hz are slightly more discriminable in frequency than a gated pure tone of the same duration at the same center frequency. The direction of frequency modulation, to higher or lower frequency, had only a small effect, even at the largest bandwidth.
Prediction of Road Traffic Noise
Authors: Kurze U. J.
Published: October 2005

A computer model for the prediction of noise from freely flowing road traffice is described. The model allows one to account for simple statistics of point sources (spatial distribution and radiated sound power) and for sound propagation with attenuation, diffraction, and reflection. The basic statistical parameters of the fluctuating noise calculated at a receiver are the cumulants of the sound intensity. These cumulants are employed to calculate probability distributions of the SPL as well as single number criteria currently used for the description of fluctuating road traffic noise. The computer model has been developed for the Transportation Systems Center, Cambridge, Massachusetts.
Binaural Analysis as a Function of Physiological Masking
Authors: Lindsey J. W. , Soderquist D. R.
Published: October 2005

Five normal-hearing subjects served as observers in a yes/no signal detection task for four different frequencies (100, 200, 300, and 5000 Hz). Two binaural listening conditions were used at all frequencies such that the interaural phase was either 0° (S0) or 180° (Sπ). Signals had a duration of 100 msec and a rise-decay time of 10 msec. All data were collected at absolute threshold. Binaural sensitivity (d′) was examined as a function of two signal onset delays in terms of the cardiac cycle (EKG R wave) of each subject. The selected delays were either coincident with the R wave (0.0 sec) or 0.5 sec later. The experiment was an attempt to investigate the possibility that the absolute threshold varies as a function of physiological masking provided by cardiac sounds. Initial results indicate substantial detection advantages associated with the 0.5-sec time delay. These data as well as the decrease in this advantage as frequency increased suggest that signals presented coincident with the EKG R wave axe masked by the cardiac sound.
Acoustical Wavetrain Signals and Equal Loudness Pressures
Authors: Victoreen John A.
Published: October 2005

Equal loudness measurements were made for 12 young adult ears over a frequency range of 250–6000 Hz. A damped wavetrain signal having a decrement of 0.90 was used and this was delivered by a pair of circumaural earphones. A well-defined but empirical relationship is shown to exist between relative loudness and sound pressure and the mathematical expression is given. Observational accuracy attainable was, when averaged, usually consistent with the calculated values to within about 12 dB over a pressure range of about 0.0001–100 μbars. With this method of measurement comfortable loudness pressure for the normal ear was found to be independent of frequency over the normal frequency range. Damped wavetrains with circumaural earphones appeared to give about four times greater accuracy than pure tones and supraaural earphones for identical measurements.
Human Monaural Localization of Noise
Authors: Gatehouse R. W. , Cox W.
Published: October 2005

Eight normals matched on age and sex with eight monaurally deaf subjects were compared on their ability to localize a brief white noise source. The monaurals were classified as sensorineural, and “severely” to “profoundly” deaf (ISO, 1964). The subjects' task was to localize eight 45° (0° azimuth reference) positions on each of five planes (the aural axis and planes 15° and 30° above and below it). Four different predetermined blocks of 40 randomized trials each were used. Therefore, each subject localized each position four times for a total of 160 responses per subject. The trial blocks were presented in two different orders to half of the subjects in each group. Matched subject pairs received the same order. The results showed that (1) monaural localization was above the chance level on all horizontal planes, although significantly inferior to binaural localization; (2) in the vertical planes, binaural and monaural localization ability did not differ; (3) monaurally, “normal” ear-side localization is highly accurate and the mean size of errors on that side is smaller; (4) for both groups errors were made by displacement of sounds to the rear of the “true” position; (5) head movements are not necessary for accurate monaural localization. These results will be discussed in the light of several previous findings.
Acoustic Measurements in the West Greenland Sea
Authors: Bradlev D. L. , Colvin G. M.
Published: October 2005

Acoustic ambient noise, transmission loss, and reverberation measurements were made in the West Greenland Sea at the edge of the permanent polar ice pack during the fall of 1971. The data were collected with the assistance of the U. S. Coast Gaurd, while deployed on one of its oceanographic data collection cruises. The sound sources for transmission loss and reverberation measurements were standard U. S. Navy explosive sound signals. The receiving system consisted of calibrated sonobuoys that were monitored both from helicopters and the Coast Guard ice-breaker. Ancillary environmental data were provided by the Coast Guard and ice conditions and ice cover information was provided by U. S. Navy ice observers. The results of data analysis are presented and compared with data from similar arctic environmental conditions. [Work supported by U. S. Naval Air Systems Command.]
Convergence Zone Propagation in the North American Basin
Authors: Shaffer John D.
Published: October 2005

The long range propagation of a CW 14-Hz signal was studied experimentally. A shallow source was towed across the North American Basin to a maximum range of about 2700 km. The signal was received on a sound channel hydrophone and the envelope recorded. Well-defined convergence zones were observed over the major extent of the tow. The existence of this mode interference wavelength as a sharp spectral line is shown in a power spectrum calculation of the envelope squared versus range.
BIFI—Normal-Mode Generation with a Vertical Array of Projectors
Authors: King L. A.
Published: October 2005

This paper describes first results from a continuing study of normal-mode generation and propagation in shallow water. A novel experimental tool used in this study is a vertical array of 25 sound projectors. With it, fundamental work has been conducted using its directional properties to transmit acoustic energy in an optimal manner. The basis of this work presumes the shallow-water channel to propagate “favored” modes. Their optimal transmission should occur by steering the acoustic energy with the array into boundary-grazing angles associated with the development of these modes. Ground work was laid using the array without time delays or amplitude shading to study patterns generated under a wide variety of propagation conditions. Measurements, made in March 1971, are presented here that depict patterns observed under isothermal conditions.
Lateralization and the Critical Period
Authors: Krashen Stephen , Harshman Richard
Published: October 2005

The percent of errors method, described in Harshman and Krashen above, was applied to dichotic listening data for children between 5 and 10 years old. No significant change in degree of lateralization was found. This supports the hypothesis that the development of lateralization is complete by age five, rather than by puberty, as argued by Lenneberg. Data cited by Lenneberg, as well as additional cases, were examined. Analysis of cases of acquired aphasia in children resulting from localized lesions revealed that right-sided lesions do not cause more cases of speech disturbance after five than in adults, indicating that the involvement of the right hemisphere in the language function in children older than five is the same as in adults; this also supports the age five hypothesis. Not enough crucial data is available from hemispherectomies to decide between the two hypotheses. The completion of lateralization by five implies that lateralization reflects the maturation of some essential component of the language faculty, rather than the termination of “organizational plasticity,” as suggested by Lenneberg.
Mutual Interference between Two Linguistic Dimensions of the Same Stimuli
Authors: Day Ruth S. , Wood Charles C.
Published: October 2005

In a previous study subjects identified binaural stimuli that varied along both a linguistic and a nonlinguistic dimension. The linguistic dimension consisted of variation in stop consonants while the nonlinguistic dimension consisted of variation in fundamental frequency. There were four stimuli: /ba/—low, /ba/ high, /da/—low, /da/—high. Reaction times were obtained in a two-choice identification task when the target dimension was the only one that varied. When there was also irrelevant variation in the nontarget dimension, reaction times increased substantially for the linguistic dimension, but only slightly for the nonlinguistic dimension. Thus the nonlinguistic dimension interfered with the processing of the linguistic dimension more than vice versa. The present study employed the same paradigm, but used two linguistic dimensions: stop consonants and vowels. The stimuli were /ba, bæ, da, dæ/. Reaction times increased substantially for both dimensions when there was also irrelevant variation in the nontarget dimension. Thus both dimensions interfered with each other to the same extent. On the basis of the dimensions examined in this paradigm thus far, it appears that two linguistic dimensions yield a mutual interference effect, while a linguistic and a nonlinguistic dimension yield a unidirectional effect.
Dichotic Fusion along an Acoustic Continuum
Authors: Cutting James E. , Day Ruth S.
Published: October 2005

When stimuli such as banket and lanket are presented dichotically, phonemic fusions often occur: subjects report hearing blanket. Previous studies have shown that stop +/r/ and stop +/l/ items have different fusion properties. For example, /l/ was sometimes substituted for /r/ (but rarely vice versa): gocery/rocery → (yielded) glocery. The present experiment varied the liquid stimuli along an acoustic continuum involving the third formant transition. For example, one set varied from ray to lay. Each was paired dichotically with an initial stop stimulus, in this case pay. All inputs (pay, ray, lay) and possible fusions (pray, play) were acceptible English words. When asked to report “what they heard,” subjects gave many fusion responses. Of these, there was a preponderance of stop +/l/ fusions (88% vs 12%). They occurred even for pairs where the liquid item was reported as an /r/ during separate binaural identification trials. Thus, given that an item was identified as ray, the same subjects reported hearing play when it was paired with pay: pay/ray → play. Despite the fact that the third formant transition is crucial for perception of /r/ vs /l/, this parameter was not responsible for the observed phoneme substitutions.
The Effect of a Word Boundary on the Perception of Timing in Speech
Authors: Huggins A. W. F.
Published: October 2005

Earlier work has shown that a change in the duration of one acoustic segment in a sentence sometimes does, and sometimes does not, require a compensatory change in an adjacent segment [A. W. F. Huggins, J. Acoust. Soc. Amer. (to be published)]. For example, in the words for paupers, compensation was required between the vowel in for and the initial p in paupers, but was not required between the initial p and the stressed first vowel in paupers. These and other results suggest that the presence or position of a word boundary may influence the need for compensation. An experiment has been designed to investigate more carefully the role played by a word boundary. The results have implications for the organization of speech production.
Multistate Dissociation and Sound Absorption in Sea Water
Authors: Fisher F. H. , Bezdek H. F.
Published: October 2005

At 75 kHz, the observed decrease of sea water sound absorption with increasing pressure is about twice that predicted from the multistep dissociation parameters selected by Eigen and Tamm [Z. Elektrochem. 66, 92–121 (1962)] to explain sound absorption in aqueous solutions of MgSO4 the salt responsible for sound absorption in sea water. To account for such a large pressure effect requires the equivalent of a single chemical reaction with a ΔV≃36 cm3/mole; for example, two successive chemical reactions each with a ΔV≃18 cm3/mole. The results are discussed in terms of three-step and two-step dissociation models. Included in our considerations are Millero's results [Geochimica et Cosmochimica Acta 35, 1089–1098 (1970)] obtained independently of acoustic data, which show only a small decrease with pressure for the concentration of MgSO4 ion pairs. [This paper represents results of research sponsored by the Office of Naval Research and the National Science Foundation.]
Small-Size High-Efficiency Underwater Loudspeaker
Authors: Lubell Alan H.
Published: October 2005

An improved underwater loudspeaker covering the frequency range from 200 Hz to 5 kHz has been developed. This transducer combines small size and high efficiency. It yields speech reproduction comparable to medium fidelity air acoustic loudspeakers. This device has been used successfully as part of a portable underwater communication system for instruction and recall of a group of swimmers or divers. Using the underwater hearing thresholds of Brandt and Hollien, estimates of range are made for the above system and compared to test results.
Relation of Hearing Impairment to Noise Exposure and Age
Authors: Botsford James H.
Published: October 2005

An equation relating prevalence of impaired hearing to age and noise exposure has been derived. It is based on the assumption that the probability of developing impaired hearing at any age is proportional to the fraction of the population of that age which has already developed impaired hearing. In other words, the stress on the auditory system of living to any age is indicated by the prevalence of impaired hearing at that age. If there is also exposure to dangerous noise, the probability of impairment increases with the severity of the exposure. The solution of the differential equation resulting from these assumptions reveals a complex relationship of age and noise exposure to impairment. The effects of age and noise are shown not to be simply additive as is often assumed.
The Syllable Nucleus as a Unit of Timing
Authors: Lehiste Ilse
Published: October 2005

The paper explores the question whether resonants preceding and following a vowel can be considered as part of the syllable nucleus. A set of monosyllabic words was studied, beginning and ending with voiced and voiceless obstruent consonants, and containing syllable nuclei of the following types: V (long and short), V+R, R+V, and R+V+R. Three speakers produced each of the 156 words five times. An analysis of the durations of the segments yields (a) that syllable nuclei consisting of V+R function as a unit with respect to the timing patterns conditioned by the voicing of the following consonant, and (b) that resonants combine with long vowels in such a way that the durational differences between syllable nuclei of the types V, V+R, and R+V are below the perceptual level (i.e., below established difference limens for duration). The evidence is considered as supportive of the assumption that timing in speech is organized with reference to major changes in manner of articulation.
Pure-Tone Octave Masking in Listeners with Sensorineural Hearing Loss
Authors: Bilger R. C. , Nelson D. A.
Published: October 2005

Phase-locked pure-tone masking was investigated in 16 listeners with sensorineural hearing loss to examine the hypothesis that the sensorineurai ear introduces abnormal distortion. Thresholds for a pure tone at f2, masked by a pure tone at f1 (where f2=2f1), were obtained as a function of the level of the f1 masker for three different f1 frequencies (250, 500, and 1000 Hz) and two different phase relations between f1 and f2 (90° and 270°). Estimates of the level of the aural harmonic were obtained from those masking functions. Analysis of the data in terms of the absolute level of f2 at masked threshold versus the absolute level of f1 results in a conclusion that these pathological ears do not perform differently from normal ears, except along the dimension of hearing loss. That is, their hearing loss does not add significant distortion to the acoustic signal. Even though the present analysis suggests that evaluation of the data for pure-tone octave masking in terms of SL leads to the specious conclusion that the sensorineural ear introduces abnormal distortion, an attempt was made to relate hearing loss to the aural harmonic in less simplistic terms [Research supported by grants from the NINDS of USPHS.]
Nonlinear Inverse Filtering
Authors: Rothenberg Martin
Published: October 2005

It has been shown by Flanagan and Landgraf [IEEE Trans. Audio Electroacoust. 16, No. 1, 57–64 (1968)] that in the transformation between glottal area and glottal volume velocity during voiced vowels, the effect of the interaction between the acoustic impedance of the glottis and that of the supraglottal vocal tract cannot always be neglected. When there is such interaction, the glottal-supraglottal acoustic system must be considered a nonlinear system with time-varying parameters. Thus, any inverse-filtering process designed to extract the glottal area waveform from measurements of supraglottal pressure or air flow must also be nonlinear. This paper reports initial efforts to determine the conditions under which a nonlinear inverse-filtering process exists that will yield a function directly related to glottal area from recordings of oral volume velocity, and how such a nonlinear inverse filter could be implemented.
Dolphin Communication
Authors: Caldwell David K.
Published: October 2005

A history of research and writing (the two not necessarily synonymous) regarding dolphin communication will be presented along with a summary of the present trends in thinking regarding this somewhat controversial topic. The primary emphasis will be placed on the “vocal” aspects of dolphin communication, but other methods of communication in this mammalian group will be outlined; i.e., such things to be discussed are non-“vocal” sounds such as the jaw clap and tail slap, body postures and positions, tactile contact, and pigmentation patterns. Signal detection systems in the dolphin will be considered as they relate to the apparent signal emission systems. Behavioral correlates will be outlined for many of these communication modes, and various experiments described that bear on the matter of whether or not presumed communication modes are indeed used for this purpose. Special attention in this regard will be given to the whistle component of the communication process.
Tire-Road Interaction Noise
Authors: Leasure William A. , Bender Erich K. , Bollinger Robert H.
Published: October 2005

The relative importance of tire noise to overall vehicle noise is established. A general discussion is given of the considerations of the tire engineering process and design procedure followed in the manufacture of a tire. The important parameters influencing tire noise are discussed based on the physical data base as it exists today and unknown and contradictory areas are identified. The basic mechanisms of tire-noise generation, although not well defined, are investigated from a theoretical viewpoint. Areas for future research and development are identified based on gaps in the existing physical data base.
The Nature of Sound Fluctuation in the Upper Ocean. I
Authors: Neubert J. A.
Published: October 2005

In this critique of sound propagation studies in turbulent fluids, the interpretations and limitations of some well known scattering theories and experiments are brought into question. First, some earlier theories of sound propagation in the turbulent ocean are reviewed. Second, some of the more recent developments in the analysis of sound propagation in turbulent fluids are presented. Finally, the earlier results and the contemporary accomplishments are compared in the single-scattering and one-dimensional cases. The more important revelations and confirmations, based on Part I, are reserved for Part II where it is shown, on the basis of turbulent scaling, that the scattering theories of Bergmann, of Mintzer, and of Potter and Murphy deserve closer scrutiny and that the Stone and Mintzer experiments were misinterpreted.
The Origin of N2 of the Cochlear Whole-Nerve Action Potential
Authors: Pugh J. E. , Anderson D. J. , Burgio P. A. , Horwitz M. R.
Published: October 2005

Several studies exist concerning the nature of the cochlear whole-nerve responses to acoustic transients. All focus on the properties of the first negative deflection N1, but none offers a satisfactory explanation for N2. A number of lines of evidence are here presented to support the concept of separate loci of generation of N1 and N2: (1) Changes in relative position of recording electrodes produce differential changes in amplitude of N1 and N2; (2) paired-click studies permit electrical summation of an N2 response with a succeeding N1 response; (3) high-frequency noise masking attenuates N1 to a greater degree than it does N2; (4) certain intensities of low-frequency masking attenuate N2 to a greater degree than they do N1; (5) a narrow-band noise-induced temporary threshold shift between 6 and 14 kHz, in behaviorally trained monkeys with chronic electrical implants, causes a marked reduction in N1 amplitude but no significant change in N2; (6) selective cooling of the apex of the guinea pig cochlea results in a relatively greater reduction in N2 than in N1. These and other lines of evidence suggest that the N2 potential may be arising from a more apical region of the cochlea than N1. [This work was supported by the John A. Hartford Foundation and by NIH.]
Optimal and Preferred Listening Levels for Speech in Aircraft Acoustical Environments
Authors: Robertson R. M. , Williams C. E.
Published: October 2005

There is some question as to whether pilots and aircrew personnel routinely adjust the audio level of their radio receivers for maximum speech intelligibility and minimal damage risk to hearing. In an effort to answer this question, data have been obtained on the preferred listening levels (PPLs) of student naval flight officers in aircraft acoustical environments. Thirty subjects were given the task of tracking continuous speech in quiet and in the presence of three levels of background noise (70, 85, and 100 dB SPL). They were asked to adjust the level of the speech for maximum intelligiblilty. Two different tracking procedures were employed: one utilizing a Békésy-type switch and the other an adjustable hold-type switch, similar to a normal radio gain control. PLLs obtained for the three noise conditions revealed that as the noise level decreased, the subjects preferred a more favorable signal-to-noise ratio. Normative PLL data and intelligibility test data for selected signal-to-noise ratios will be presented and discussed.
Reduction of Noise Generated by Flow of Fluid over Plate
Authors: Pinkel B. , Scharton T. D.
Published: October 2005

This paper describes a method of reducing the noise generated by a fluid stream flowing subsonically over the edge of a plate and also presents some substantiating test data. This concept may prove useful for reducing the noise of STOL aircraft employing the externally blown flap or the augmenter wing, which configurations are now under exploratory development.
Speed of Pitch Change
Authors: Ohala John J. , Ewan William G.
Published: October 2005

In an attempt to determine the response characteristics of the larynx in voluntary pitch change, five adult male subjects were instructed to execute a variety of continuous pitch changes, as rapidly as possible, within the range 90–220 Hz. For a given pitch interval, there was a marked tendency for all upward pitch change to take longer than a downward pitch change. Also, unexpectedly, there was no marked tendency for a change involving a wide pitch interval to take longer than a change involving. a smaller interval. Speculations on the physiological reasons for these relations, as well as their possible relevance to the phonology of tone and intonation, will be offered. [Supported by the National Science Foundation and a University of California Faculty Research Grant.]
Pure-Tone and Speech-Evoked Responses in Normal and Noise-Exposed Squirrel Monkeys
Authors: Maioriello Richard P. , Wilpizeski Chester R.
Published: October 2005

Monkeys were implanted with permanent recording electrodes having tips placed in the auditory nerve-cochlear nucleus region. AP input-output relationships and VDLs were obtained from computer-averaged evoked responses to pure-tone pulses and selected monosyllabic words before and after five consecutive daily 15-min exposures to 115 dB SPL of steady broad-band noise. Threshold shifts and sustained reduction in AP amplitudes occurred at higher frequencies. Response patterns evoked by speech appeared coded in the form of amplitude modulation, and words could be identified by the summed waveform associated with each stimulus. Response patterns for some words were altered by noise exposure. Results suggest that noise intensity-duration combinations currently accepted as nonhazardous to hearing (on the basis of TTS recovery) may produce persistent changes in hearing function for suprathreshold sounds, and that speech reception may be altered by noise stimulation followed by only minimal changes in pure-tone VDLs.
Asymptotic TTS in Chinchillas
Authors: Melnick William , Migliore Mariann , Lim David
Published: October 2005

Six chinchillas were monauralized and were trained to produce behavioral audiograms using a shock avoidance procedure. The animals were then exposed to a 300- to 600-Hz octave band of noise at 85 dB octave band level for a period of 96 h. Thresholds were measured at 10 test frequencies ranging from 250 to 8000 Hz at varying intervals during the exposure. Results from the present investigation were remarkably similar to those reported by Carder and Miller (1960). The growth of TTS followed a triphasic pattern. Initially there was a period of slow growth which lasted approximately 6–12 h; then there was a period of rapid growth, and finally an asymptote was reached after a period of 24–48 h. The asymptote obtained in the present investigation was predicted fairly well by the equation TTS = 1155 (octave band level −65). All 10 of the test frequencies showed TTS. Recovery from asymptotic TTS was complete for most animals by 12 days postexposure, slightly longer than that reported by Carder and Miller. [Partially supported by Air Force Contract.]
Under-Ice Reverberation Modeling by Means of Multiple Regression
Authors: Birch W. B.
Published: October 2005

Multiple regression techniques are being used to produce a model of under-ice reverberation when minimal information exists concerning the nature of the under side of the ice. Field recorded acoustic data have been used to generate a series of equations that estimate the reverberation signal at the transducer face for each of several times following transmission of an acoustic pulse. The highest percentages of explained deviation have been obtained using a linear regression equation of the form Y′ = b0+b1X1+b2X2+b3X3+b4X4, where Y′ is the signal amplitude; X1, X2, X3, X4 represent, respectively, the independent variables of transducer elevation angle, pulselength, depth, and beamwidth; and b0, b1, b2, b3, b4 are the regression coefficients. Confidence limits for the coefficients and the relative contribution of each variable to the regression are provided by an analysis of variance. The final model is intended to permit prediction of the reverberation sound pressure level at a transducer face for known transducer acoustic and physical parameters.
An Investigation of Internal Combustion Engine Silencing Using Reflection and Absorption Phenomena
Authors: Mukherjee A. , Mitchell W.
Published: October 2005

An investigation has been made to determine the most influential parameters for efficient silencer design. These parameters lead to new insights into silencer operation containing both reflection and absorption phenomena, where damping is found to be effective at lower frequencies. Hence, objectionable deep exhaust tones of engines at frequencies of about 80–100 Hz can be significantly reduced. Efficient and economic silencing of engine exhaust noise can be applied to a large number of internal combustion engine installations including 2- and 4-cycle engines—e.g., cars, buses, trucks, locomotives, lawn mowers, chain saws, and motorcycles. Two important factors were considered simultaneously, i.e., the aerodynamic criterion (which specifies the maximum permissible average pressure drop through the silencer at a given temperature and mass flow) and the geometrical criterion, which specifies maximum allowable volume and restrictions on shape. Results of this study are: (1) Identification of parameters influential to silencer design. (2) A better understanding of silencer operation incorporating reflection and absorption phenomena. (3) A more efficient overall silencer system. (4) Lower noise levels associated with internal combustion engine operation.
Vibration Suppression in Wood Planer Noise Control
Authors: Hart F. D. , Ferioli D. A. , Stewart J. S.
Published: October 2005

Board vibration has been identified as the dominant noise generating mechanism for a majority of wood planers. The effectiveness of compact enclosures is greatly diminished owing to board vibration, since a portion of boards of normal stock length is always outside of the enclosure. A vibration suppression system has been designed to operate inside of an enclosure to reduce the amount of vibratory energy transmitted outside through the boards being machined. The system developed and its effectiveness in reducing wood planer noise when used in conjunction with a compact enclosure is described in detail. [Newman Machine Company and NASA are acknowledged for support of this work.]
The Equation of State of Water and Seawater as Determined from Sound Velocity Data
Authors: Fine Rana A. , Wang Dong Ping , Millero Frank J.
Published: October 2005

Using the high-pressure (0 to 1000 bars) sound-velocity measurements of Wilson (1960), an equation of state for PVT properties of water and seawater has been developed based on a modified Tait equation of the form V°−VPV°P=1B+A1P+A2P2, in which V° is the specific volume at atmospheric pressure, VP the specific volume at pressure P, and B, A1, and A2 are functions of temperature and salinity. The equation has been fit with a maximum deviation in compressibility of 0.01×10−6 bar−1 for seawater and 0.02×10−6 bar−1 for pure water. The data from this equation will yield specific volumes that show the excellent consistency of Ekman's (1908) measurements with the sound data. The results for pure water show a definite shift in Kell and Whalley's (1965) measurements and the superiority of the PVT data generated from the sound data to direct experimental measurements.
Acoustical Testing of Potentially Hazardous Noise-Producing Toys
Authors: Cadoff Marilyn A. , Blomquist Donald S.
Published: October 2005

In recent years, a great concern has been expressed for consumer protection and safety, especially for children. As an outgrowth of this concern, acoustical testing of potentially hazardous noise-producing toys has been carried out at the National Bureau of Standards for the Bureau of Product Safety (FDA). This talk will discuss the work that has been done on cap pistols and carbide cannons. The discussion will focus particularly on the development of a standard firing apparatus for testing paper caps, and on the problems encountered and the solutions arrived at for testing carbide cannons.
A Parallel between Degree of Encodedness and the Ear Advantage: Evidence from an Ear-Monitoring Task
Authors: Cutting James E.
Published: October 2005

Some phoneme categories undergo more acoustic variation in different environments than do others. The phonemes that undergo the most context-conditioned variation are said to be highly encoded. There appears to be an encodedness continuum, extending from the highly encoded stop consonants through the liquids and other sounds, and finally to the least encoded vowels. Stop-liquid-vowel nonsense syllables such as GLAE were used in a dichotic ear monitoring task. There were two possible phonemes in each class: /g/ and /k/ for stops, /l/ and /r/ for liquids, and /æ/ and /e/ for vowels. Subjects reported only the syllable presented to a given ear for each block of dichotic trials. Primary analyses were performed on phoneme contrast trials, e.g., GLAE/KLAE for stops, GLAE/GRAE for liquids, and GLAE/GLEH for vowels. Data were scored in terms of percent-correct phoneme identifications for each ear. There was a large right-ear advantage for stops, a smaller right-ear advantage for liquids, and no ear advantage for vowels. The ordering of phoneme classes along the ear advantage continuum, therefore, was in parallel with the ordering of the same classes along the encodedness continuum.
Masking with Ripple Noise and Spatial Frequency Analysis
Authors: Yost W. A. , Bergert B.
Published: October 2005

A low-pass noise (1500-Hz cutoff) with a sinusoidal variation in its amplitude spectrum (ripple noise) was used to mask a 1000-Hz signal (10 msec) in both a forward and a simultaneous masking procedure. The masked thresholds of the signal were measured as a function of the number of peaks (ripples) in the amplitude spectrum of the noise. The procedure was similar to that used by Houtgast who reported it at the 83rd meeting of the Acoustical Society. Houtgast used a pulsation threshold technique with ripple noise to study frequency selectivity. Pulsation threshold is similar to simultaneous forward and backward masking. The data of the present study indicate that results similar, but not identical, to Houtgast's can be obtained with forward masking alone. The frequency selectivity obtained with the forward masking procedure is sharper than has been previously obtained and might indicate the presence of lateral inhibition.
Phonetic Disambiguation of Syntactic Ambiguity
Authors: Lehiste Ilse
Published: October 2005

It has been frequently claimed that the meaning of syntactically ambiguous sentences (such as “Visiting relatives can be a nuisance”) can be made explicit by phonetic means such as stress and intonation. This study describes some ways in which such disambiguation can be accomplished. Fifteen ambiguous sentences were first read by four speakers. The ambiguities were then pointed out, and each speaker stated which meaning he had intended to produce. Each sentence was then produced again twice, the speaker making a conscious effort to differentiate between the two potential meanings. Thirty listeners tried to identify the meaning which the speakers had intended. In 10 out of 15 cases, listeners performed at better than chance level, which implies that the intention of the speakers was successfully communicated to the listeners. The suprasegmental patterns employed by the speakers in successful disambiguation were established by acoustic analysis. While stress and intonation play a part, timing seems to have been the principal means by which the two meanings of the sentence were differentiated.
Parametric Echoscanner for Biomedical Diagnostics
Authors: Muir T. G. , Talkington C. M. , Shaw B. S. , Adair R. S. , Willette J. G.
Published: October 2005

The nonlinear interaction of two high-frequency high-intensity waves to produce a highly directive difference frequency wave is known to be of value for systems requiring good angular resolution at operating frequencies not limited by absorption. The technique has recently been successfully applied to problems in marine bathymetry [J. Acoust. Soc. Amer. 50, 1085–1087 (1971)] and archeology [Paper F6, 83rd Meeting, Acoust. Soc. Amer.]. An analysis of the potential utilization of this technique in ultrasonic diagnostics is presented in the present paper. This analysis includes a comparison of parameters attainable by both nonlinear and conventional methods, as well as a design description of a prototype parametric echoscanner. This device utilizes a 0.25-in. piston to transmit interacting waves at 7.25 and 8.75 MHz. The results of measurements on the amplitude and beampattern of the 1.5-MHz difference-frequency wave are presented. Echolocation data obtained with several simple targets are also presented to demonstrate the resolution capability of the instrument.
Response of Orthogonally Stiffened Plates to Jet Noise
Authors: Gupta G. Sen
Published: October 2005

Depending upon the spatial correlation of the noise pressure field and the frequency of excitation, the dynamic behavior of the stringers, frames, and the interaction of the adjacent panels considerably affect the vibrations of the attached skin in an aircraft fuselage structure. This problem has been studied by analyzing an infinite plate stiffened by two sets of stiffeners at regular intervals and at right angles to each other. These stiffeners represent the frames and stringers of the fuselage. The jet noise is represented by a random pressure field with a band-limited white noise spectrum, traveling along the structure in an arbitrary direction with a given convection velocity. Initially, propagation of plane flexural waves in the structure has been studied. The effect of changing the direction of propagation of these waves has been observed. The existence of frequency zones of free propagation has been predicted. The bandwidth of these zones varies with direction of propagation and certain “preferred” directions of propagation, along which the bandwidth reaches maximum values, have been identified. The effect of the external noise pressure field on the structure has been studied next, to predict the response spectrum and the rms response. The effects of different convection velocities at various directions of propagation have been studied. The peak response is largest when the pressure field wave pattern matches with the structural wave pattern and the direction of propagation of the pressure field coincides with one of the “preferred” directions of propagation of the flexural waves. The method is also used to predict the natural frequencies and the response of a skin-stringer structure, taking the frame stiffnesses into account.
Fluid-borne acoustic energy transfer in complex multienclosure systems
Authors: McLauchlan R. A.
Published: October 2005

The diffuse field equations of architectural room acoustics are used to derive an engineering model of the fluid-borne acoustic energy transfer in complex, multienclosure systems. This coupled enclosure model relates unknown internal-enclosure sound-pressure levels to known external boundary sound-pressure levels. It is defined by a set of matrix equations relating internal enclosure intensities to external boundary sound-intensity loadings. These equations result from considering an energy balance for each enclosure including internal absorption and feedback energy transfer with nearest neighbor enclosures having common wall boundaries. Measured and/or calculated transmission and absorption acoustic energy partition coefficients at normal incidence are used to define the enclosure-enclosure interaction and external boundary-enclosure compatibility coefficient matrices over frequency and ambient pressure, etc., ranges of interest. An inverse formulation of the coupled enclosure model is given for the evaluation of unknown external boundary loadings from known but incomplete enclosure sound-pressure-level measurements. Nondimensioned results are presented which show the application of the coupled enclosure model in submarine habitability, self-noise suppression, and airplane-minimal added weight contexts as a function of acoustical material treatments.
Effectiveness of optimum beamforming by amplitude shading of transducer arrays
Authors: Wang H. S. C.
Published: October 2005

Since array amplitude shading can be implemented with relative ease in sonar receiving systems, the effectiveness of optimum beamforming by amplitude shading [H. S. C. Wang, J. Acoust. Soc. Am. 56, S18(A) (1974)] is investigated in more detail. It is demonstrated that in the case of broadside arrays in an isotropic noise field, the optimized amplitude shading previously reported by the author is identical to the conventional optimum solution allowing both amplitude and phase shading [see, for example, D. K. Cheng, Proc. IEEE 59, 1664 (1971)]. When the ambient noise and interference field is anisotropic, the two solutions are distinct from each other, with the latter yielding slightly lower noise and interference power for a given constrained received signal power. The difference between the noise and interference power at the output of the two optimum beamformers is, however, too small to cause any significant difference in the performance of practical receiving systems. A quantitative comparison of array performance with conventional amplitude shading, optimized amplitude shading, and optimized amplitude and phase shading under various field conditions is exhibited. This further supports our earlier belief that adaptive beamforming based on amplitude shading can provide maximum performance with minimal amount of circuit hardware and/or data processing.
Effect of ground impedance on sound propagation from a source near the surface
Authors: Hadden W. James , Turner Eddie L. , Kindred Erick D.
Published: October 2005

Laboratory experiments were conducted to determine the effect of ground-plane impedance on sound propagation from a source near grazing incidence. Measurements were made in an anechoic chamber of the farfield pressure from a point source as a function of source height and frequency, using one hard and several absorbent surfaces. Comparisons of these results with values calculated from normal-incidence impedances, obtained from impedance tube measurements, are discussed. [Work supported by NASA-Langley Research Center.]
Snowmobile noise and temporary threshold shift: an update
Authors: Chaney R. B. , McClain S. C. , Harrison R. T.
Published: October 2005

Significant progress by snowmobile manufacturers in quieting their machines may have lessened the hazard to the hearing of snowmobile users. Previously reported work [“Relation of noise measurement to temporary threshold shift in snowmobile users,” J. Acoust. Soc. Am. 54, 1219 (1973)] indicates that significant temporary threshold shift (TTS) occurs in a majority of snowmobile operators and passengers after only one-half hour of exposure. To determine if this hazard still exists with current 1975 model snowmobiles, tests were conducted to determine: (1) operator at-ear A-weighted exposure patterns; (2) A-weighted levels at 50 ft, using the recently approved SAE J192A test method; (3) the TTS of snowmobile operators. Also, noise measurements made at 50 ft in the field were compared to measurements published by the snowmobile's manufacturer.
Comparison of measurement techniques for the determination of statistical noise indicators
Authors: Breslau D.
Published: October 2005

Comparison of six methods for the determination of L10 and L50, the criteria contained in recent noise standards promulgated by the Minnesota Pollution Control Agency for the State, has been carried out for traffic and aircraft noise sources. The methods include: field sampling every 10 seconds, sampling every 10 seconds on a level recorder tape, field sampling over a three-second period every 30 seconds, and employment of the Brüel & Kjær 166 Environmental Noise Classifier, 4420 Statistical Analyzer, and SP 321 Data Analysis System. Noise levels were monitored near an arterial, freeway, and under a takeoff path near the Minneapolis-St. Paul International Airport. The maximum difference in computed level was 4 dBA for traffic noise. Limited aircraft data led to a simpler method of computing L levels, based upon measurement of total time in excess of a given level. It was shown that the 10-second sampling technique adequately represented L10 and L50 levels for airport noise, based upon a simple statistical argument. Although all systems proved adequate for the computation of L levels, problems of unattended monitors make them less desirable from an enforcement position.
Comparison of community noise exposure parameters
Authors: Connor William K.
Published: October 2005

As an initial effort in the development of a city noise control program, noise exposure was determined for 31 sites variously affected by noise from traffic, boats, trains, aircraft, and other sources. Digital monitoring equipment with a 100-dB dynamic range was used to obtain sound-level data for a minimum of 24 hours at each site, with a sampling rate of once per second. Data were reduced in terms of Leq, Ldn, CNEL, and sound-level percentile values. The correlations among these parameters show a dependency on types of noise present and also have implications for selection of limiting values.
Predicting noise environments around proposed industrial sites
Authors: Keast David N.
Published: October 2005

It is increasingly necessary to predict the sound-pressure levels that would exist at remote locations due to the operation of some proposed industrial or transportation facility. This is necessary not only to prepare environmental impact statements, but also to predict noise-reduction requirements for compliance with community noise ordinances. In this paper, a procedure is described for predicting the distribution of received sound levels at points remote from a source, based upon varying meteorological and terrain conditions observed at the site. The procedure, or model, is described in the form of a computer program. It considers the effects of shadow zones due to vertical gradients of the speed of sound, foliage, barriers, “ground attenuation,” atmospheric absorption, and inverse-square law. The output is a statistical distribution of received sound levels from which long-term Leq and Ldn values can be computed. Limited experimental verification of the model indicates that it overestimates the received A-weighted sound level by about 4 dBA, with a standard deviation of about 7 dBA. [This work was supported by the Long Island Lighting Company of Hicksville, New York.]