bluuebunny/crossref_metadata_2025 huggingface dataset:
Balloon impulse techniques for engineering estimates
Authors: Heymann R. , Sachs F.
Published: October 2005

Knowledge of the room constant of an interior space is usually required whenever engineering noise control measures are to be contemplated. Easily usable and transportable experimental methods to determine the room constant are therefore desirable. One convenient method is the balloon impulse method where the impulse produced by bursting a toy balloon is used to produce a high-level broad-band excitation for decay time measurements. Extensive use of the balloon impulse method has been made in determining the room constants of beth small (typical office spaces of 5000 to 10 000 ft3) and large (200 000-ft3 factory spaces and larger) spaces. The balloon impulse method has produced results consistent with values obtained from the steady-state large-room-volume equation using steady-state decay field sound-pressure levels measured at specified distances. However, the lack of diffuse field conditions and the nature of the true directivity factor had to be considered in the comparison. Room constant determinations made solely from calculations based on estimated sabin absorption coefficients were found risky. Serious errors are possible if misjudgment of surface properties is made. This is particularly true in large volume spaces.
Average build-up of sound-pressure level on a person in an ordinary room
Authors: Young Robert W.
Published: October 2005

Spatial mean-square sound pressure due to steady sine-wave excitation was measured in a room whose volume is 65 m3 (2300 ft3) and reverberation time about 0.6 sec. A multi-direction sound field was measured by rotating a 12-in. random-incidence electret microphone one revolution in one minute on a circle of 1-m radius, at the center of the room, mounted either on a boom or on the experimenter, who walked around the circle just back of the boom. Measurements of mean-square sound-pressure level were quite consistent (often within 0.5 dB) despite relative interference minima like −40 dB and movement of the experimenter during a rotation. A noise-average meter made by Computer Engineering Ltd. was used, modified to measure the level of the time integral of squared sound pressure called exposure level. When the microphone was at the breast pocket of a thin shirt worn by the experimenter walking around the circle, the mean-square sound-pressure level was greater than it was on the same circle in the absence of the experimenter, in round numbers, by 1, 2, 3, 2, 0, and −1 dB, respectively, at 125, 250, 500, 1000, 2000, and 4000 Hz. The result was nearly the same for a heavy wool jacket and hat, except −4 dB at 4000 Hz. On a shoulder or at an ear, the buildup at the six frequencies was quite similar.
Bull Session on Masking-Noise Systems
Authors: Coffeen Robert C.
Published: October 2005

A group discussion of current performance criteria, design techniques, and equipment and materials relating to the introduction of masking noise into offices and similar spaces to increase speech privacy. This discussion will be led by several consultants, equipment and material manufacturers, and sound-system contractors who are actively engaged in masking-noise projects. The discussion will be conducted in an informal manner with time allocated for questions and comments by all in attendance.
Hazard of intermittent noise exposures
Authors: Ward W. D.
Published: October 2005

The chief shortcoming of the “equal energy” hypothesis—the notion that equal products of time and intensity provide equal hazard—is that the recuperative powers of the auditory system are essentially ignored. A single sustained stimulus is regarded as no more dangerous than an intermittent one of the same total energy. A two-year study of the effect of intermittency on the TTS produced in normal young adults by 6- or 8-h exposures to octave bands of noise whose center frequencies ranged from 250 to 4000 Hz indicates that even for the most hazardous noise (the 4000-Hz OB), cutting the cumulative exposure time in half by interjecting regular quiet periods will permit an increase in level of 5 dB for constant TTS, at least up to about 100 dB SPL. At 1000 Hz, the trading relation is 6–7 dB for halving time, and at 250 Hz is even greater. Thus the 5-dBA-per-halving-time relation employed by the present OSHA standard is essentially correct for intermittent noise, except perhaps above 100 to 105 dBA, where the equal-energy hypothesis may be more appropriate for spectra with high-frequency dominance. A single 5-dBA “correction for intermittency” is an oversimplification. [Research supported by the National Institute for Occupational Safety and Health, Public Health Service.]
State activities and responsibilities for noise control
Authors: Dietrich C. W.
Published: October 2005

States have, up to this decade, played a weak role in the comprehensive regulation of environmental noise. Noise was not a state problem at first—it was a city problem. The passage of the Federal Noise Control Act of 1972 has been seen as a reason for continued inaction. The Federal law neither absolves the state from an necessity to act nor gives the states absolute freedom to regulate all major noise sources. The states have a great deal that they alone can do effectively. They must plan carefully, for their programs need to be coordinated with both Federal and local antinoise programs. Antinoise statutes that either establish or authorize the establishment of quantitative noise limits are now found in over 18 states. The provisions of these statutes are analyzed. These laws are compared with a model State Noise Control Act, developed jointly by the U. S. Environmental Protection Agency and the Council of State Governments in 1973. Eight general provisions are found in the model, which was intended by its authors to give a state the maximum authority to regulate noise pollution consistent with the preemptive provisions of Federal law. Many significant differences are found between the model, which is yet to become law in any state, and the provisions found in current state laws.
Spectrographic analysis of the coarticulatory effects of consonants on the reduction of vowel targets
Authors: Ohde Ralph N. , Sharf Donald J.
Published: October 2005

In order to determine the effects of consonants on vowel target production, five male subjects recorded bisyllabic nonsense syllables of the type CVCV. Right-to-left (R-L) coarticulatory effects were measured from CVCVs in which the initial consonant was always /h/ and the second consonant was /b,d,g/. Left-to-right (L-R) coarticulatory effects were assessed from CVCVs in which the initial consonant was /b,d,g/, while the second consonant was /h/. Both vowels in each utterance were either /i/ or /u/. By means of wide-band spectrograms and narrow-band sections, vowel targets were established for each subject from isolated productions of /i/ and /u/ and F2 measurements were made at the most stationary portion of the initial vowel in each CVCV. Vowels for each subject were selected within restricted duration ranges. Reliability cheeks of acoustic measurements manifested a high-percentage agreement between experimenter and checker. The findings were (1) L-R coarticulatory effects of consonants on vowel reduction were significantly greater than R-L effects; (2) there were significant differences between consonants for the reduction of /u/ but not for /i/; and (3) the magnitude of vowel reduction was significantly greater for /u/ than /i/ only in the /dVhV/ environment. The results appear to support a CV syllable model of speech production.
F
dynamics in bilabial closure
Authors: Hanson Robert J.
Published: October 2005

Data were gathered on the changes in F0 which occur during bilabial closure in sequences of a vowel /a,u,i/ and a bilabial consonant /p,b,m/. Five male subjects produced several repetitions in a test phrase of each of the possible VC combinations. The period of subject's F0 was measured in real time using a laryngograph and a PDP-12 computer. F0 data for each VC sequence were synchronized on the period during which lip contact occurred, as determined by a pair of lip electrodes. The findings of this study replicate many earlier studies of such topics as intrinsic pitch of vowels (/u/ was highest and /a/ lowest) and corroborate many findings in the area of articulatory dynamics (e.g., F0 decreased sooner in /u/ context than for /a/ and /i/). Furthermore, several new observations are reported concerning the details of F0 fluctuation in the post-lip-closure periods when standard acoustic measurements would be difficult due to the low level of radiated energy. [Supported in part by grant GU-1508 to the Phonetics Laboratory, University of Texas.]
Spectral and aerodynamic properties of normal vs defective /s/
Authors: Allen George D. , King Herbert A. , Warren Donald W.
Published: October 2005

Temporary anterior open-bite malocclusion was experimentally induced in 15 normal speakers by introducing posterior bite blocks. Speech samples produced at 0, 1, 3, and 6 mm incisal spacing, both with and without peripheral masking, were analyzed for spectral and aerodynamic features. Selected /s/ sounds were judged for acceptability by naive and phonetically trained listeners. Preliminary analysis indicates (1) judged dysfluency increased both with increasing anterior spacing and in the presence of masking noise; (2) the presence of masking noise had little effect on oral constriction; (3) the relationship between anterior spacing and degree of constriction was complex, speakers with wider than average constriction widening further with increasing spacing, those with normally tight constriction narrowing still further; (4) dysfluent /s/ spectra tended to have lower amplitude and frequency than normal productions by the same speaker. These data indicate differences among speakers in adaptive response to anterior spacing. [Supported by NIH Grant No. AF446, NIDR Grant No. DE03533, and SRS Grant No. 44P20078.]
Acoustical characteristics of speech to young children
Authors: Garnica Olga K.
Published: October 2005

Recent research indicates that adult speech directed to children differs markedly from speech directed to other adults. This study reports on an experimental investigation of the acoustical characteristics of such speech. Twenty-four female speakers performed several verbal tasks during two sessions. In one session speech was directed to another adult and in the other to the speaker's own two-year-old or five-year-old children. Measurements of fundamental frequency and duration were made on a subsample of sentences from each session. In comparison with the speech to the adult, speech to the two-year-olds was characterized by higher average fundamental frequency, a greatly expanded frequency range, longer durations of content words, and rising fundamental frequency at the end of declarative and imperative sentences. Speech to the five-year-olds was characterized by a greater frequency range and longer durations of only some content words. These characteristics of speech directed to the young child are discussed in terms of two functions they serve: (1) a social function, to capture and retain the child's attention to the adult's speech, and (2) an analytic function, to aid the child in its linguistic analysis, by emphasizing key words and specifying the constituents of sentences.
Perception and production of word-initial voiced and voiceless labial stops by eight English and eight Spanish monolinguals and eight English-Spanish bilinguals
Authors: Williams L.
Published: October 2005

Subjects performed in identification and discrimination tasks with synthetic speech stimuli varying in equal steps of voicing onset time (VOT) from voicing lead to voicing lag. Measurements of VOT were taken from spectrograms of initial voiced and voiceless labial stops. Average identification crossover and discrimination maxima differed significantly for the two monolingual groups. Within each group, values of VOT for voiced and voiceless tokens in production straddled the group location of identification crossover and discrimination maximum. Identification crossover matched discrimination maximum for individual bilinguals, but these locations varied across individuals, distributing themselves between the monolingual Spanish and English values. There was no significant difference in the values of VOT for voiced and voiceless tokens in Spanish words spoken by bilinguals and Spanish monolinguals. However, there was a significant difference in values of VOT for voiced and voiceless tokens in Spanish words spoken by bilinguals and Spanish monolinguals. However, there was a significant difference in values of VOT in voiced and voiceless tokens in English words spoken by bilinguals and English monolinguals. Tokens of /b/ in English words were prevoiced more by billinguals than by English monolinguals.
Voice onset and voice termination times of children and adult stutterers
Authors: Agnello J. G. , Wingate M. E. , Wendell M. V.
Published: October 2005

A modified measure of voice onset time (VOT) and voice termination time (VTT) was obtained from four groups: 12 children with normal fluency, 12 children who exhibited stuttering, 12 adults with normal fluency, and 12 adults with the problem of stuttering. The modified measure of VOT and VTT employed simultaneous patterns of intraoral air pressure and wide-band analysis of spectrograms. The mean age of the children was 6.5 years and of the children was 6.5 years and of the adults 28.6 years. Statistical results yielded significant VOT and VTT differences between children and adults. Children with stuttering exhibited longer VCT than their counterparts. Adult stutterers lagged in VOT and were statistically slower in VTT than their adult counterparts.
Effects of attention state and intensity level on human auditory evoked (averaged) cardiovascular response
Authors: Lassman Frank M. , Seewald Richard C.
Published: October 2005

Effects of varying listening postures and different intensity levels on averaged cardiovascular responses to acoustic signals were studied, Twenty-four normal-hearing female volunteers were offered five 1000-Hz tones (800-msec duration, 19-msec rise/decay), one signal each 45 seconds. EKG activity was recorded by a Medtronic Tachograph and then “averaged” through a Fabri-Tek FT 1052. Half the subjects received a 30-dB-SL signal first, the other half a 70-dB-SL signal first. Within a month, the experiment was repeated with the other sensation level, i.e., 70 dB SL on 30 dB SL, respectively. Listening conditions included: counting, reading, repose, and a nonstimulus control. Listening order was balanced. For all listening and intensity conditions, a multiphasic response pattern of initial deceleration, followed by acceleration, a second deceleration, and a long return to base-line was usually observed. At 70 dB SL, response patterns appeared uniform regardless of listening state. But at 30 dB, counting showed a significantly larger change than reading and heart rate took longer to return to baseline at all listening conditions. Counting appeared to maximize the response to the 30-dB signal.
Interpretation of the human frequency-following response
Authors: Davis H. , Hirsh S. K.
Published: October 2005

The human frequency-following response (FFR) is recorded (vertex to mastoid) by standard response-averaging methods. 500-Hz tone bursts with 4-msec rise time are excellent stimuli. The threshold is sharp at approximately 40 dB SL. FFR is weak in a subject with abrupt high-tone hearing loss. We believe that FFR is evoked primarily by stimulation of the basal turn of the cochlea. Each sound wave evokes a quasi-rhythmic sequence of waves, like the midbrain response to a click, and the sequences overlap. Experimental proof is difficult because the identity and latency of the first waves of FFR are uncertain and there are differences among subjects in the waveform of the midbrain responses and of their overlap when repeated at 500 Hz. Masking with high-pass (2000 Hz) noise sometimes reveals an apically generated FFR with a longer latency corresponding to the traveling-wave delay, but this result is clearer with brief low-frequency transients than with tone bursts. In a clinical setting FFR is not likely to yield information about the apical portion of the cochlea, and for the basal turn the midbrain responses at 6 to 9 msec evoked by high-frequency tone pips (4000 Hz) have lower threshold and are very reliable.
Auditory evoked responses recorded from the skull in unanesthetized parakeets (Melopsittacus undulatus)
Authors: Walsh James K. , Dooling R. J.
Published: October 2005

Average auditory evoked responses were collected from the skulls of awake, unrestrained parakeets. Evoked responses were collected at eight intensities of a 1000-Hz tone. The waveform of the evoked response was highly consistent across birds, with a major positive deflection occurring at 20–30 msec after tone onset followed by a negative deflection at about 35–45 msec and a second positive deflection at 100–120 msec. Over the intensity range examined, the size of the evoked response is linearly related to the intensity of the stimulating tone. The slopes of these functions show a zero crossing between 5–15 dB which compares favorably to the behaviorally determined threshold at 1000 Hz for this species.
Choosing among intense acoustic background stimuli—an acoustic “menu.”
Authors: Zerdy G. A. , Molino J. A.
Published: October 2005

Preferential relations among acoustic stimuli were determined for human subjects by a procedure that employed no verbal descriptions of the stimuli. Stimuli were presented in pairs to subjects as they studied Russian on a teaching machine. Thirteen subjects were employed in each of two separate experiments. They were instructed that they could “change the sounds that (they) hear” by pressing a telegraph key. Each key press switched the acoustic background from the current to the alternate member of each stimulus pair. The pair members were reversed periodically independently of the subjects' responses. The stimuli were four pure tones (125, 1000, 4000, and 8000 Hz at A-weighted intensity levels ranging from 90–112 dB) and a white noise (64 dB SPL). The proportion of time which subjects spent in the acoustic background stimuli varied significantly as a function of frequency even though equivalent A-weighted sound levels were presented. Thus the A-weighted sound levels do not accurately describe the indifference relationships among the stimuli employed.
Measurement of human aversion to intense acoustic stimuli
Authors: Wakeford Onslow S.
Published: October 2005

The relative aversiveness of tonal stimuli was measured as a function of their intensity and frequency by a procedure which employed no verbal descriptions of the stimuli. In three separate experiments 12 human subjects responded on a telegraph key in order to terminate, temporarily (5–25 sec), intense acoustic stimuli. The stimuli were presented at frequencies of 125 Hz, 1.0 kHz, and 8.0 kHz and ranged in intensity from 96 to 131 dB SPL. The opportunities to escape the acoustic stimuli were scheduled to occur after intervals of variable duration (3–33 sec). The subjects' rates of responding increased as a function of increasing stimulus intensity. The tonal stimuli presented at 125 Hz and 8.0 kHz were found to be less aversive, relative to the 1-kHz tone than would be expected from verbally derived contours such as loudness, annoyance, etc. The results indicate that A-weighted sound levels do not accurately describe relative human aversion for the stimulus frequencies used in this experiment.
Review of electroacoustic transducers
Authors: Killion M. C.
Published: October 2005

A review of miniature audio-frequency microphones and earphones will be presented. A discussion of the mechanical and electroacoustic characteristics will be given for a variety of transducer types. Typical constructions will be illustrated.
Directional ultrasonic radiators in air and water
Authors: Sunthankar Y.
Published: October 2005

A technique for producing highly directional ultrasonic radiation in the end-fire direction has been developed. The radiator presently. described consists of two thin rectangular brass blades (100 mm × 0.43 mm × 15 mm) clamped at one end. Mounted on each blade, near the clamped end, are two piezoelectric strain gauges. These gauges are connected in parallel and are excited by an applied voltage resulting in a strain in the blades. The frequency of excitation voltage can be adjusted so that the blades oscillate with a standing-wave pattern of flexural vibrations. This pattern of standing wave acts as an array of ultrasonic radiators, which, with suitable choice of blade material and thickness can emit a narrow beam in the end-fire direction. The device will also act as an ultrasonic receiver with a highly directional sensitivity. Different materials for blades have been tried and results are discussed. A similar radiator which will emit directional ultrasonic radiation in water has also been developed [Y. Sunthankar, “A novel ultrasonic radiator,” Trans. IEEE sonics Ultrason. (July 1973)].
Acoustic determination of rotor-blade load harmonic amplitudes
Authors: Kasper P. K.
Published: October 2005

It has been recognized that the magnitudes of discrete frequency tones radiated by a rotating blade are strongly influenced by the presence of a nonuniform distribution of aerodynamic forces over the rotor disk. When expressed in terms of a Fourier series in angular position about the rotor axis, the nonuniform forces are commonly referred to as blade lead harmonics. By assuming that the applied force acts at a given effective radius, a mathematical model was developed which relates nearfield sound harmonic amplitudes along the rotor axis to the blade lead harmonic amplitudes. This relationship was used to determine a set of blade load harmonics from measured on-axis acoustic spectra for a variety of rotor hover conditions. The inferred blade lead harmonic amplitudes tended to follow an inverse power law relationship with harmonic blade lead number. Empirical curve fits to the data showed the exponent of the harmonic number to be in the range −1 to −1.5. These empirical power law relationships were used to provide blade leading input to a farfield rotational noise prediction model. The predicted discrete frequency sound levels showed reasonable agreement with measured values.
On driving a transducer to produce pulses shorter than the natural period of the transducer
Authors: Winter T. G. , Pereira J.
Published: October 2005

When an acoustical transducer is given a short electrical impulse, the pressure wave produced is usually some sort of damped sine wave whose exact shape is determined by the physics/properties of the transducer and the medium to which it is coupled. In order to produce pressure pulses shorter than this, it is necessary to drive the transducer with a more complex voltage waveform. A method of calculating and producing the necessary voltage waveform to make a transducer produce a pressure pulse of specified shape and width will be described. Examples of the voltage waveforms necessary to drive a loudspeaker to produce pulses shorter than the natural resonant period of the loudspeaker will be shown.
Computer optimization of transducer array patterns
Authors: Wilson G. L.
Published: October 2005

A modified linear programming procedure is described for the derivation of shading coefficients for minor-lobe control from symmetrical, but possibly irregularly shaped, transducer arrays, for which the relationship between the coefficients and output pressure is linear. Examples are included for the traditional problems of finding optimum coefficients for uniform and low minor-lobe response from planar arrays, including one of a “honeycomb” array on a hexagonal grid, which could not be handled by analytical methods employed hitherto. [Supported by Naval Sea Systems Command, Code 034.]
Data requirements for the mapping of ultrasonic fields with conventional light diffraction
Authors: Berlinghieri Joel C. , Cook Bill D.
Published: October 2005

A procedure has been proposed by Cook [J. Acoust. Soc. Am. 53, 330(A)(1972)] through which a cross-sectional mapping of a progressive sound beam could be obtained by conventional light diffraction. This technique requires that a series of optical diffraction measurements be taken using a parallel beam of light passing through and perpendicular to the sound beam. These measurements are taken laterally across the field, for a large number of rotations about the sound field's major axis. Since the number of measurements could become excessive, an investigation of the data requirements of this technique has been performed. Computer-generated data were calculated of the integrated optical effect (both magnitude and phase) produced by the pressure field of a circular plane piston in an infinite rigid baffle. From these data a cross-sectional map was obtained using an effective two-dimensional Fourier transform, as well as the two-dimensional fast-Fourier-transform algorithm. The cross-sectional mapping was evaluated at different axial positions, using one set of data generated at a single axial distance. Data requirements were obtained by varying the data set and comparing the results to those obtained from the diffraction integral. The data requirements were found to be not excessive.
Experimental study of punch press noise
Authors: Stewart N. D. , Daggerhart J. A. , Bailey J. R.
Published: October 2005

An experimental study was made of the noise produced during a single-cycle punching operation. A 60-ton power press with a “C-frame” punch and die unit was used. Sources identified by time history analysis were found to be air exhausts, ram and stripper impacts, and the punching noise radiated by the workpiece. Two types of mufflers were found equally effective in reducing the air noise. The impact noises were found to increase with punch size and impact velocity. A detailed study of the punching noise showed that it increased significantly with larger punch and die clearances. The difference between high and low clearance noise was found to be even greater on the A scale. Shear punches were found to be useful in reducing the noise at high clearances. Empirical equations were developed to describe the punching noise as a function of the force required, punch velocity, workpiece density, punch design, material fracture characteristics, and punch and die clearance. [The work was completed under Grant No. 1 RO1 OH 00494-01A1 from the National Institute for Occupational Safety and Health of the Public Health Service, Department of Health, Education and Welfare.]
Vibration mode discrimination using pulsed holography
Authors: Shajenko Peter , Cable Peter
Published: October 2005

Mode discrimination of a vibrating mechanical structure using pulsed holographic interferometry is presented. In general, a mechanical structure with many degrees of freedom vibrates in many modes simultaneously, which are displaced in phase. By obtaining holograms sequentially shifted along the excitation cycle, the various vibration modes can be selected, their relative amplitudes and phases can be measured, and the effects produced can be studied. A mode discrimination technique was applied to an elastic sphere filled with water and driven at a set of frequencies 25 Hz and above by externally applied forces. The resulting mode structure was holographically recorded. Each such holographic interferogram was obtained by superposition of two holographic exposures using a double-pulsed laser output: one exposure corresponds to the structure being in a nonvibrating position, and the second exposure was obtained at the predetermined phase shift interval. Time-lapse motion pictures of a sphere vibrating in various modes are shown.
Forced vibration of a disordered periodic beam
Authors: Lin Y. K. , Yang J. N.
Published: October 2005

An ideal periodic Structure is one which is constructed by connecting together identical units. Since manufacturing in-accuracy and material inhomogeneity are always present in practice, ideal periodic structures never actually exist. The term “disorder” is used here to indicate the departure from a perfect periodicity. The present paper explores the effect of random span-length deviations of an otherwise perfect periodic beam on many hinge supports as manifested by the random values of frequency response functions. Two types of excitation are considered. The first is either a concentrated force or a concentrated moment. The second is a frozen force distribution convected at a constant velocity. Four types of response are treated simultaneously, including deflection, slope, moment, and shear at any location on the beam. It is shown that the magnitude of the statistical average of a frequency response function can be considerably greater than the value computed without taking into account the disorder in span lengths, especially near the resonance frequencies. It is also near these frequencies that the standard deviation of a frequency response function becomes quite large, indicating greater uncertainty in such regions. Furthermore, in the case of convected loading, the use of a perfect periodic model cannot account for the response in certain vibration modes while these modes can be actuated in a disordered system.
Method for determining the elastic constants of solids
Authors: Nigro Nicholas J. , Huang Pangnan
Published: October 2005

A method is presented for determining the elastic constants of general anisotropic solids. The methods utilizes a numerical parameter estimation technique to determine the values of the elastic constants such that the phase velocitites (as a function of wavenumber) calculated from theory fit (in a least-square sense) those obtained experimentally.
Diffraction of a plane wave by a half plane in a subsonic and supersonic medium
Authors: Candel Sebastien M.
Published: October 2005

A technique is presented for transforming certain acoustical boundary value problems in subsonic moving medium to a problem involving a stationary medium. The method is described by discussing the Sommerfeld problem of diffraction of a plane wave by a half plane immersed in a subsonically moving medium. It is shown that additional sources are induced by the flow at a leading edge impinged by a plane wave, while a trailing edge only gives rise to the usual diffracted wave. The flow also convects the geometrical acoustics part of the field. A transformation applied to the supersonic diffraction problems yields a unique reference problem, which is solved by Fourier transform methods. The pressure field is decomposed in a sum of a geometric acoustics field and a supersonic diffracted wave showing some remarkable similarities with the subsonic solution.
Vibration of statically deformed beams and plates
Authors: Davies Huw G. , al Sowayel Saud
Published: October 2005

The response of beams and plates to fluctuating loads with high mean values is considered. The static deformation is obtained separately; the vibration of the statically deformed structure is then discussed in terms of the induced static in-plane membrane stresses. It is shown that the response of a deformed plate can be predicted by defining an effective uniform tension. Simple expressions are obtained for the loss factor in terms of the impedance of the supports of the beam or plate. Expressions are given for the changes of modal resonance frequencies and loss factors due to the tension, with the assumption of constant boundary impedance. The predicted changes in loss factors agree quite well with some previously published experimental data for very thin plates. The changes for most cases of practical interest, however, are small.
Pressure distribution in a fluid layer bounded by elastic plates
Authors: Easter J. Russell , Torvik Peter J.
Published: October 2005

Pressures are determined in a layer of fluid bounded by two parallel elastic plates, one of which is harmonically excited at a point. The response of the coupled plate-fluid system is obtained for infinitesimal displacements in both the plate and the fluid. The pressures are obtained through a numerical integration of the inverse Hankel transform along an approximation to the steepest descent path. Some numerical results obtained for frequencies both above and below the coincidence frequency are given. These show a complex spatial variation in pressure in addition to that on the scale of the wavelength in the fluid.
Parametric receivers with spherically spreading pump waves
Authors: Berktay H. O. , Shooter J. A.
Published: October 2005

A closed-form solution is presented describing the performance of a parametric receiver using a pump wave which is spherically spreading in the interaction region. The development of this solution is simplified by restricting the width of the pump beam to a value not greater than the beamwidth of the parametric receiver. The results are shown to be in good agreement with those obtained by the numerical evaluation of the scattering integral using the method discussed in the paper of G. R. Barnard et el. [J. Acoust. Soc. Am. 52, 1437 (1972)]. The same approach is used to develop a closed-form solution for the nearfield performance of a parametric receiver. Experimental results are presented and compared with computed results, showing good agreement.
Transmission and reception of transient signals in a SOFAR channel
Authors: Porter Robert P.
Published: October 2005

The time-frequency structure of wide-band pulses propagated to long ranges in a deep sound channel is investigated with normal-mode theory. The WKB approximation is used to predict the pressure field in channels with arbitrary sound-velocity profiles. The pressure field due to nondispersive pulses such as the impulse and dispersive pulses such as the linear-FM signal is calculated. The time-frequency structure of the field is compared with experiment. Observation of combined ray and mode behavior is predicted in a straightforward manner. The response of signal-processing receivers to the sound field is investigated for matched and nondispersive filters. The peak output of the matched filter is shown to be the weighted sum of the energies in each of the transmitted modes.
Structural information theory
Authors: Barrett T. W.
Published: October 2005

A method of defining structural information in Hilbert space is described. Instead of commencing an information theory analysis with a simple signal and progressing to an n-dimensional information space, the reverse procedure can be followed: the signal is defined completely in both real and imaginary spaces, and is then represented as a dimensionless number in Hilbert space. Thus, a signal can be analyzed into a Hilbert space measure of information. This measure has similarities to the relativity of states of Everett's (1957) reformulation of quantum mechanics involving observer-observed interaction. Whereas Everett's theory deals with the totality of all possible ways in which a state function can be decomposed into the sum of products of state functions for subsystems of the overall system, the theory presented here deals with the totality of possible ways in which a Hilbert space measure of signal state can be decomposed by signal definition into reciprocally related measures of the state for subsystems of the overall system. In the overall system presented here, a signal is given a concise representation either as a quadratic form on a Hilbert space, or as a Fourier coefficients in isomorphic function space. The total information content of a signal qualified as a dimensionless number in Hilbert space may be given a representation in familiar units by the use of such methods. A primary postulate of quantum mechanics is obeyed in that all physically relevant information about a system is derivable from the knowledge of the state function of the system. Thus, a signal is defined firstly as an information measure, and secondly in the familiar units of frequency, bandwidth, midperiod, and duration.
Evoked-response audibility curve of the chinchilla
Authors: Henderson Donald , Hamernik Roger P. , Woodford Charles , Sitler Ronald W. , Salvi Richard
Published: October 2005

The audibility curve of the chinchilla was measured on 76 animals using the auditory evoked response (AER). The standard behavioral measures of sensitivity and the AER measures are shown to agree within an average of 5 dB through the 0.25 to 8 kHz range. Furthermore, the AER is shown to reflect temporary and permanent partial losses of hearing due to noise exposure. It is concluded that the AER is a useful index of auditory sensitivity for the brief tones of the order of 20-msec duration.
Interaction between two factors that influence vowel duration
Authors: Klatt Dennis H.
Published: October 2005

It is well known that stressed vowels are shorter before voiceless consonants than before voiced, and that stressed vowels are shorter before an unstressed syllable in a bisyllabic word than in a monsyllabic word. A set of test materials was designed to study the interaction between these two rules. Results suggest that vowels become strongly incompressible beyond a certain amount of shortening and that vowel duration modification rules should have the form Do = k (Di − Dmin)+Dmin, where Di is the input duration to the rule, Do is the output duration of the rule, Dmin is the minimum duration for the vowel, and the scale factor k is greater than zero and depends on the particular rule. The data indicate that Dmin is about 45% of the inherent duration of a given vowel.
Spatial predictability of noise fields and singular detection in optimum array processing
Authors: Lichtenberger G. B. , Schultheiss P. M.
Published: October 2005

An expression is derived which relates the array gain of an optimal beamformer to that of a simple delay and sum beamformer in terms of the correlation between noise received on the signal beam and that received on all other beams. The relation of the result to the phenomenon of singular detection is discussed briefly.
Helmholtz Resonators as Sonic Bubble Chambers?
Authors: Tschiegg Carl E. , Greenspan Martin
Published: October 2005

It has been found possible to develop alternating pressures of up to 10 aim in liquid-filled Hemholtz resonators. Some advantages and disadvantages of the construction of a rapid-cycling bubble chamber along such lines are discussed.
Minimum audible angle underwater: a replication under different acoustic and environmental conditions
Authors: Feinstein S. H.
Published: October 2005

The minimum audible angle underwater was replicated with a less intense stimulus (26 dB vs 40 dB re 1 μbar) and in this instance the diver/subjects wore no neoprene hood. The data obtained in the present study were compared with the earlier data [S. H. Feinstein, J. Acoust. Soc. Am. 53, 393–399 (1973)] and no differences were noted. Moreover, the MAA procedure appeared to be a reliable measure of localization capacity when tested under extremely different environmental conditions.
Masking produced by sinusoids of slowly changing frequency
Authors: Ronken Don A.
Published: October 2005

A fixed amplitude sinusoid that was frequency modulated by a sawtooth or triangle wave was used to mask a 20-msec pure-tone signal. The linear portions of the modulating waveforms were 150 msec in duration and swept the masker frequency between 1.5 and 0.75 kHz. A frequency contour of the masking was obtained when the temporal position of the signal was fixed relative to the sawtooth or triangle and the signal frequency was varied. A temporal contour of the masking was measured when the signal frequency was fixed and the temporal position of the signal was varied. Temporal and frequency selectivity indicated by differences of 30–40 dB of masking were observed in both kinds of contours. A linear model consisting of a bandpass filter followed by a power integrator provided a fair approximation to principal features of the masking contours when the bandwidth of the filter was 100–200 Hz and the time constant of the integrator was 10 msec. Similar resonant systems are found in spectrum channel vocoders and in instruments that produce speech spectrograms. The model tends to underestimate the masking at the higher frequencies and does not exhibit the type of deep, narrow-band notches that are found in frequency contours of the masking.
Acoustic behavior of the outer ear of the guinea pig and the influence of the middle ear
Authors: Sinyor A. , Laszlo C. A.
Published: October 2005

The sound-pressure transformation of the pinna and the ear canal of the guinea pig has been measured in the frequency range 1–15 kHz. Below 1 kHz, the outer ear does not cause any significant modification in sound pressure. Between 3 and 10 kHz, the pinna provides a boost in pressure which can specifically be attributed to resonance in the concha. This boost, however, is dependent on the location of the sound source with respect to the pinna. The largest amplification is obtained when the speaker is pointed directly into the entrance of the ear canal. The acoustic behavior of the ear canal of the guinea pig is similiar to that of a rigid circular cylinder, open at both ends, about 9 mm long and 2.5 mm in diameter. The pressure transformation between the eardrum and the entrance to the ear canal is strongly dependent on the loading effect of the middle ear. Thus, experimentally induced changes in the impedance of the middle ear, and natural changes due to disease alter the sound transmission across the eardrum of this animal. In normal animals, the eardrum pressure is roughly 5 dB higher than the free-field pressure in the frequency range 1–10 kHz. This boost is attributed partly to the effects of the body and partly to the sound-pressure transformation by the outer ear.
Reverberation-room qualification for determination of sound power of sources of discrete-frequency sound
Authors: Ebbing Charles E. , Maling George C.
Published: October 2005

In practice, many sources of sound such as motors, pumps, fans, blowers, and transformers radiate sound having discrete frequency components. The reverberation room is a particularly convenient environment in which to determine the sound power produced by such sources provided that the measurement uncertainty can be reduced to an acceptable value. If the measurement uncertainty lies within standardized limits, the room is said to “qualify” for measurements on sources of discrete-frequency sound. The causes of the various uncertainties in the determination of sound power have been considered. It is shown that, in effect, the discrete-frequency room qualification procedure allows the measurement uncertainty to be estimated for a monopole-type sound source. The problems involved with discrete-frequency and swept-frequency qualification procedures are discussed, and experimental qualification data for several rooms with and without vanes and other accessories are presented. Methods of generating the frequencies necessary for the room qualification procedure are examined. From both theoretical and experimental studies it can be concluded that a major factor affecting the qualification of the reverberation room is the uncertainty in the measurement of the mean-square sound pressure throughout the room. This factor can be minimized by increasing the number of independent samples that one uses to estimate the mean-square pressure in the room, either by using a sufficiently long continuous microphone traverse or by using multiple microphones. At low frequencies (say, below 500 Hz in a 280-m3 reverberation room) the variability of the sound-power output with source position (change in radiation impedance) is also a major source of the uncertainty of the sound-power estimate if the sampling of the sound field has been accomplished adequately.
Sound-power testing experiences of an independent laboratory
Authors: Kodaras Michael J. , Blanck Michael W.
Published: October 2005

Approximately 150 sound-power-level tests have been conducted of unitary and room air-conditioning equipment at Kodaras Acoustical Laboratories (KAL). This paper submits a complete description of the reverberation rooms used in conducting the tests as well as information regarding the temperature- and humidity-control systems, room noise levels with and without the control systems operating, and the measurement instrumentation used at KAL. In addition, problems encountered in selecting microphone locations, loading the test specimens, dealing with pure tones and other every day practical problems and their solutions are discussed. Future changes that will be made to this facility as a result of our experience will be presented.
Outlook for in-situ measurement of noise from machines
Authors: Schultz Theodore J.
Published: October 2005

In the past we have known, from first principles, that estimates of the sound power radiated from large machines, based on measurements of only the pressure near the source, are likely to be wrong. There has been substantial progress, during the last few years, in our understanding of how serious the errors may be and also how to minimize the error by suitable choice of measurement technique. This paper summarizes these conclusions briefly and suggests possibilities for further study.
Community noise survey of Medford, Massachusetts
Authors: Wesler J. E.
Published: October 2005

An extensive noise measurement survey was made in Medford, Massachusetts, suburb of Boston, during March, April, and May 1971, to assess the importance of transportation noise in a typical urban community, and to obtain validation data for a mathematical model developed to simulate such noise levels. Noise measurements were made at 49 locations distributed uniformly across the community, with continuous 24-h measurements at five of the locations. The median noise level over the entire community was 54 dBA during the morning rush hour, and 51 dBA during the midday period. Noise levels were influenced primarily by highway traffic, with a major highway arterial corridor producing the highest noise levels in the community.
Simulation of sound absorption spectra of seawater systems
Authors: Garland F. , Patel R. C. , Atkinson G.
Published: October 2005

Sound-absorption spectra of three chemical systems (I: CO2/H2O, II: Mg++/CO2/H2O, III: Mg++/SO4=/CO2/H2O) are simulated on a computer using available, and estimated kinetic and thermodynamic data. System III is used as a simplified model for seawater and is described by a nine-state mechanism. Using the chemical-relaxation theory described, six nonzero relaxation times are obtained for III. The relaxation frequency and absorption amplitude of two of the times agree reasonably well with oceanic data, which indicate excess sound absorption in the 1–5- and 150-kHz frequency regions.
Intensity discrimination of clicks: the effects of click bandwidth and background noise
Authors: Penner M. J. , Viemeister Neal F.
Published: October 2005

Intensity discrimination of filtered clicks was investigated. For broadband and high-pass filtered clicks, the data are consistent with Weber's law. For low-pass filtered clicks, however, the Weber fraction decreases with increasing click intensity. In contrast to earlier findings, the addition of background noise to a broadband click raised the threshold for detection but did not markedly affect the Weber fraction. Theoretical implications of these results are discussed.
Convection velocities of pressure fields on plane boundaries
Authors: Brackenridge J. B. , Geib F. E. , Maidanik G. , Remmers G.
Published: October 2005

Two wavevector filters were designed for investigating the nature of the pressure field induced on a flat boundary by a highly subsonic turbulent boundary layer. The wavevector filters were designed specifically for investigation in the spectral range where the spectral density of the pressure field is high. Preliminary experiments have been carried out, and the results relating to the convection velocity are reported. The major objective of the paper is, however, to present an analysis that makes it possible to properly interpret the results and allows for a more satisfactory comparison between the results reported in the paper and the available data in the literature.