bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency-Response or Impedance Approach to Experimental and Theoretical Studies
Authors: Rubin S.
Published: October 2005

The basis of the approach is described, fundamental terms are defined, and assumptions and limitations are identified. Experimental determinations of frequency response are reviewed from a conceptual viewpoint. Uses of the measurements to construct various other forms for describing a system are presented. Examples of these other forms are normal-mode parameters, mass-stiffness-damping parameters, and transfer functions in the Laplace variable. Next, theoretical descriptions of systems of a frequency-response type are discussed. Noted are matrices of the types: transmission (or transfer), impedance (or dynamic stiffness), and admittance (or mobility or dynamic flexibility)—and their interrelationships are emphasized. The direct determination of transmission matrices from a governing differential equation is noted. Finally, several engineering applications are presented of the frequency-response or impedance approach to the analysis of a complex system treated in terms of the independent behavior of parts of the system. Situations that lend themselves best to the approach are identified. It is concluded that the analyst should be aware of the power and utility of the approach, both experimentally and theoretically, so that it can become an effective tool for his solution of engineering problems.
Impedance Measurements Using Impact Techniques
Authors: Schloss F.
Published: October 2005

If time is of the essence and space for auxilliary equipment is at a premium, the mechanical impedance of a structure may be obtained using a commercially available electric hammer as a broad-band source of excitation and a real-time analyzer for the measurement of the response. The hammer used produces a peak force of over 3000 lb of about 65-μsec duration at a repetition rate of 50 per sec resulting in a spectrum of lines 50 Hz apart with the first null at 16 kHz. The calibration and method of attachment are discussed. Impedance measurements in 13-oct bands using the hammer compare favorably with those obtained using the more conventional impedance head.
Articulatory Rate versus Acoustical Invariants in Speech Perception
Authors: Summerfield A. Quentin , Haggard Mark P.
Published: October 2005

Voice onset time (VOT) has proved in many languages to be a useful descriptive variable with which stop consonants may be classified in respect of the distinction voiced/unvoiced. The question arises as to whether this variable also has fundamental perceptual relevance. Experimental evidence suggests that if VOT as such is registered in preception, then it must be registered in a fashion relative to other ongoing temporal events; for example, we have shown that perception of voicing depends on over-all syllabic rate. However, a separate effect of the rate of transition of the first formant from the onset of voicing to the steady state in the vowel is also evident. Stevens and Klatt (1971) proposed that the presence of a significant and rapid spectral change in the F1 region at the onset of voicing was the positive cue for voicedness. It is possible to go further and attempt to separate the effects of the extent, duration, and rate of the first formant transition. In such a synthesis experiment where VOTs were held constant, we obtained differences in voiced/unvoiced responses that supported Stevens and Klatt's suggestion that VOT is not the real perceptual cue, only appearing so because of the tied variables mentioned. Our results further indicate that there is little or no effect of the extent or duration of the transition, but that a critical rate of transition for perception as optimally voiced may be operating: The implications of these findings for feature detecting mechanisms in speech perception are discussed. [Work supported by J.S.R.U.—U.K.]
Some Perceptual Mechanisms in Speech Processing
Authors: Haggard Mark P. , Summerfield A. Quentin
Published: October 2005

Enough is known about the acoustical cues in speech to enable highly intelligible synthesis from simple algorithms, but, in most cases, the most valid expressions of cues from the point of view of perception and the mechanism of detection, weighting, and decision are not known. Experiments that manipulate several cues and the phonetic context offer some hope of charting information flow through the human perceptual process and providing detailed block diagram models. Several examples are given. Perception of voicing in initial stops depends upon the place of articulation as well as the traditional voicing cues such as VOT—i.e., the boundary VOT value differs with place. Two separate experiments show that this effect is carried not by acoustical place information but by a perceptual decision about place, logically prior to the: voicing decision. But, in another context effect, dependence of consonant place upon the adjacent vowel, the effect appears conditioned by the acoustical vowel information and not by the decision as to linguistic identity. Implications for perceptual theory and speech recognition are pointed out. [Work supported by J.S.R.U.—U.K.]
Guide to the Three Special Sessions on Nonlinear Acoustics
Authors: Blackstock David T.
Published: October 2005

As an introduction to the material that is to be covered in the three special sessions on nonlinear acoustics, the principal analytical tools used in the field will be reviewed. These include Earnshaw-Riemann theory, weak-shock theory, Burgers' equation, and Westervelt's method (the Green's function solution of an inhomogeneous wave equation). The review will take the form of an historical account of activity in the field since 1930. Landmark results during this period include the solutions of Fay [(1931). J. Acoust. Soc. Amer. 3, 222–241] and Fubini [(1935). Alta Frequenza 4, 530–581], the N-wave solutions of Landau [(1942). J. Phys. Acad. Sci. USSR 6, 229–230(A); (1945). 9, 496–500], Mendousse's solution [(1953). J. Acoust. Soc. Amer. 25, 51–54] of Burgers' equation, and Westervelt's parametric array [(1960). J. Acoust. Soc. Amer. 32, 934–935(A); (1963). 35, 535–537].
Nonlinear Theory of Sound Propagation through a Random Medium
Authors: Howe M. S.
Published: October 2005

The theory of propagation of weakly nonlinear waves through random media is discussed. The wavefield is partitioned into mean (ensemble average) and fluctuating components, and a nonlinear equation is derived governing the evolution of the mean field. This equation contains a pseudoviscous term that takes account of the irreversible transfer of energy from the mean wave to the fluctuating field. By balancing nonlinear effects against this dissipation, the existence of steady-state shock-like waves is deduced for the mean field, and this is illustrated by reference to the propagation of sound through an atmosphere in which the sound speed is a random function of position and through one subject to turbulent fluctuations. The difficulty encountered in applying the theory to sonic-boom propagation is briefly discussed. [Supported by the Bristol Engine Division of Rolls Royce (1971) Ltd.]
Electrophysiologic Study of Descending and Ascending Detection Threshold Discrepancy in Guinea Pig
Authors: Forbes William I. , Wilpizeski Chester
Published: October 2005

CM and AP VDLs for continuous trains of clicks were recorded from guinea pigs having permanently fixed round-window membrane electrodes. The experimenter monitored oscilloscope-displayed evoked responses on line by manual adjustment of a motor driven recording attenuator. Békésy-audiometric-type graphical traces were obtained having at least 8-dB discrepancy (“amplitude” or envelope width) between descending and ascending VDLs. Comparable VDLs were also recorded photographically by making alternate down-up sweeps across nominal threshold level with no feedback control of the attenuator. Frame-by-frame analysis of the film was made off line by measuring stimulus pulse intensity associated with the disappearance (descending VDL) and reappearance (ascending VDL) of the evoked response. No significant overlap of descending and ascending thresholds was found using the photographic method. Statements in the audiologic literature postulating hypothetical auditory nerve processes underlying Békésy trace width are challenged. [Supported in part by NINDS.]
Effects of Medial Geniculate Lesions on Primary Evoked Potentials in Cats
Authors: Ryan A. , Miller J.
Published: October 2005

The click-evoked primary potential was examined in barbiturate-anesthetized cats. Normal and medial geniculate lesioned animals were studied. The lesions, electrolytically produced, were placed stereotaxically at various points in the medial geniculate nucleus three days to three weeks prior to electrophysiological recording. The location and extent of medial geniculate destruction was histologically evaluated in each lesioned animal. Bipolar surface potentials were mapped through AI, AII, and Ep. Systematic changes were observed in the cortical evoked potential maps. These changes were found to vary with the location and extent of the medial geniculate destruction. The greatest reduction in evoked potentials throughout these cortical areas was observed associated with ventral division lesions. A much smaller effect was observed with medial and dorsal division lesions. In general, the changes may be interpreted to agree with those expected on the basis of anatomical studies of the auditory thalamo-cortical projection system. Changes in the evoked potential map associated with varying ventral division lesions will be described. [This research was supported by NIH grants.]
Acoustical Observations at Blossom Music Center
Authors: Shankland R. S.
Published: October 2005

Acoustical observations and measurements have been made at the Blossom Music Center since its inception. The first involved measurements of background noise and wind to determine a suitable site. Over 100 locations near Cleveland were studied before the final location was chosen. The acoustics of the pavillion seating 4500 people has been studied in detail. Reverberation times have been measured at numerous locations showing that it has an excellent reverberation time versus frequency characteristic for orchestral music (2.1 sec in midfrequency range). Speech articulation tests have been made, which indicate satisfactory intelligibility even in seats at the rear of the pavillion. The stage shell, designed by Peter van Djik is exceptional in that it provides early reflected sounds throughout the entire pavillion seating area. The pavillion and orchestra shell acoustics make it possible for symphony concerts to be clearly heard by 4500 listeners without sound amplification. For large additional audiences on the lawn sound amplification is provided by a time-delay system, which gives sound that blends perfectly with that coming directly from the stage and the illusion of live sound is achieved for all listeners. For programs other than regular symphony concerts, additional sound amplification is provided within the pavillion.
Sound Insulation at Low Frequencies
Authors: Mulholland K. A. , Lyon R. H.
Published: October 2005

The response of two rooms coupled by a panel has been investigated at frequencies of the order of the lowest room mode frequency. At these frequencies both individual room modes and individual panel modes may be expected to contribute to the transmission of sound through the panel. The role of resonant and nonresonant response both in the rooms and in the panel has been investigated both theoretically and experimentally. It will be shown that transmission is dominated by resonant room modes and nonresonant panel response with some interference from nonresonant room modes.
Study of the Acoustical Performance of a Landscaped Office
Authors: Warnock A. C. C. , Northwood T. D. , Henning D. N. , Hegvold L. W.
Published: October 2005

The occupants of a newly opened landscaped office were subjected to two different masking spectra each day for an extended period. They were polled daily as to their preference and were allowed to comment on the sound masking. Levels of 51 dBA produced unanimously strong disapproval and rejection. Reactions at 48 dBA, while not so strong, were still negative towards the idea of added noise. Natural sound levels in the office were lowered to about 35–40 dBA, but even this relatively quiet condition was preferred to a low level of masking noise (45 dBA). The effectiveness of the noise for masking speech was measured using the rhyming test described by Griffiths [J. Acoust. Soc. Amer. 42, 236 (1967)] and a test crew. The results obtained showed a predictable relation to articulation index calculations based on S/N ratios. Physical measurements were also made to determine the effect of the acoustical ceiling, baffles, and acoustical screens on sound propagation in the landscaped office. The results suggest that there is currently perhaps undue stress on the need for the ultimate in absorption.
Special Electret Transducers
Authors: Reedyk C. W.
Published: October 2005

Electret transducers are capacitive transducers, which depend on a semipermanent electric charge imbedded in the surface of a dielectric to provide the bias field in an airgap. After many years of experimentation in the laboratory, electret microphones have now become commercially available. The purpose of this paper is to highlight some of the properties of electret transducers and electret materials that make them attractive in some special applications. The basic form, an electret diaphragm stretched over a perforated backplate, is a first-order differential microphone. The response of a first-order differential capacitive microphone, the simple construction, and low sensitivity to shock and mechanical vibration make the electret suitable for use in close-talking microphones, for example, in telephone operator's headset. A simple electret microphone can be used to sense the arrival of the wavefront in a shock-wave tube. The stored charge in the electret has been used in experimental key transducers to produce voltage pulses from 5 to 25 V.
Difference Frequency Parametric Array Using an Exact Description of the Primary Sound Field
Authors: Willette J. G.
Published: October 2005

In parametric arrays, the nonlinear interaction between two, harmonic time-dependent waves creates sum and difference frequency radiations. A solution for the pressure field of the secondary radiations has been obtained numerically for interaction in the farfield of a circular piston source [Papers CC4, 80th meeting, and FF7, 81st meeting of the Acoust. Soc. Amer.]. In the present analysis, this solution is extended to include interaction in the nearfield as well as the farfield of the circular piston. A single intergral expression, which describes the piston nearfield exactly, is derived from the impulse response of a circular piston. The results are compared to experiments involving the amplitude and azimuthal response of a difference frequency radiation. The theoretical results are also compared to other models using (1) plane-wave and (2) spherical-wave approximations of the primary sound field. [This work was sponsored by the U. S. Navy Office of Naval Research.]
Array of Parametric Receiving Arrays
Authors: Berktay H. O. , Muir T. G.
Published: October 2005

Theory is developed to describe the performance of arrays whose elements consist of parametric receiving arrays. The directivity of the resulting array of parametric receivers is shown to depend upon the separation of elements as well as the separation between pumps and receivers. The theory evolved is validated by comparison to experimental data obtained with a two-element array in a fresh water lake. Electronic steering of this type of array is also discussed. [Work supported by Office of Naval Research.]
How is Pitch Lowered?
Authors: Ohala John J.
Published: October 2005

Is the pitch of voice lowered (a) by the active contraction of some laryngeal muscles, (b) by the relaxation of those muscles that raise pitch, or (c) by both mechanisms? Evidence will be presented that supports (c). Specifically, electromyographic recordings point to the sternohyoid muscles' participation in pitch lowering, independent of their activity in other speech gestures, e.g., jaw opening. Further, there is evidence of a probable causal correlation between larynx height and pitch of voice (which accounts for the sternohyoids' activity in pitch lowering). Vertical movements in the larnyx, it will be argued, change the pitch of voice by changing primarily the vertical, not the anterior-posterior, tension of the vocal cords. [Research supported in part by the National Science Foundation.]
The Temporary and Permanent Threshold Shifts Produced by Three Levels of Impulse Noise
Authors: Sitler Ronald W. , Henderson Donald , Hamernik Roger P.
Published: October 2005

Monaural chinchillas (15) were exposed to 50 impulses of either 155 or 161 or 166 dB peak SPL. The imuplses were generated by a shock tube and had an A duration of 1 msec. Quiet threshold was measured at 0.25, 0.5, 1, 2, 4, and 8 kHz using the average evoked response (AER) technique. Recovery was monitored for 31 days. The median PTS for all frequencies was determined by the level of the impulse: the 155 dB level produced essentially no PTS, the 161 dB level produced approximately 10 dB PTS across all frequencies, and the 166 dB level produced 13 to 35 dB PST. For moderate to severe TTS, as much as 14 h were .necessary to reach maximum TTS. Unlike PTS results, TTSmax was not strictly determined by the level of the impulse. Specifically, the correlation between the PTS and TTSmax ranged from only r = 0.34 to r = 0.75. The results will be discussed in reference to existing damage-risk criteria for impulse noise. [Research supported by the Hendricks Foundation.]
Recovery from Sound Exposure: Comparison of Human Performance and Responses from Single Auditory-Nerve Fibers in the Cat
Authors: Young E. D. , Sachs M. B.
Published: October 2005

Following moderate exposure to pure tones (1 min, less than 70 dB SPL), the discharge rate of cat auditory-nerve fibers in response to near threshold tones is depressed. Recovery to normal (preexposure) firing rate follows a time course well approximated by the simple exponential function A[1−b exp(−t/τ)] [YOUNG, E. D., AND SACHS, M. B. (1971). J. Acoust. Soc. Am. 50, 94(A)]. We have measured probability of detection of near-threshold tones in human subjects following similar exposures. The recovery of detection probability is similar to recovery in the neural data. Recovery time constants are usually under 10 sec. These time constants decrease as the test-tone level is increased. As exposure level is increased, time constants for neural data increase. Psychophysical time constants increase with exposure level below about 40 dB SPL; unlike neural time constants they decrease at higher levels. The relationship of these data to TTS will be discussed. [Supported by the National Institute of Neurological Diseases and Stroke and the U. S. Air Force Office of Scientific Research.]
Coarticulation of Nasality: Evidence from Hindi
Authors: Dixit R. Prakash , MacNeilage Peter F.
Published: October 2005

The temporal scope of nasal coarticulation and its dependence on segment type, syllable boundary, and word boundary was investigated in Hindi, which, unlike English, has contrastive nasality in vowels as well as consonants. Various words with nasalized and nonnasalized vowels and nasal and nonnasal consonants and with syllable boundary falling at different places were selected and inserted in the meaningful sentences, which provided preceeding and following word boundaries to the inserted words. Electromyograms were recorded together with simultaneous recording from oral and nasal microphones. It was shown that (1) the effect of coarticulatory nasalily stretches beyond two segments on both sides of a nasal—vowel or consonants; (2) the temporal scope of coarticulatory effects was unrestricted by syllable or word boundary; and (3) left-to-right effects were as extensive as right-to-left effects. These results are discussed in relation to results of previous studies. [This work was supported by grants from the National Science Foundation.]
Some Determinants of Vowel Duration in Swedish Words
Authors: Lindblom Björn E. F. , Rapp Karin
Published: October 2005

Observations on the systematic variation of vowel duration in Swedish words as a function of word length, position, and stress are presented. The results reported are similar to the data presented in a previous study [Lindblom, STL-QPSR 2, No. 3, 1–5 (1968)] in that the compensatory adjustment of vowel duration is found to be only partial with respect to word length. Reinvestigating the problem quantitatively we have developed a formula around the assumption that “effective” word length is equal to “actual” word length raised to a power. Since the exponent is always < the actual number of syllables per word seems to be “underestimated.” We shall present several types of evidence that appear to support this suggestion. First of all, an accurate description of vowel durations in word-initial positions will be obtained. Second, in combination with a specific interpretation of the role of position, the introduction of the power transformation paves the way for a natural account also of the noninitial data, e.g., the so-called “final-lengthening” effect. [This research was supported by the National Institutes of Health under a research grant.]
Vowel Duration in Polysyllabic Words in American English
Authors: Umeda N.
Published: October 2005

The durations of vowels in polysyllabic words were studied from natural readings of texts by several speakers of various dialects. Durations of vowels in prepausal and word-final stressed syllables follow the same rules as those of monosyllabic words. They are affected strongly by pitch manipulations that reflect the word's syntactic position and semantic value [cf., N. Umeda and C. H. Coker, J. Acoust. Soc. Amer. 49. 123(A) (1971)]. Vowels in other positions in polysyllabic words are comparatively free of higher-level lengthening phenomena; durations are well accounted for by purely phonological conditions. Data are grouped into the following classes: (1) individual vowels with primary stress in non-word-final syllables; (2) vowels in word-initial unstressed syllables; (3) vowels in post-stressed, non-word-final syllables, and (4) vowels in word-final, unstressed syllables (with subclasses according to the type of ending: -ing, -ness, -ment, -er, etc.). Distribution patterns of data for different speakers are very similar; slight differences in average value are plausibly explained by differences in speech rate. After the above factors are taken into account, the remaining effects in these data from readings of texts do not positively support a direct influence of the number of syllables in a word on the duration of each vowel.
Ultrasonic Cutting of Rock Materials
Authors: Durley B. , Feith K. E. , Whymark R. R.
Published: October 2005

Low-frequency reciprocatory-rotary motion is imparted to a conventional axially vibrated ultrasonic cutter (18 kHz) that is impregnated with diamond grit of average size 0.003 in. The rotary motion is in a plane normal to the cutter axis. Cutting rates in rock materials of 10 ft/h are exceeded for 1-in. diam circular holes drilled to depths greater than 1 ft. Peak axial amplitude was 1.6 mil and the rotary motion was less than three to-and-fro oscillations per minute. Specific energy of the cutting process was measured to be less than 100 J/cm3 or less than that involved in the rotary cutters used for oil well drilling. Pulsed excitation at a 50% duty cycle leads to an 8%–10% increase in drilling rate for the same power input. Self pumping of the abraded material is obtained through subharmonic vibration of the cutter on pulse excitation. Static pressure, peak amplitudes, and rotary motion are optimized.
A Discussion of Ultrasonic Intensity Measurements as Related to the Radiation Control for Health and Safety Act
Authors: Smith S. W. , Stewart H. F.
Published: October 2005

The Bureau of Radiological Health is currently implementing an ultrasonics program to develop and evaluate measurement techniques, perform product evaluation, and assess potential hazards with the ultimate goal of determining the need for equipment performance standards under the Radiation Control for Health and Safety Act, Public Law 90-602. The program will include studies of ultrasonic radiation emissions and safety features for industrial, medical, and consumer devices. The initial research effort includes the development of a primary measurement calibration system applicable to plane-wave ultrasonic radiation in pulsed or CW mode; and the construction of secondary portable measurement devices suitable for field measurements.
Monte Carlo Applications to Acoustical Field Solutions
Authors: Haviland J. K. , Thanedar B. D.
Published: October 2005

The Monte Carlo technique is proposed for the determination of the acoustical pressure-time history at chosen points in a partial enclosure, the central idea of this technique being the tracing of the rays. A statistical model is formulated and an algorithm for pressure is created, the confirmity of which is examined critically by different approaches and is shown to give the known results. The concepts that are developed are applied to the determination of the transient field due to a sound source in a homogeneous medium in a rectangular enclosure with perfect reflecting walls, and the results are compared with those presented by Mintzer based on the Laplace transform approach, as well as with a normalmode solution. In contrast with these, the Monte Carlo approach is not restricted to the case of perfect reflecting walls, since absorptive walls can be handled. Possible future developments are indicated that would, it is believed, make the Monte Carlo method a valuable tool when boundary conditions are complex or when the medium is inhomogeneous. [Aided by NASA grant.]
Historical Notes on the Use of Horns for Sound Reproduction
Authors: Hilliard John K.
Published: October 2005

This paper will start with the early application of horns for sound reenforcement beginning around 1920 and describing the changes and types of driver units used. The introduction of sound to motion pictures required intensive applications of efficient drivers and horns because of limited amplifier power. The evolution of theater and high-power sound-projection systems will be described and how these changes have provided better distribution, increased-frequency range, and lower distortion.
Steady-State Noise Characteristics of Semireverberant Spaces
Authors: Ingalls Douglas J.
Published: October 2005

The use of a steady-state reference sound source, such as the Ilg Reference Sound Source, for determining the acoustic nature of semireverberant spaces is explored with emphasis on what precautions should be observed if useful eugineering results are to be obtained. For reasonable acoustic environments, the steady-state method can also be used to estimate the room absorption or, by the substitution technique, the sound power of an unknown source.
Practical Aspects of Machine Noise Measurement as Installed
Authors: Bell L. H. , Mull Harold R.
Published: October 2005

Many industrial manufacturing and processing companies, at the urging of plant engineers and safety directors, are requiring maximum noise level guarantees for purchased machines. Since “as installed” measurements form the basis of acceptance and provide plant engineers the only information available to assess noise impact, many questions are being asked about the value and practical aspects of these measurements. Presented in this paper are some practical aspects that must be considered in (1) choice of instrumentation; (2) treating unwanted reflecting surfaces and background noise; (3) dealing with pure tones and nonsteady noise levels; and (4) assessment of probable range of errors. The discussion will also include some practical applications of “as installed” measurements.
New Boundary Conditions and Results for the Peterson-Bogert Model of the Cochlea
Authors: Geisler C. D. , Hubbard A. E.
Published: October 2005

The Peterson-Bogert model of the cochlea [J. Acoust. Soc. Amer. 22, 369–381 (1950)] specifies, as one of its boundary conditions, zero pressure at the round window. This specification is equivalent to eliminating the round-window membrane. We have changed this boundary condition to include the round-window membrane, representing it with an acoustic compliance. With the new boundary condition, the equation for p+(x) requires a new solution, and a new value of p−(x) at x = 0 is needed. The new solution for p+(x) and the new value of p−(0) are given, for sinusoidal stimulation, as a function of frequency. The latter value is needed as the input to the Peterson-Bogert type of model of the basilar membrane. The model's input impedance as well as the relative displacement between the oval and round windows are also given. These relationships are compared with experimental findings.
Rippled Noise Investigations of Lateral Inhibition in the Ear
Authors: Feth L. L. , Green D. M. , Yost W. A.
Published: October 2005

Linear spatial analysis techniques have shown marked success in recent applications to vision. Determination of observers' modulation transfer functions (MTF) for sinusoidal intensity gradients has led to acceptable explanations for Mach bands and other contrast-enhancement phenomena. Fourier transformation of the MTF produces a spread-of-excitation function which shows a central excitatory area with an inhibitory surround. We have conducted analogous experiments in audition using wide-band noises with sinusoidally rippled spectra. Using a 2IFC tracking paradigm, listeners were asked to discriminate between rippled- and flat-spectrum noise bursts. Plots of ripple sensitivity as a tunction of ripple (spatial) frequency are analogous to the visual MTF. Fourier transforms of these functions do not exhibit the inhibitory surround, but this is probably due to a pitch cue provided by the rippled noise. [This research was supported by the National Institutes of Health, U. S. Public Health Service, Department of Health, Education, and Welfare.]
On Loudness Enhancement of a Tone Burst by a Preceding Tone Burst
Authors: Sokolich W. G. , Zwislocki J. J.
Published: October 2005

According to preceding experiments, loudness effects in pairs of tone bursts are controlled by two processes, loudness enhancement and loudness summation. This paper deals with the effects of intensity, time, and frequency differences between the bursts on the loudness enhancement of the second burst. Listeners were asked to match the loudness of a third (comparison) burst to the loudness of the second burst of a monotic burst pair. All three bursts had a duration of 10 msec, and the second and third bursts were at 1000 Hz. The intensity of the first burst was either +20, 0, or −20 dB re the intensity of the second burst, which was always at a sensation level of 40 dB. The interval between the onsets of the first and second bursts was varied stepwise between 10 and 500 msec, and the frequency of the first burst, between 200 and 4000 Hz. The results indicate a loudness enhancement that increases with the intensity of the first burst and decreases as the time interval and the frequency difference between the bursts in the burst pair increase. When the first burst was at an intensity level of −20 dB, a loudness decrement occurred.
The Critical Masking Interval
Authors: Penner M. J. , Robinson Charles E. , Green David M.
Published: October 2005

We investigated the concept of a critical masking interval, the time period during which noise is effective in masking a brief signal. The signal was a 100-μsec click temporally placed in the center of a gated-noise masker. Both the click and the noise were lowpass filtered so that the power spectra of signal and noise have similar shape. The duration of the noise masker was varied from 100 μsec to 100 msec and two noise levels were employed. Like the estimate of the critical bandwidth, the estimate of the critical masking interval can be made in two independent ways. First, for long durations of the noise masker, the ratio of click energy to over-all noise power, adjusted for energy resolution, indicates that the critical masking interval is about 14 msec. Second, progressively shortening the duration of the noise masker did not improve detectability until the duration was less than approximately 10 msec. The near agreement of these two independent estimates supports our interpretation of the data in terms of the concept of a critical masking interval.
Developments in the Use of Acoustic Shock Pulses in the Study of Elastic Properties of Solids
Authors: Nakamura A. , Yasumoto Y. , Takeuchi R.
Published: October 2005

A nondestructive method of measurement is being developed for the purpose of investigation of the dynamic behavior of solids, especially concerned with nonlinear elasticity. In this paper, we discuss a method of generation of reproducible acoustic shock pulses in various solids, and also discuss the measurements of the stress-strain relationship using intensive acoustic shock pulses. Results obtained are the following: In aluminum samples, a linear relationship between stress and strain is found experimentally for acoustical pressures up to 130 bar before annealing and also up to 65 bar after annealing. On the other hand, after annealing the specimens, we found a variation of pulse shape and a decrease of peak value compared with the pulse shape before annealing. A qualitative discussion is given of photographs of changes in the shapes of the shock pulses that have propagated through solids.
Optical Determination of the Nonlinearity Parameter of Water
Authors: Cook B. D. , Martin N. C.
Published: October 2005

The optical methods of investigating ultrasonic waves played an important role in the early investigations of finite-amplitude acoustics, particularly in experimental determinations of the nonlinear parameter B/A of water. However, after thermodynamic methods were discovered for obtaining B/A, the optical methods did not then, and have not as yet, yielded values in agreement. This paper discusses a new attempt to evaluate B/A for water, utilizing the optical techniques and taking in account a correction for the nearfield of the transducer. Assumptions made for smoothness of the second harmonic nearfield and the accepted value of the piezooptic coefficient are discussed.
Acoustic Study of Register Equalization in Singing
Authors: Large Joan W.
Published: October 2005

A paired comparison technique in which fundamental frequency (330 Hz), phonemic category, /a/ and sound level (comfortable but equal) were held constant with register as the variable of primary interest was utilized with subjects who sang tone pairs varying in degree of audible-register timbre difference or equalization. The paired tones were presented to a panel of 12 expert listeners for judgments of register identification and ratings of register equalization. The vowels produced were labeled by a trained phonetician. These judgments were compared with the acoustic records from a Sonograph modified to permit 24-msec sections to be made at five positions within selected vibrato cycles: two peaks, two slopes, and a valley. The mean values for each partial and each subject were pooled in mean spectra for comparison of female chest and middle registers. The values for the paired tones judged to be “best equalized” were also compared across registers and with the spectra of the “least equalized” paired tones. It was found that chest register was characterized in general by greater energy in the partials above the third partial, especially partials 4 and 5, and that the middle register had a stronger fundamental.
Interaction of the Clarinet Reed with an Air Column Having a Single Resonance
Authors: Backus John
Published: October 2005

A study of the interaction between the reed and air column in the clarinet is underway, using a synthetic clarinet reed in a mouthpiece adapted to accomodate resonant air columns of various kinds. Measurements of the air flow into the reed-mouthpiece combination mounted in an artificial embouchure show the negative resistance characteristic necessary to sustain oscillations in an attached resonant air column; the value of this resistance is varied by changing the gap between the reed tip and the mouthpiece. A system resembling a stretched-out Helmholtz resonator and having a single pronounced resonance was made to oscillate by attaching it to the mouthpiece and blowing on the artificial embouchure. The input impedance of the system at its resonance frequency was measured on an impedance tube, and it was expected that the system would oscillate when this input impedance was approximately equal to the negative resistance of the reed-mouthpiece combination. However, experiments showed that oscillations did not take place until this negative resistance was about half the input impedance. [This work was supported by a grant from the National Science Foundation.]
Effects of High-Intensity Sound on Muffler Element Performance
Authors: Sacks M. P. , Allen D. L.
Published: October 2005

This paper presents the results of an experimental investigation designed to study the effect of high-intensity sound on muffler element performance. Five prototype mufflers were built and tested over a wide range of frequency and intensity. The mufflers were chosen as being representative of basic single element and combination reactive mufflers. The test facility consisted of an acoustic transmission line driven by an electromagnetic sound source and terminated anechoically. Attenuation data is presented superimposed on curves derived from linear acoustic theory. Conclusions are stated for expansion chamber mufflers at higher SPLs than could be produced by the test equipment by using constriction-tube data and acoustic similarity between these elements. It is shown that the expansion chamber muffler will operate as a linear element when subject to incident SPLs of 165–180 dB depending on muffler attenuation. Mufflers containing resonator elements show no deviation from a linear theory when subject to SPLs of the order of 160 dB except at points near a resonant frequency.
Sound Attenuation in Ducts Lined with Nonisotropic Material
Authors: Kurze U. J. , Vér I. L.
Published: October 2005

This paper deals with the sound attenuation in rectangular ducts with nonisotropic lining. The nonisotropy may be due to the basic structure of the fibrous lining material or it may be deliberately created by rigid partitioning of the lining perpendicular to the duct axis. The propagation constant in the axial direction is obtained in the form of a transcendental equation which includes as special cases the locally reacting lining investigated by Morse and Cremer for infinite flow resistance in the direction of the duct axis, and the homogeneous lining as treated by Scott. A simple approximate solution of the transcendental equation for low frequencies indicates that optimum attenuation of the fundamental mode is achieved using & nonisotropic lining with a flow resistance in the direction of the duct axis that increases with increasing frequency. At middle and high frequencies, the propagation constant is evaluated numerically using a Newton-Raphson scheme for several typical silencer geometries.
Development of a Computer Program for the Determination of Sound Absorption in Cylindrical Ducts Lined with Porous Materials
Authors: Jhaveri A. G.
Published: October 2005

A computer program has been developed that allows a determination to be made of the sound absorption in cylindrical ducts. The computer program is based on a realistic mathematical model for computing sound absorption of a very long cylindrical duct lined with porous material of uniform thickness. For simplicity, it is assumed that there :is no airflow in the duct. The program computes sound absorption of the fundamental mode, the solution being for a single-frequency component of an unaveraged time signal. These calculations must be repeated for each of the frequencies being considered, a special feature of the program. The results of this program are in reasonably good agreement with the: experimental data. The predicted curve has both qualitative: and quantitative agreement with that obtained from actual test results, in terms of the amplitude and location of the resonance.
Acoustics as a Physical Science
Authors: Beyer Robert T.
Published: October 2005

A comprehensive review of the field of acoustics, from the perspective of its relationship to physics, has been completed. Contrary to conclusions of many colleagues in the field of physics, acoustics retains a vital role in the search for knowledge about our physical universe. Additionally, the physical concepts developed in studies of acoustics continue to play an important part in support of the several aspects of acoustics that are categorized as parts of other fields. These viewpoints are supported by several selected examples in order to provide a meaningful understanding by workers in the several subfields of acoustics.
Applied Acoustics and Its Role in Modern Society
Authors: Flynn Daniel R.
Published: October 2005

Acoustics has been a wonderful science for the thousands of workers in that field. Yet, we find ourselves today with an unfulfilled wanting for rewards from the scientific accomplishments. It is easy to name dozens of specific problems of very practical importance today which need solutions based upon these accomplishments. These problems cover a wide range—from health, pleasure, and other human problems to engineering problems of all sorts, including excavation, chemical reactions, sonar, and so forth. Some of these problems and proposed solutions will be described in terms of real world needs of today.
Vortices and Turbulence as a Cavitation Nucleation Mechanism
Authors: Finch R. D.
Published: October 2005

Several experiments using liquid helium as a medium of study have indicated that superfluid vortices or turbulence enhance ultrasonic cavitation. The possible mechanisms of this process and its possible applicability for normal liquids are discussed.
Experimental Study of Transient Response Spectra of the Double Acoustical Resonator
Authors: Reddy N. N. , Lowery R. L.
Published: October 2005

Experiments were conducted to study the pressure transient response of an adjustable double acoustic resonator. The excitation was provided by a transducer at the end of a 32-ft plane-wave tube. Pressure histories were measured in both cavities of the resonator. Pressure magnifications as high as 6.0 were measured in one cavity. The experimental results are compared with Helmhoitz theory.
Interior/Exterior Noise Levels of Over-the-Road Trucks
Authors: Quindry Thomas L. , Leasure William A.
Published: October 2005

Interior/exterior measurements were made on 15 trucks covering many makes, models, and drive-train combinations to provide an information base concerning vehicle interior noise levels for rulemaking by the Bureau of Motor Carrier Safety, Department of Transportation. Measurements were made 6 in. from the left and right ears of the drivers under various vehicle operational modes with windows open and closed. Stationary tests included: (a) low idle, (b) acceleration from low idle to maximum governed rpm with wide open throttle while in neutral gear; and (c) high idle. In addition to the acceleration and deceleration tests specified by SAE J366 (Exterior Sound Level for Heavy Trucks and Busses), an additional moving test was performed to simulate a truck starting up in city traffic. In order to study the effect of total truck noise on the community, simultaneous exterior measurements were made with an array of six microphones. The data obtained, as well as the test procedure and measurement techniques utilized, will be discussed.
The World of Deafness—As Viewed by An Insider
Authors: Norwood Malcom
Published: October 2005

A first-person account of the experiences and problems encountered in a world of silence. Described are a personal reaction to the loss of hearing and the reaction of the family; educational experiences; social life; methods of communication; and problems constantly faced in a competitive professional world.
Sources of Probability in Predicting Passive Sonar Performance
Authors: Andrews F. A.
Published: October 2005

There are three sources of probabilistic statements found in predicting passive sonar performance. These are (1) the detection process for a single observation time T; (2) the sequence of multiple observations carried out by a sonar operator resulting in N independent observations; and (3) the availability of a given level of input signal to noise (S/N) ratio. The first two considerations result in a conditional detection and false-alarm probability given a fixed value of input S/N ratio. Recognition differential is seen not as the value of input S/N ratio required for detection probability 50% but rather the minimum value of S/N ratio that will trigger the sequential observation process and lead to a detection probability near unity and false-alarm probability near zero. The third consideration results in a probability density distribution for input S/N ratio because one wishes to predict detection for an ensemble of targets, propagation loss conditions, sea states, and sonar operators. The probability of detection for a given variance and expected value of input S/N ratio and given value of recognition differential is seen to be the integrated product of the first two probabilities times the third. The probability of a false alarm in passive sonar operation is negligibly low because of the sequential observation process. A sample problem for aural detection and for detection by time-bearing plot will be presented.
The Directivity of Sonar Receiving Arrays: The Non-Omnidirectional Case
Authors: Queen William C.
Published: October 2005

The limiting case of a continuously distributed array has long been recognized as a useful aid in the design and study of sonar receiving arrays consisting of a large number of elements. In a paper appearing in 1963, Anderson and Munson utilized this approach to determine the directional characteristics of spherical arrays, and more recently (1970), W. C. Queen pursued this idea further to include more general configurations. In all these analyses, the hydrophones were considered to be omnidirectional. In this present paper, the more general situation of a continuously distributed array of nonomnidirectional elements is considered, and results are given for the special case of a spherical array whose elements exhibit hypercardioid response patterns.
Reduction of Peak Jet Noise using Jet Refraction
Authors: Morris P. J. , Richarz W. , Ribner H. S.
Published: October 2005

The directivity pattern of sound generated by a subsonic jet exhibits a peak at angles between 15° and 45° to the jet axis decreasing to a minimum on the axis. Theoretical and experimental investigations have previously demonstrated that this minimum is due to refraction of sound by the jet flow. The present experimental study considers the effect of the introduction of a second jet of smaller exit area near to the main jet. It is shown that the second jet imposes its own heart-shaped directivity pattern on that of the first jet. Alteration of the angle between the two jets leads to a reduction in the peak sound level. Spatial distributions and spectra employing unfiltered and filtered measurements are presented for changes in the temperature ratio of the two jets and their geometrical configuration.