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Steady-state evoked potentials were measured from unanesthetized chinchillas both before and after carboplatin-induced selective inner hair cell loss. Recordings were made from both the inferior colliculus (IC) and the auditory cortex (AC). The steady-state potential was measured in the form of the envelope following response (EFR), obtained by presenting a two-tone stimulus (f1 = 2000 Hz; f2 = 2020, 2040, 2080, 2160, or 2320 Hz), and measuring the magnitude of the Fourier coefficient at the f2-f1 difference frequency. From the IC, precarboplatin, EFR amplitude vs difference tone frequency showed a bandpass pattern, with maximum amplitude at either 160 or 80 Hz, depending upon stimulus level. Postcarboplatin, the preferred difference frequency was 80 Hz for all stimulus levels. From the AC, EFR amplitude versus difference tone frequency also showed a bandpass pattern, with the maximum amplitude at 80 Hz both pre- and postcarboplatin. EFR amplitude from the IC was decreased for some conditions postcarboplatin, while the amplitude from the AC showed no significant change.

In the region where a sinusoidal wave in the cochlea reaches its maximum amplitude, the long-wave (or one-dimensional) model of the cochlea is deficient. In this region a short-wave model is more appropriate. However, in its current form, the short-wave model supports only waves in one direction. Therefore, it cannot cope with reflection effects associated with, e.g., inhomogeneities. Theoretical explorations of creation and internal reflection of otoacoustic emissions have almost exclusively been based on the long-wave model. In this article the road is paved for future explorations on a generalized form of the short-wave model, one that supports forward as well as backward waves, and thus can include internal reflections.

Sound pulse propagation in shallow water is studied. We assume a geometry where an acoustic track crosses the wave‐front of a moving internal soliton (IS) or train of solitons. During propagation, sound pulses undergo perturbation due to mode coupling. For each individual mode selected at the receiver, we observe a set of incoming pulses, each having different arrival times. Time‐frequency analysis is carried out for the modal arrival times for different frequencies, emphasizing the dependence on position of the moving solitons. It is shown that the maximum amplitude of the incoming pulses created at the ISs due to mode coupling has approximately the same arrival time, independent of frequency. This invariant arrival time is determined by waveguide parameters and corresponds to maximal coupling of different pairs of modes. Analysis is carried out both for a model shallow water channel and for real experiment data (SWARM95, NRL acoustic track). Satisfactory agreement is demonstrated, and physical interpret...

The acoustical properties of a multipurpose hall (opera mode) were measured in a 1:10 scale model to investigate the effect of diffuse reflections. Measurements were made in stall areas with and without diffusers on the walls adjacent to the pit and on the side walls. The diffusers consisted of 15‐ to 25‐cm‐high hemispheres and 25‐cm high polygons. A mix of these diffusers was used to cover about 40% of the area of the side walls. It was found that 1‐IACCE3 increased at positions close to the walls adjacent to the pit and the first reflection with maximum amplitude increased in some seats. The possibility of diffuse reflections either hitting the proscenium wall or soffit close to the side wall first, as well as reflections coming from both sides of the hall explains the reason for the bunch of early reflections in the impulse responses. The effect of diffusers at each receiver position was investigated via subjective evaluation. The results from the subjective evaluation indicated that diffuse reflections were preferred to specular reflections.

An infrasound observation system is installed in Isumi, Japan (35.3N, 140.3E) as the component of the International Monitoring System for CTBT. The observation system was deployed on November 2004. It comprises a six‐element array. Five elements of the array are deployed as a pentagon with sides approximately 1.2 km long. The sixth element is located within the pentagon‐shaped array. Until now, some interesting infrasound signals were observed. One of them was the infrasound wave produced by the large earthquake that occurred off the Pacific coast of North‐East Japan on 16 August 2005. The infrasound wave‐train, which had a spindle‐shaped envelope, was detected following the arrival of the seismic wave. The arrival direction of the infrasound wave, which had maximum amplitude, indicated the direction of the land area, which had maximum intensity. The time difference between the on‐set time of that infrasound wave and the origin‐time of the earthquake coincided with the travel time for propagation in the atmosphere between the area that had maximum intensity and the observation site. Therefore, it was estimated that the observed infrasound waves were produced by shaking ground. In this paper, some remarkable infrasound signals including the above are discussed.

Male Pacific treefrogs (Hyla regilla) use advertisement and encounter calls to regulate intermale spacing within breeding choruses. Encounter calls are produced when a neighbor’s advertisement calls exceed a threshold amplitude. These aggressive thresholds are plastic; males resume advertisement calling (i.e., accommodate) to repeated presentation of advertisement calls at amplitudes 4–8 dB above their aggressive threshold. Correspondingly, a male’s aggressive threshold for the advertisement call is positively correlated with the maximum amplitude of neighbors advertisement calls measured at his position. The aggressive thresholds of males for the encounter call are also plastic but not correlated with the maximum call amplitude of their neighbors. This disjunction stems from the fact that males in stable choruses are not regularly exposed to suprathreshold encounter calls. Accommodation to one call type fails to significantly alter a male’s aggressive threshold to the other call type, which suggests that...

Early d scussions of the acoustic correlates of stress suggested that stressed syllables are produced with greater amplitude than unstressed syllables [e.g., H. Sweet, A Primer in Phonetics (Clarendon, Oxford, 1890]. More recently, increased fundamental frequency (F0) change and duration have been demonstrated to be more reliable cues of stress than increased amplitude [e.g., D. Fry, Lang. Speech 1, 126–152 (1958)]. Nevertheless, none of these acoustic parameters has been consistently connected with stress, and their relative importance as cues for stress appears to vary across languages. In the present study, English and French monolinguals produced sentences containing sententially stressed and unstressed monosyllabic words. In addition to F0 change, duration, and amplitude, the relative positions of the maximum and minimum amplitude were measured. The results indicate that: (1) increased F0 change, duration and amplitude are associated with stress in English, but not in French; and (2) an early maximum amplitude is associated with stress in both English and French. The present study suggests that early discussions of amplitude as an important acoustic correlate of stress may not have been far off, but that the position—rather than the relative level—of the maximum amplitude is the pertinent parameter.

In English, sentence stress is used both to mark a phrase boundary and to provide focus for new discourse information. The goal of this study is to describe the behavior of the acoustic signal when phrase‐final and focal stress occur in the same sentence. Two questions were addressed: (1) How do acoustic correlates of stress behave when phrase‐final and focal stress converge within a sentence? (2) How do acoustic correlates of stress behave when phrase‐final and focal stress occur separately in a sentence? Subjects produced sentences containing monosyllabic works in phrase‐initial and phrase‐final position which were either focused or non‐focused by the discourse. Fundamental frequency change, vowel duration, amplitude, and the position of the maximum amplitude were measured. The results indicate that for the parameters investigated (1) the acoustic correlates of stress are additive when phrase‐final and focal stress converge in a sentence; and (2) the acoustic correlates of stress are more dominant for phrase‐final stress than for focal stress when they occur separately in a sentence. These findings suggest that sentence stress simultaneously signals phrase‐final and focal stress by superimposing one on the other.

An analysis is made of the low-frequency behavior of a three-dimensional hydroelastic model of the cochlea. In essence, the fluid motion is described using the linearized Navier-Stokes equations and the basilar membrane is modeled as an elastic plate. It is found that, for the lower frequencies, resonating frequencies are present and are approximately 4 HZ apart. The problem is solved and an analysis is made of the effects of the geometry on the motion of the wave. To conclude, an asymptotic formula is derived for the place of maximum amplitude and it is found to compare favorably with von Békésy's experimental results.

The phenomenon of the fatigue in elastic materials is represented by introducing a derivative of real order in the stress–strain relation. It is found that this phenomenon occurs when aγ/ηD (Q is the specific dissipation, η the elastic parameter, ? the yield stress, D the maximum amplitude of the cyclic strain applied with period 4a) is near the critical value 1+0.113/Q. This model allows also to estimate the number of cycles which would give the fatique as function of the maximum strain applied and of its frequency.

The technique of forced vibration has been applied to the study of the properties of viscoelastic materials. It is found, through the analysis of a free sphere with a harmonic oscillating internal source, that the vibration‐amplitude ratio of two measuring points is associated with the complex dilational constants and a complex ratio directly related to the complex Poisson's ratio of the material. From the criterion of maximum amplitude ratio (i.e., by adjustment of the frequency of the source for the amplitude ratio to reach a maximum), these properties can be expressed in terms of the amplitude ratios and their frequencies. For the convenience of laboratory testing, two particular amplitude ratios, in conjunction with their frequencies, have been considered for this purpose. Simple expressions are given, relating the properties of the test material to quantities measurable in the laboratory: namely, the maximum amplitude ratios and their corresponding frequencies.

Following previous investigations on forced‐vibration methods of determining dynamic mechanical properties of viscoelastic materials, this article is proposing a similar technique for determining the complex Poisson's ratio and the complex dilatation constants. Through the study of forced vibration of a free viscoelastic sphere with internal harmonic oscillating source, it is found that the above mentioned properties of the test material are related to the ratio of the vibration amplitude of two measurable points. Thus, when using the criterion of this ratio approaching its maximum, the maximum amplitude ratio, these properties can be expressed in simple relationship with the laboratory‐measurable quantities: namely, the maximum amplitude ratios and their corresponding vibration frequencies. Investigations have been carried out for three sphere sets.

Calculations were made of the dimensions of traveling‐wave envelopes in four species. The calculations were based on Bekesy's measurements of the tuning curves of single points on the basilar membrane of each species, and on four empirical functions, one per species, relating frequency to position of maximum amplitude on the basilar membrane. The functions were in approximate agreement with other observations by Bekesy. It was found that the distances over which a traveling wave damps from maximum amplitude to fractions of maximum amplitude—i.e., to one‐half maximum, to two‐tenths maximum, or to “zero” amplitude, respectively—appear to be approximately constant, independent of the position of maximum amplitude on the membrane. In comparing the traveling wave envelopes of the four species, elephant, man, guinea pig, and chicken, it was found that (1) the shape of a traveling‐wave envelope is quite similar among the four species, (2) the distance over which a traveling wave damps from maximum to “zero” amplitude is the greater the longer the basilar membrane, (3) this distance, in the species compared, seems to be an approximately constant fraction of the length of the basilar membrane, independent of the length of the membrane.

The history of piano development indicates that tone quality has often suffered because the soundboard lacked the optimum response to vibration of the strings. This lack has been particularly noticeable in the high treble notes. Early experimentation in design attempted to correct this difficulty by extreme variations in size and shape of the board and by the use of special resonating chambers. Eventually such radical departures were discarded in favor of the present type of soundboard. This paper describes experimental work that has been conducted in an effort to determine some of the factors of soundboard behavior which influence the tone quality of the piano. Apparatus was constructed for measuring the amplitude of vibration at different points over the surface of the board when the keys were actuated by a mechanical striker. The results show that for a given piano the most acceptable tone quality is obtained when the soundboard vibrates more or less as a diaphragm with the maximum amplitude near the center. Changes in the compression or loading of the board which tend to reduce this diaphragmatic action also produce a less acceptable tone quality. In order to retain desirable tone quality in small pianos, it was necessary to compensate for the limitations of shorter strings and smaller soundboard area by changes in the structural design of the soundboard itself. Comparative measurements made on small pianos with old and new types of soundboards show that in the latter (1) the board vibrates more nearly like a diaphragm, (2) the treble tones have a higher initial intensity and (3) the treble tones decay at a slower rate.

Ultrasonic absorption measurements were made to compare the relative effectiveness of H2O and D2O molecules in influencing thermal vibrational relaxation in N2O molecules. The displacement rates of the absorption per wavelength maxima induced by H2O and D2O were compared in N2O ‐ H2O and N2O ‐ D2O mixtures. Experimental apparatus was constructed for these measurements which utilized the “direct” absorption technique in conjunction with pulsed sound waves, having a frequency of approximately 113 kc. The parameter of frequency/pressure was varied by changing the gas pressure.The data were taken at a temperature of 21°C in the frequency/pressure range of 100–700 kc/atmos. The maximum amplitude of the molecular absorption coefficient per wavelength in dry N2O was 0.153 and this occurred at 210 kc/atmos. Measurements were taken in N2O ‐ H2O and N2O ‐ D2O mixtures at H2O‐vapor and D2O‐vapor concentrations of 0.39%, 0.77%, and 1.14%.The usual single relaxation time theoretical absorption curve could be fitted to...

A method and apparatus are described for detecting an acoustic wave in a waveform produced from a sonic receiver in response to an acoustic investigation of a borehole. The maximum amplitude of the waveform is measured and a portion thereof utilized as a threshold for comparison with successively different combinations of initial portions of the waveform and the waveform location, where the threshold is exceeded, is identified as the location of the wave. A pattern comparison is made between waveform segments where the acoustic wave is initially located to provide a correction factor for a more accurate locating of the acoustic wave. A parameter of the wave, such as its interval travel time is measured with the acoustic wave locating techniques.

This was an investigation of acoustic‐reflex adaptation in ten adults in each age decade between 20 and 79 years. Reflex‐activating stimuli, presented by earphone to the ear contralateral to the acoustic‐immittance probe, were four tones (0.5, 1.0, 2.0, and 4.0 kHz) and two filtered noises. Sound pressure levels were +5, +10, +15, and +20 dB re: acoustic‐reflex threshold. Stimulus duration was 60 s. Reflex responses were measured with both components of aural acoustic admittance. Custom software was written for automated digitization, storage, quantification, and plotting of the responses. Statistical analyses of conductance and susceptance data included static acoustic admittance, acoustic‐reflex threshold. maximum amplitude of reflex, rate of adaptation, and shift of baseline during reflex activation. Adaptation rate was highest for the 4.0‐ and 2.0‐kHz activators and varied with stimulus level. Comparison of multiple regressions revealed age‐related trends in measures of adaptation. [Work supported by ...

The basic theory of sound fields induced by vorticity [see “Vortex Sound,” Dept. Eng. Rept. 61–70 (1961)] is briefly reviewed, and applied to the following situation. Two parallel rectilinear vortices of length l and of the same circulation Γ are distance 2y apart, and spin about the axis lying between them. The sound field is like that of a lateral quadrupole, rotating with the spinning flow field, the directional pattern somewhat resembling a doughnut, without a hole, threaded on the axis of spin. The maximum amplitude of the pressure perturbation at distance x is very easily shown to be (ρ0/xc02)(Γ/4πy)4l, where ρ0 is the fluid density and c0 is sound speed. This simple result applies to weak vortices, Γl/(2πy2c0)≪1. The rotating quadrupole may be represented by sinusoidally varying fixed quadrupoles, either by one lateral one together with longitudinal ones of opposite sign aligned along each of the axes of the lateral ones, or by two lateral ones that have their axes bisecting each other. The sound p...

A computer program for syllable detection was developed for possible application in future speaker independent speech recognition systems. Usage of both peak‐to‐peak (P‐P) amplitude and rms intensity measurements was considered, but it was observed that P‐P amplitude measurements alone provided good results, and that almost none of the resulting syllable detection errors could be eliminated through the additional consideration of rms intensity information. Syllable detection was based upon the recognition of the variations in amplitude which frequently accompany the onset and offset of both syllable nuclei and associated nonvowel sonorants. Changes in P‐P amplitude and the maximum amplitude occurring within each change were therefore the primary measurements considered in the recognition process. Thus far, an averaged syllable detection accuracy of 86% has been obtained for nine talkers speaking a total of 3.5 min of continuous speech, with individual syllable detection results ranging from 74% to 96%. Mi...

A system for carrying out vibrational analysis of machinery and the like wherein a voltage controlled filter is combined with a phase-locked feedback loop to detect maximum amplitude within a given frequency band. A simply derived readout of frequency and amplitude is made available with the arrangement and operation over three or more decades of frequency is availed without manual switching and the like.

The amplitudes of auditory‐evoked responses recorded from chronic electrodes in the inferior colliculus of the chinchilla were measured before and after acoustic trauma. Acoustic trauma was induced using a 2‐kHz continuous tone that resulted in either 30–40 dB of TTS or PTS between 2–8 kHz. The high‐intensity exposures resulted in systematic changes in the input/output functions of the evoked response. The most striking change was an increase in the maximum amplitude (“enhanced”) of the evoked response at frequencies below and at the low‐frequency edge of the hearing loss (0.5 and 2 kHz). By contrast, the maximum amplitude seen at frequencies near the middle of the hearing loss or its high‐frequency border (4 and 8 kHz) was generally depressed. In addition to the change in maximum amplitude, there were also changes in the slope of the evoked response input/output functions. The results will be related to the pattern of hair cell loss as well as to possible underlying neural mechanisms. [Work supported by ...

A comparative study was conducted on the relative latency of the acoustic reflex in alcoholic vs. nonalcoholic test sessions on seven normal hearing adults. Acoustic reflex data were collected using impedance audiometry. Reflex eliciting stimuli were a 500‐Hz pure tone, and a low frequency band of Noise 500–1000‐Hz wide. The parameters analyzed were defined as: (1) L1, the onset of the signal to the initiation of the reflex, (2) L2 the initiation of the reflex to 90% of the maximum amplitude, (3) L3, the offset of the signal to the initiation of the reflex decay, and (4) L4, the initiation of the reflex decay to 10% of the maximum amplitude. Alcohol levels were monitored using a breath‐analyzer test. Results showed that overall, alcohol had little effect on the L1 and L3 durations, whereas, the L2 and L4 latencies were longer in the alcohol than in the nonalcohol condition. There was a definite trend toward increased variability among the subjects for all responses under the alcohol condition when compared to the nonalcohol condition. [Work supported by NIH.]A comparative study was conducted on the relative latency of the acoustic reflex in alcoholic vs. nonalcoholic test sessions on seven normal hearing adults. Acoustic reflex data were collected using impedance audiometry. Reflex eliciting stimuli were a 500‐Hz pure tone, and a low frequency band of Noise 500–1000‐Hz wide. The parameters analyzed were defined as: (1) L1, the onset of the signal to the initiation of the reflex, (2) L2 the initiation of the reflex to 90% of the maximum amplitude, (3) L3, the offset of the signal to the initiation of the reflex decay, and (4) L4, the initiation of the reflex decay to 10% of the maximum amplitude. Alcohol levels were monitored using a breath‐analyzer test. Results showed that overall, alcohol had little effect on the L1 and L3 durations, whereas, the L2 and L4 latencies were longer in the alcohol than in the nonalcohol condition. There was a definite trend toward increased variability among the subjects for all responses under the alcohol condition when compare...

Glottal sound waveforms were derived by an inverse filtering method from sustained vowels uttered by 217 patients suffering from 15 kinds of laryngeal diseases and by 20 normal speakers. Various parameters which indicate individual characteristics were extracted from autocorrelation function, correlograms of time series of fundamental period and maximum amplitude in each fundamental period, and spectral envelope of the glottal sound waveform. Then, dependency on each other among acoustical parameters was examined by principal component analysis. Meanwhile, medical parameters utilized in diagnosis were evaluated quantitatively, and the relation between those and the acoustical parameters was examined also by principal‐component analysis. Combining those results, more than 10 acoustical parameters which seemed to be useful for diagnosis and to be rather independent of each other were selected. Using canonical analysis the axes which discriminate the kind of disease best were obtained based on those acoustical parameters of the patients of several diseases and normal speakers, and the degree of discrimination and the contribution of each acoustical parameters to each axis were examined.

A laser light scattering interferometer was used to measure the amplitudes of sound induced vibrations of the tympana of two amphibian (Bufo americanus and Hyla cinerea) and one reptilian (Chrysemys scripta elegans) species. The maximum amplitude varied somewhat across species but was on the order of several hundred Angstroms for a stimulus intensity of 90 dB SPL. In Bufo americanus the vibration amplitude is fairly constant to about 1.75 kHz then decreases at a rate of 21 dB/octave whereas in Hyla cinerea the roll off begins above 2.5 kHz and has a slope of between 14 and 22 dB/octave. In Chrysemys scripta elegans the vibration amplitude increases up to 500 Hz, drops off slowly (6.5–11 dB/octave) between 650 and 1250 Hz then more steeply (8.5–15 dB/octave) above 1250 Hz. In each species the frequency at which the vibration amplitude starts to decrease is correlated with the highest best excitatory frequency found in eighth nerve fibers, suggesting that the upper frequency of hearing is limited by the mid...

1. A system for locating a radiating source comprising a plurality of mutly spaced radiation detectors, first means for correlating the output of one of said detectors with the output of a second of said detectors, second means for correlating the output of the second of said detectors with the output of a third detector, means coupled to said first and second correlating means for separately integrating the outputs thereof to produce a pair of integrated signals, and means for delaying one of said integrated signals with respect to the other of said integrated signals, whereby the delay is indicative of the range of the source from the detectors when the maximum amplitude of the delayed integrated signal coincides with the maximum amplitude of the other integrated signal.

The Doppler‐shift compensation behavior of the CF‐FM bats was studied by making three Pteronotus parnellii parnellii fly through an array of seven vertically strung nylon monofilament lines (1.0 mm in diameter) placed near the center of a flight room (12.4 m long, 2.5 m wide, and 2.0 m high). By means of an electric motor. the aluminum frame in which the lines were strung could be made to oscillate in the horizontal direction parallel to the alignment of the obstacles. The maximum amplitude of oscillation was 31 cm and the average speed was 10.3 cm/s. All three bats negotiated moving lines more successfully than stationary ones. The flight speed was about 2.0–2.8 m/s as a bat approached and passed the lines, but it was only about 0.5–0.7 m/s during the final phase of negotiation of lines. Analysis of the emitted signals indicated that each bat appropriately adjusted its emission frequency according to its flight speed during different phases of flight in order to accurately compensate the positive Doppler‐shifted echoes. [Work supported by NSF BNS 80 07348 and USPH 1‐KO4‐NS00433‐01.]

An oscillation dampening system composed of masses, in which a spring and dampeners are clamped together and coupled to a railroad track to prevent the formation of ripples on the track. The system is tuned to the characteristic frequency of the railroad track and is coupled thereto to reduce the maximum amplitude of oscillation at the characteristic frequency and to shift the occurrence of other amplitudes of oscillation to frequencies away from the characteristic frequency and to reduce the amplitudes of oscillation at the shifted frequency. The maximum of the shifted amplitudes of oscillation is reduced by ten percent from the maximum at the characteristic frequency.

Two distinct periodic variations in the underwater noise level have been observed in coastal waters off San Diego. The first has been previously reported and appears diurnally before sunset, reaches maximum amplitude just after sunset, and then fades away within 3 h. This variation is observed in the 100‐ to 1000‐cps band and raises the sound‐pressure level 5–20 dB above the normal background, with maximum duration and intensity occurring in the Summer months. This effect is occasionally noted at sunrise, though with lower amplitude than at local sunset. The second periodic variation has a period of 25–40 sec and is observed only at night in the late Spring and Summer months. Its amplitude is commonly from 3 to 6 dB but maximums of 16 dB have been noted. It is observed above the background in the 300‐ to 800‐cps band, with peak amplitude occurring at about 450 cps. Two members of the croaker family—spotfin, Roncador stearnsi, and yellowfin, Umbrina roncador—are in part responsible for the periodic variations.

The “negative” summating potential as recorded on the first and second turn of the cochlea for high and middle frequencies is linearly proportional to the logarithm of the duration of the sound stimuli within the range of values that have been investigated, from 20 msec to 2 sec. Preliminary calculations of the output‐input functions of the potentials for different frequencies in different turns of the cochlea show that its magnitude is linearly related to the strength of the stimulus for middle range of sound‐pressure levels. Their slope is higher in each turn for the frequencies near the ones for which this region of the cochlear partition has the maximum amplitude of displacement.

Analysis of computer‐summed click‐evoked APs recorded from the round window of rats at ages from 1 to 24 months revealed that: (1) The mean visual detection levels of unaveraged APs rises progressively from 6 to 24 months by 16.5 dB. (2) N1 amplitude rises from 1 to 12 months, and then declines to 24 months at all but the lowest level (50 dB SPL P.E.) as reported at the previous meeting of this society. (3) Conversion of N1 amplitudes to percents of maximum amplitude for each animal eliminates the above age effect, as expected. (4) N2 amplitude increases from 1 to 6 months, but shows only a slight decline to 24 months. (5) The positive peak separating N1 and N2 remains fairly constant between 1 and 12 months and rises sharply to 18 months, followed by a decline to 24 months. For rats from 1 to 18 months, the general effect of increasing click level is to increase the amplitude of this peak, while at 24 months, the peak decreases and becomes negative at 120 dB SPL P.E. (6) N1 latency decreases with click l...

The detectability of a sinusoidal signal masked by a sinusoid of fixed frequency (920 Hz) was measured in a 2IFC task. The signal and masker were gated with fixed starting phase such that the resultant started at maximum amplitude. For fixed duration of the observation interval (T = 500 msec), there was a slight improvement in performance with increasing frequency difference between signal and masker (Δf = 2.0, 4.0, or 6.0 Hz). With Δf = 4.0 Hz, there was a monotonic improvement in performance with increasing duration (T = 125, 250, or 500 msec); the four observers required an average of 6.2 dB less signal power for constant performance with T = 500 msec as compared with T = 125 msec. For a single beat in the signal interval, there was a monotonic improvement in performance with decreasing frequency difference (Δf = 2.0, 4.0, or 8.0; T = 1kΔf). The average improvement was 3.6 dB over the range in Δf. With Δf = 4.0 Hz, T = 250 msec, the average slope of the Weber function was 0.88. Performance in classical intensity discrimination (Δf = 0.0) was better than in some beat conditions. [Supported by a NIH predoctoral fellowship and by the Air Force Office of Scientific Research.]

AC cochlear potentials were recorded from the round window of guinea pigs anesthetized with Nembutal. Following placement of the electrode, the auditory bulla was closed and pure tones were presented via a speaker located 5 cm from the ear. Intensities were determined with calibrated Bruel & Kjaer probe tubes and condenser microphones at the opening of the external auditory meatus. One microvolt contours examined with a General Radio wave analyzer (3‐Hz bandwidth) across frequency (0.2 to 20 kHz) were found to agree with accepted guinea pig sensitivity curves. Following oral administration of choline salicylate, a rapid and significant decrease in the AC cochlear potential was observed. Following a peak effect (at 3–4 h) and plateau, initial recovery was noted. The effect was drug dose dependent. The effect was frequency specific, with the greatest influence on the middle‐frequency range. The maximum amplitude at the point of nonlinearity of the AC cochlear potential was reduced with drug. Also the point o...

Masking overshoot (increase in masking at either the transient onset or offset period) was measured at nine test frequencies surrounding a 1000‐Hz, 50 dB SPL masker of 1000‐msec duration. The brief maskees (5‐msec duration at maximum amplitude) were presented near masker onset (initial position) at the midpoint of the masker (medial position) and near‐masker offset (final position). Averaged across subjects and frequencies, onset overshoot was significant while offset overshoot was not. Onset overshoot occurred at all test frequencies and its magnitude was directly related to the magnitude of initial‐position masking. The magnitude of onset overshoot was less than reported by Zwislocki et al. [Perception Psychophys. 2, 59–64 (1967) and J. Acoust. Soc. Amer. 43, 1257–1271 (1968)]. Offset overshoot appeared primarily at the lower frequencies but was not significant at any frequency. A follow‐up study compared masking at the medial position with steady‐state masking. The steady‐state masker was more efficien...

Measurements were made to compare the relative effectiveness of H2O and D2O molecules in influencing thermal relaxation in N2O gas. Thermal relaxation times were obtained from absorption measurements taken in N2O‐H2O and N2‐D2O mixtures. The “direct” absorption technique was employed in conjunction with pulsed sound waves having a carrier frequency of 110 kc. Data were taken in the region of 100–700 kc/atmos and at a temperature of 21°C. Commercial anhydrous N2O was used in this research. In dried N2O a value of 0.153 was obtained for the maximum amplitude absorption coefficient per wavelength. Measurements were taken at vapor concentrations of 0.39%, 0.77%, and 1.14%; an average value of 1.70 was obtained for the relative collision transition efficiencies of N2O‐H2O and N2O‐D2O. This value is comparable to the figure of 1.86 obtained by D. Sette and J. C. Hubbard [J. Acoust. Soc. Am. 25, 994 (1953)] for CO2‐H2O and CO2‐D2O. This work was supported by the Office of Naval Research.