摘要:

Masked audiograms were used to measure critical bandwidth. On the assumption that critical bands represent equal distances on the basilar membrane and that critical bandwidth increases exponentially with distance from the helicotrema, functions were derived which (1) relate critical bandwidth to frequency and to position on the basilar membrane and (2) relate position of maximum amplitude to frequency. The functions are consistent with Békésy's optical observations and Mayer's psychophysical data. The frequency‐position function isf = A (10ax − 1). The coefficientais numerically identical with the coefficient in the exponential function fitting Békésy's elasticity data. Functions of this form fit data from seven other species and the values of the coefficientaseem related to their respective elasticity, functions The interpretation of critical bandwidth as the frequency interval over which the cochlea sums power is supported by data of Mayer, and the hypothesis that critical bands represent equal distances on the basilar membrane is strengthened, one critical band corresponding to one millimeter. Problems for cochlear theory are posed (1) by the apparent equivalence of critical bandwidth, the derivative of the frequency‐position function, and the frequency interval over which spatial integration takes place, and (2) by the proportionality of these three at a given point to the compliance at that point.

ISSN:0001-4966    

DOI:10.1121/1.1908437

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The perception of sounds characterized by a moving resonance was investigated a series of experiments. Stimuli were generated by exciting a tuned circuit with a short train of pulses of repetition rate 100/sec. The resonant frequency of the tuned circuit was changed in a piecewise linear manner over a 500‐cps range. Subjects matched the test stimuli by adjusting the resonant frequency of a fixed (i.e., nonvarying in time) resonant circuit until the test and comparison stimuli were judged to be most alike. Results indicate a strong tendency for subjects to adjust the frequency of the fixed resonant circuit until it is close to the terminal resonant frequency of the time‐varying circuit. This tendency depended to some extent on the direction and rate of the frequency change in the test stimulus. The implications of the results for auditory theory and speech perception are discussed briefly.

ISSN:0001-4966    

DOI:10.1121/1.1908439

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Typical methods for observing pitch changes with intensity for pure tones consist of varying the frequency of one tone of fixed intensity (the comparison tone) so as to match the pitch of a second tone of fixed frequency (the tone under test) when the latter is set at different intensities. Differences between the comparison and test‐tone frequencies, when equated in pitch under these conditions, are ascribed to their intensity differences and used as a measure of the pitch intensity shifts for the test tone. The comparison and test tones may differ in frequency, however, even when they are matched in pitch under equal intensity conditions. These frequency differences, called pitch‐matching errors, may be identical to those noted above for comparable conditions and consequently nullify the apparent pitch‐intensity shifts. This possibility was studied in two experiments which sought to reproduce the pitch intensity relationship as defined by the data of Stevens and Snow. In more than half the comparisons made under various frequency and intensity conditions, apparent pitch shifts for 50, 75, 100, 200, 400, 700, 1500, and 6000 cps were found to be not significantly different from pitch‐matching errors. When averaged, the remaining shifts followed the directions of Stevens' curves but were small (2% or less). Pitch‐intensity functions for the lower frequency tones were particularly variable and generally bore little relationship to Snow's functions for such tones.

ISSN:0001-4966    

DOI:10.1121/1.1908441

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Two experiments are reported regarding man's sensitivity to waterborne sound. The first study investigated the threshold sensitivity to tones of 250, 500, 1000, 1500, 2000, 3000, 4000, and 6000 cps and the attenuation due to the diver's hood. The second experiment obtained data on the “tolerance” to a high‐intensity tone of 1500 cps.The sound‐pressure level needed to reach threshold in water is about 40–70 db higher than the MAP threshold in air. The greatest loss in sensitivity occurs in the regions of greatest air sensitivity. The diver's hood was found to provide about 20 db or more of attenuation of underwater sound at frequencies above 1000 cps.The “tolerance” limits for hoodless divers is approximately 174 dbre0.0002 dyne/cm2. When wearing the hood divers were able to tolerate at least 180 db, the system's maximum output. Above 165 db all divers reported some distortion of the visual field.

ISSN:0001-4966    

DOI:10.1121/1.1908443

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Evidence from studies of tactual sensitivity indicates that transient suprathreshold stimuli presented simultaneously with and contralateral to test signals will mask such signals more effectively than do steady stimuli. The present report presents evidence that when pulsed masking sounds are presented simultaneously with pulsed auditory signals, two major effects are observed: First, a significantly greater amount of contralateral masking is obtained with the pulsed masker than with the steady masker, and, second, the pulsed masker is more effective in the monaural condition also. Furthermore, the masking effect of pulsed maskers increases with the increase of signal frequency, but not with increase of masker intensity. The frequency of the masker must be near that of the signal to be effective, and if pure‐tone maskers are used with pure‐tone signals, the masking effect shifts continuously to the localization effect as the signal frequency approaches the masker frequency. Some explanations of binaural and contralateral masking are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1908445

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The following problem is examined theoretically: A pressure is applied to an open‐circuited bar of piezoelectric ceramic; after steady‐state conditions have been achieved, an electrical resistanceRis connected between the electrodes and simultaneously the pressure is removed. General equations describing the subsequent current and energy dissipation in the resistor are developed, and examined in detail for a specific transducer of lead zirconate‐titanate ceramic. The general equation for current consists of a series of time‐delayed functions, signifying physically that a mechanical wave propagates through the transducer with successive reflections at the end faces, releasing strain energy originally stored in the material; this energy is then dissipated in electrical form in the resistance. The initial current h*s two components, an exponential function representing the discharge of energy stored in electrical form in the transducer capacitanceC0(about 10% of the total stored energy), and a step function representing the release of energy stored in mechanical form (remaining 90%). IfRis small the exponential function predominates, and has a time constant which is approximatelyRC0; the stored electrical energy is released very rapidly, while the mechanical energy is released much more slowly. IfRis large (of the order of 104ohms), exponential function and step function are of comparable magnitudes, and the time constant of the exponential is modified by the mechanical impedance of the transducer.

ISSN:0001-4966    

DOI:10.1121/1.1908447

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

This investigation reports acoustical differences found for drumheads made of Mylar plastic instead of the conventional calfskin. Two identical bass drums and two identical field drums were fitted with heads of the two materials. A professional drummer was engaged to adjust and play these drums with several tension adjustments. A tape‐recorded analysis was made of their sounds, including single impact beats and steady rolls. The sound spectra of the quasi‐steady‐state drum rolls were determined by half‐octave bands, by a method similar to that of Sivian, Dunn, and White. Spectra of the peak sound‐pressure levels were obtained with a General Radio impact sound analyzer. The buildup and decay of the drum sounds were analyzed in chosen frequency bands by use of a high speed level recorder. The chief physical differences found are: (1) the calfskin head is capable of a much larger range of tension adjustment, and (2) under certain conditions has more damping. When the bass drum is tuned to concert tightness, there is a significant difference between the spectra of the plastic and calfskin drumheads and in the time variation of sound output. For the field drum there is little spectral difference, but the calfskin gives a more staccato beat with less “metallic” ringing.

ISSN:0001-4966    

DOI:10.1121/1.1908449

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Previous calculations of the statistical behavior of a hard spring oscillator excited by purely random and Gaussian noise are extended. The moments of the displacement and its extrema are found in an analytic form and their interrelations are exploited. Recurrence relations, asymptotic expressions, and computations of the moments are presented. Envelope autocorrelations for three narrow‐band linear filters are found, and the mean size of clumps of cycles exceeding predetermined levels is obtained. For the hard‐spring oscillator we find that the relative envelope fluctuation is less than that of a linear oscillator and that the mean clump size is also smaller in general.

ISSN:0001-4966    

DOI:10.1121/1.1908451

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

The response of an oscillator with a nonlinear stiffness of the hard‐spring type to narrow band Gaussian random noise is analyzed theoretically by using the method of quasi linearization. The particular point of interest is the possibility of an occurrence of multiple valued response or “jumps” such as one observes when the exciting force is sinusoidal. It is argued that while it does not seem possible to have multivalued response with wide‐band (white noise) excitation, the response to narrow band excitation might exhibit such behavior owing to the temporal correlation of the source with the response. Numerical computations of the response curves do suggest multivalued response. In experiments with a nonlinear oscillator, multivalued response was observed, but agreement between theory and experiment may only be claimed to be qualitative.

ISSN:0001-4966    

DOI:10.1121/1.1908454

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Ultrasonic attenuation measurements were made in liquid carbon disulfide‐alcohol mixtures over a frequency range from 5 to 155 Mc at a temperature of −63°C. From these measurements the vibrational relaxation frequency for the liquid was calculated. Methyl, propyl, and butyl alcohol were added in various concentrations up to 0.6 mole percent. In every case the relaxation frequency increased with the addition of the impurity. This increase was found to be a linear function of the impurity concentration which is consistent with the assumption that the vibrational‐translational energy transfer is a binary collision process. The shifts in relaxation frequency per mol % of impurity were found to be a linear function of the molecular weight of the impurity molecules for both the gas and liquid data.A comparison was made of the ratio of collision efficiency of like to unlike molecules in both the gas and liquid state. It was found that within experimental error this ratio is the same in both states. This was interpreted as meaning that the vibrational relaxation process for unlike collisions was the same in both liquids and gases. Further, it appears that the efficiency of an AB‐type collision is more strongly temperature dependent than for the AA‐type collisions.

ISSN:0001-4966    

DOI:10.1121/1.1908456

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP