摘要:

Frequency modulation of speech is an effect produced by periodically modulating the speech frequencies during transmission. This effect is detectable by the wavering or buzzing quality that it imparts to the speech as received. The detection limits of frequency modulation of speech were determined using the Békésy tracking technique. Modulation rates from 10 to 200 cps were used on speech produced by both male and female talkers. Detection limits, expressed as a function of signal to sideband ratio, were found to vary as a function of sex of the talker, modulation rate, and received‐speech level. Detectability is greater with female than with male talkers, and peaks at a higher modulation rate for the female talkers than for the male talkers.

ISSN:0001-4966    

DOI:10.1121/1.1939272

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

The set of subchannel signals of a vocoder can be transmitted by a time—or a frequency—multiplexing system. It is shown that pulse techniques allow for a considerable reduction of hardware of the desired goal for a vocoder system is not minimum transmission‐channel capacity but minimum hardware. Instead of using a fixed time frame for the transmission signal and a fixed sampling rate, the simplified system samples and transmits spectral data at the instantaneous pitch frequency. Besides its application for speech transmission, the described system offers several advantages for speech processing with relatively small and slow computers. Experiences with a channel vocoder system connected to an IBM‐1401 are reported.

ISSN:0001-4966    

DOI:10.1121/1.1939276

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

This paper is Pt. I of a trilogy [Pt. II: T. G. Bell, “Field Data.” Paper K2, this meeting. Pt. III: H. W. Horton, “Model Studies.” Paper K3, this meeting]. Theoretical topics that are relevant to the most important effects observed in the field are discussed. These are grouped under intensity of reflection, distortion of reflected wave, and scattering, and include models predicting effects of absorbing bottoms, layered media, and irregular boundaries.

ISSN:0001-4966    

DOI:10.1121/1.1939282

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An energy approach is used to study the flexural vibration of a ring mass‐loaded in a plane‐symmetric manner. The effects of rotary inertia and shear are neglected. Computed natural frequencies and mode shapes are compared to those obtained experimentally.

ISSN:0001-4966    

DOI:10.1121/1.1939289

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

A small experimental transducer array was designed, constructed, and tested to demonstrate the feasibility of enclosing the elements in a liquid‐filled housing that requires no pressure‐release materials. The transducer consists of four dumbbell‐type lead zirconate titanate transducer elements that are set in close‐fitting cavities in a high ρcmetal block. The entire housing is filled with a silicone fluid and provision is made to maintain the inside pressure equal to the pressure on the outside at all times. Presentation of frequency‐response curves, electrical input impedances, and efficiencies demonstrates that the transducer characteristics are relatively insensitive to ambient pressures up to 1000 psi, the maximum pressure available for test. The transducer is further characterized by high power capability, good efficiency, a lowQ, and a high effective electromechanical‐coupling coefficient. [Research sponsored by the USN Bureau of Naval Weapons.]

ISSN:0001-4966    

DOI:10.1121/1.1939294

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

In the region of 100 cps, the attenuation, as measured by the treshhold shift, of an ear defender with a rigid frame supporting the cups with liquid‐filled cushions is very nearly the same as when the cups are supported by a flexible frame. However, when using an artificial head, the attenuation is appreciably different for the two frames, even though sponge rubber is used to simulate the flesh. If only the spring constant of the system were important, the difference in attenuation for the two frames should be about 20 dB. The actual difference for the artificial head was about 8–15 dB. It is postulated that the lack of rigidity of the human skin may be the relevant factor, since this would allow a certain amount of flow in response to the sound pressure.

ISSN:0001-4966    

DOI:10.1121/1.1939303

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Previous attempts to validate the SAL audiometric procedure by comparison with conventional bone‐conduction (BC) audiometry have been subject to two sources of error: (1) the occlusion effect produced by standard earphone cushions and (2) proper masking of the nontest ear during conventional BC audiometry. This study removed the occlusion effect as a source of error by employing earphones enclosing a very large volume (M. P. Pedersen, type B228‐A). The masking problem was eliminated by employing, as experimental subjects, only individuals whose nontest ear showed a severe or total sensorineural hearing loss. Under these conditions, SAL and conventional BC thresholds were measured with a Békésy audiometer, in plugged normal ears and in ears with both conductive and sensorineural hearing loss. In all groups, SAL and BC results were equivalent. The effects of force of application of the bone vibrator, linearity of the masking effect, duration of SAL noise exposure, and direction of frequency changes of the Békésy audiometer are also considered. [Study supported by the Vocational Rehabilitation Administration under research grant RD‐1297S.]

ISSN:0001-4966    

DOI:10.1121/1.1939304

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Normal subjects hear complex or vibratoed musical tones as “brighter” than steady pure tones. The reasons that underlie these subjective judgments are difficult to assess. Human patients with stenotic lesions of a vertebral artery, which may impair the blood supply to the brain stem and cochlea, have been found to require unusually long stimuli to achieve a sensation of tone rather than noise from short pure tones. The use of various complex and vibratoed stimuli with these patients supports the data found with pure tones but also shows measureable differences in the speed of tonal processing, and especially suggests improvement in tonal projection. Thus, the data suggest that musical phenomena of “brightness,” “extension,” and the like are linked to the neural efficiency of the hearing process.

ISSN:0001-4966    

DOI:10.1121/1.1939311

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

Observers adjusted the center pulse of a 3‐tone/pulse series by either increasing or decreasing the frequency to achieve the criterion that the center pulse was heard to occur either first or last. At the beginning of each trial, the frequency of all three pulses was the same. The frequency increase or decrease necessary to achieve the temporal‐order criterion was examined in the frequency range of 500–4000 cps, at pulse durations and intervals in the range from 10 to 80 msec, and for various SPL. The results indicated that the required change in frequency of the center pulse to alter perceived order increased as the test frequency increased and that the values were similar to those for critical bands. The phenomenon was also examined for two‐ and five‐pulse series. For some observers, temporal perception different from actual order was reported. [Research supported by U. S. Aeronautical Systems Division, Wright‐Patterson Air Force Base, under contract AF 33 (615)‐1181.]

ISSN:0001-4966    

DOI:10.1121/1.1939314

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP

摘要:

An investigation of the sound field of a corrugated acoustic waveguide has been conducted. The waveguide was constructed by stacking equally spaced circular disks coaxially along a solid rod to form a corrugated cylindrical surface of circular cross section. Measurements of the sound field near the surface of the waveguide show that a dominant mode that has the form of a cylindrical surface wave exists at the corrugated surface. These experimental results are used as the basis both for the development of a theoretical model for the corrugated region of the waveguide and for the theoretical analysis of the farfield radiation pattern of the waveguide. Farfield radiation patterns were measured as a function of the length of the waveguide. These measured patterns are compared to the theoretical radiation patterns. [Work done under a contract with the U. S. Office of Naval Research.]

ISSN:0001-4966    

DOI:10.1121/1.1939324

出版商:Acoustical Society of America    

年代:1964

数据来源: AIP