摘要:

The response of a filter matched to a delayed, Doppler‐shifted version of a narrow‐band transmitted signal in white noise is considered. Conditions under which the response is the one expected are arrived at by (1) setting up the response to a more accurate representation of the echo waveform, (2) applying Taylor's theorem, with the response considered a function ofv/c(range rate over the speed of propagation), and (3) requiring that the remainder be small relative to the leading term (expected response). The resulting validity criteria differ from that put forward by several authors, namely, 2(|v|/c)B T≪ 1 (one also sees<), whereBis a signal bandwidth, andTis the signal duration. It is shown that, to good approximation, the old criterion implies the new, and that modulations exist such that one of the new criteria is satisfied but the old is not.

ISSN:0001-4966    

DOI:10.1121/1.1913488

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Subject's ability to localize transient signals presented in a free field depends primarily on low‐frequency energy. The minimum audible angle is about 3/4° for all transients containing energy below 2000 Hz.

ISSN:0001-4966    

DOI:10.1121/1.1913489

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Subjects with normal hearing were tested to determine thresholds of hearing when audio stimulation was applied to various teeth and the forehead at frequencies from 250 to 4000 Hz. The resulting data indicate that the teeth are more sensitive than the forehead by 5 to 10 dB in detecting the rms force applied. Comparison of the experimental results with recently published threshold values for the forehead and mastoid indicates that the teeth are comparable with the mastoid for audio sensitivity in bone conduction. This result, together with low measured power requirements, indicates that the teeth are an attractive site for the introduction of audio energy for hearing.

ISSN:0001-4966    

DOI:10.1121/1.1913490

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The results of the present experiment indicate that the electrophonic effect can be readily explained as a microphonic phenomena. Electrophonic stimulation produced bone vibrations of sufficient amplitude to account for the sound heard by the listener.

ISSN:0001-4966    

DOI:10.1121/1.1913491

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

By means of the spectral representation, a simple mathematical procedure is possible in deriving the moving frame formulation of jet noise.

ISSN:0001-4966    

DOI:10.1121/1.1913492

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A study is made of the forced oscillations of a thin flexible cylinder towed in a viscous fluid. It is shown that the forcing frequency has a dominating influence on the modal‐shape amplitude of the towed cylinder. A study of the movement of the free end of the towed cylinder reveals that the phenomenon of “whipping” can occur during a severe resonance.

ISSN:0001-4966    

DOI:10.1121/1.1913493

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Free torsional vibrations of conical and cylindrical shells of thickness varying as a power of distance have been discussed. The solutions depend upon a linear differential equation of second order. The governing equation is solved for shells with both edges fixed. The numerical values of the frequency parameter for the first three modes of vibration are computed for shells of linearly and parabolically varying thickness for several different ratios of terminal radii.

ISSN:0001-4966    

DOI:10.1121/1.1913494

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Whereas it has been recognized for some time that the absorption of sound in suspensions of erythrocytes is primarily a macromolecular phenomenon, recent observations have led us to believe that interactions between macromolecules may play a significant role as well. Two tests of the interaction postulate are reported: (i) Acrolein or glutaraldehyde fixing of bovine erythrocytes, which cross‐links macromolecular hydrophobic groups, causes an increase in specific absorption by as much as a factor of five at 30 MHz. The absorption increase is greatest at 30 MHz and above. (ii) Suspension of fixed erythrocytes in low‐dielectric constant liquids (ethylene glycol and ethanol), thus increasing forces between ionic groups, further increases the specific absorption by as much as a factor of four at 10 MHz. The absorption increase associated with solvent changes is greatest at 10 MHz and below. Scattering, viscous relative motion, and thermal absorption have been ruled out as explanations for the observations. The explanation is more apt to lie in some forms of chemical or structural relaxations.

ISSN:0001-4966    

DOI:10.1121/1.1913495

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP