Directional microphones

Hj) Height of Burst (Sonic) Test. The purpose of this test is to det the height of burst of a fuze using sonic techniques. This technique requires the measurement of the time of arrival of sound at directional microphones precisely placed in a plane. A brief description of this test is given on p IIIB-20 Ref 39 Addnl info can be obtd from "Instrumentation Section, Technical Services Laboratory, Ammunition Development Division, Ammunition Engineering Directorate, Picatinny Arsenal, Dover, NJ 07801 H2) Hydraulic Ram and Vibrator Test. This test could be used to simulate impact shock on bombs or rockets assembled with fuzes that are launched from aircraft. It also could check the transportability of fuzes that experience this environment. This test is listed, but not described in Ref 39, p IIB-37... 

Kompis and Dillier, 1994] Kompis, M. and Dillier, N. (1994). Noise reduction for hearing aids Combining directional microphones with an adaptive beamformer. J. 

Hawkins and Yacullo, 1984] Hawkins, D. and Yacullo, W. (1984). Signal-to-noise ratio advantage of binaural hearing aids, directional microphones under different levels of reverberation. J. Speech and Hearing Disorders, 49 278-286. 

Soede et al., 1993b] Soede, W., Bilsen, F., and Berkhout, A. (1993b). Assessment of a directional microphone array for hearing-impaired listeners. J. Acoust. Soc. Am., 94 799-808. 

Government Research. Researchers funded by the National Institute on Deafness and Other Communication Disorders (NIDGD) are looking at ways that hearing aids can selectively enhance sounds to improve the comprehension of speech. A related research team is studying ears on animals to fine-tune directional microphones that may make conversations... 

Frequency response often is affected by the polar pattern of the microphone. As mentioned previously, the frequency response may vary depending on the direction of the sound source and the distance from the sound source to the microphone. Most directional microphones exhibit proximity effect, an unnatural... 

Fig. 2.1 Some of the biomimetic-originated successful stories in biomedicine artificial cornea (A), insect ear-inspiration for miniature directional microphone (B) and furanones—the compounds excluded by Delisea pulchra for biofilms inhibition (C).

The Calibration of the positioning system is carried out using a bar with a given distance which is placed between the referenspoint on the microphone collar and the probe. The distance is then entered into the acquisition software together with informations of the air temperature close to the tested object, pipe dimension, type of UT-probe (probe height) and scanning direction. 

Recall that the calculation of 4>m relies on equation 13.4. It is important to emphasize that the validity of this equation rests on two assumptions. The first is a direct consequence of the way the microphone responds to the rate of the process, as it originates the photoacoustic wave. All the fast processes yield a measured waveform with the same time profile all the slow processes produce virtually no signal. Between these two extremes an intermediate regime exists, in which the time profile of the measured waveform varies to reflect the rate of the process. The fast and slow process rates are defined in relation to the intrinsic response of the microphone, determined by its characteristic oscillation frequency v. 

Fig. 12.4. Single-tube STM. The tube piezo scanner is adhered inside a sturdy metal cylinder, which sits on three screws on the base plate. The two front screws make the coarse approaching. The rear screw makes fine approaching by using the two front screws as the pivot axis. The rear screw is actuated by a stepping motor for automatic approaching. The preamplifier (not shown) is mounted directly on top of the metal cylinder to eliminate the microphone effect of the coaxial cable between the tip and the input of the preamplifier. The entire unit is rigid enough that a mediocre vibration isolation device can provide atomic resolution. (After Hansma et al., 1988.)...

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