Acoustic signal

The aim of the experiment was to study the transmission of a signal through the weld and to measure the frequency and phase dependencies of parameters of acoustic signals from the angle of incidence and beam path within the weld volume. One of the shift of the spectral characteristics the signal is shown in Figure 4(a,b). 

This corresponds to the physician s stethoscope case mentioned above, and has been realized [208] by bringing one leg of a resonatmg 33 kHz quartz tiinmg fork close to the surface of a sample, which is being rastered in the x-y plane. As the fork-leg nears the sample, the fork s resonant frequency and therefore its amplitude is changed by interaction with the surface. Since the behaviour of the system appears to be dependent on the gas pressure, it may be assumed that the coupling is due to hydrodynamic mteractions within the fork-air-sample gap. Since the fork tip-sample distance is approximately 200 pm -1.120), tire teclmique is sensitive to the near-field component of the scattered acoustic signal. 1 pm lateral and 10 mn vertical resolutions have been obtained by the SNAM. 

The use of ultrasonic energy is different in on/off switches and in transmitters. Switches act on the attenuation of the acoustic signal in the gap between two crystals, while transmitters measure the time of flight of the ultrasonic pulse. 

A closely related technique useful for localized gas concentrations and leaks is photoacoustic detection and ranging (padar) (90). A laser pulse tuned to an absorption line generates an acoustic signal that is detected by a paraboHc microphone. A range resolution of 1 cm out to 100 m is feasible. 

Flgura 4.13. Contributing acoustic signals superimposed on distributed-voiume source model for a pancake-shaped vapor cloud explosion. 

The acoustic spectra were recorded simultaneously as other process experiments, in themselves not related to acoustic chemometrics, were carried out. This resulted in many days with stable conditions in the reactor, and no particular variations in the acoustic signals. Therefore there were only a limited number of days (hours) which displayed significant variation in process parameters, which are necessary for successful multivariate analysis and calibration. 

The predicted versus measured plot in Figure 9.9 shows the correlation between the acoustic signal and crystallization temperature, and hence its ability to predict it on-line. 

There has been some discussion as to whether acoustic signals result from the fracture that occurs when adhesion Is lost at the paint-metal Interface during blistering and cathodic disbonding. In the present study, very sensitive Acoustic Emission measurements have been made In systems exhibiting these types of breakdown. 

Fuze, Mine. A fuze designed to initiate a train of fire in a land mine. For initiation of underwater (sea) mine a device known as "Firing Mechanism, Underwater Mine" It is a device contg combustible or explosive components, which can be actuated by an acoustic signal, impact, hydrostatic pressure, and/or magnetic influence (Ref 40a, pp 71... 

Signaling pathways are also critical for the processing of sensory information. External stimuh, such as optical and acoustic signals, stress, gradients of nutrients, and so on, are registered in sensory cells and are transmitted to other cells of the organism via signaling pathways. 

TF Systems A TF is a device whose spectral transmission can be controlled by applying a voltage or acoustic signal. There are two main TF devices acousto-optical TF (AOTF), based on diffraction, and liquid crystal TF (LCTF), based on birefringence. An AOTF is a transparent crystal in which an ultrasonic wave field is created,... 

The nature of the signal processing, and its potential effectiveness, depends on the characteristics of the auditory system. The ear transforms the incoming acoustic signal into mechanical motion, and this motion ultimately triggers neural pulses that carry the auditory information to the brain. The essential components of the ear are shown in Fig 6.1. 

Quatieri et al., 1995] Quatieri, T., Dunn, R.,, and Hanna, T. (1995). A subband approach to time-scale modification of complex acoustic signals, Proc. IEEE Trans. Speech and Audio, 3(6) 515-519. 

Yang et al., 1992] Yang, X., Wang, K., and Shamma, S. A. (1992). Auditory representations of acoustic signals. IEEE Trans, on Information Theory, 38 824-839. 

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