Frequency sound

The links between levels of exposure and inconvenience caused by ventilation noise are described in an investigation carried out on office workers.- Technical measurements and analyses of the ventilation noise at 155 typical office workplaces were in this study combined with assessments by the office workers of the level of disturbance that they experienced, the effect on working performance, fatigue, stress-related pain, and headaches. The average noise level was about 40 dB(A) at two of the workplaces, while it was about 35 dB(A) at two others. It emerged from rhe narrow-band analyses that the sound pressure levels of rhe infrasound were not in any event of an order that this type of sound frequencies (below 20 Hz) could contribute to any disturbance effects. Any steps taken to counter the sound frequencies of the ventilation noise under 50 Hz, i.e., the point of btersection between the threshold curve of auditory perception and the spectral level distribution curve of... 

Resonant frequency The sound frequency for which a particular system provides the maximum absorption. The amount of sound absorption in a system depends on the degree of damping achieved this depends on the mass and the associated air space. 

According to the above expressions the value of a/f is a constant for a given liquid at a given temperature. Any increase in sound frequency,/ must result in a compensatory increase in a and thus a more rapid attenuation of the sound intensity with distance (Eq. 2.14). This has important consequences. Consider for example the passage of sound through water at room temperature. According to Fox and Rock [10] the value of a// for a wide variety of frequencies in water is 21.5 x 10 cm. Using this value the absorption coefficients at 21.5 kHz and 127.0 kHz can be deduced to be... 

Sound waves provide a periodic oscillation of pressure and temperature. In water, the pressure perturbation is most important in non-aqueous solution, the temperature effect is paramount. If cu (= 2 nf, where/is the sound frequency in cps) is very much larger than t (t, relaxation time of the chemical system), then the chemical system will have no opportunity to respond to the very high frequency of the sound waves, and will remain sensibly unaffected. 

For a monatomic gas, where the heat capacity involves only translational energy, V is independent of sound oscillation frequency (except at ultra-high frequencies, where a classical visco-thermal dispersion sets in). For a relaxing polyatomic gas this is no longer so. At sound frequencies, where the period of the oscillation becomes comparable with the relaxation time for one of the forms of internal energy, the internal temperature lags behind the translational temperature throughout the compression-rarefaction cycle, and the effective values of CT and V in equation (3) become frequency dependent. This phenomenon occurs at medium ultrasonic frequencies, and is known as ultrasonic dispersion. It is accompanied by... 

Figure 5. Microwave-induced sound frequency as a function of head radii or circumference (([J) constrained surface (O) stress-free)...

Cavitation begins at much smaller intensities when low sound frequencies are applied. Fig. 5 describes how the threshold intensity increases with increasing frequency. Drawing a vertical line at approximately 20 kHz, as one moves up this vertical line, wave intensity increases [W/cm2]. The first thing one encounters as the intensity is increased is the curve for aerated water, or water saturated with air. The intensity at this point is sufficient to produce cavitation as desorbed air contributes to bubble nucleation. As one continues to increase intensity, one will encounter the curve for degassed cavitation. This intensity is the absolute maximum intensity allowed (at standard conditions) for sound traveling in water at this frequency. Most of sonochemistry are performed at intensity levels between these two values. 

Sound frequency is the reciprocal of the period of the sound wave. It is denoted by the symbol v and expressed in cycles per second with the Hertz (s 1) as unit. Also the angular frequency is used the latter is symbolised by co, which is identical with 2nv. 

Although, as the name implies, the frequency region in all US applications is always beyond the sound frequency, the prefix sono and the adjective acoustic are commonly... 

Sound frequency is usually expressed in units of cycles per second or hertz (Hz). Humans have a useful hearing range of 20-20 000 Hz, but are most sensitive to frequencies between about 1000 and 6000 Hz. (For reference, the lowest and highest notes on the piano are 27.5 and 4186 Hz, respectively.) This increased sensitivity is due in part to the shape of the external portion of the ear and the ear canal, which serve to amplify frequencies in this range. 

Hearing and Speech Threshold factors (UA. UT, UU) Speech Sound Discrimination (US) General Sound Discrimination (U3) Sound—Frequency Discriminalion (U5) Sound-Intensity/ Duration Discrimination (U6) Musical Discrimin-nation Judgment (Ul. U9) Resistance lo Auditory Stimulus Distortion (UR) Temporal Tracking (UK)... 

Figure 363. Plot of particle entrainment factor versus particle size at different sound frequencies ...

According to the Fourier method, the measured line integral p r,4>) in a sinogram is related to the count density distribution A(x,y) in the object obtained by the Fourier transformation. The projection data obtained in the spatial domain (Fig. 4.2a) can be expressed in terms of a Fourier series in the frequency domain as the sum of a series of sinusoidal waves of different amplitudes, spatial frequencies, and phase shifts running across the image (Fig. 4.2b). This is equivalent to sound waves that are composed of many sound frequencies. The data in each row of an acquisition matrix can be considered to be composed of sinusoidal waves of varying amplitudes and frequencies in the frequency domain. This conversion of data from spatial domain to frequency domain is called the Fourier transformation (Fig. 4.3). Similarly the reverse operation of converting the data from frequency domain to spatial domain is termed the inverse Fourier transformation. 

The toxicity of gentamycin to the ear may be detected by histopathology or more easily by the Preyer reflex test which measures hearing thresholds for particular sound frequencies. 

In the ultrasonic pretreatment, the fraction of die broken bonds is in direct proportion to the collision energy of the particles suspended in the solution. A particle generates a deformation depth Z> on a contact surface Sp on a substrate. The collision energy may be correlated to the mass of a particle mp and the speed of sound y,. The total number ofthe collisions is assumed to be roughly independent of the particle concentration due to the high sound frequency (10 Hz) and the relatively short pretreatment duration ( 30 min). If the particle concentration in the solution is kept constant, diamond nucleation density can then be correlated to the mean size of diamond particles suspended in the solution such as... 

Here ceff represents the effective speed of sound, c0 is the actual speed of sound in free space, y is the specific heat ratio, and kt is the isothermal compressibility of the fluid. A fraction of shell volume occupied by tubes, solidity o can be easily calculated for a given tube pattern. For example, o = 0.9069(d lp,)2 for an equilateral triangular tube layout, and o = 0.7853(d /p,)2 for a square layout. Coefficients a, are the dimensionless sound frequency parameters associated with the fundamental diametrical acoustic mode of a cylindrical volume. For the fundamental mode al = 1.841, and, for the second mode, a2 = 3.054 [122],... 

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