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Noise Pollution
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
Sound is a disturbance that propagates through a medium having the properties of inertia (mass) and elasticity. The medium by which audible sound is transmitted is air. The higher the wave, the greater its power; the greater the number of waves a sound has, the larger is its frequency or pitch. The frequency can be described as the rate of vibration that is measured in Hertz (Hz, cycles per second). The human ear does not hear all of the frequencies. The normal hearing range for humans is from 20 to 20,000 Hz. In addition, the human ear cannot define all sounds equally. Very low and very high notes sound fainter to the ear than do 1000 Hz sounds of equal strength; that is how the ear functions. The human voice in conversation covers a median range of 300–4000 Hz; the musical scale ranges from 30 to 4000 Hz. Hearing also varies widely between individuals.
Noise
Published in Martin B., S.Z., of Industrial Hygiene, 2018
The model for analysis of a single system is a single degree of freedom system where a mass vibrates in a constrained manner and only in the vertical direction. This means decreasing the transmission of the vibratory motion from one structure to another. Isolation then means placing a flexible material along the path to reduce and/or absorb the vibratory energy. This can be a rubber pad, for example, or a spring isolator can be used to support, as well as isolate the equipment from the structure. Flexible connections can also be used in a pipe or duct to break the path. The reduction of vibration energy depends on the efficiency of the isolator. This is a function of the driving frequency of the vibratory energy, and the natural frequency of the isolator when deflected. The driving frequency is based on the equipment speed. For example, a motor that rotates at 1800 rpm has a driving frequency of 30 cycles per second or Hz (1800/60). If the motor is driving a pump that has 7 vanes on the impeller, another driving frequency is the vane passing frequency. This is the number of times the vanes pass the cut-off in the pump case. This frequency is the pump rpm divided by 60 times the number of vanes on the impeller, or 210 Hz for this example.
Practical Antenna Systems
Published in Jerry C. Whitaker, The RF Transmission Systems Handbook, 2017
Wavelength is the distance traveled by one cycle of a radiated electric signal. The frequency of the signal is the number of cycles per second. It follows that the frequency is inversely proportional to the wavelength. Both wavelength and frequency are related to the speed of light. Conversion between the two parameters can be accomplished with the formula c=f×λ where c is the speed of light, f is the operating frequency, and λ is the wavelength. The velocity of electric signals in air is essentially the same as that of light in free space (2.9983 × 1010 cm/sec).
Advanced methods of spinal stimulation in the treatment of chronic pain: pulse trains, waveforms, frequencies, targets, and feedback loops
Published in Expert Review of Medical Devices, 2019
Ankit Maheshwari, Jason E. Pope, Timothy R. Deer, Steven Falowski
Essentially this is a new class of spinal cord stimulation where variations of traditional spinal cord stimulation typically at subparesthesia thresholds are being tried because of the flexibility of programming in all available devices. Programming of spinal cord stimulation utilizes three components that describe an electrical pulse: Frequency, amplitude, and pulse width. Amplitude describes the maximum value of the current or voltage delivered and is dependent on the electrode type and nerve target. Frequency is measured in cycles per second and ranges from 40 to 10,000 Hz. Finally, pulse width describes the duration of each electrical stimulus and ranges from 30 to 1000 µs. Changes in frequency and pulse width can change the current density delivered by orders of magnitude and may impact the quality of stimulation. Variations of these parameters typically with frequency >1000 Hz which are not classically used in traditional spinal cord stimulation fall under the umbrella term of high-density stimulation. There is considerable overlap of this category/nomenclature with traditional SCS and HF SCS. The study cited under this category, for example Thomson et al. [28] could very well be under the HF category since that is an arm of the study. There are some case series that have reported improvement in pain mostly in patients who already had traditional spinal cord stimulation but were getting inadequate pain relief. Overall, literature pertaining to this mode of therapy is scant (Table 5).
Frequencies Wave Sound Particle Swarm Optimisation (FPSO)
Published in Journal of Experimental & Theoretical Artificial Intelligence, 2022
Ahmad K. Al Hwaitat, Rizik M. H. Al-Sayyed, Imad K. M. Salah, Saher Manaseer, Hamed S. Al-Bdour, Sarah E. Shukri
Frequency can be defined as a measurement in cycles per second. Wavelength is the measure of distance from one wave crest to the next wave crest, see Figure 3. When considering sound waves, amplitude is related to loudness of the sound and frequency to pitch. The higher the frequency, the higher the pitch. The speed of the sound can be related to eq. (3),
Performance, asymmetry and biomechanical parameters in wheelchair rugby players
Published in Sports Biomechanics, 2021
Sadate Bakatchina, Thierry Weissland, Marjolaine Astier, Didier Pradon, Arnaud Faupin
Asymmetry (Asymme) was the difference in the absolute values of the peak velocities of the right and the left wheels (Equation 1) Goosey-Tolfrey et al. (2018). Cycle frequency was defined as the number of cycles per second.