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These phenomena can potentially generate vibrations of the ferromagnetic, conductive parts, coils and permanent magnets of electrical, magnetic and electromechanical device, resulting in an audible sound if the frequency of vibrations lies between 20 Hz and 20 kHz, and if the sound level is high enough to be heard (e.g. large surface of ...
Mains hum, electric hum, cycle hum, or power line hum is a sound associated with alternating current which is twice the frequency of the mains electricity.The fundamental frequency of this sound is usually double that of fundamental 50/60 Hz, i.e., 100/120 Hz, depending on the local power-line frequency.
A buzzer or beeper is an audio signaling device, [1] which may be mechanical, electromechanical, or piezoelectric (piezo for short). Typical uses of buzzers and beepers include alarm devices , timers , train and confirmation of user input such as a mouse click or keystroke.
So while threshold levels of for the microwave audio effect of 267mW/cm² for 1.3GHz and 5000mW/cm² 2.9GHz, respectively, were reported by Frey in 1961, for the peak amplitude (providing the pops) and would only give an average (sustained) power density of only 0.4mW/cm² and 2mW/cm² respectively [7] similar to current cellphones.
The sound was made into a mobile phone ringtone, which could not be heard by teachers if the phone rang during a class. [13] Mobile phone speakers are capable of producing frequencies above 20 kHz. [14] This ringtone became informally known as "Teen Buzz" [15] or "the Mosquito ringtone" and has since been sold commercially.
A piezoelectric speaker (also known as a piezo bender due to its mode of operation, and sometimes colloquially called a "piezo", buzzer, crystal loudspeaker or beep speaker) is a loudspeaker that uses the piezoelectric effect for generating sound. The initial mechanical motion is created by applying a voltage to a piezoelectric material, and ...
Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, [1] [3] which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
A noise-cancellation speaker emits a sound wave with the same amplitude but with an inverted phase (also known as antiphase) relative to the original sound. The waves combine to form a new wave, in a process called interference , and effectively cancel each other out – an effect which is called destructive interference .