Simple ear-protection devices use materials that reflect or absorb sound before it reaches the ears. A newer technology, sometimes called noise cancellation, uses a microphone to produce an electrical signal that mimics the noise. The signal is modified electronically, then fed to the speakers in a pair of headphones. The speakers emit sound waves that cancel the noise. On what principle is this technology based? What kind of modification is made to the electrical signal?

A person is sitting $200m$ away from a $20hertz$ sound source. What is the time interval at which successive compressions pulses from the source reach him?

Sound waves with frequency smaller than 20 Hz are called:
ultrasound
infrasound
nanosound
minisound

Why is momentum conserved?

What type of wave travels slower through gases than it does through solids?

Which of the following is an example of longitudinal wave?

What are the properties of sound waves?

What are some examples of resonance.

If the amplitude of a sound in doubled, then the loudness increases:
A)Remains same
B)Increases three times
C)Increases four time
D)Increases two times

1 db is equal to how many hertz?

How do sound waves travel in air medium?

What is the period of the Great Clock's, Big Ben, pendulum.

Sound waves with a frequency of 20 Hz to 20,000 Hz are called_______. A. Audible sounds B. Inaudible sounds C. Infrasonics D.Ultrasonics

Do all EM waves travel at same speed?

What is the wavelength of light (nm) that has a frequency $4.62\times {10}^{14}{s}^{-<!--\; -\; -->1}$?
A. $932$
B. $649$
C. $1.54\times {10}^{-<!--\; -\; -->3}$
D. $1.07\times {10}^6$

A person has a hearing range from $20Hz$ to $20kHz$. What are the typical wavelengths of sound waves in air corresponding to these two frequencies? Take the speed of sound in air as $344\frac{m}{s}$.