Which of the following may be causedby noise?

1. Production and Propagation of Sound:

(i) Production of sound: Sound is produced by the vibration of the panicles of a medium.

(ii) Propagation of sound: Sound is a form of energy that is transferred as vibrations through the air or any other medium, in the form of waves.

(iii) Speed of the sound, $v=\nu \lambda$

where $\nu$ is the frequency and $\lambda$ is the wavelength.

2. Mechanical Waves and Characteristics of Wave Motion:

(i) Types of mechanical waves:

(a) Transverse wave

(b) Longitudinal wave

(ii) In a transverse wave, the particles of the medium vibrate in a direction perpendicular to the direction of propagation of the wave.

(iii) In a longitudinal wave, the particles of the medium vibrate in a direction parallel to the direction of propagation of the wave.

3. Sound and Its Properties:

(i) Amplitude: Maximum displacement of a vibrating particle from its mean position.

(ii) Frequency: The number of vibrations produced by a vibrating body in one second.

(iii) Hertz: The SI unit of frequency. Frequency is one hertz when one vibration is produced in one second.

(iv) Loudness: Characteristic of sound which distinguishes a feeble sound from a loud sound of the same frequency.

(v) Pitch: The effect of sound of different frequencies on the ears.

(vi) Shrillness: The effect of sound at a very high frequency on the ears.

4. Musical Instruments:

Musical sound: A sound which has a pleasing effect on the ears.

5. Sound Produced by Humans:

(i) Infrasonic vibrations have frequency less than $20 \mathrm{Hz}$ and are inaudible to the human ear.

(ii) Sonic vibration has frequency between $20 \mathrm{Hz}$ and $20,000 \mathrm{Hz}$.

(iii) Ultrasonic vibrations have frequency above $20,000 \mathrm{Hz}$ and are inaudible to the human ears.

(iv) Loudness of the sound is measured in decibel $\left(\mathrm{dB}\right)$.

6. Noise Pollution and Methods to Control Noise Pollution:

(i) Noise: A sound which has unpleasant effect on the ears.

(ii) Noise pollution creates problems such as deafness, headache and loss of concentration.

(iii) Sound of loudness more than $80 \mathrm{dB}$ is shrill and unbearable. It causes a lot of noise pollution.