Test: Sound - 1 - Class 8 MCQ

Our ears can usually hear sounds that range from 20 to 20,000 vibrations per second. This means we can hear many different sounds around us, from music to voices to noises like horns or construction sounds. It's like our ears have a special range for hearing different things!

Speed of sound depends upon nature of medium, temperature, humidity and source of sound but nature of medium influence the speed of sound most. Sound travels faster in solid medium than air and water.

If the tension in the string is increased, the pitch (the shrillness) becomes higher. Increasing the tension, also increases the frequency of vibration. Therefore, pitch is intimately related to frequency

• Loudness is directly proportional to the square of the amplitude of sound waves.
• If the amplitude is high then sound will be louder and the sound will be feeble if the amplitude is low.
• Loudness is measured in units called decibels. 

The length of the vocal chords differs in men and women, which is why there is difference in the quality of their voice. The length of the vocal chord in men is approximately 20 mm and in women it is 15 mm.

Dogs have the ability to hear sounds that are higher than 20,000 vibrations per second. This means they can hear sounds that are very high-pitched, which humans cannot hear because they are too high for our ears to pick up.

- Vibration is also known as Oscillatory Motion.
- Explanation:
- Oscillatory Motion refers to a repetitive back-and-forth or to-and-fro motion around a central position.
- Vibratory motion involves a periodic motion about an equilibrium point.
- It is characterized by a regular and repeated pattern of movement.
- Correct Answer: C: Oscillatory Motion.

Sound propagates best in:
Solids: Due to the tightly packed particles, sound waves can travel faster and more efficiently through solids..

When a tightly stretched band is plucked, it vibrate and produce sound due to disturbance in medium. When it stops vibrating, it does not produce any sound.

• Sound is produced by vibration of object.
• Vibration creates disturbance in medium which reaches to observer ear through air, water or solid medium.
• In human, muscles push air up from lungs and through the narrow opening between the vocal cords. The force of the air causes the vocal cords to vibrate. The vibrating vocal cords produce sound waves.

• The vibrations of object are not visible because in most of the cases amplitude of waves are very small.
• The vibrations are easily visible when amplitude of waves is high.
• Amplitude is the maximum displacement from mean position.