ICSE Physics Class 7 Notes Chapter 6 Sound
→ Sound is a form of energy which produces the sensation of hearing.
→ Sound requires a medium to travel. It cannot travel in vacuum.
→ Sound travels in all directions. Sound can travel through solids, liquids and gases.
→ Sound travels faster in solids than in liquids and gases.
→ The loudness of sound is measured on a special scale called the decibel scale.
→ Sound is classified into two groups.
- Musical sound.
- Noise.
→ Musical sound is produced by periodic vibrations.
→ Noise is produced by non-periodic motions.
→ What the sound gets repeated after reflection from a distant body, is called an echo.
→ Multiple echoes are called reverberations.
→ Sonar is method used to measure the depth of a sea and is based on the principle of echo.
→ Music is pleasent to hear and is caused by periodic vibrations.
→ Noise is irritating and is produced by an irregular pattern of waves.
→ The three characteristics of sound are loudness, pitch, quality or timbre.
→ Loudness depends upon many factors, e.g. amplitude, distance, waves of the vibrating body, humidity, pressure, wind velocity etc.
→ Pitch depends on the frequency of sound. Higher is the pitch, shriller is the sound.
→ Loudness is merely a sensation.