Test: Sound - 1 - UPSC

• Pitch is that characteristic of a musical sound by which a shrill sound can be distinguished from a grave one, even though the two sounds may be of the same intensity.
• It is also defined as that characteristic of sound by which the ear assigns it a place on a musical scale.
• When a stretched string is plucked, a sound of a certain pitch sensation is produced.
• 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.
• But frequency alone does not determine the pitch. Below 1000Hz, the pitch is slightly higher than the frequency and above 1000Hz the position is reversed.
• The loudness of sound also affects the pitch up to 1000Hz. An increase in loudness causes a decrease in pitch. From about 1000 to 3000Hz, the pitch is independent of loudness, while above 3000Hz an increase in loudness causes an increase in pitch.

Hence, pitch of sound depends upon its frequency.

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.

• 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 audible range for human beings is about 20Hz to 20,000Hz. This frequency is required to generate vibrations in the tympanic membrane. 
• If any sounds exceed this range, the sound remains undetected, whatever the amplitude may be. 

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.

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.

1Hz= 1 vibration/second

1 minute=60 seconds
Hence, 1 hertz = 60 vibrations /minute

• 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.

• 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. 

Sound is produced by vibration of body. In flute, the vibrating part is air column inside the flute.