Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Loudness: It is the characteristic of sound that distinguishes a loud sound from a faint one. It depends on the Amplitude () of vibration. Loudness is directly proportional to the square of the amplitude (). The SI unit for loudness level is the decibel ().
Pitch (Shrillness): It is the characteristic of sound that distinguishes a shrill sound from a grave (flat) sound. It depends on the Frequency () of vibration. High-frequency vibrations produce high-pitched sound (e.g., a whistle), while low-frequency vibrations produce low-pitched sound (e.g., a drum).
Quality (Timbre): It is the characteristic that allows us to distinguish between two sounds of the same loudness and same pitch produced by different instruments (e.g., a flute and a violin). It depends on the waveform and the presence of subsidiary vibrations called overtones.
Frequency (): The number of vibrations or oscillations completed by a body in one second. It is measured in Hertz ().
Time Period (): The time taken by a vibrating body to complete one full vibration. It is measured in seconds ().
📐Formulae
💡Examples
Problem 1:
An object vibrates times in seconds. Calculate its frequency and time period.
Solution:
,
Explanation:
Frequency is calculated as . The time period is the reciprocal of frequency: .
Problem 2:
If the amplitude of a vibrating string is doubled, how will the loudness of the sound produced change?
Solution:
The loudness will become times its original value.
Explanation:
Since loudness () is proportional to the square of the amplitude (), . If the new amplitude , then the new loudness . Therefore, .
Problem 3:
Two sound waves, and , have frequencies of and respectively. Which sound is shriller?
Solution:
Sound wave is shriller.
Explanation:
Shrillness is another term for pitch. Pitch depends on frequency. Since the frequency of sound () is higher than that of sound (), sound has a higher pitch and is shriller.