1. The time period of a sound wave is the time taken to complete one full cycle of vibration. Its S.I. unit is the second (s). It is inversely related to frequency: T = 1/f, where T is the time period and f is the frequency.
2. Ultrasonic sounds are sound waves with frequencies higher than 20,000 Hz, which is beyond the upper limit of human hearing.
3. Astronauts talk to one another on the surface of the moon using radio waves because sound cannot travel through the vacuum of space; there is no medium to carry sound waves.
4. a) Loudness is determined by the amplitude of the wave. b) Pitch is determined by the frequency of the wave.
5. In wind instruments, pitch is altered by changing the length of the air column inside the instrument — shorter columns produce higher pitches, and longer columns produce lower pitches.
6. We hear thunder a few seconds after seeing the flash because light travels much faster (approximately 3 × 10⁸ m/s) than sound (approximately 343 m/s in air), so the visual signal reaches us almost instantly while the sound takes time to travel.
7. The range of audible frequency for human beings is typically from 20 Hz to 20,000 Hz.
8. a) Pinna: Collects and directs sound waves into the ear canal. b) Eardrum: Vibrates when struck by sound waves, transmitting vibrations to the middle ear. c) Ear bones (ossicles): Amplify and transmit vibrations from the eardrum to the inner ear. d) Tiny hair in the inner ear: Convert mechanical vibrations into electrical signals that are sent to the brain via the auditory nerve.
9. Time period = total time / number of oscillations = 5 s / 40 = 0.125 s. Frequency = 1 / time period = 1 / 0.125 = 8 Hz.
10. The air chamber in stringed instruments amplifies the sound produced by the vibrating strings by resonating with the vibrations, making the sound louder and richer.
11. Speed of sound = distance / time = 900 m / 3 s = 300 m/s.
12. Amplitude of a vibration is the maximum displacement of a particle from its mean (rest) position during oscillation. It determines the loudness of a sound wave.
Parent Tip: Review the logic above to help your child master the concept of science sound worksheet.
