Sound Flashcards
Describe the nature of sound waves and explain how they propagate through a medium.
- Sound waves are longitudinal waves, meaning the vibrations are parallel to the direction of wave travel.
- They require a medium (such as air, water, or solids) to propagate and cannot travel in a vacuum.
- Sound propagates through compressions (high-pressure regions) and rarefactions (low-pressure regions) as particles vibrate and transfer energy.
Define compressions and rarefactions in a sound wave and describe their role in sound propagation.
- Compressions: Regions of high pressure and density where air particles are pushed together.
- Rarefactions: Regions of low pressure and density where air particles are spread apart.
- Together, they allow sound to travel as a series of pressure variations in the medium.
Explain how sound waves can be reflected and refracted, giving one example for each.
- Reflection: Occurs when sound waves bounce off a surface, creating an echo (e.g., shouting in a canyon).
- Refraction: Happens when sound waves change speed as they enter a different medium, causing bending (e.g., sound waves bending at night due to temperature differences in the air).
Describe how sound waves refract when passing from a region of warm air to a region of cooler air.
- When sound moves from warm air to cooler air, it slows down because the air molecules move less rapidly.
- This causes the sound wave to bend downwards, following the curve of the temperature gradient.
- This effect allows sound to travel longer distances at night when the air near the ground is cooler than the air above.
State the frequency range for human hearing and explain what happens if a sound is outside this range.
- The human hearing range is 20 Hz to 20,000 Hz (20 kHz).
- Sounds below 20 Hz are called infrasound and cannot be heard by humans.
- Sounds above 20 kHz are called ultrasound and are used in applications like medical imaging and sonar.
Practical: Describe an experiment to measure the speed of sound in air using echoes.
Method:
1. Choose a large flat surface such as a wall at a known distance.
2. Have a person clap while another starts a stopwatch.
3. The listener stops the timer when they hear the echo of the clap returning.
4. Measure the total distance sound traveled (to the wall and back).
5. Use the equation Speed = Distance / Time to calculate the speed of sound.
6. Repeat multiple times and take an average for accuracy.
What is an oscilloscope, and how is it used to display a sound wave?
- An oscilloscope is a device that shows sound waves as a graph on a screen.
- A microphone picks up sound and converts it into an electrical signal.
- The signal is displayed as a waveform on the oscilloscope screen.
- The time base setting helps measure the wave’s frequency and amplitude.
- The closer the wave peaks, the higher the frequency, and the taller the wave, the greater the amplitude.
Practical: How can an oscilloscope be used to determine the frequency of a sound wave?
Method:
1. Connect a microphone to an oscilloscope.
2. Produce a sound wave using a tuning fork or speaker.
3. Observe the waveform and measure the time period (T) of one full cycle.
4. Use the formula f = 1 / T to calculate frequency.
5. Adjust the time base setting for accuracy.
6. Repeat with different sounds and compare frequencies.
Describe how the pitch of a sound is related to the frequency of vibration of the source.
- Pitch is how high or low a sound appears to be.
- A higher frequency results in a higher pitch (e.g., a whistle has a high pitch).
- A lower frequency results in a lower pitch (e.g., a drum has a low pitch).
Explain how the loudness of a sound is related to the amplitude of vibration of the source.
- Loudness is determined by the amplitude of the sound wave.
- A greater amplitude means more energy, producing a louder sound.
- A smaller amplitude results in a quieter sound.
