Chapter 12 - Sound Flashcards
What is the normal hearing range for humans?
20 - 20,000 Hz
greater than 20,000Hz is ultrasonic
less than 20Hz is infrasonic
What does attenuation mean for sound waves?
Sound waves decrease in intensity and energy as they get farther away from the source. The wave spreads out and the sound energy is converted to thermal energy.
How does frequency affect how far a sound wave travels?
Sound waves with higher frequencies don’t travel as far because their energy is lost much faster.
Sound waves with low frequencies can travel much farther through air.
What is an elastic vs inelastic substance? How does that affect the transmission of sound?
- Elastic substances have atoms that are close
together and can transmit energy with little loss. - Inelastic substances have atoms that are far apart,
and more energy falls through the cracks and is lost. - Sound transmits better and farther in elastic objects.
What state of matter transmits sound the best? The least?
Solids are very elastic so they transmit sound the best.
Liquids are second, and gases are the worst.
Speed of sound in steel vs air? Water vs air?
Speed of sound is…
- 4x faster in water than in air
- 15x faster in steel than in air
What factors affect the speed of sound (in air)?
- Wind (bends the waves)
- Temperature (molecules move faster when hot)
- Humidity (high humidity = more condensed and
closer together = faster sound) - The medium determines the speed
What factors do NOT affect the speed of sound?
loudness and frequency
What does our ear help us determine?
The ear helps us determine loudness and pitch.
What is pitch?
Our perception of frequency.
What is frequency?
How often the pattern of motion repeats itself; the number of to and fro motions in a given time.
Doppler effect
The change in frequency due to the motion of the source.
In the Doppler effect, what happens as an object travels toward you?
High pitch, high frequency, short wavelength
- Increase in pitch
- crests of waves hit your ear more frequently
- Shorter wavelengths
In the Doppler effect, what happens as an object travels toward you?
Low pitch, low frequency, long wavelengths
- drop in pitch
- crests of waves hit your ear less frequently
- longer wavelengths
How does the Doppler effect apply to ultrasound?
- Ultrasound uses sound waves to create images of structures inside the body.
- It works by measuring the frequency of sound waves reflected off moving objects in the body.
- Different structures will give off different frequencies based on their position in the body, how fast they are moving, and in what direction.
