PHYS 10.01 Sounds
What is the necessary condition for an echo to be heard distinctly?
(i) To hear a distinct echo, the time interval between the original sound and the reflected one must be at least 0.1 s. (ii) For hearing distinct echoes, the minimum distance of the obstacie from the source of sound must be 17.2 m. Echo is a repetition of sound due to the reflection of original sound by a broad and hard obstacle.
What is the average range of a young person's hearing?
20-20,000 hertz
What is the speed of sound in dry air at 20°C?
340 m/s
What beat frequency will occur when a 370-Hz and a 374-Hz sound source are sounded together?
4hz
How does a radio wave differ from a sound wave?
A radio wave is an electromagnetic wave that travels at the speed of light, whereas a sound wave travels at the speed of sound through air or another elastic medium.
Why does sound sometimes refract under water?
Changing temperature changes the speed of sound in water
What factors does the speed of sound depend upon? What are some factors that it does not depend upon?
Depends on wind conditions, temperature, humidity and does not depend on loudness or frequency of sound
What is the pitch of a sound wave?
It has to do with the frequency. High-frequency sound waves have a high pitch, and low-frequency waves have a low pitch.
What happens to a medium in which sound waves propagate?
Nothing. The medium does not move but the pulse does.
What are some applications of the acoustic phenomenon known as an echo?
Reflecting surfaces are suspended above the stage in some concert halls
What is ultrasound?
Sound above the frequency of human hearing
What is sound? How is it produced?
Sounds are waves produced by vibrations
Which is normally greater: the energy in ordinary sound or the energy in ordinary light?
The energy in ordinary light is greater than the energy in ordinary sound. The speed of sound is a million times less than the speed of light.
How did wind-generated resonance affect the Tacoma Narrows Bridge in Washington in 1940?
The resonant amplification of bridge motion destroyed the bridge.
What is the result of a mirror image of a sound signal combining with the sound itself?
The second is cancelled when added to its mirror image
Why does a struck tuning fork sound louder when it is held against a table?
The table is forced to vibrate, and its large surface vibrates more air than the tuning fork.
What are ultrasonic and infrasonic frequencies?
Ultrasonic - frequencies above 20,000 hertz Infrasonic - frequencies under 20 hertz
What is the cause of refraction?
When a sound wave continues through a medium and bends
How do forced vibrations relate to resonance?
When the frequency of forced vibrations match an object's natural frequency, resonant amplification occurs. It does need a force to pull it back into its starting position, and enough energy to keep it vibrating.
What kind of waves can exhibit interference?
all kinds of waves
When you listen to a radio, why do you hear only one station at a time rather than hearing all stations at once?
because you're only tuned in to the frequency of one radio station
What ultimately becomes of the energy of sound in the air?
becomes thermal energy
Does sound tend to bend upward or downward when its speed is less near the ground?
downward
Give at least two factors that determine the natural frequency of an object.
elasticity and shape of the object
What characteristics are required in a medium for the propagation of sound?
has to be elastic and not in vacuum, has to be vibrating, sound is detected
Does sound travel faster in warm air than in cold air?
in warm air
When is it possible for one wave to cancel another?
only when sound waves with high frequencies
What physical phenomenon underlies the production of beats?
periodic vibration due to interference
Do compressions and rarefactions travel in the same direction, or in opposite directions, in a wave?
same direction, same speed
In which medium—gaseous, liquid, or solid—is the speed of sound highest?
solids
