Why are sound waves in air characterized as longitudinal?
Because air molecules vibrate in a direction parallel to the direction of wave motion
What is the difference between frequency and pitch?
Frequency is an OBJECTIVE measure of the rate of particle vibration.
Pitch is a SUJECTIVE quality that depends on the listener.
What are the differences between infrasonic, audible, and ultrasonic sound waves?
Infrasonic waves are below 20 Hz, audible waves are between 20 and 20 000 Hz, and ultrasonic waves are greater than 20 000 Hz.
Explain why the speed of sound depends on the temperature of the medium. Why is this temperature dependence more noticeable in a gas than in a solid or a liquid?
Molecules that have more motion (higher temperature) can transfer their vibrations more easily. This is less noticeable in liquids and solids because the particles are closer together.
You are at a street corner and hear an ambulance siren. Without looking, how can you tell when the ambulance passes by?
The pitch will drop
Why do ultrasound waves produce images of objects inside the body more effectively than audible sound waves do?
Because their short wavelengths can image small objects
If the wavelength of a sound source is reduced by a factor of two, what happens to the wave's frequency?
What happens to its speed?
Frequency doubles
Speed is constant
As a result of a distant explosion, an observer first senses a ground tremor, then hears the explosion. What accounts for this time lag?
Sound travels faster through the ground
By listening to a band or an orchestra, how can you determine that the speed of sound is the same for all frequencies?
Because the notes that are played at the same time, they reach your ears at the same time.
A fire engine is moving at 40 m/s and sounding its horn. A car in front of the fire engine is moving at 30 m/s, and a van in front of the car is stationary. Which observer hears the fire engine's horn at a higher pitch, the driver of the car or the driver
Van
A bat flying toward a wall emits a chirp at 40 kHz. Is the frequency of the echo received by the bat greater than, less than, or equal to 40 kHz?
Greater than 40 kHz
What is the difference between decibel level and intensity?
Intensity = power per area
dB level = measure of relative intensity
Under what conditions does resonance occur?
when a forced vibration is the same as the natural frequency of a vibrating system
The dB level of an orchestra is 90 dB, and a single violin achieves a level of 70 dB. How does the sound intensity from the full orchestra compare with that from the violin alone?
Sound intensity from full orchestra is 100x that from the violin
A noisy machine in a factory produces a dB rating of 80 dB. How many identical machines could you add to the factory without exceeding the 90 dB limit set by federal regulations?
add 9
(Well with the one you have already --- 10 total)
Why is the intensity of an echo less than that of the original sound?
because intensity decreases
with distance and the sound has traveled from the source to a reflecting surface and back
Why are pushes given to a playground swing more effective if they are given at a certain, regular intervals than if they are given at random positions in the swing's cycle?
Bc the swing's amplitude is most effective/maximized when the pushes match the swing's natural frequency
Although soldiers are usually required to march together in step, they must break their march when crossing a bridge. Explain the possible danger of not taking this precaution while crossing a rickety bridge.
Vibrations could set the bridge in motion if they match one of the bridge's natural frequencies.
What is fundamental frequency? How are harmonics related to the fundamental frequency?
the lowest possible frequency
of a vibrating system;
They are integral multiples of the fundamental frequency.
Why does a pipe closed at one end have a different harmonic series than an open pipe?
Closed end = Node
Open end = Antinode
Explain why a saxophone sounds different from a clarinet, even when they sound the same fundamental frequency at the same dB level.
The instruments have different harmonics present at various intensity levels.
Why does a vibrating guitar string sound louder when it is on the instrument than it does when it is stretched on a work bench?
The guitar's body transfers the string's vibrations to the air more efficiently, which increases the intensity of the sound.
Two violin players tuning their instruments together hear 6 beats in 2 s. What is the frequency difference b/t the two violins?
3 Hz
What is the purpose of the slide on a trombone and the valves on a trumpet?
to change the length of the air
column, thereby changing the fundamental frequency
A student records the first 10 harmonics for a pipe. Is it possible to determine whether the pipe is open or closed by comparing the difference in frequencies b/t the adjacent harmonics with the fundamental frequency? Explain.
Yes;This difference will equal the fundamental frequency if the pipe is open at both ends but will equal twice the fundamental frequency if the pipe is closed at one end. >>>>
Difference = fundamental freq. if pipe open @ both ends
Difference is 2(Fun. Fr
A flute is similar to a pipe open at both ends, while a clarinet is similar to a pipe closed at one end. Explain why the fundamental frequency of a flute is about twice that of the clarinet, even though the length of these two instruments is approximately
The first possible wavelength is 2L for flute and 4L for clarinet.
Because the speed of sound is the same in each and v = Lf, the flute's fundamental frequency is twice the clarinet's.
Flute Fun. Freq. = 2(Clarinet fun. freq.)
The fundamental frequency of any notes produced by a flute will vary slightly with temperature changes in the air. For any given note, will an increase in temperature produce a slightly higher fundamental frequency or a slightly lower one?
As temperature increases, the speed of sound in air increases. Because f1 is proportional to v, fundamental frequency also increases.