Sound Flashcards
What are the two things that must be present in the production of sound?
Something that vibrates
Something that Resonates
Number of waves per second
Frequency (measured in Hz)
Frequency is perceived subjectively as what?
Pitch
The lower the pitch, the lower the ______________?
Frequency
A lower pitch has a ________(longer, shorter) wave.
Longer
Speed of Sound in AIR
340 m/sec
What is the human range for frequency?
20-20,000 Hz
Below 20 Hz
infrasonic
Above 20,000 Hz
ultrasonic
Measurement unit for loudness
Decibels (dB)
Practical range for loudness (humans)
0 dB to 120 dB
If the decibel level is 10 times greater, the sound is _____ as loud.
Twice.
What type of wave is sound?
Longitudinal
Why is it silent in outer space?
There is not medium (no air) for sound to travel in.
A vibrating object forces a second object to vibrate
Forced vibration
An object with elasticity will vibrate at its own frequency. This is the object’s ___________________.
Natural Frequency
This happens when forced vibrations take place at the natural frequency, creating a peak of energy
Resonance
What happens when two identical waves come together and are out of phase?
The sound becomes muted or muffled.
What happens when two identical waves come together and are in phase?
The amplitude of the wave is increased and the sound becomes louder.
The difference in two sounded frequencies is called what?
The Beat Frequency
If two tones of slightly different frequencies are sounded together, what happens to the sound?
There is a periodic variation in the loudness of the sound.
A periodic variation in the loudness of sound
Beats
Doppler Effect
An apparent shift in frequency due to the motion of a source, an observer or both
With the Doppler Effect, the wavelength is _____________ as a source approaches, making the frequency __________________.
Shortened; Higher
With the /Doppler Effect, the wavelength is ______________ as a source leaves, making the frequency ___________.
Lengthened; Lower
Doppler Effect can occur with ___________ or _____________.
Sound; Light
If objects move away from an observer, there is a ______________ frequency or a _____ shift.
Lower; Red
If objects move towards the observer, there is a _______________ frequency or a ________ shift.
Higher; Blue
