Vibrations and Sound Flashcards
How would you demonstrate sound interference?
Set up an audio signal generator to two speakers.
The sounds emitted will be coherent because they’re coming from the same source.
Walk in a line from A to B to experience differences in sound caused by constructive and destructive interference (louder and quieter).
Give an application of sound interference.
Can be used as a form of riot control (constructive interference in a specific area will produce a high amplitude).
How would you demonstrate that sound needs a medium to travel but light (EM) does not?
Place a phone in a bell jar with flashing LEDs and a song playing.
As the air is removed, the sound will diminish but the LEDs are still perfectly visible as before.
What determines the pitch of a note?
The note’s frequency.
What determines the ‘loudness’ of a note?
The note’s amplitude.
What determines the quality of a note?
The number of overtones and relative strength determines the quality of a note.
What is the first fundamental frequency in terms of the first harmonic?
1f = 1st harmonic
What is the fundamental frequency in terms of the first overtone?
2f = 1st overtone.
What are overtones and harmonics? What is the difference between them?
They are integer multiples of the fundamental frequency.
The first harmonic is 1f while the first overtone is 2f.
What would a rise in 3dB mean with respect to sound intensity?
Sound intensity doubles every 3dB;
A 6dB rise is a quadrupling in sound intensity, 3dB decrease is a halving in intensity, etc.
What is the formula for sound intensity?
Power (W) / Area (m^2)
Define resonance.
The transfer of energy between two bodies with the same natural frequency.
How would you demonstrate the resonance of sound?
Using Barton’s pendulum, attach masses to strings of varying lengths.
Keep two of the lengths the same.
Swing the mass on one of these lengths.
The corresponding mass with the similar length will begin to swing as well (resonance).
Give a real world example of resonance.
Your ear receives sounds as air vibrations that causes the eardrum to vibrate and resonate.
A wine glass an be broken by singing at its fundamental frequency (its wobbles and eventually breaks due to energy transfer).
What is the length of an OPEN pipe at its fundamental frequency?
Half of the wavelength.
0.5 lambda
