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...Phys1062_files/What do we know about sound

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What do we know about
sound?
• Where does it come from?
1. Vibrating bodies
2. Changing airflow
3. Time-dependent heat
sources
4. Supersonic flow
How do we know it is there?
• 1. Biological receptors:
– Pressure changes on eardrums, skin
• 2. Technical receptors:
– microphone
• 3. Mechanical vibrations
• 4. Other indication (reactions of animals)
How do we characterize sound?
• 1. loudness
loud, intense vs. soft, silent
• 2. pitch
high pitched vs. low pitched
bass vs. soprano
• 3. timbre or “color”
warm, soft vs. shrill, piercing
• 4. duration
How does it get from the source to
the receptor?
• Travels through a medium (gas, liquid,
solid)
• “waves”
• Medium modifies the sound
• Distance changes loudness
• Motion of source or observer changes
pitch.
Is there a place of absolute
silence?
• Physically?
• Physiologically?
How will we be able to understand
some of these observations?
We will have to study some Physics
fundamentals:
Motion, force, pressure, energy, power,
oscillations, waves, resonance, …
Let’s go!
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