1. What do we know about sound?

2. Where does it come from? 1.Vibrating bodies 2.Changing airflow 3.Time-dependent heat sources 4.Supersonic flow

3. 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)

4. 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

5. 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.

6. Is there a place of absolute silence? Physiologically? Physically?

7. 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!