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!