2. Resonance, Sound Intensity, & Sound Quality Resonance, Sound Intensity, & Sound Quality

3. Forced Vibrations... n …occur when we make an object produce a sound. Ex. –Clapping your hands –Hitting a tuning fork –Playing a musical instrument

4. Natural Frequency... n …the frequency at which an object produces a sound. n The natural frequency of a body depends on its elasticity, shape, & material composition.

5. Resonance... n A type of energy transfer n Occurs when the natural frequency of two or more objects match. n High intensity waves can destroy the object that is vibrating.

6. n More energy put into a forced vibration increases sound intensity!!! n Increased wave amplitude n The “intensity” refers to the amount of energy that moves through a sound wave. Intensity = P / (4πr²)

7. Loudness n the physiological sensation related to sound intensity. n Intensity increases by 10x and volume 2x for every increase in 10 decibels. Source of SoundLoudness (db) Threshold of Hearing0 Conversation60 Ear Damage Begins85 Amplified Music110 Jet Airplane at 30 meters140

8. Sound Quality n Timbre (tamber) is the sound quality produced by an object or instrument.

9. n Beats - the periodic variation in loudness of two sounds played together. n A result of alternating constructive & destructive interference. Ex. Instruments that are out of tune w/ each other n The beat frequency is equal to the difference in the frequency of the two sounds.