1. MUSICAL ACOUSTICS Chapter 1 What is Sound? The Science of Sound

2. EXAMPLES OF WAVES Longitudinal waves (air molecules) in a sound wave created by a loudspeaker. Transverse waves on a rope shaken up and down at one end.

3.  VIBRATING BODIES drum head air column of a trumpet air in the vocal tract piano soundboard  CHANGING AIRFLOW vocal folds opening and closing lips of a brass player siren  TIME-DEPENDENT HEAT SOURCE electric spark lightning  SUPERSONIC FLOW ”crack” of a rifle bullet sonic “boom” SOME SOURCES OF SOUND

4. EXAMPLES OF SOUND SOURCES (d) Concert Bass Drum Concert Bass Drum Vibrating drumhead causes pressure Changes In the air nearby Holes in a rotating siren alternately pass and stop an air stream Explosion rapidly Heats the air nearby Supersonic airplane creates shock waves

5. Curves of uniform and changing motion Shrinking Δy and Δt to obtain instantaneous speed Speed as a function of time GRAPHICAL REPRESENTATION OF MOTION

6. Stroboscopic observation of motion: Constant speed Increasing speed Constant speedIncreasing speed

7. DISTANCE BETWEEN TWO POINTS IN A COORDINATE SYSTEM

8. MOTION

9. FORCE – can be described as a “push” or a “pull” Applying a force may result in a distortion, an acceleration, or both Acceleration is proportional to force: a F Newton’s second law of motion: a=F/m (or F=ma) The force of gravity (W) produces an acceleration (9) W=mg (compare F= ma) g=9.8 m/s 2 ( ≈10m/s= 2) Don’t confuse Force and Pressure Pressure = Force/Area

10. VIBRATORY MOTION in which y, v, and a all change with time

11. PRESSURE and BUOYANCY PRESSURE in a container of fluid: (a) acts on all surfaces; (b) is proportional to depth. BUOYANT FORCE (dashed arrow) on the immersed object is due to the excess upward force.

12. BUOYANCY OF ICE

14. GRAPHICAL REPRESENTATION OF A SOUND WAVE

15. WORK AND ENERGY WORK is average FORCE times DISTANCE moved parallel to the force W=Fd If an object with weight mg falls a DISTANCE h, the WORK done by gravity is W=mgh A baseball moving at speed v has KINETIC ENERGY KE=1/2mv² An object lifted to a height h above the floor has POTENTIAL ENERGY PE=mgh

16. POWER POWER IS ENERGY (or WORK) DIVIDED BY TIME P=W/t ENERGY IS EXPRESSED IN JOULES (J) POWER IS EXPRESSED IN WATTS (W) 1 watt = 1 joule/second

17. UNITS The preferred system (used all over the world) is the SI (Système International) or mks (meter-kilogram-second) system. Besides the three basic units (meter, kilogram, second) the system includes such units as newtons, joules, watts, pascals, hertz, etc. which are derived in a logical manner from the basic units. newtons (force) energy (joules) power (watts) pressure (pascals) freqency (hertz)