Music, Math, and Motion Dr. E.J. Zita The Evergreen St. College Winter week 6 Friday 13 Feb. 2009

Ch.12: Intro to SOUND Where to find solutions to HW online Overview of 12a: § 1, 2, 3 Discuss sections Practice problems together Choose homework together, due next Friday Looking ahead

Giancoli solutions on Moodle

Overview of Ch.12.1: Characteristics of Sound You already know sound = longitudinal PRESSURE waves and that the speed of sound depends on its medium. using PV = nKT (ideal gas law). The result can also be expressed as v ~ ( T ) m/s (where temperature T is in Kelvin)

Overview of Ch 12.2: Intensity of Sound: Decibels Intensity = I = Power / Area of sound wave (in W/m 2 ) Loudness =  = perceived sound level (in decibels) Basic tutorial in logarithms: In general, if m x = y ↔ log m y = x, or, in words If m to the x power = y, then the (log of y to the base m) = x. For example, log base 10, or common logs: 10 x = y ↔ log 10 y = x 10 0 = 1 ↔ log 10 1 = = 10 ↔ log = = 100 ↔ log = 2

Overview of 12.3: The Ear and its Response: Loudness Sound (pressure waves)  channeled down ear canal  tympanum (eardrum) vibrates  middle ear transfers and amplifies signal (x 40) to “oval window” in  cochlea, which transforms vibrational energy to electrical energy  to brain. Sensitivity varies with frequency.

Jigsaw learning-through-discussion 1. Count off by 1, 2, 3 Each team discuss your section Identify key points Zita will circulate, answering questions 2. Mix teams so there is one expert for each chapter on each team Discuss all sections – share your key points 3. Whole group gather: resolve questions, share insights and examples, and choose homework together

Let’s try some HW together – you choose which

HW Ch.12. 2

HW Ch.12.3

General Problems Ch

Looking ahead TODAY