ch13_ecls

Chapter 13: Sound Section 1 (Sounds Waves) **
 * Vocab: **
 * Compressions:** areas of high pressure
 * Rarefactions:** areas of low pressure
 * Pitch:** the frequency a sounds wave is percieved to have
 * Infrasonic:** frequencies below 20 Hz
 * Ultrasonic:** frequencies above 20,000 Hz
 * Doppler Efect:** sound source and the detector are moving relative to one another

Humans can hear sounds from about 20 Hz to 20,000 Hz Speed of sound is approximately 343 m/s

math f' = f \frac{v+v_d}{v-v_s} math

v= speed

math v_d= detector moving at velocity math

math v_s= source moving at velocity math

f' = pitch f= frequency Vocab: **
 * Section 2 (Sound Intensity and Resonance) **
 * Intensity:** the rate at which energy is transferred from one molecule to the next
 * Perceived intensity:** dependent on the logarithm of the intensity and is measured in decibels.
 * Resonance:** response at certain frequencies
 * Resonant frequency:** the amplitude of its vibrations

math intensity= \frac{P}{4 \pi r^2} math
 * Threshold of hearing: **

math 1.0 x 10^{-12} \frac{W}{m^2} math
 * Threshold of pain: **

math 1.0 \frac{W}{m^2} math

math dB= 10log_{10} \frac{intensity}{intensity_r} math
 * Intensity: ** is the intensity of the sound being measured.

math Intensity_r:1.0 x 10^{-12} math An increase of 10 decibels will be perceived as being twice as loud, and intensity will be increased by a factor of 10
 * Section 3 (Standing Waves) **
 * Vocab: **

math Fundamental frequency (f_1): math The lowest frequency able to form a standing wave


 * Harmonics:** frequencies above the lowest frequency
 * Harmonic series:** the frequency of each harmonic frequency is equal to the fundamental frequency multiplied by the harmonic number (n)
 * Timbre**: sound quality of the resulting sound
 * Beat**: two sources that admit sound waves close to each other but are not exactly the same

(Section 1) 1. A ambulance passes a stationary listener at 25 m/s. If the frequency of the ambulance's siren is 530 Hz what frequency will the listener hear s the ambulance is approaching and moving away?
 * Fun review problems that YOU SHOULD TRY ** :

(Section 2): 1. If the intensity of a person's voice is 4.6x10 -7 W/m2 at a distance of 2.0 m, how much sound power does this person generate? 2. The power output of a piccolo is 0.35 W. At what distance is the sound intensity of the piccolo 1.2 x 10 -3 W/m2?

(Section 3) 1. What is the fundamental frequency of a .20 m long wine bottle that is closed at one end, when the speed of sound in the pipe is 352 m/s? 2. Mr. Strong uses a 392 Hz tuning fork (when at his side job as a piano tuner) to tune the wire for G natural hears 4 beats per second. What are the two possible frequencies of vibration of this piano wire?

Faughn, Jerry S., and Raymond A. Serway. __Physics__. Austin: Harcourt Classroom Education Company, 2002.