ch13_csnk

=__Chapter 13- Sound __=

=**__Section 13-1: Sound Waves__**= math f' = \frac{V + V_d}{V - V_s} math
 * Sound waves are longitudinal
 * Consist of compressions (areas of high pressure) & refractions (areas of low pressure)
 * Sound waves radiate out in spherical wavefronts from a vibrating object.
 * Pitch is known as the frequency that a sound wave is perceived to have.
 * Sound waves travel outward in 3 dimensions.
 * Frequencies between 20 Hz and 20000 Hz can be picked up by humans.
 * Frequencies lower than 20 Hz are identified as infrasonic.
 * Frequencies higher than 20000 Hz are identified as ultrasonic.
 * The speed of the sound wave depends upon the medium.
 * The speed of sound at sea level & room temperature is about 343 m/s.
 * The freeuncy shift between the relative motion between an observer and the source of waves is known as hte Doppler Effect.
 * The Doppler Effect can be seen if a sound source and the detector are moving relative to one another.
 * **__//Formula for pitch://__**

=**__Section 13-2: Sound Intensity__**=

__Intensity__ math I=\frac{P}{4 \Pi r^2} math __Perceived Intensity__
 * As a sound wave travels thorough a medium,energy is transfered to the next molecule.
 * Intensity is known as the rate which the energy is transferred.
 * Intensity is measured in watts per square meter.
 * __//**Formula for intensity:**//__
 * threshold of hearing: the quietest sound audible to humans
 * Approx. 1.0 X 10^-12 W/m2
 * threshold of pain: the loudest sound a typical person can tolerate
 * Approx. 1.0 W/m2
 * The perceived loudness of a sound is dependent of the logarithm of hte intensity.
 * It is measured in decibels (dB).
 * The sound level measured in decibels is:
 * dB = 10log)_10 intensity
 * "Intensity" is the intensity of sound being measured.
 * " Intensity//r// k"is the relative intensity
 * Decibel level is a measure of relative intensity in terms of logarithm.
 * A forced vibration at the natural frequency produces resonance.

=**__Section 13-3: Harmonics__**= math f_n = n \frac{v}{2L} math n = 1, 2, 3... math f_n = n \frac{v}{4L} math n = 1, 3, 5... >
 * Fundamental Frequency- the lowest frequency of vibration of a standing wave.
 * Fundalemental frequency is the lowest possible frequency of a standing wave.
 * Harmonics of a vibrating string or pipe open at both ends is found by the equation:
 * Harmonics of a pipe closed at one end is found by the equation
 * Harmonic Series- a series of frequencies that includes the fundamental frequency and integral multiples of the fundamental frequency.
 * Timbre- the quality of a steady musical sound that is the result of a mixture of harmonics present at different intensities.

=Practice Problems:= > > __**Works Cited:**__ > Faughn, Jerry S. and Raymond A. Serway. __Physics.__ New York: Holt, 2004. > Strong, Tom. Course notes. Honors Physics, Dept. of Science, Mount Lebanon High School. May and June 2009.
 * The fundamental frequencies produces by a typical piano range from 26.0 Hz to 4435 Hz. What are the wavelengths of these frequencies? (Answer: wavelength= 13.3 m, wavelength= 0.0778 m)
 * Two cars are moving towards each other, the one on the left at 20.0 m/s and the one on the right at 30.0 m/s. The car on the left sounds its horn with a frequency of 440.0 Hz. What pitch will the driver in the car on the right hear? (pitch= 508 Hz)