7.2 Sound Flashcards
sound
a longitudinal wave transmitted by the oscillation of particles in a deformable medium
(sound cannot travel through a vacuum)
speed of sound equation
bulk modulus
a measure of the medium’s resistance to compression
increases from gas to liquid to solid
pitch
the frequency of a sound
lower frequency = ____ pitch
lower
higher frequency = ____ pitch
higher
infrasonic waves
soundwaves with frequencies below 20Hz
(humans cannot hear)
ultrasonic waves
sound waves with frequencies above 20,000 Hz
(humans cannot hear)
doppler effect
describes the difference between the actual frequency of a sound and its perceived frequency when the source of the sound and the sound detector are moving relative to one another
example: an ambulance with its sirens blaring has a distinct drop in pitch as it passes your car
doppler effect equation
f = perceived frequency
f0 = actual emitted frequency
shock waves
the highly condensed wave front that results when an object moves faster than the speed of sound
sonic boom
the nouse heard from the shockwave of an object travelling at or faster than the speed of sound
sound volume
this is subjective
depends on brain function, damage to the ear, etc.
sound intensity
objectively measureable
the average rate of energy transfer per area across a surface that is perpendicular to the wave
the power carried by sound waves per unit area in a direction perpendicular to that area
SI unit for intensity
watts per square meter
sound intensity equation
Intensity = power / area
watts / square meter
relationship between intensity and amplitude
intensity = amplitude squared
(doubling the amplitude quadruples the intensity)
Sound level (β)
used to measure the intensity of sound within an easier to measure range
sound level unit
decibels (dB)
sound level equation
I = intensity of sound
I0 = threshold of hearing = 1 x 10^-12 W/m^2
attenuation/damping
the system decreases in amplitude during each oscillation due to friction and nonconservative forces
this is why it is more difficult to hear in a cluttered space; the friction from the surface of objects decreases the amplitude of sound waves
sound damping does NOT affect __________
frequency/pitch
beat frequency
when two sounds of slightly difference frequencies play in proximity at the same time, it sounds like volume is oscillating between loud and quiet
the rate of this oscillation is the difference between the two frequencies
objects that support standing waves have:
boundaries at both ends
how is ultrasound used in medicine
ultrasound is used to visualize organs, anatomy, and pathology
high frequency sound waves outside the range of human hearing is used to compare the relative densities of tissues in the body
components of an ultrasound machine
transmitter: generates a pressure gradient
receiver: processes the reflected sound
usually packaged in a single device
how does ultrasound imaging work?
the speed of the wave and travel time is known
the machine can then generate a graphical representation of borders and edges within the body by calculating the traversed distance
sound travels fastest through —– and slowest through —–
sound travels fastest through solids and slowest through gases
(less resistance to compression = faster speed)
which is faster, speed of light or speed of sound?
light travels faster than sound
