P12 - Sound Flashcards
speed of sound and temp
varies with temp
speed of sound
340 m/s @ 15.c
sound and a vacuum
cannot travel through a vacuum
compressions and rarefactions
as the object vibrates
-pulls/pushes repeatedly on air
sound and ear
as the object vibrates
-pulls/pushes repeatedly on air
-wave reaches ear
-makes eardrums vibrate
-send signals to brain
why is sound longitudinal
-air vibrates along direction of energy transfer
how to investigate waves methods
-ripple tank for water waves
-stretched string for waves in a solid
-signal generator/loudspeaker for sound waves
echo
reflection of sound that can be heard
-smooth hard surfaces (bare walls)
time delay
time taken for sound to travel to wall + back
speed of echo
-distance to wall and back/time delay
why can sound not travel through a vacuum
no matter for vibrations to work on
increasing loudness =
increasing amplitude (taller wave)
pitch increases =
frequency increases
hearing range for humans
20 Hz to 20KHz
why do humans have a limited hearing range
-conversion of sound waves to vibrations only happens over a limited frequency range
how do vibrations travel through a solid
-sound entering a solid is converted into vibration
-able to travel through
speed of sound changes as
-mediums vary
changes when sound moves from 1 medium to another
no change in frequency
-change in speed/wavelength
echo sounding purposes
-pulses of high frequency sound waves are sent to detect object in deep water
-measures water depth below ship
echo sounding works by
-pulses are reflected by object
- detected by receiver at same height as transmitter
-time is measured
formula for depth of water by echo sounding
0.5 x speed x time
ultrasound waves
above frequency humans can detect
-above 20kHz
uses for ultrasound waves
-prenatal scans
-images of organs
-
scanning with ultrasound method
-transducer placed on body surface and displays on screen
transducer
produces and detects pulses /ultrasound waves
how do ultrasounds work
-waves are partially reflected from diff tissue boundaries in its path
-waves are returned to transducer as a sequence of reflected waves arriving at diff times
-forms image on a screen
pros of ultrasound use
used to scan organs/ soft tissues (unlike x rays)
-non ionising = harmless
non ionising
not enough energy to remove an electron to ionise an atom
Industrial imaging and ultrasounds purpose
-flaws in metal castings can be detected
Industrial imaging and ultrasounds method
-transducer sends waves into block
-ultrasound waves are partly reflected + detected
-displayed on screen
ultrasound formula for distance travelled by wave
speed of ultrasound waves x time taken
