Sound
Loud sound
Quiet sound
Low pitch
High pitch
Loud speaker
The loudspeaker vibrates the
air particles and the sound
energy is transferred
air particles and the sound
energy is transferred
BUT REMEMBER IF YOU ARE TRYING MEASURE THE DISTANCE
BETWEEN YOU AND THE OBJECT CAUSING THE ECHO (eg THE
WALL IN THE ABOVE ANIMATION) YOU HAVE TO DIVIDE THE
ANSWER BY 2 BECAUSE THE SOUND TRAVELS TO THE WALL
AND BACK.
Therefore if the echo above was heard after 4 seconds the sound would
have travelled 4 x 330 = 1320 metres
The distance to the wall would therefore be 1320÷ 2 = 660 metres
This tequique is more often used with ULTRASOUND
BETWEEN YOU AND THE OBJECT CAUSING THE ECHO (eg THE
WALL IN THE ABOVE ANIMATION) YOU HAVE TO DIVIDE THE
ANSWER BY 2 BECAUSE THE SOUND TRAVELS TO THE WALL
AND BACK.
Therefore if the echo above was heard after 4 seconds the sound would
have travelled 4 x 330 = 1320 metres
The distance to the wall would therefore be 1320÷ 2 = 660 metres
This tequique is more often used with ULTRASOUND
Sound waves can be reflected, echoes are evidence of this.
It is possible to calculate distance using echoes If you
rearrange the speed equation
Speed = distance
time
You get distance = speed x time
The speed of sound in air is 330 m/s, so if you measure
the time before you hear the echo and multiply
this by 330 you get the distance the sound
has travelled.
It is possible to calculate distance using echoes If you
rearrange the speed equation
Speed = distance
time
You get distance = speed x time
The speed of sound in air is 330 m/s, so if you measure
the time before you hear the echo and multiply
this by 330 you get the distance the sound
has travelled.
ECHOES
Normally sound vibrations that can be heard by the
human ear are in the frequency range 20 to 20,000 Hz.
Frequencies above 20,000 Hz, which cannot be detected by the
human ear are know as ULTRASOUND
human ear are in the frequency range 20 to 20,000 Hz.
Frequencies above 20,000 Hz, which cannot be detected by the
human ear are know as ULTRASOUND
SOUND CANNOT
TRAVEL THROUGH
A VACUUM (such
as space)
TRAVEL THROUGH
A VACUUM (such
as space)
Ultrasonic waves are usually produced by electronic systems but are
produced in nature by creatures such as bats which comunicate
using ultrasonic signals
produced in nature by creatures such as bats which comunicate
using ultrasonic signals
Uses of Ultrasound
In this example ultrasonic
pulses are reflected from
the sea bed. The time between
The pulse being sent and the
echo being received is
recorded on an
oscilloscope and the depth
of the sea calculated using
the same equation as in the
calculation above.
The speed of sound in water
Is 1500 m/s so if the time
between the pulse and the echo
Is 2 seconds.
The depth is (1500 x 2)/2
=1500 metres
pulses are reflected from
the sea bed. The time between
The pulse being sent and the
echo being received is
recorded on an
oscilloscope and the depth
of the sea calculated using
the same equation as in the
calculation above.
The speed of sound in water
Is 1500 m/s so if the time
between the pulse and the echo
Is 2 seconds.
The depth is (1500 x 2)/2
=1500 metres
Depth sounding
The pulse and echo are shown on the screen of an
oscilloscope. The time between the pulse and the echo
Is shown on the X axis. Sometimes smaller echo pulses are
seen between the two larger pulses. This could occur when a
shoal of fish pass beneath the boat. Fishing boats use
ultrasound in this way as fish finders
oscilloscope. The time between the pulse and the echo
Is shown on the X axis. Sometimes smaller echo pulses are
seen between the two larger pulses. This could occur when a
shoal of fish pass beneath the boat. Fishing boats use
ultrasound in this way as fish finders
Pre-natal scans
Ultrasonic waves are partially
reflected at the boundaries of
materials of differing densities
the amount of wave reflected
depends on the extent of the
difference in density
reflected at the boundaries of
materials of differing densities
the amount of wave reflected
depends on the extent of the
difference in density
An image of an unborn baby can be built up using theses
reflections
reflections
Utrasound is also used in medicine to treat gall stones and
kidney stones
Ultrasound is used in industry to scan materials for internal
defects and for cleaning
Some tooth brushes use utrasonic waves \to clean between
teeth
kidney stones
Ultrasound is used in industry to scan materials for internal
defects and for cleaning
Some tooth brushes use utrasonic waves \to clean between
teeth
