SOUND
Direction: Below is an illustration of a wave. Identify the
parts of the wave asked in the given item.
Would you like to try placing your palm on your throat
while saying – What are you doing? What did your
palm feel?
Were there vibrations in the throat?
Try it again and this time, say – “For the win!”
Sound is an example of longitudinal wave. It is
also classified as a mechanical wave.
There has to be matter for which sound should
travel and propagate. This matter is known as
medium.
SOUND AND ITS MEDIUM
In which media does sound travel fastest?
Sound travels better through high-density material
The closer the molecules are together, the faster they
can collide and transfer energy. Sound travels fastest in solids and
slowest in gases.
FACTORS AFFECTING THE SPEED OF SOUND
Did you know that lightning and thunder occur at the same time?
However, we often see lightning much earlier than the
corresponding thunder. This is because the speed of light (c = 3
x108 m/s) is much faster than the speed of sound.
The speed of sound in dry air at 0°C is about 331.5 m/s.
However, the speed of sound in air is not constant.
1. Atmospheric pressure - At higher atmospheric pressure, sound waves
travel faster.
2. Relative humidity - The higher the relative humidity, the faster the
sound is transmitted. This is due to the fact that at a higher relative
humidity there is more water vapor in the atmosphere which makes
the particles in the atmosphere a little closer than at low relative
humidity.
3. Atmospheric temperature- Each degree rise in temperature above
0C, speed of sound in air increases by 0.6 m/s
CHARACTERISTICS AND PROPERTIES OF SOUND
1. PITCH - the highness or lowness of sound or musical note.
• The pitch of a high frequency sound is high and low
frequency sound, the pitch is low
1. Which string vibrates fastest when strummed?
2. Which string vibrates slowest when strummed?
3. Which string has the highest frequency?
4. Which string has the highest pitch?
5. Which has the lowest frequency?
6. Which string has the lowest pitch?
7. How would you relate pitch and frequency?
HEARING AND THE HUMAN EAR
THE THREE MAJOR PARTS:
A. OUTER EAR – called pinna, collects the sound waves and focuses them into the
ear canal
TYMPANUM/EARDRUM MEMBRANE – separates the outer and middle ear.
B. MIDDLE EAR
Air vibrations set the eardrum membrane in motion that causes the three
smallest bones( hammer, anvil and stirrup) to move. These three bones convert
the small amplitude vibration of the eardrum into large-amplitude vibrations.
These vibrations are transferred to the inner ear through the oval window.
C. INNER EAR
Behind the oval window is a snail-shell shape liquid-filled organ called the
cochlea. The large amplitude vibrations create waves that travel in liquid and are
converted into electrical impulses, which are sent to the brain by the auditory
nerve. The brain interprets these signals as words, music or noise.
2. LOUDNESS AND INTENSITY
INTENSITY – refers to the amount of energy a sound wave
carries.
High amplitude sounds carry large energy and have higher
intensity
Low amplitude sounds carry lesser amount of energy and
have lower intensity.
Measured by an instrument called the oscilloscope
The unit for intensity of sound is the decibel (dB), named
after Alexander Graham Bell who invented the telephone.
LOUDNESS – is a psychological sensation that differs for different
people. It is subjective.
KINDS OF SOUND WAVES
1. AUDIBLE SOUND – human ear can hear
- frequency range of 20
Hz – 20, 000 Hz
2. ULTRASONIC FREQUENCIES – vibrational frequencies beyond or
above 20,000 Hz
- human ear cannot
detect ultrasonic sounds
but some animals do.
Dogs can detect up to 50,000 Hz and bats can hear up to
100,000 Hz
3.Uses in Ultrasound
INFRASOUND – vibrational frequencies below 20 Hz
- it cannot be heard by human ear but can
cause damage
Sources of Infrasound
Vibrating heavy machines
Volcanoes
Earthquake
