Sounds

• Sound is a form of energy that is transferred from one point to another in the form of a longitudinal wave.
• The wave motion of sound resembles that of a slinky spring showing regions of compressions and rarefactions.
• Vibrating objects will generate sound waves in a medium.
• The medium may be in the form of a solid, liquid or gas.
• When a sound wave travels through air it causes a change in air pressure.
• Region of compression has a slightly higher air pressure compared to the surrounding air pressure.
• Region of rarefaction has a slightly lower air pressure compared to the surrounding air pressure.
• Sound waves are mechanical waves and require a medium in order to be transmitted from one place to another. Therefore, sound cannot be transmitted through a vacuum.
• Light waves which are electromagnetic in nature does not require a medium in order to be transmitted.
• Any medium with vibrating particles can transmit sound.
• The more closely packed the particles, the faster the speed of transmission of sound.
• Different people have different audible range. Generally, the audible range for a human being is between 20 Hz to 20000 Hz.
• The ability of our ear drums to detect sound decreases as we age when the lower limit of audibility increases and upper limit of audibility decreases.
• Human beings are unable to detect sounds that are lower than 20 Hz (infrasound) and higher than 20000 Hz (ultrasound).
• As in electromagnetic waves, sound waves also undergo reflection.
• Echoes are sounds reflected off a smooth and hard surface at a distance away.
• Our ear can detect the loudest reflected sound when its angle of incidence (i) equals to the angle of reflection (r).
• Multiple reflections can occur when a sound is reflected off the walls and the ceiling in an enclosed building (e.g. enclosed school hall).
• Our ear will detect multiple echoes instead of one distinct echo.
• Reverberation is the phenomenon when our ear detects prolonged sound due to the merging of many echoes.
• Too much reverberation causes musical sound to appear less distinct and too little reverberation causes the sound to appear weak.
• Sound pulses can be sent by a ship as a signal to the bottom of the sea to determine its depth by noting down the time taken for the echoes to travel to and fro the receiver and the sea bed (we know the speed of sound in sea water).
• A sound is said to have a high pitch if it has a high frequency.
• The higher the frequency, the higher the pitch of a sound.
• When we say that the pitch of a sound is increased by one octave, the pitch of sound is doubled.
• Loudness is related to the amplitude of a sound wave.
• The higher the amplitude of 6a sound, the louder it is.