Sound

• Sound waves travel through a medium, such as air, water, or solids.
• Sound waves can be described by their frequency (number of oscillations per second) and amplitude (height of wave).
• The human ear is sensitive to sound frequencies between about 20 Hz and 20,000 Hz.
• Amplitude determines the loudness of a sound.
• Higher-frequency sounds are perceived as higher pitched, while lower-frequency sounds are perceived as lower pitched.
• Characteristics of sound are pitch, loudness and timber
• Pitch is the measure of shrillness of a sound, high pitch sounds are more shrill than low pitch sounds
• Number of oscillations completed in one second is known as frequency
• Frequency is measured in hertz (Hz)
• Sound is a form of energy that is transmitted through vibrations.
• Timbre describes the quality of a sound, such as whether it is harsh or smooth.
• The distance between two successive crests or troughs (or) successive compressions and rarefactions is called wavelength (λ).
• Amplitude is measured in meter(m)
• When the prongs of a tuning fork move inwards it causes the surrounding air particles to move apart, this results in a low pressure area called rarefaction
• When the prongs of a tuning fork move outwards it causes the surrounding air particles to come close, this results in a high pressure area called compression
• The outer ear consists of the pinna, ear canal and ear drum(tympanum)
• The middle ear consists of three tiny bones, the hammer, anvil and stirrup
• The inner ear consists of the cochlea, which is a long coiled tube, it is filled with fluid and has numerous highly sensitive hair cells
• When sound waves hit an obstacle, it gets reflected back by it. This is known as reflection of sound(echo)
• SONAR (Sound Navigation and Ranging) is a technique used to detect objects underwater and measure the depth of seas and oceans
• SONAR sends ultrasonic sound down into the ocean and when it gets reflected back from the obstacle the time is used to calculate the distance between the source of sound(the ship) and the object
• Stringed instruments

  Thicker wire - low pitch

  Thinner wire - high pitch

  Short wire - high frequency

  Long wire - low frequency
• Comfortable sound level for human ears is 60 - 65 decibels