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This content explores the fundamental properties of sound, detailing its classification into longitudinal waves created by vibrations. It covers concepts like pitch, determined by frequency, and loudness, influenced by amplitude. Various sound levels are quantified in decibels, illustrating the potential for hearing loss at volumes over 85 dB. Additionally, it touches on ultrasound and its range of hearing in humans and animals, along with its various applications, including measurements and navigation techniques like those used by bats.
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Sound is made by vibrations Vocal chords in the throat
Sound travels through the air Ear drum Sound source
Low pitch Low frequency
High pitch High frequency
Quiet • Turn down the volume on your system Small amplitude
Loud Turn up the volume on your system Big ampltitude
Loudness and Pitch • Pitch is controlled by frequency – high frequency waves make a high pitch sound. • Loudness or volume is controlled by amplitude – large amplitude waves make a loud sound.
Loudness and decibels The loudness of a sound is measures in decibels. If you stand near to these • Silence - 0 dB • A whisper - 15 dB • Normal conversation - 60 dB • A car engine - 90 dB • A car horn - 110 dB • A rock concert or a jet engine - 120 dB • A gunshot or firework - 140 dB
Loudness and decibels • Any sound above 85 dB can cause hearing loss. • Eight hours of 90-dB sound can cause damage to your ears • Exposure to 140-dB sound causes immediate damage (and causes actual pain
Ultrasound • Humans can hear sounds ranging from a frequency of about 20Hz up to 20 000Hz depending on their age and other factors • Sound of frequency higher than this is called ultrasound. • Ultrasound can be heard by some animals • Many uses have been found for Ultrasound.
Ultrasound reflection The reflection of ultrasound enables distances to be measured. transducer Reflections here
