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Notes 21.1 – Properties of Sound. Pitch – how the human brain hears and interprets sounds of different frequencies. Higher pitch = higher frequency Humans can hear frequencies between 20 Hz and 20,000 Hz. Tuning forks produce single pitch (frequency) sounds.
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Pitch – how the human brain hears and interprets sounds of different frequencies. • Higher pitch = higher frequency • Humans can hear frequencies between 20 Hz and 20,000 Hz.
Tuning forks produce single pitch (frequency) sounds. • Most other objects create sounds that are a combination of frequencies. Acoustics – the science and technology of sound.
The loudness of a sound is measured in decibels (dB). • Louder sound waves have greater amplitudes and more energy. • The decibel scale shows how some sounds compare.
Speeds of Sound • The speed of a sound depends on the medium. • Speed of sound in air at 0°C is about 330 m/s (750mph). • Typically, sound travels faster in liquids, fastest in solids. • As the air gets warmer, the speed increases. • Subsonic – moving slower than sound • Supersonic moving faster than sound
Sonic boom – a build up of sound waves from an object traveling faster than sound.
Doppler Effect – the shift in the frequency of a wave as the wave source moves. • If an object is moving toward you, the sound waves get closer together (higher frequency or pitch). • If the object is moving away, the waves spread out (lower frequency, pitch)