Sound waves can be described by its
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- a) Frequency,
- b) Amplitude and
- c) Speed
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Frequency
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- It refers to the number of oscillations or vibrations per unit of time.
- In the context of sound, it determines the pitch of the sound.
- If we can count the number of the compressions or rarefactions that cross us per unit time, we will get the frequency of the sound wave.
- Unit: Hertz (Hz) is used to measure frequency, which represents one cycle per second.
- High Frequency Sounds: It has a high pitch, like a whistle or a bird’s chirp.
- Low Frequency Sounds: It has a low pitch, like the rumble of thunder.
- Example: The frequency of a typical conversation is about 300 to 3,000 Hz.
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Amplitude
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- It refers to the maximum displacement or distance moved by a point on a vibrating body or wave from its equilibrium position during one complete vibration.
- In the context of sound, it determines the loudness or intensity of the sound.
- Unit: The unit of amplitude is usually measured in decibels (dB) in acoustics.
Sound propagates as density or pressure variations as shown in (a) and (b), (c) represents graphically the density and pressure variations.
- Example: A loud shout will have a greater amplitude compared to a soft whisper.
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Speed
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- Speed of sound is the distance travelled per unit time by a sound wave as it propagates through a medium.
- Unit: The speed of sound is typically measured in metres per second (m/s).
- The speed of sound varies depending on the medium.
- In air, at a temperature of about 20°C, it’s approximately 343 metres per second.
- Example: In dry air at 20°C, sound travels at around 343 metres per second.
[Low pitch sound has low frequency and high pitch of sound has high frequency]
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