This topic accounts for approximately 7% of your exam marks.
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Speed of sound calculations, echo timing and ultrasound uses are standard shorter questions.
Pitch is set by frequency
The pitch of a sound is how high or low it sounds to the ear
Pitch is determined by the frequency of the vibrating source:
A vibration at a high frequency produces a high-pitched (treble) sound
A vibration at a low frequency produces a low-pitched (bass) sound
On the oscilloscope: a higher pitch shows more wave cycles in the same horizontal width, and a shorter peak-to-peak distance
Loudness is set by amplitude
The loudness of a sound is how strong it sounds to the ear
Loudness is determined by the amplitude of the wave (the size of the back-and-forth movement of the air):
A larger amplitude produces a louder sound
A smaller amplitude produces a quieter sound
On the oscilloscope: a louder sound shows a taller wave from the centre line, while a quieter one has a shorter trace
Independence
Pitch and loudness are independent properties of a sound wave; either can be changed without affecting the other
A single tuning fork struck softly and then struck hard produces the same pitch each time; the trace keeps the same horizontal spacing but the second strike gives a taller wave
A flute playing a high note quietly and a tuba playing a low note loudly differ in both pitch and loudness simultaneously, but the two properties are independent in principle