This topic accounts for approximately 7% of your exam marks.
stable
Low
Stable7%
Speed of sound calculations, echo timing and ultrasound uses are standard shorter questions.
Pitch is set by frequency
The of a sound is how high or low it sounds to the ear
Pitch is determined by the 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 of a sound is how strong it sounds to the ear
Loudness is determined by the 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
Exam tip
State the wave property that determines pitch (or loudness)
What comes up: a one-mark question asking which wave property determines the pitch of a sound.
Write: frequency. Give only one property — the mark scheme credits frequency alone and rejects any response that names more than one quantity.
Watch out: do not write "frequency and wavelength" or "frequency and amplitude" — the mark scheme explicitly rejects an answer that names more than one quantity/property.