Sound wave properties on oscilloscope: amplitude for loudness, frequency for pitch

Steps:

• Amplitude of the wave trace indicates loudness; increasing amplitude means getting louder.
• Frequency (or 1/period) indicates pitch; decreasing frequency means pitch decreases.
• Examine each trace for changes in peak height (amplitude) and wave spacing (period).
• Identify the trace with rising peaks and widening spacing over time.

Why B is correct:

• Trace B shows increasing amplitude (taller peaks) and increasing period (wider waves), per the definitions of loudness and pitch in wave physics.

Why the others are wrong:

• A: Amplitude constant, frequency increases (pitch rises).
• C: Amplitude decreases, frequency constant (gets quieter, pitch unchanged).
• D: Amplitude increases, frequency increases (gets louder, pitch rises).

Final answer: B