Which of the following factors will affect the velocity of sound?

Analyze the question: We need the factor that actually changes the speed (velocity) of sound in air.

Concept: The speed of sound in a medium depends on the properties of the medium, not on the properties of the sound wave itself. For a gas:

v = √(γP/ρ)

• It depends on temperature, the type of gas, humidity, and the motion of the medium (wind).
• It does not depend on frequency (pitch) or amplitude (loudness).

Check each option:

• A. Pitch (frequency): Pitch depends on frequency. If frequency increases, wavelength decreases, but v = fλ stays the same. No effect.
• B. Loudness (amplitude): Loudness depends on amplitude, which relates to energy and not to speed. No effect.
• C. Wind in the same direction as the sound: The wind moves the air itself, so the sound's speed relative to the ground is v + v_wind. The velocity of sound therefore changes. This does affect the velocity.
• D. Change in atmospheric pressure at constant temperature: Since v = √(γP/ρ) and, for an ideal gas at constant temperature, P/ρ is constant (Boyle's law), a change in pressure changes density in proportion. The two cancel, so there is no effect.

Tip: Remember that the speed of sound depends on the medium (temperature, wind, type of gas), not on the sound (pitch, loudness). Also, pressure alone does not matter at constant temperature. JAMB likes to test this.