Effects of Sound Waves (Cambridge International IGCSE Physics)

Pitch & loudness

Spec point — 3.4.3 · Describe how changes in amplitude and frequency affect the loudness and pitch of sound waves

• Changes in frequency and amplitude affect the pitch and loudness of sound waves

• The frequency of a sound wave is related to its pitch

  • Sounds with a high pitch have a high frequency (or short wavelength)
  • Sounds with a low pitch have a low frequency (or long wavelength)

• The amplitude of a sound wave is related to its loudness

  • Sounds with a large amplitude have a greater loudness
  • Sounds with a small amplitude have a decreased loudness

Pitch and loudness of sound

Echoes

Spec point — 3.4.3 · Describe an echo as the reflection of sound waves

• Sound waves reflect off hard surfaces

  • The reflection of a sound wave is called an echo

A clap sound is reflected off a wall. When the reflected sound is heard, this is the echo

• The distance to the surface where the echo reflects can be calculated using the equation:

$\mathrm{distance}=\frac{1}{2}\times\mathrm{speed}\times\mathrm{time}$

• Where:

  • distance = half the total distance travelled by the sound wave, measured in metres (m)
  • speed = speed of sound in air, measured in metres per second (330 – 350 m/s)
  • time = total time for sound wave to travel to the surface and back, measured in seconds (s)