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Unit 6: Sound and space

Loudness And Pitch Of Sound — HIA International - Grade 8 Revision Notes & Topical Questions

5 min read 9 parts Lesson 7 of 14 2 quizzes

📚 HIA International - Grade 8 Hub / Topical Revision
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Lesson summary

Loudness and pitch of sound — HIA INTERNATIONAL notes: Link amplitude to loudness and frequency to pitch and read these from wave diagrams.Loudness = how quiet or loud a sound appears.Vibration size — the greater the range of each vibration, the louder the sound.Distance — the fu…

  • Measurement
  • Link to loudness
  • Oscilloscope
  • Link to pitch
  • Calculation
  • Shorter vibrating part

Section 1 of 9Loudness

Loudness
Loudness how quiet or loud a sound appears.
Vibration size
  • Vibration size the greater the range of each vibration, the louder the sound.
Distance
  • Distance the further away the vibrating object, the quieter the sound, because energy dissipates.
Measurement
  • Measurement loudness is measured in decibels (dB).

Section 2 of 9Amplitude

Amplitude
Amplitude the maximum distance particles move forward or backward in a sound wave.
Graph
  • Graph the distance from zero to a peak (top) or from zero to a trough (bottom) are equal.
Link to loudness
  • Link to loudness as amplitude increases, loudness increases.
Oscilloscope
  • Oscilloscope a microphone detects the sound and a screen shows the wave; a louder sound has a taller wave.

Section 3 of 9Pitch and frequency

Pitch
Pitch how high or low a sound appears on a musical scale.
Frequency
Frequency the number of vibrations in each second, measured in hertz (Hz).
Example
  • 500 Hz means 500 vibrations every second.
Link to pitch
  • Link to pitch the higher the frequency, the higher the pitch.
Wave diagram
  • Wave diagram a higher-frequency wave has more waves in the same time.
Calculation
  • Calculation frequency = number of vibrations ÷ time taken.

Section 4 of 9Comparing waves on an oscilloscope

ChangeAmplitudeFrequencyResult
Taller wave, same spacingIncreasesSameLouder, same pitch
Waves closer together, same heightSameIncreasesHigher pitch, same loudness
Smaller waveDecreasesSameQuieter

Section 5 of 9Musical instruments

Musical instruments
Shorter vibrating part
  • Shorter vibrating part gives a higher pitch, e.g. shorter strings on a gayageum or guitar.
Mass
  • Mass heavier strings vibrate more slowly and have a lower pitch.
Plucking harder
  • Plucking harder increases amplitude and loudness.
Piano
  • A notes double in frequency each octave: 27.5, 55, 110, 220 and 440 Hz.
Soft pedal
  • Soft pedal lowers amplitude without changing frequency.

Section 6 of 9Human hearing

Range
  • Range about 20 Hz to 20 000 Hz, and it narrows with age.
Ultrasound
  • Ultrasound sound above 20 000 Hz.
Damage
  • Damage prolonged loud sound above about 85 dB can damage hearing.

Section 7 of 9Investigating a vibrating ruler

1
Clamp a ruler to a bench with a mass taped to its free end.
2
Pull and release it, and count the complete vibrations in 10 seconds.
3
Divide by 10 to get the frequency in hertz.
4
Repeat with at least five different masses and repeat each reading.
5
Plot frequency against mass.
Independent variable
  • Independent variable mass.
Dependent variable
  • Dependent variable frequency.
Control variables
  • Control variables length of ruler and how far it is pulled.

Section 8 of 9Key terms

TermMeaning
AmplitudeThe maximum distance particles move from rest in a sound wave.
FrequencyThe number of vibrations per second, in hertz.
LoudnessHow loud or quiet a sound appears.
PitchHow high or low a sound appears.
OscilloscopeA device that displays sound waves on a screen.
HertzThe unit of frequency, Hz.
PeakThe highest point of a wave.
TroughThe lowest point of a wave.

Section 9 of 9Exam technique

1
A louder sound has a higher pitch — loudness depends on amplitude and pitch on frequency.
2
Amplitude is the distance from the top to the bottom of the wave — it is from zero to the peak or trough.
3
Quiet sounds have lower frequency — frequency affects pitch, not loudness.
4
Frequency is measured in decibels — it is measured in hertz.

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